well last week i got to the dyno to tune my car since i upgrade my secondaries to 800cc, well it happens to be that it didn't turn out as i expected, we didn't manage to tune the car properly cause everytime we tune the safc the car didn't want to get rich, last time on the dyno i managed to put 220whp with less modifications and very easy tunning. now i have put other mods, fpr, turbosmart bc, spalm e-fan, 800cc secondarys, koyo rad. last time my safc was running at +22%, now i was at +30% and the car didn't wan to get rich, the afr were crazy, it was to lean, my thought is that im not getting enough fuel pressure, my fpr is an ebay one so maybe that's the problem??? also my walbro 255 fuel pump was like going up and down, up and down, it make a really strange sound. if im correct with the bigger injectors my safc is supposed to run lower than the last time i tuned the car with the stock injectors that it was at +22%. we managed to do 1 pass a little good but the afr was still crappy, at 8 psi i think it made 212whp but when whe try to up the boost it was good bye for the afr. i already bought an aeromotive fpr to see if that's the problem, other than that i don't know what it could be. any help would be apreciate it. car is a 1990 Turbo II

complete mods: RB turbo back, safc, 800cc secondarys, spalm e-fan, koyo rad, turbosmart bc, turbosmart bov,fpr,walbro 255 fp, trying to run 12psi.

 

The S-AFC can only "add" so much fuel because it is limited by the ECU. The ECU will only drive the injectors so hard (I think the stocker will go to only 80% duty cycle, but don't quote me on that). That's why the S-AFC is much better at removing fuel then adding, so the standard practice is to upsize the injectors and then trim fuel with the S-AFC.

Now as for the fuel pump. Your best bet is to connect a fuel pressure gauge and monitor the pressure. If it falls, then you have pump issues.

Also, have you done the fuel pump rewire? The stock wiring is kind of old and it's common for voltage to fall dramatically at the pump (BAD thing!).

 

Like Aaron said, the limitation is the ECU, although not for the reason he suggested. Fuel controllers all work on the same principle of modifying the AFM signal voltage to make the ECU inject more or less fuel. The AFM takes a 5V reference voltage from the ECU and sends back a reduced voltage corresponding to airflow. This voltage signal decreases as airflow increases (~4.0V when it's fully closed and ~0.4V with the flap fully open). By trying to add fuel with the S-AFC you are lowering the signal voltage seen by the ECU. But if the actual signal from the AFM is already close to zero, the S-AFC won't be able to lower it much further before hitting 0V. With your +30% correction, when the actual AFM signal is 2.0V the ECU will see 1.1V, and when the signal is 1.15V the ECU will see 0V. As airflow keeps increasing the ECU keeps seeing the same signal and so will keep adding the same amount of fuel, which now isn't enough.

Doesn't it have a pressure gauge? If it does then you should be able to quickly see any problem. If not how did you set it to the correct pressure?

That myth has been proven wrong. I know Hailers has seen 100%.

This is definitely recommended . The Walbro pumps draw a lot more current than the standard one.

 

well after a log time of seeing my fc on the garage i finally fixed all the problems i have. like aron told me i did the fuel pump rewire and it fixed the problem of the bouncing and im getting consistent fuel pressure without any problems, also did a couple of things while the car was sitting, i did the tid mod, bought the aeromotive fpr and everything is running smoothly. i will be going to the dyno preety soon, i just want to ask, i know i can make 230whp but is there a way i can reach 240whp or maybe a bit more with these mods i have. im trying to make 250whp with my stock turbo before i replace it with the t4 compressor that i have, my brother keeps saying me that if i put racing gas(vp) i will see great results and i believe him. just want to know your thoughts.

thanks

 

Your brother is an idiot.
Stop listening to him.


-Ted

 

93 octane should be good for 12psi with a good tuning. you dont need race gas unless your running big turbo and 18+ psi. (correct me if im wrong)

 

the idiot here is you jackass, be more polite next time. and i do listen to him because hes my tunner and help me out with the mechanic, and correct me if im wrong but even if your running stock turbo or anything the race gas is going to give you best hp, im not saying this because i think so, i have seen it, it's not something im just bragging about. oh an another thing im just planning using the race gas for the dyno only so why not take the shot and see what my engine can really do.

 

No, race gas will not give you the "best horsepower". Race gas only allows you to run higher boost levels and more advanced timing while lessening the chance of detonation. If you just dump it into a stock car, you are going to make a lot less power then you would have running the correct fuel. Also if it's leaded it will destroy the O2 sensor and cats.

Also, take it down a notch. While I agree that Ted's original response could have been a little more civil, that does not give you the right to attack him and call him names. Please reread the rules sticky at the top of this forum.

 

Dumping "race gas" without changing anything else will not make the engine magically make more power.
In fact, it should actually make LESS power, cause it burns slower.

Screw it...the OP is on my ignore list.
Be happy I won't be responding to anymore of your posts.


-Ted

 

race gas has very similar AFR values as pump fuels while burning, putting race fuel in your car will not solve your lean issues and is just a waste of money if you are not running at the track 100% of the time or running it at the drag strip pushing 16+psi of boost.

like everyone said, check your fuel pressure, check for codes, check your AFM connection and make sure your SAFC vehicle settings are correct.

 

"Your brother is an idiot.
Stop listening to him.


-Ted"

lol that's tough love right there.
But the truth.

 

do what makes you happy man, i assure you im not going to be sad if you don't respond to any of my posts that's for sure.

 

i've talked people out of tuning with race gas plenty of times, unless you are running a turbo that can push 30psi or so efficiently there is no gains from it aside from the safety level it provides at higher HP.