Guys,
Well, back in June (2006) I contacted JWT via email to basically get more valid information about the fwd roller variant of our motors; Well I ended up getting a phone call in return... and a great deal of information from that long conversations. Clark Steppler is a very knowledgable guy... and I commend him for sitting down and talking to me. Here is a passage that I wrote around 6 months ago in response... and its been sitting on my HD since then.
I have tried to get in contact with Clark for 5 months or so via email so that he can proofread it, so I can omit redundant information but I have not been able to do so. This could be due to the fact that they are a very busy company.
So in that respect, please take this as opinion & as simple instigation for good conversation... I had hoped to post this a long time ago but was reluctant to. I thought people would tear me apart since I don't have a ton of support. I'm not really afraid anymore and in that event I'll just remove it.
Please read the disclaimer and take it seriously, and please be respectful.
Ameen B. aka "Tokes"
Intro: Discrepancies and Controversies
Well, The main point of creating this passage is not to start arguments within the community. it was written to raise awareness in the differences of the roller engine and the conventional SR20 motor (highport/lowport spraybar). There is a lot of delusion around the forums when this subject was concerned. And frankly I got tired of it. Well most of you know that this sparked the beloved "JDM/USDM Roller Rocker SR20 Information Thread"
Check that thread here: http://sr20forum.com/showthread.php?t=147888
This all surfaced when I was asked a question "What would happen if a highport cam was installed in a RR motor?" From reading I assumed it wasn't possible. well, come to find out that the install unintentionally happened (not telling who) and there is a motor (could be more) that has supposedly been running for over a year like this. I was baffled. and I just don't like not understanding things. So I asked around, I read, I researched. and honestly I hit a wall. I thought I knew about the SR20. well frankly, and you can quote me here, "I don't know anything". I just read things and absorb passed knowledge before me.
Well, I asked around. and got together with James from the forum []98sr20de(t)[] and he helped me come up with a few unanswered questions. We decided to get some true camshaft/valvetrain information from some people that have had experience with the SR20DE from its introduction to its retirement. I emailed/called JWT's Support/Research & Development Team.
Here are the questions that were asked: http://sr20forum.com/showpost.php?p=...&postcount=110
The funny thing is, I went in with only a few questions about a roller rocker and came out with a lot of information that I thought some of you may like to read.
Disclaimer:
Please take the following information lightly and with open hearts and ears. The technical information that is displayed here was recorded from my recollection during a phone conversation with Mr. Clark Steppler (from JWT Support) and I. I take full responsibility for the information displayed here if it is incorrect. Anything I am unsure of has been shown in gray text.
*** Feel free to comment, but if it sparks any sort of break in unification, disrespect toward anyone on the forum and/or JWT, or argument. it will be removed, plain and simple. If there is something you don't agree with here, please take the time to send me a PM and we can discuss it. ***
Conventional SR20 Information and Other things you MAY NOT KNOW!
Rocker Arms
First, to my understanding I always thought that the conventional rocker arms were made of stamped steel... I was told that this is NOT true. They are actually molded powdered metal.
The Conspiracy of the 94 Cam
Originally I had always thought that the only specific grinds for the stock FWD SR20's were.
Stock Spraybar Molded Rocker SR20DE Camshaft Information
Intake: Duration = 248* / Lift = 10.0mm (Highport)
Intake: Duration = 232* / Lift = 8.66mm (Lowport)
Exhaust: Duration = 240* / Lift = 9.2mm
Stock Non Spraybar Roller Rocker SR20DE Camshaft Information
Intake: Duration = 232* / Lift = 10mm
Exhaust: Duration = 240* / Lift = 9.2mm
Well, it appears that I forgot about a certain series in the mix. In the stock 94 Sentra lowport head, housed a 240* duration and 9.2mm lift intake cam... which is essentially a replica of the SR exhaust cam. This was the first and only year they used that cam profile in the Sentra SE-R... but the interesting thing is that they continued to build the Nissan Primera/Infiniti G20 in 95 and 96 with this special 94 intake cam as well. So, according to the cam change in the SR20 Motor (From 240* to 232* in the B14 SE-R), the rev limit went from 7.5 to 7k because of the intake cam, but in the 95/96 g20s the rev limit still remained at 7.5k...
In essence, the reason the rev limit was minimized is because the 232* duration cam doesn't function well at 7.5k. Most know when you switch the 91-93 highport cam in the lowport head there is a gain in power.. but your stability at 7.5k is now attainable as well. Also when you switch the 94 lowport SR20 intake cam, or 94-96 Primera/G20 lowport intake cam into your late lowport engine there will be a gain in power as well. and your 'stability' at 7.5k is then "regained". Even though this 'stability' is attainable, it does not mean it's advisable to rev that high... mainly because the SR20DE stock does not make its best power at this rpm. Remember, just because something is attainable doesn't mean it should be pushed to the limit. constant load at high rpm to redline isn't advisable all the time, unless you like engine wear. Additionally, no matter what camshaft is in your lowport SE-R, your rev limit will obviously be governed by the ECU that you are currently using.
Lowport or Highport Head. Which Flows Better (Stock)?
I never understood why this is such a huge issue around the forums. In all honestly, it doesn't really matter to me. but the internet is a huge ego measuring contest. so here goes. Everyone knows that the later lowport (95-99 SE-R at least in the US) was basically detuned from the demand of emission standards from my favorite agency in the world. As a direct result the cam changes (shown above) were implied. Even though the late lowport SR20 had a lower duration intake cam and a less aggressive lift the HP rating for the motor remained the same at the crank. 140hp from the factory. Now what does that mean? I'll tell you. It means in order to compensate for the less aggressive camshaft (to reduce emissions) something had to be done in order to match the HP ratings of the previous highport SR20 motor. Cue the enter for the Nissan Engineering Team.
The LOWPORT head flows better than the HIGHPORT head STOCK... out of the box... un-ported, untouched, tit for tat, STOCK. If it is modified (i.e. port work) the highport head has a higher potential of better flow. The reason is because there is a bump in roof of the port for the lash adjuster in the head of the lowport. The highport head has more potential for head flow because it necks down to go around the hydraulic lash adjuster... the area in the head on the short intake port is better.
Why are they "Detuning" our Cars? (Very Opinionated)
Well even in the late 90's emissions and other factors like fuel economy came into mind. In 2006 it is evident that the age of import scene lives, but there is something that is generally more important to this nation. Would you like to have a guess at what that is?
Well, the answer to the above question is FUEL ECONOMY aka good ol' mile per gallon. Think of this situation: if you are a car manufacturer and your only two options were deciding between designing an engine for power and performance, or designing it for fuel economy, which would you choose? Now take into account that the majority of people that represent the car buying force don't give a flying focus svt about air/fuel ratio, wideband, variable timing, whp, or anything else performance related. Car manufacturers provide for what the public wants, and the demand for a performance vehicle is below the demand for a fuel efficient econo-box at the moment. So what is Nissan (or any other car company/manufacturer) do in this case? You got it. they give in to the hype. It's either that or potentially lose revenue. Why else do you think that MPG rating is shown in every single car commercial you see anymore?
Well that is what I think. Now on to the Roller Rocker.
More Roller Rocker Differences from Conventional SR20DE (Stuff not in RR Info Thread):
The Head, Valve-Train, Spring Rates, and What's good about the RR SR20DE.
The Roller Rocker cylinder head is not different from the normal SR20... There are different code numbers but the head is essentially the same. The conventional head and roller head is essentially the same, aside from the fact that the Roller Rocker Motor has longer cam cap bolts...
The spring rates between the conventional SR20 and the Roller Rocker valve springs are different because of the difference in weight distribution and moment of inertia of the roller rocker arm. The pressure needed to compress the spring is very close.
The RR Motor has lighter pistons than the conventional SR20. Some versions used lightweight pistons because they have a smaller bore and 4CW crank. Keep in mind that the RR motor has been used in other countries before 2000 in Japan, UK, etc. (Almera, Primera, et cetera.)
As some of you know, the Roller Rocker motor and the SR20VE share the similar type Valve Cover. For this design the black oil separator (or sometimes referred to as the OEM "catch" can on the forums) was removed. A baffle was incorporated into the cover and the top was raised to compensate. A tube for Crankcase Ventilation was inserted at the lower right and the PCV Valve was moved from the left upper side to the upper right side of the valve cover. Through past experience in development the dumping of crankcase ventilation was determined to be better for turbo installation on the RR/VE valve cover... The RR cover has a better design hands down, and has more function.
The B15 & G20. Hmmm Compression Differences
Well in 2000 the Sentra was still selling in the US, but the B15 was Born, w/ a Roller Motor. In addition the G20 was still selling and housed a Roller Rocker motor as well. The b15 Roller Rocker Motor had a 2cc smaller combustion chamber, which is evident through its slightly higher compression than conventional (Discussed a bit in the RR Info Thread). The b15 uses the same type concave dishes on its pistons as previous rocker so nothing was roller specific. The g20 in 2000 variation has a 2cc smaller head, but has a bigger dish so that is why the compression is the same as the normal roller rocker.
For the Roller Rocker SR20DE, the camshaft profiles aren't all the same stock around the world. At this point the US has only had one set for intake and exhaust camshafts... but in Japan, Europe, etc, there are a few lists of durations/lifts. Some engines used different variants for valve springs as well... This explains why there are different rev specs for Roller Rocker motors overseas (i.e. 7.1k for some opposed to 6.8k or lower for USDM RR Motors.)
One interesting fact is that before the B15 ever sold in the US, JWT was already considering developing a cam using the roller rocker arms. This would have involved using the roller rocker arms and putting them in the conventional SR20... but the conversion would entail changing the valve train around. (changing valves, cams, springs, etc.) not promising. At this point in time I believe it was referred to as the "small base radius" cam.
Why are the Cams different in a Roller SR20. Why Can't I just throw Non Roller Cams in there?
You can throw a monkey in a gorilla suit in the Congo and he will live, but it doesn't mean he will function correctly. In other words, yes, now I understand that it has been done, a non roller camshaft has been installed in a roller rocker head. but it doesn't mean it is advisable. I have no clue what power it may or may not yield... but from a long discussion and a little thinking I know now that each cam (roller & non roller) has applications for each valve train's attributes. Let me explain what I found out from JWT:
The intake & exhaust valves are 3mm shorter in a roller rocker engine... then non roller SR20DE has a 40mm install height and different valve springs then roller. The RR has a 37mm install height. The center of bearings of the RR camshafts are all the same diameter as the conventional SR20, but lobes are very, very, very different. The rocker arms are different; the radius of contact is different, the distance from pivot point, the moment of inertia, the mass of the rocker, etc.
The initial point on which cam contacts the roller is different... by implementing a different cam into the wrong valve train one can incoherently advance or retard the cam motion... The phasing of it where it first touches the rocker arm is different. The Radius of curvature can make a great deal in the difference in contact stresses as well. It can produce a valve motion that it wasn't design for. In theory it can mess up harmonics of the valve train and at a certain rpm it may excite them...
The Roller Rocker arm has a different moment of inertia; the valve spring has to overcome the open and close motion of this arm at different RPM speeds... What controls this motion??? The valve spring controls this motion, and inherently controls stability of the valve train...
Obviously we know now that it is not impossible to run the non roller cam in a roller engine; I now know it has been done. The engine may run, but it may not run efficiently or the way it was designed (i.e. valve float).
When Designing the S3R (and other SR20 Camshafts & Valve Springs):
Brief General Knowledge on Camshaft Design
There is a lot of information that goes undermined when the research and development of a camshaft is discussed. A lot of the information that was discussed about design brought me back to my first years of engineering because we were talking about mass flow data, spring rate, inertia, kinematics, etc. Some of the stuff went over my head. and I was so intrigued and flattered during the conversation that some of the stuff I didn't write down because I was so into it. But in a nutshell I will just say that there are a lot of factors investigated, and there is a lot of math used. So I will keep it pretty general.
When designing camshafts for the SR20 the two first things to do are to attain a model head, and attain measurements to make a blueprint. This is a very difficult task as many things need to be taken into account. For example:
1) Cylinder Head - take cylinder head off and take measurements of it
2) Rocker Arm - out and take measurements to make a blueprint.
3) Where is the pivot ball at??
4) Spring Retainer Height??
5) Rocker Arm Height & Weight??
6) Etc.
The idea here is to make a model that is basically an exact replica of the motor that the camshaft(s) are being designed for. It is very important to create a precise model so that the flow data recorded will be similar and the cam will be functional. These representative models are built and tests (kinematics models) are run to acquire more information during the research and development stage. the more area under the lift curve
Different combinations of duration and lift are applied to the model. The tests data from the head/cylinder flow analysis is represented by graphs. This data is used to iterate and find power in one degree increments to find optimum performance for the applicable cam. The area under the lift curve generated is found using integration (remember calculus/physics/hydraulics much???). The more area under this curve the more flow/power. With the use of these models the optimum percent (%) increase of the number for mass flow data is recorded. This has to be very close to natural engine performance... so there is a lot of time and emphasis put in at this stage.
Specific Info for the S3R Camshaft
Well, if you didn't get the idea from the rest of this multiple prolonged paragraphs in this novel. the S3R and S3 cam grinds are different for a reason. the radius of curvature is different in each stock cam, which entails a whole different design for JWT. So vitally it's not just, and I quote, "cut and paste"... Because of difference in length of the valve heights, the orientation of the rocker arm, and the radius contact ratio of the stock roller rocker, the base circles of the stock cam lobes are a different diameter... For the S3R Roller Cams, the base radius on the cam lobe is smaller than on the S3... the lift is a little higher on the RR, but more duration had to be introduced. Again, the roller rocker arm is heavier, so its moment of inertia is different so therefore has to be modeled. The number of coils in the valve spring is different, as well as the spring coil diameter... although main pressure for each spring is similar, and the spring curves aren't that different, the spring rates are.
When designing the S3R, JWT originally came up short on flow so they increased the lift to get about the same performance of s3 cam on conventional engine. (just a bit lower).
Non Specific Information on the SR20 Valve Train (Engineering)!
Ideally, the higher the natural frequency of a valve spring, the more harmonics that can introduced. The more harmonics, the higher the engine speed, the more potential power. (I said ideally!!!)
In theory and you can push on the spring and it doesn't matter how much pressure is pushing back, the important thing is that valve spring has to be able to push the mass (in each case; the rocker arm) back to keep in contact with the cam lobe. If it doesn't then valve float can be introduced. Because the rocker arm is so heavy, to go higher rpm, a bigger spring must be introduced... There is a 50% weight difference for each rocker arm... so the moment of inertia is almost double.
When designing a spring, it is to my understanding that engineers may ask questions like.
1) How fast are we accelerating here?
2) Do we have enough spring force to control the mass?
3) Should I go to Wendy's??? I'm really hungry.
4) At what RPM will this spring hit resonance?
If you need a good definition of resonance, please take a look here, it mainly discusses sound waves, and wave amplitude, but the same information applies:
But, when an engine reaches a certain level of RPM, the valve spring can reach resonance where serious vibration takes place. At this point it can surge, spring can lose its function and wear, and damage can occur. So, in conclusion. Engineers design valve springs and the valve train together for a reason. further explaining the importance of matching camshafts to its applicable valve train.
Here is a quick link of some stuff about spring resonance: (It's a new subject to me; I don't know much)
Future Applications from JWT?!?!?!
Well, in talking with from JWT I had the opportunity to hear a few prospective designs currently in the air. So lets get to the good stuff.
Will there be any more Roller Rocker cams in the Making?
There is a possibility to run a more aggressive cam and valve spring combination that the S3R for the roller rocker motor. So yes, the possibility is there, but it really depends on how good the market is for them. There needs to be a show in potential buyers. Simple economics. if there is no demand and supply is high, they will lose money. If you have serious interest I can tally this somewhere with full names and info and forward to JWT. The chances of finding enough serious people will be tough, but the possibility is there.
Special Roller Camshafts. with the Conventional SR20 Valves/Springs?
There is a possibility of doing a special camshaft profile where you can use the roller rocker arms and roller cams but with the conventional longer valve (40mm) and spring, but in this case there would be a need for a dual valve spring... This is if you SR20 people were interested, so it would depend on how many products they could sell to our community. The gains are having a very efficient valve train (less friction) and being able to utilize power by raising the potential rev limit.
I'm sure the development of this application will only further itself if there is a demand for it as well.
VVL Camshafts. Yes, VE Aftermarket Cams from JWT.
Some of you may already know this, and I may be relaying old information to you, but:
The VVL camshaft is currently in design at JWT. I was told that it will be coming within a few months... I don't know any numbers nor do I know any more information than that. I was just told that I could share it with you!
Reference Section:
Clark Stepplar - JWT Support, Research & Development
Thanks Again...
Ameen B
Here is a copy of some of the emails that were sent out for reference... They are pretty old though
Well, back in June (2006) I contacted JWT via email to basically get more valid information about the fwd roller variant of our motors; Well I ended up getting a phone call in return... and a great deal of information from that long conversations. Clark Steppler is a very knowledgable guy... and I commend him for sitting down and talking to me. Here is a passage that I wrote around 6 months ago in response... and its been sitting on my HD since then.
I have tried to get in contact with Clark for 5 months or so via email so that he can proofread it, so I can omit redundant information but I have not been able to do so. This could be due to the fact that they are a very busy company.
So in that respect, please take this as opinion & as simple instigation for good conversation... I had hoped to post this a long time ago but was reluctant to. I thought people would tear me apart since I don't have a ton of support. I'm not really afraid anymore and in that event I'll just remove it.
Please read the disclaimer and take it seriously, and please be respectful.
Ameen B. aka "Tokes"
The Differences in RR/Conventional SR20DE Cam Design + More info from JWT
Intro: Discrepancies and Controversies
Well, The main point of creating this passage is not to start arguments within the community. it was written to raise awareness in the differences of the roller engine and the conventional SR20 motor (highport/lowport spraybar). There is a lot of delusion around the forums when this subject was concerned. And frankly I got tired of it. Well most of you know that this sparked the beloved "JDM/USDM Roller Rocker SR20 Information Thread"
Check that thread here: http://sr20forum.com/showthread.php?t=147888
This all surfaced when I was asked a question "What would happen if a highport cam was installed in a RR motor?" From reading I assumed it wasn't possible. well, come to find out that the install unintentionally happened (not telling who) and there is a motor (could be more) that has supposedly been running for over a year like this. I was baffled. and I just don't like not understanding things. So I asked around, I read, I researched. and honestly I hit a wall. I thought I knew about the SR20. well frankly, and you can quote me here, "I don't know anything". I just read things and absorb passed knowledge before me.
Well, I asked around. and got together with James from the forum []98sr20de(t)[] and he helped me come up with a few unanswered questions. We decided to get some true camshaft/valvetrain information from some people that have had experience with the SR20DE from its introduction to its retirement. I emailed/called JWT's Support/Research & Development Team.
Here are the questions that were asked: http://sr20forum.com/showpost.php?p=...&postcount=110
The funny thing is, I went in with only a few questions about a roller rocker and came out with a lot of information that I thought some of you may like to read.
Disclaimer:
Please take the following information lightly and with open hearts and ears. The technical information that is displayed here was recorded from my recollection during a phone conversation with Mr. Clark Steppler (from JWT Support) and I. I take full responsibility for the information displayed here if it is incorrect. Anything I am unsure of has been shown in gray text.
*** Feel free to comment, but if it sparks any sort of break in unification, disrespect toward anyone on the forum and/or JWT, or argument. it will be removed, plain and simple. If there is something you don't agree with here, please take the time to send me a PM and we can discuss it. ***
Conventional SR20 Information and Other things you MAY NOT KNOW!
Rocker Arms
First, to my understanding I always thought that the conventional rocker arms were made of stamped steel... I was told that this is NOT true. They are actually molded powdered metal.
The Conspiracy of the 94 Cam
Originally I had always thought that the only specific grinds for the stock FWD SR20's were.
Stock Spraybar Molded Rocker SR20DE Camshaft Information
Intake: Duration = 248* / Lift = 10.0mm (Highport)
Intake: Duration = 232* / Lift = 8.66mm (Lowport)
Exhaust: Duration = 240* / Lift = 9.2mm
Stock Non Spraybar Roller Rocker SR20DE Camshaft Information
Intake: Duration = 232* / Lift = 10mm
Exhaust: Duration = 240* / Lift = 9.2mm
Well, it appears that I forgot about a certain series in the mix. In the stock 94 Sentra lowport head, housed a 240* duration and 9.2mm lift intake cam... which is essentially a replica of the SR exhaust cam. This was the first and only year they used that cam profile in the Sentra SE-R... but the interesting thing is that they continued to build the Nissan Primera/Infiniti G20 in 95 and 96 with this special 94 intake cam as well. So, according to the cam change in the SR20 Motor (From 240* to 232* in the B14 SE-R), the rev limit went from 7.5 to 7k because of the intake cam, but in the 95/96 g20s the rev limit still remained at 7.5k...
In essence, the reason the rev limit was minimized is because the 232* duration cam doesn't function well at 7.5k. Most know when you switch the 91-93 highport cam in the lowport head there is a gain in power.. but your stability at 7.5k is now attainable as well. Also when you switch the 94 lowport SR20 intake cam, or 94-96 Primera/G20 lowport intake cam into your late lowport engine there will be a gain in power as well. and your 'stability' at 7.5k is then "regained". Even though this 'stability' is attainable, it does not mean it's advisable to rev that high... mainly because the SR20DE stock does not make its best power at this rpm. Remember, just because something is attainable doesn't mean it should be pushed to the limit. constant load at high rpm to redline isn't advisable all the time, unless you like engine wear. Additionally, no matter what camshaft is in your lowport SE-R, your rev limit will obviously be governed by the ECU that you are currently using.
Lowport or Highport Head. Which Flows Better (Stock)?
I never understood why this is such a huge issue around the forums. In all honestly, it doesn't really matter to me. but the internet is a huge ego measuring contest. so here goes. Everyone knows that the later lowport (95-99 SE-R at least in the US) was basically detuned from the demand of emission standards from my favorite agency in the world. As a direct result the cam changes (shown above) were implied. Even though the late lowport SR20 had a lower duration intake cam and a less aggressive lift the HP rating for the motor remained the same at the crank. 140hp from the factory. Now what does that mean? I'll tell you. It means in order to compensate for the less aggressive camshaft (to reduce emissions) something had to be done in order to match the HP ratings of the previous highport SR20 motor. Cue the enter for the Nissan Engineering Team.
The LOWPORT head flows better than the HIGHPORT head STOCK... out of the box... un-ported, untouched, tit for tat, STOCK. If it is modified (i.e. port work) the highport head has a higher potential of better flow. The reason is because there is a bump in roof of the port for the lash adjuster in the head of the lowport. The highport head has more potential for head flow because it necks down to go around the hydraulic lash adjuster... the area in the head on the short intake port is better.
Why are they "Detuning" our Cars? (Very Opinionated)
Well even in the late 90's emissions and other factors like fuel economy came into mind. In 2006 it is evident that the age of import scene lives, but there is something that is generally more important to this nation. Would you like to have a guess at what that is?
Well, the answer to the above question is FUEL ECONOMY aka good ol' mile per gallon. Think of this situation: if you are a car manufacturer and your only two options were deciding between designing an engine for power and performance, or designing it for fuel economy, which would you choose? Now take into account that the majority of people that represent the car buying force don't give a flying focus svt about air/fuel ratio, wideband, variable timing, whp, or anything else performance related. Car manufacturers provide for what the public wants, and the demand for a performance vehicle is below the demand for a fuel efficient econo-box at the moment. So what is Nissan (or any other car company/manufacturer) do in this case? You got it. they give in to the hype. It's either that or potentially lose revenue. Why else do you think that MPG rating is shown in every single car commercial you see anymore?
Well that is what I think. Now on to the Roller Rocker.
More Roller Rocker Differences from Conventional SR20DE (Stuff not in RR Info Thread):
The Head, Valve-Train, Spring Rates, and What's good about the RR SR20DE.
The Roller Rocker cylinder head is not different from the normal SR20... There are different code numbers but the head is essentially the same. The conventional head and roller head is essentially the same, aside from the fact that the Roller Rocker Motor has longer cam cap bolts...
The spring rates between the conventional SR20 and the Roller Rocker valve springs are different because of the difference in weight distribution and moment of inertia of the roller rocker arm. The pressure needed to compress the spring is very close.
The RR Motor has lighter pistons than the conventional SR20. Some versions used lightweight pistons because they have a smaller bore and 4CW crank. Keep in mind that the RR motor has been used in other countries before 2000 in Japan, UK, etc. (Almera, Primera, et cetera.)
As some of you know, the Roller Rocker motor and the SR20VE share the similar type Valve Cover. For this design the black oil separator (or sometimes referred to as the OEM "catch" can on the forums) was removed. A baffle was incorporated into the cover and the top was raised to compensate. A tube for Crankcase Ventilation was inserted at the lower right and the PCV Valve was moved from the left upper side to the upper right side of the valve cover. Through past experience in development the dumping of crankcase ventilation was determined to be better for turbo installation on the RR/VE valve cover... The RR cover has a better design hands down, and has more function.
The B15 & G20. Hmmm Compression Differences
Well in 2000 the Sentra was still selling in the US, but the B15 was Born, w/ a Roller Motor. In addition the G20 was still selling and housed a Roller Rocker motor as well. The b15 Roller Rocker Motor had a 2cc smaller combustion chamber, which is evident through its slightly higher compression than conventional (Discussed a bit in the RR Info Thread). The b15 uses the same type concave dishes on its pistons as previous rocker so nothing was roller specific. The g20 in 2000 variation has a 2cc smaller head, but has a bigger dish so that is why the compression is the same as the normal roller rocker.
For the Roller Rocker SR20DE, the camshaft profiles aren't all the same stock around the world. At this point the US has only had one set for intake and exhaust camshafts... but in Japan, Europe, etc, there are a few lists of durations/lifts. Some engines used different variants for valve springs as well... This explains why there are different rev specs for Roller Rocker motors overseas (i.e. 7.1k for some opposed to 6.8k or lower for USDM RR Motors.)
One interesting fact is that before the B15 ever sold in the US, JWT was already considering developing a cam using the roller rocker arms. This would have involved using the roller rocker arms and putting them in the conventional SR20... but the conversion would entail changing the valve train around. (changing valves, cams, springs, etc.) not promising. At this point in time I believe it was referred to as the "small base radius" cam.
Why are the Cams different in a Roller SR20. Why Can't I just throw Non Roller Cams in there?
You can throw a monkey in a gorilla suit in the Congo and he will live, but it doesn't mean he will function correctly. In other words, yes, now I understand that it has been done, a non roller camshaft has been installed in a roller rocker head. but it doesn't mean it is advisable. I have no clue what power it may or may not yield... but from a long discussion and a little thinking I know now that each cam (roller & non roller) has applications for each valve train's attributes. Let me explain what I found out from JWT:
The intake & exhaust valves are 3mm shorter in a roller rocker engine... then non roller SR20DE has a 40mm install height and different valve springs then roller. The RR has a 37mm install height. The center of bearings of the RR camshafts are all the same diameter as the conventional SR20, but lobes are very, very, very different. The rocker arms are different; the radius of contact is different, the distance from pivot point, the moment of inertia, the mass of the rocker, etc.
The initial point on which cam contacts the roller is different... by implementing a different cam into the wrong valve train one can incoherently advance or retard the cam motion... The phasing of it where it first touches the rocker arm is different. The Radius of curvature can make a great deal in the difference in contact stresses as well. It can produce a valve motion that it wasn't design for. In theory it can mess up harmonics of the valve train and at a certain rpm it may excite them...
The Roller Rocker arm has a different moment of inertia; the valve spring has to overcome the open and close motion of this arm at different RPM speeds... What controls this motion??? The valve spring controls this motion, and inherently controls stability of the valve train...
Obviously we know now that it is not impossible to run the non roller cam in a roller engine; I now know it has been done. The engine may run, but it may not run efficiently or the way it was designed (i.e. valve float).
When Designing the S3R (and other SR20 Camshafts & Valve Springs):
Brief General Knowledge on Camshaft Design
There is a lot of information that goes undermined when the research and development of a camshaft is discussed. A lot of the information that was discussed about design brought me back to my first years of engineering because we were talking about mass flow data, spring rate, inertia, kinematics, etc. Some of the stuff went over my head. and I was so intrigued and flattered during the conversation that some of the stuff I didn't write down because I was so into it. But in a nutshell I will just say that there are a lot of factors investigated, and there is a lot of math used. So I will keep it pretty general.
When designing camshafts for the SR20 the two first things to do are to attain a model head, and attain measurements to make a blueprint. This is a very difficult task as many things need to be taken into account. For example:
1) Cylinder Head - take cylinder head off and take measurements of it
2) Rocker Arm - out and take measurements to make a blueprint.
3) Where is the pivot ball at??
4) Spring Retainer Height??
5) Rocker Arm Height & Weight??
6) Etc.
The idea here is to make a model that is basically an exact replica of the motor that the camshaft(s) are being designed for. It is very important to create a precise model so that the flow data recorded will be similar and the cam will be functional. These representative models are built and tests (kinematics models) are run to acquire more information during the research and development stage. the more area under the lift curve
Different combinations of duration and lift are applied to the model. The tests data from the head/cylinder flow analysis is represented by graphs. This data is used to iterate and find power in one degree increments to find optimum performance for the applicable cam. The area under the lift curve generated is found using integration (remember calculus/physics/hydraulics much???). The more area under this curve the more flow/power. With the use of these models the optimum percent (%) increase of the number for mass flow data is recorded. This has to be very close to natural engine performance... so there is a lot of time and emphasis put in at this stage.
Specific Info for the S3R Camshaft
Well, if you didn't get the idea from the rest of this multiple prolonged paragraphs in this novel. the S3R and S3 cam grinds are different for a reason. the radius of curvature is different in each stock cam, which entails a whole different design for JWT. So vitally it's not just, and I quote, "cut and paste"... Because of difference in length of the valve heights, the orientation of the rocker arm, and the radius contact ratio of the stock roller rocker, the base circles of the stock cam lobes are a different diameter... For the S3R Roller Cams, the base radius on the cam lobe is smaller than on the S3... the lift is a little higher on the RR, but more duration had to be introduced. Again, the roller rocker arm is heavier, so its moment of inertia is different so therefore has to be modeled. The number of coils in the valve spring is different, as well as the spring coil diameter... although main pressure for each spring is similar, and the spring curves aren't that different, the spring rates are.
When designing the S3R, JWT originally came up short on flow so they increased the lift to get about the same performance of s3 cam on conventional engine. (just a bit lower).
Non Specific Information on the SR20 Valve Train (Engineering)!
Ideally, the higher the natural frequency of a valve spring, the more harmonics that can introduced. The more harmonics, the higher the engine speed, the more potential power. (I said ideally!!!)
In theory and you can push on the spring and it doesn't matter how much pressure is pushing back, the important thing is that valve spring has to be able to push the mass (in each case; the rocker arm) back to keep in contact with the cam lobe. If it doesn't then valve float can be introduced. Because the rocker arm is so heavy, to go higher rpm, a bigger spring must be introduced... There is a 50% weight difference for each rocker arm... so the moment of inertia is almost double.
When designing a spring, it is to my understanding that engineers may ask questions like.
1) How fast are we accelerating here?
2) Do we have enough spring force to control the mass?
3) Should I go to Wendy's??? I'm really hungry.
4) At what RPM will this spring hit resonance?
If you need a good definition of resonance, please take a look here, it mainly discusses sound waves, and wave amplitude, but the same information applies:
But, when an engine reaches a certain level of RPM, the valve spring can reach resonance where serious vibration takes place. At this point it can surge, spring can lose its function and wear, and damage can occur. So, in conclusion. Engineers design valve springs and the valve train together for a reason. further explaining the importance of matching camshafts to its applicable valve train.
Here is a quick link of some stuff about spring resonance: (It's a new subject to me; I don't know much)
Future Applications from JWT?!?!?!
Well, in talking with from JWT I had the opportunity to hear a few prospective designs currently in the air. So lets get to the good stuff.
Will there be any more Roller Rocker cams in the Making?
There is a possibility to run a more aggressive cam and valve spring combination that the S3R for the roller rocker motor. So yes, the possibility is there, but it really depends on how good the market is for them. There needs to be a show in potential buyers. Simple economics. if there is no demand and supply is high, they will lose money. If you have serious interest I can tally this somewhere with full names and info and forward to JWT. The chances of finding enough serious people will be tough, but the possibility is there.
Special Roller Camshafts. with the Conventional SR20 Valves/Springs?
There is a possibility of doing a special camshaft profile where you can use the roller rocker arms and roller cams but with the conventional longer valve (40mm) and spring, but in this case there would be a need for a dual valve spring... This is if you SR20 people were interested, so it would depend on how many products they could sell to our community. The gains are having a very efficient valve train (less friction) and being able to utilize power by raising the potential rev limit.
I'm sure the development of this application will only further itself if there is a demand for it as well.
VVL Camshafts. Yes, VE Aftermarket Cams from JWT.
Some of you may already know this, and I may be relaying old information to you, but:
The VVL camshaft is currently in design at JWT. I was told that it will be coming within a few months... I don't know any numbers nor do I know any more information than that. I was just told that I could share it with you!
Reference Section:
Clark Stepplar - JWT Support, Research & Development
Thanks Again...
Ameen B
Here is a copy of some of the emails that were sent out for reference... They are pretty old though
Hello Clark,
I've taken the time to write about the stuff that we discussed about on the phone last week. This is the stuff below if you would like to proof read it. I tried to highlight the things that I was unsure about... it is quite extensive, but I wanted to send it to you first before I showed anyone as I don't want to reference you without your knowledge. If you would like anything taken out, or something doesn't sound right, please let me know. I took a lot from our conversation and I appreciate it very much.
Here it is...
-----Original Message-----
From: Clark S.
To: xxtokesxx
Sent: Tue, 27 Jun 2006 14:37:26 -0700
Subject: Re: contact list dist.:S3RvsS3
Ameen,
Is this your work number? What time zone are you in?
Clark
----- Original Message -----
From: xxtokesxx
To: Support1
Sent: Tuesday, June 27, 2006 1:24 PM
Subject: Re: contact list dist.:S3RvsS3
Yes my number is 513-xxx-xxxx
I usually work from 9-5 or 6:00pm but I'm pretty good about calling people back promptly.
Thanks for the fast return...
Ameen A. Bakare
-----Original Message-----
From: Clark S
To: xxtokesxx
Sent: Tue, 27 Jun 2006 09:21:43 -0700
Subject: Re: contact list dist.:S3RvsS3
Ameen,
I looked at your thread, seems like a lot of misinformation is going around. I'll try to answer your questions, but the phone would be better for me. Can you send your phone number?.... I will try to find time to call.
Thanks, Clark
----- Original Message -----
From: xxtokesxx
To: Multiple recipients of list contactlist
Sent: Sunday, June 25, 2006 7:10 PM
Subject: contact list dist.:
To JWT Research & Development, To Whom it may concern:
A team of friends from SR20forum.com and I had been doing some work on finding information on the Roller Rocker SR20DE Engine. The main cause was to raise awareness in the differences of the roller engine and the regular highport/lowport spraybar engines, and to clear the misconceptions being thrown around. We have most of the differences nailed aside from the true camshaft/valvetrain information. We had a few questions and we were wondering if the people at JWT could help (considering the experience, knowledge, and development your company has provided with this motor).
Here is the information that we have gathered.
-------------------Here are our questions pertaining to the SR20-------------------
1) The main question that we were pondering was - What is the main difference between these stock camshaft profiles besides the duration and lift? Are their differences in the lobe base radius? This is what we know.
Stock Spraybar Stamped Rocker SR20DE Camshaft Information
Intake: Duration = 248* / Lift = 10.0mm (Highport)
Intake: Duration = 232* / Lift = 8.66mm (Lowport)
Exhaust: Duration = 240* / Lift = 9.2mm
Stock Non Spraybar Roller Rocker SR20DE Camshaft Information
Intake: Duration = 232* / Lift = 10mm
Exhaust: Duration = 240* / Lift = 9.2mm
2) We understand that the cams from a spraybar sr20 & a RR SR20 are from a different grind... We were told that this was because the valves for the RR engine were a little bit shorter that the spraybar engine. Do you know the length specs of the different valves?
3) There has been an occurence where a stock spraybar highport intake cam has been afitted into a roller rocker SR20. The car has been driving with no problems for over a year. The engine was pushed hard and driven everyday. Can you provide some feedback on this? Why did this work? Could this yield any damage?
4) Is there a difference in height of the stock stamped rocker arm and the stock roller rocker arm? If so, how does this effect cam design?
5) Was there a difference in the development for the S3 & S3R camshafts? In other words was their testing done on the cams individually, or was the S3R's design the same as the S3 with just the valve heights taken into account?
The following are the specs for the S3 & S3R series cams provided per your website...
Intake/Exhaust S3 cams = .442" lift, 260 degrees duration
Intake/Exhaust S3R cams = .450" lift, 262 degrees duration
This yields a 0.008" lift difference in lift & two degree duration...
6) Lastly we understand that the SR20 motor is no longer in production, but, is there going to be any more research and development for another roller rocker camshaft in the future?
Please let us know if we need to be more elaborate with these questions... Please let us know if you can be of assistance.
Thank you for your time and patience,
Ameen B. (SN: xxtokesxx at sr20forum.com)
James W. (SN: 98sr20de(t) at sr20forum.com)
I've taken the time to write about the stuff that we discussed about on the phone last week. This is the stuff below if you would like to proof read it. I tried to highlight the things that I was unsure about... it is quite extensive, but I wanted to send it to you first before I showed anyone as I don't want to reference you without your knowledge. If you would like anything taken out, or something doesn't sound right, please let me know. I took a lot from our conversation and I appreciate it very much.
Here it is...
-----Original Message-----
From: Clark S.
To: xxtokesxx
Sent: Tue, 27 Jun 2006 14:37:26 -0700
Subject: Re: contact list dist.:S3RvsS3
Ameen,
Is this your work number? What time zone are you in?
Clark
----- Original Message -----
From: xxtokesxx
To: Support1
Sent: Tuesday, June 27, 2006 1:24 PM
Subject: Re: contact list dist.:S3RvsS3
Yes my number is 513-xxx-xxxx
I usually work from 9-5 or 6:00pm but I'm pretty good about calling people back promptly.
Thanks for the fast return...
Ameen A. Bakare
-----Original Message-----
From: Clark S
To: xxtokesxx
Sent: Tue, 27 Jun 2006 09:21:43 -0700
Subject: Re: contact list dist.:S3RvsS3
Ameen,
I looked at your thread, seems like a lot of misinformation is going around. I'll try to answer your questions, but the phone would be better for me. Can you send your phone number?.... I will try to find time to call.
Thanks, Clark
----- Original Message -----
From: xxtokesxx
To: Multiple recipients of list contactlist
Sent: Sunday, June 25, 2006 7:10 PM
Subject: contact list dist.:
To JWT Research & Development, To Whom it may concern:
A team of friends from SR20forum.com and I had been doing some work on finding information on the Roller Rocker SR20DE Engine. The main cause was to raise awareness in the differences of the roller engine and the regular highport/lowport spraybar engines, and to clear the misconceptions being thrown around. We have most of the differences nailed aside from the true camshaft/valvetrain information. We had a few questions and we were wondering if the people at JWT could help (considering the experience, knowledge, and development your company has provided with this motor).
Here is the information that we have gathered.
-------------------Here are our questions pertaining to the SR20-------------------
1) The main question that we were pondering was - What is the main difference between these stock camshaft profiles besides the duration and lift? Are their differences in the lobe base radius? This is what we know.
Stock Spraybar Stamped Rocker SR20DE Camshaft Information
Intake: Duration = 248* / Lift = 10.0mm (Highport)
Intake: Duration = 232* / Lift = 8.66mm (Lowport)
Exhaust: Duration = 240* / Lift = 9.2mm
Stock Non Spraybar Roller Rocker SR20DE Camshaft Information
Intake: Duration = 232* / Lift = 10mm
Exhaust: Duration = 240* / Lift = 9.2mm
2) We understand that the cams from a spraybar sr20 & a RR SR20 are from a different grind... We were told that this was because the valves for the RR engine were a little bit shorter that the spraybar engine. Do you know the length specs of the different valves?
3) There has been an occurence where a stock spraybar highport intake cam has been afitted into a roller rocker SR20. The car has been driving with no problems for over a year. The engine was pushed hard and driven everyday. Can you provide some feedback on this? Why did this work? Could this yield any damage?
4) Is there a difference in height of the stock stamped rocker arm and the stock roller rocker arm? If so, how does this effect cam design?
5) Was there a difference in the development for the S3 & S3R camshafts? In other words was their testing done on the cams individually, or was the S3R's design the same as the S3 with just the valve heights taken into account?
The following are the specs for the S3 & S3R series cams provided per your website...
Intake/Exhaust S3 cams = .442" lift, 260 degrees duration
Intake/Exhaust S3R cams = .450" lift, 262 degrees duration
This yields a 0.008" lift difference in lift & two degree duration...
6) Lastly we understand that the SR20 motor is no longer in production, but, is there going to be any more research and development for another roller rocker camshaft in the future?
Please let us know if we need to be more elaborate with these questions... Please let us know if you can be of assistance.
Thank you for your time and patience,
Ameen B. (SN: xxtokesxx at sr20forum.com)
James W. (SN: 98sr20de(t) at sr20forum.com)
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