71Y0F: cold engine stalls

[WalknBullzEye]

My car is a Nissan Pulsar N14 GTI with modified highport SR20DE + GT2871R turbo. Because I changed a lot of things and recently bought a HPX N1 MAF, I tried to make a new fresh ECU file. What I did was:

1. Flashed the NIStune board with the newest feature pack: 71Y0F. The ECU partnumber is 71Y05

2. Changed the MAF table to "HPX N1 insert 3" tube"


3. Changed the injector size from stock 259cc to 740cc


With these changes made, I thought I've made a good file to let the engine run at least idle. But it wouldn't run idle at all. It ran like crap and hitting the gas pedal made it even worse. I double checked everything, but my conclusion was I didn't made a mistake.

So I started by changing the total injection multiplier. I found that changing this from 179 to 341, the car runs great. Idle is now stable and hitting gas is also smooth.

What I really want to know is, did I something wrong? Why did I need to change the multiplier from 179 to 341? I doesn't make any sence to me.
The factory injectors are 259cc and I use NISMO 740cc injectors. Also, the NISMO fuel pressure regulator is adjusted at 3.0 bar idle (43.5 psi) with vacuüm hose unplugged.

[Matt]

You will not be using the full capacity of the HPX MAF so you will need to reduce K constant further until your load runs all the way accross the fuel map

Reducing K will also reduce fueling, so increase TIM higher to compensate for this

Once you trace the entire load area of the map you have K in the right place. Once you get cruise mixtures 14.7:1 (without changing fuel map) by adjusting TIM (and near 0% fuel trim adjustment FTLT/FTST) then this will be in the right spot also

[WalknBullzEye]

When cold, the engine stalls and it is hard to let it run idle.
After cranking, it immediately runs. Air fuel ratio goes to 11.0 and after 5 seconds it goes to lean: 15, 16, 17... At that moment, if I don't hit gas, the engine will stall.

What I did with the original feature pack ROM (71Y0F);
- Adjusted MAF to HPX 3"
- Adjusted injector size to Nismo 740cc
- Adjusted K constant to adjust load (K = 31206)
- Adjusted TIM with warm engine, until measured "AFR" = almost same as "fuel map" and also near "short fuel trim 0%" (TIM = 370)

Here I am stuck, because WARM the engine runs fine, but COLD it doesn't and stalls.

I made a log file and also uploaded the ECU file. Hopefully there is someone who can help me to solve this problem. Or at least to give me a hint.
I tried to increase TIM, but it did not help. At the end, I increased TIM from 370 (in little steps) to 500 and I could hear it ran way too rich.

My conclusion: changing TIM won't solve the problem

Logfile: http://s000.tinyupload.com/index.php?fi ... 2390157195
ECU file: http://s000.tinyupload.com/?file_id=000 ... 8626729356

[Matt]

For this initial setup, untick the 'TIM' tickbox when resizing injectors

What will happen is resize to HPX will increase K constant, and then with 'TIM' unticked, the resize to 740CC will reduce K constant

Get the car warm and when around 80+ degC and then once you increase revs see how far TP goes, and adjust K constant to suit.

When adjusting K constant, use TIM to offset changes here

When the car is cold, if the TP is too far out of wack things wont run right and be inconsistent when warm. Once TP/K are in the right place then cold start should work normally

[WalknBullzEye]

Thanks Matt for your reply.

I tried what you said today;

1. Started with original ROM 71Y0F
2. Changed to HPX (this increased K constant from 31206 to 58657)
3. Changed injector size from 259cc to 740cc (this lowered K constant from 58657 to 20529)



*I didn't select "Adjust Load scalers". I tried this, but then TP is way too high, because the settings are lowered in "fuel load scale" table. Even if K constant is lowered to 0, TP is still too high at idle. So I unticked this tickbox (same as image above).

4. Replaced fuel and ingnition tables from last dyno session

After these changes TP was at the right spot at idle. But unfortunately it didn't ran right. After changing K constant from 20529 to 31206, it ran better. Thereby I lowered TIM from 512 to 400 to get keep the engine running at idle.

Now idle is set at 12.0:1 and when I increase revs AFR goes to lean 18.0:1

When I increase TIM, it is almost impossible to prevent it from stalling at idle. The benefit of this is AFR is much better at higher RPM (but still too lean). I also tried a lower TIM setting to increase AFR at idle to 14.7:1. This is almost impossible and causes the engine to stall.

There must be a solution for this problem. Luckily I have a lot of patience. Any thoughts Matt?

For those who want to see the ROM file: http://s000.tinyupload.com/index.php?fi ... 9386623174

[Matt]

I'm not sure why you setting the base tune of the vehicle at idle. Worry about initially getting the engine to run properly on cruise and going on to boost (so make sure wideband around 14.7:1 AFR with 0% trims)

Adjust TIM to get the fueling correct at this stage... so you have good AFRs when the car is on cruise.

With 740CC injectors you will have to flatten the fuel map (to about half the current values) otherwise it will go too rich on boost

Once you have done this, see how far the maptrace cursor goes when you go on boost. If it goes not far enough then increase K, if too far then decrease K

You want K in the perfect spot where your maptrace can access the whole map scaling. Offset any AFR changes with TIM

After this you can focus on idle using Injector latency and TP min tables if too rich/lean at idle

[WalknBullzEye]

It is not possible to drive with the car, because of an expired MOT. That is why I am setting things up at idle. I thought, once idle is steady it must be good also while driving. Then I can drive it to a workshop for MOT. When this is done it is legal to drive at the streets.

What about the load scale box (adjust load scale). Do I need to select this option while rescaling injector size?

What do you mean exaclty with flatten the fuel map?

"With 740CC injectors you will have to flatten the fuel map (to about half the current values) otherwise it will go too rich on boost"

[Matt]

I thought, once idle is steady it must be good also while driving.

Unfortunately not. I've tried this before and then had to readjust everything once the O2 trimming starts happening in cruise. You can only try and adjust the K and TIM to kind of get it running at idle but needs to be drivable to get it spot on

What about the load scale box (adjust load scale). Do I need to select this option while rescaling injector size?

Not needed with feature pack

What do you mean exaclty with flatten the fuel map?

Lower the values in the fuel map. See example image attached. Half the current values when on boost since injector size has doubled from previous