Advancing Camshaft

[wittsend]

I'm in the process of repairing damage done by a loose crank pulley on my 2000, 1.6, 5 speed Protege. The end result is similar to the Miata short snout crank problem. However, in this case the fault is mine (not the design) as I didn't get the crank bolt tight enough.

Since I'm already "in there" for the fix I won't be wasting my time advancing the cam as I need to replace the crank key anyway. I realize with a DOHC engine the cams are often adjusted independently. And I realize there are adjustable cam sprockets and performance cams etc. but I'm not looking to go that route.

In my case I'm just looking to move the existing torque curve a bit lower in the RPM range. This is no race car, I'm only looking for better response at lower RPMs as I drive in a somewhat hilly area. I have a machinist son who can cut me an offset crank key to advance the timing.

So, Yes, I understand that changing the timing on a stock cam usually doesn't show much change. And, Yes, I understand the best results are found by changing the timing independently on each cam (at a cost).

I'm not here to argue those points. The bottom line is my son can cut the offset crank key in short order (we have already done the math). And, I need to replace the key anyway. So, there is virtually nothing invested. I'm not looking for a horsepower gain I know isn't there. I'm only looking to find a bit more torque in the idle to 3,000 RPM range the car spends 99% of its time in.

That all said with a stock cam can anyone make a recommendation regarding the amount of cam advance I should limit to? I've often heard 4 degrees is about the limit - in general. Thank you for your time.

[FE3-323]

I highly discourage anyone from using an offset woodruff key. they shear far too easily & usually create immense extra headaches when that does happen.

Now if you are talking about the camshaft itself & removing it to "Re-Key" its position. then that yes i would say go ahead. its been done before on the BP engines by many miata folks. either by modifying the cam gear. or the cam itself.

all that aside have you played around with ignition timing any?

[wittsend]

Thank you. While I understand your concern regarding key shearing the crank bolt on my car was loose for at least 6,000 miles. I would hear a slight ticking sound at idle that would disappeared with a slight throttle application. The bolt never felt loose or looked backed out and there was no visible pulley wobble. So, it was hard to detect. Regardless the crank/key/pulley were constantly getting whacked back and forth without the key shearing. I see this as assurance the key is more than sufficient.

The factory key slot is 5mm (roughly .200). My intentions are to take .050 off each opposing ends of a 1/4" (.250) key. This equates to slightly over 5 degrees advance. This still leaves 75% (.150) of the metal at the likely shear point. And, as I mentioned earlier I have crank damage like the Miata short snout encounters. So, I will be using the Loctite 660 repair. This will take up any key slop and act as a secondary bonding means to prevent the pulley from rotating on the crankshaft. This is just my mild mannered daily driver that barely gets to 3,000 RPM. For fun I have my 2.3 Turbo Pinto. And, with a non-interference engine there is little to worry about valves and piston should a key shear.

However, as a back up consideration I'm also debating opening the lower timing belt pulley .050 on the side that would create the advance. I'll just cut the .250 key down to .200 at the front to keep the timing at factory for the portion that indexes the front pulley. And I'll keep the extra .050 on the rear, upper half to fill in for the extra .050 I cut into the lower timing belt pulley creating the advance. This way I lose nothing strength wise (probably gain a little at the timing belt pulley) and get my cam advance.

Regarding your recommendation for ignition timing advance, is there an article or recommendation? I assume the method would be to reposition the crank sensor? I'm very much a fabricator/modifyer than I am a purchaser. A 57 year old, retired early, old fart who likes to tinker. BTW, since I only drive 3,000-4,000 miles a year buying upgrade gas is not really an issue for me.

[jay]

5 degrees is more than you wanna do... if it was at the cam. At the crank, I wonder if 5 degrees js gonna be notuced. That said I wouldn't dare go pastt that, as advancing the camshaft timing is really only advantageous on the intake side. Advancing at the crank of course advances everything.. I kinda think you might be better off leaving the crank timing alone and buy one adjustabke cam pulley. They don't cost that much and you can play just with intake timing and, big big bonus, you can change it back if you don't like the results....not an option, if relocating the crank timing.

[goldstar]

There is really very little that can be done to increase the performance of a stock ZM-DE 1.6 L engine. Advancing the intake cam timing generally results in a loss of low speed torque - just the opposite of your intention. To increase torque requires an increase in BMEP (brake mean effective pressure), which requires either an increase in the CR or some form of forced induction (turbocharging).

FYI, here are the stock cam specs for your engine:
Intake cam opens: 1* BTDC
Intake cam closes: 45* ABDC
Intake cam duration: 226*

Exhaust cam opens: 52* BBDC
Exhaust cam closes: 1* ATDC
Exhaust cam duration: 233*

Valve overlap: 2*

As you can see, the stock cams have very mild specs and have been engineered to provide the best possible torque curve, in the interest of best possible drivability, for this particular engine. Note, for example, that any change in the valve timing that would increase valve overlap, as would happen if you advanced the intake cam timing, would result in a loss of low speed torque without a commensurate increase in BMEP.

Happy Motoring!

[wittsend]

Thank you everyone for your input. As I eluded in the posts above I was simple looking for "any little bit that might help." My previous car was a 1991, Mazda 323 with the 8 valve, 1.6 engine. Even at 180,000+ miles that car had more torque in the "driving range" (idle to 3,000 RPM) than my 2000 Protege, 1.6 (both 5 speed manual). I even took the '91 323 from 175-70-13" tires to 185-60-15" (a 10% increase) and never noticed the change. So, for the everyday "daily driver" aspect of the 2000 Protege it has been disappointing and frankly frustrating.

I'm a bit confused? At the Comp Cams site they have a list of what the effect is for advancing and retarding cam timing events. In the proposed case here the intake is being advanced AND this is tightening the LSA. Comp Cams states this will both increase maximum torque and move it to a lower RPM. Also, if the overlap on the stock cam(s) is 2 degrees it seems adding a few degrees will occur with minimal piston travel (near TDC) to have any significant effect on compression. Here is the link: http://www.compcams.com/Pages/413/ca...ion-angle.aspx

I realize every engine is different, but I have a Mopar small block with a mild performance cam. The overlap is 58 degrees. There was a very subtle (almost unnoticeable) decrease in idle to 1,500 RPM and a significant increase in mid-range power.

[wittsend]

OK, I'll close this out by saying the damaged keyway repair was a success (and I didn't use that ridiculous Loctite 660 either). 660 is titled a "metal filler" with a .020 limit and only cures in the absence of air (oxygen). Why people use it on Miata cranks with significantly greater damage is a mystery. Secondly the product is intended to assemble all at once. WHAT? So, you have a sloppy keyway and your torquing the parts together where they can slip out of alignment??? Wouldn't it make far more sense to repair the keyway - THEN bolt everything together. Hey if others have had success, great, but logically it seems ridiculous.

In the end I elected to advanced the intake cam 3 degrees. I based that on Miata dyno information (2-3 degree advance) with similar stock cam engine specs. I'd also note that I looked at other Mazda engines similar to the ZM-DE and saw that they had far more overlap (granted some engines variable). To that end the factory sprockets had 1 degree play each. Thus it is possible to have 2 additional degrees of overlap unintentionally. So, I don't see my 3 degrees advance (5 degrees total overlap) where piston travel is minimal as any great detriment. Lastly I advanced the ignition timing 4 degrees by slotting the reluctor wheel bolt holes and pin. Again I based this on similar Miata information. It was a warn, dry air day (So. Cal. in January) and accelerating on hills produced no discernible pinging. In the end I had down time waiting for parts and didn't mind the tinkering. I can't say any of this added anything, but I will say there is no perceivable indication it took anything away either. But, given the theory is the modifications enhance low end torque I'll rest with the fact that no matter how minimal it probably did. Over and done.

[FE3-323]

main point is its back up & going again after all said is done

[wittsend]

I just thought I'd report back an update on my cam/ignition advance results now that 6 months have passed. The alteration was 3 degree intake cam advance and 4 degrees ignition advance on an otherwise stock 1.6 Protege, 5 speed. While I came from a damaged crank key that was robbing power I still feel that the car accelerates better than before the problem occurred. It is nothing earthshaking, just a subtle but noticeable difference that makes me glad I performed the changes. The change values were taken from reading a lot of posts and finding information that 3 degrees intake advance and 4 degrees ignition advance had show in testing (assumed dyno) to be subtly effective on the 1.6 motor.

In my preparation I notice that the "play" in the (stock) cam sprocket slots/pins can account for 2 degrees by themselves (1 degree each way). So, where as I deliberately created 3 degrees intake cam advance (and thus 3degrees of overlap) it is possible that loosening the bolts and tightening the pulleys towards each other can bring 2 degrees overlap. I mention this mostly because some had advised against any overlap, but in fact it can haphazardly happen without even trying.

In doing the crank key repair I opted to change out the leaking cam seals too. Therefore, in my case everything in the crank/cam drive system was apart anyway. One would have to determine for themselves if they feel this is worth their effort for no other reason. AND..., whatever you do, you do at your own risk/responsibility.

The ignition advance is very simple I just elongated the bolt holes on the reluctor wheel with a round file. I just used a paper printout of a timing wheel, an indicator and filed the four slots until I could get 4 degrees advance. Do insure that you hold the reluctor wheel in the advanced position while tightening the bolts.

For the cam advance I'm too low budget to purchase an adjustable sprocket. I just used a round file on the outer end of the sprocket slot (note I got a spare sprocket to do this at Pick A Part). I taped a portion of the printed out timing wheel to the head, centered on the cam, tightly wrapped a wire/pointer around the sprocket and between filing and rocking the sprocket left/right could see when I had 3 degrees advance. This left about a .020-.022 gap between the back edge of the sprocket and the pin. I Dremeled a narrow piece of saw blade that was the correct thickness and ran it down the length of the sprocket slot. I superglued it in place and after tightening the cam I filled the entire slot with silicone as a secondary adhesive/dampener. I feel very confident that the shim is going nowhere.

Thus far I have no CEL's, no pinging on regular gas (I tested down from premium). I truly feel that in the normal driving RPM range (1,500-3,500) there is a "little something" to be gained. And, therefore I am glad I opted to tinker while doing my repair. I saw no change in mileage. I was probably able to just push the safety margin Mazda designed into the engine. I was a bit concern that the cam sensor is on the exhaust cam which didn't get advanced but given it bolts to the cam cover which has a degree of tolerance perhaps it only detects the range of a full tooth skip.

[FE3-323]

well i'll be damned. clever work sir!!