Fuel cut problems @ 6000rpm R34 GTT RB3025

[Matt]

Second problem is that I must unhook the MAP sensor to make the car run smooth when pushing the throttle. If i let it hooked, when I push the throttle, the car goes lean (20 AFR) and engine falls and I need to push harder to make it go strongly in the RPMs. quite undrivable.

I've got a similar problem on my R34. It was fine after the injector upgrade. However somewhere after the turbo, cams and MAF I get a hesitation taking off also and more prominent during hot weather. Something to do with the MAP sensor, because when disconnect the engine runs fine.

So far I've reverted back to factory MAF, using stock maps (apart from 370CC > 480CC adjustment to K) but still the same issue. I'm thinking the cams have affected operation of the MAP sensor on this vehicle. Anyway taken some logs last weekend and will look at it so see what can be done. May need to dig into MAP operations further since incorrect placement can cause massive throttle opening/acceleration issues

I'm going to add an additional injection adjustment to this ECU so I am not modifying K constant (similar to the S13-S15 SR20s I've done over the last few weeks) and test that

[lolo37]

Thanks for your post MAtt.

I have now aftermarket cams (tomei 256 / 8.5m) and also my Mustang MAF and my 800cc injectors and no problems of eratic functionning on mine with the map correctly connected... So I find it weird you experience problems with the map as I don't.

About my engine that stalls after have push the throttle to 4000+rpm, I had a look with another French Nistune Specialist and (like I did) he couldn't find any REFUELING MAP DECELERATION.
My engine doesn't give a bit of fuel @ 1500rpm to slower the rev falling.

Do you have an idea for that Matt?

I had the second round of the French Drift Championship this week end and it is not possible to continue to make the engine restart with inertia after each handbrake ! ^^

[Matt]

Okay I have looked into that further. The TP min and TP max tables are important here!

During the injector resize, the TP min tables are lowered too far for these engines... I've put the TP min values back to factory

132 132 132 132 132 132 132 132 132 132 132 150 162 170 176 200

The number are a lot higher than other cars, because I think there is a +128 offset in these ECUs (eg would normally be 4,4,4 etc)

TP Max is used to limit the maximum injection. If you get any MAF spiking and TP max is too high then it will overfuel. Drop the values of the TP Max table lower. Refer to factory at the bottom end (32 + 128 offset for 3/4 of the table)

Factory
164 164 164 164 164 164 164 164 164 164 164 182 194 202 208 232

[lolo37]

I have no overfueling and I must say that i've nearly maxed the TP so I prefer to let 255 from 4800rpm for TPmax
Apart from that, I've put all these number you said and i'll try tomorow.
TPMAX 164 164 164 164 164 164 164 164 175 200 230 245 255 255 255 255
TPMIN 132 132 132 132 132 132 132 132 132 132 132 150 162 170 176 200

If it is not that, maybe I should try to clean the AAC valve but how could I know before it is worth it? (my AAC valve will be a pain in the arse to get out...)

[lolo37]

http://m.youtube.com/results?q=stalling ... rrect&sm=3

Hi !

As tp limit didnt solved the problem,
i decided to show you what is going on with another video (link on top)

if you need any other info in nistune or in the engine, just ask !

Thanks in advance for your help

[Matt]

Just watching the video. Some things looking over your AA502_V2.0 tune file and video

1. Ignition and fuel scaling is too high. You have it going upto 255. What is the maximum TP that you reach on boost? What your maximum TP value is should be what you scale upto (refer to tuning guide on our website)

2. I would suggest leaving Alpha/N as the factory values

3. Idle/decel timing = 15 deg BDTC but your consult timing 25 deg BDTC. It may be adding another 10 degrees BDTC because < 85 degC but I cannot see why (would need to look into that further). Usually the 'after start' timing tables are multiplied together and added to the idle/decel timing

4. Can you post another log in stream mode with the TTPmin set to the factory values of the decel issue this time? What your main problem is probably going to be is a common problem with AFMs... reversion. On deceleration if there is a spike in AFM voltage due to reverse airflow (or lack of plumbed back BOV) then the mismeasurement of airflow will cause over injection and then under injection (rich then lean)

Are you using the factory BOV still? Where is it venting to? Is there any possibility of venting into the MAF or reversion into the MAF. You will see this in your logging with spikes in the AFM voltage

Please use the latest test version so you can log TP also (which will be BFuel schedule parameter)