Running a standard Ecu and safc with big turbo on r33 skyline gtst?

[royal]

Just wanted to ask as I was chatting with one of the guys about this earlier.

Are there any drawbacks or trip ups running a stock ECU with 1bar boost (big turbo on just waste gate pressure) so long as you run a fuel computer such as an Safc or similar to sort out the fueling ? I'm worried the stock computer ignition tables wouldn't be up to it at higher boost but not sure if this would only be an issue at much higher boost?

What airflow does the stock R33 gtst MAF measure to? If the stock MAF was maxed out and you replaced the sensor with something that can flow the larger amount of air such as a 300zx one, and then used a Fuel computer to add how ever much extra fuel was needed across the board to keep the A/F ratio correct, I'd have thought all would be dandy?

Would the stock ignition tables be sufficient at higher boost? The way I see it the ECU would be fueling for say 0.8 bar but in reality it was 1 bar with the SAFC adding the extra fuel. But the ECU would adjust the ignition timing as if it was 0.8 bar. Is there a boost point where the stock map timing is dangerous, as well as not getting optimum power?

[gunni]

In any way or form if you can control fuel then your fine. no matter if it´s your grandma pouring it down a funnel in front of the turbo or whatever. If the control is good then your fine.

If you replace the MAF the ECU will actually be assuming less MASS of air then is actually being reported,
This will cause incorrect fuelling at all loads and rpms.
3volts will not only be 0.2kg/s instead of the assumed 0.27kg/s as an example,
The MAF scalar will have to be adjusted inside the ECU for this to work.

The ignition map would now produce higher advance as the ecu is thinking that there is less load going on.
Again the MAF scalar would need to be re tuned for the replaced MAF.

The mods you are thinking about will require that the ECU is tought how to read the bigger MAF. This can be simple if you can replace the MAF scalar and adjust the load column in the ECU to show higher load values.

If you must run a piggyback be sure to run something that can adjust timing as well. A fuel only piggyback is just a bag of crap.
A standalone is thousand times nicer to tune.

[royal]

Thanks gunni, thanks great. Have I got things mixed up then with the MAF signal if teh scaler wasn't changed at the ECU? If you put a MAF from a bigger car on there could you not just scale the fuel with the SAFC to compensate?

Ahh just reread the bit about the ignition, so am I along the right lines thinking you could scale the fuel with the SAFC but you'd have too much advance on the timing?

My mate can't afford to buy anything else at the moment so its either run the car like this or not at all, so he wants to know how risky it is. Plus its learning for me

[gunni]

You can´t replace the MAF with another one and then retune the fuel,. it´s going to get you nowhere.
The scalar in the ecu chip will need to be changed to work with another MAF.

The advance will be more as the ecu thinks there is less load, less load means more advance, more advance means more danger.

You could install bigger injectors to compensate for the smaller PW for the same given airflow. But this will always lead your to over advanced timing. If your piggyback can´t do timing then you might want to consider other piggybacks.

[rob@vems.co.uk]

There are some built-in MAF configurations in the SAFC.  I was under the impression that the SAFC actually controls fuel by re-interpreting the MAF voltage.

Personally if I was going this direction I'd look at NIStune, I've been in email conversation with the makers of Nistune as they wanted to have a VEMS wideband gauge input.

[royal]

 Can you explain the MAF bit to me a bit more? I'm inexperienced so speculating a lot. I thought that if you changed the MAF to a bigger 300zxTT one for example you'd still get a voltage from 0 - 5V (or whatever it is) so the ecu would interpret it as say 75% of the actual air flow. Then you could use the SAFC to scale the amount of fuel delivered at that point by 133% to make it up to the required amount?  The timing bit makes sense to me but not sure what I've missed on the MAF stuff.

Rob: I havn't looked at Nistune, I'll do some reading. In this guys case I think when he's got money he'll get a decent ECU but is trying to run the car as it is if its safe to do so.