MS1: 400kPa MAP and VE/Spark table scaling

[atledreier]

Hey!

Got the PNP kit from Lex for my 323 GTR. Works fine and all that, I need to get it mapped properly, hopefully next week.

The thing that has me a bit uncertain is the 400kPa MAP sensor scaling. The manuakl says to just scale the table's vertical axis to match your MAP sensor. But I just can't see how that can work. Then the existing map will be stretched, and the vacuum/boost transition for fuel and spark is no longer at 100kPa, since the data in the table is untouched. Or am I misunderstanding something here?

[therieldeal]

you need to compress the map, figure out where you can take out a line here and there so you can add empty lines to the top. tiny example:

5 5 5 5 5
4 4 4 4 4
3 3 3 3 3
2 2 2 2 2
1 1 1 1 1

if you want to be able to go up to 7, do something like this

7 7 7 7 7
6 6 6 6 6
5 5 5 5 5
3 3 3 3 3
1 1 1 1 1

btw you certainly dont have to have bins all the way up to 400kpa unless you are actually boosting that high. if you are boosting like 30 psi you could set your top bin to 300kpa and be just fine.

[Lex]

I think Jon has explained it quite well. Whatever the row for 250Kpa is now, should remain the same for 250kPa.

In other words, as you compress the map, you lose tuning resolution so don't compress the map up to 4bar unless you really need it.

Because the MAP sensor is not saturated at 250Kpa, if you run slightly above that pressure, fuel will still be added based on the increase in Kpa sensed by the 4 bar sensor, so you may be fine ... depending on how much more boost you are running. Fueling equation is this:

PW = REQ_FUEL * VE * MAP * E + accel + Injector_open_time

So with a 250Kpa sensor, MAP no longer increases above that pressure but with a 4bar sensor it does.

[atledreier]

Thanks, guys! That makes sense. I'm not plannning on going very much above 250kPa, maybe around 270-280.

Another thing;
In the fuel table there are % over 100. Hvat is the actual value you are entering in the fuel map? If it's injector duty cycle, how can you go above 100, or even go above 80-ish?

[Lex]

It is volumetric efficiency. The VE table estimates the volumetric efficiency of the motor at different pressure and RPM points. The PW (pulsewidth) in milliseconds is then calculated through the equation: PW = REQ_FUEL * VE * MAP * E + accel + Injector_open_time

Duty cycle you can see in your logs and it depends on PW and RPM.

[atledreier]

Awesome, thanks!

And ANOTHER thing, when I have you here....

Spark timing; The manual says to adjust it to 10 degrees and do the rest by mapping. I assume then, that the supplied map is with a base timing of 10 degrees.
The manual for the GTR states that the base timing should be set to 12 degrees, and that's where mine is. Can I just subtract 2 degrees in the static trim and it's fine, or do I need to set the distributor to 10 degrees and the trim to 0? Seems to be exactly the same to me.

Come to think of it... The spark timing readout would be 2 degrees off then, and the logs too, right?

[therieldeal]

all you need to do for spark timing is this:

get the engine idling, look at the MS readout to see how much timing MS thinks it is running at idle (doesnt really matter what the number is, just note it). personally i run 14* of advance at idle.

hook up your timing light and either turn the distributor until it matches the readout in MS, or adjust the trigger offset in MS. either one will have the same effect... you just need the actual measured timing to match what MS is showing.

once youve done this any change to the timing map will also match what you see on your timing light. i check it periodically, as a degree or two can make all the difference at 20+ psi.

[atledreier]

Thanks alot, I'll get it done.