DCX Engineer

Can the A/F ratio problem when using the larger crank pulley be overcome by installing the A'pexi S-AFC Piggy Back Fuel Computer. Benzy230 had one of these on his C230 before he blew it up using the 100hp NOS kit. I don't think this can compensate enough for that large of NOS load by itself, but maybe the boost increase with pulley upgrade. He also needed to dial back the spark timing.

This unit can be purchased for around $300. It modifies the MAF sensor signal to the ECU. It is programmable by RPM.

What do you guys think???

http://www.apexi-usa.com/electronics_safc.asp

Buellwinkle

Sounds good, are you going to try it? I feel that a good chip will not only correct the problem but get you 10-15 extra ponies so it's a good buy and it's been tested (thanks to Mark Cummins with his pulley on the Upsolute chip). The problem with doing what you proposed is that the best you'll do is compensate for fuel but because you may not be able to vary it at different points in the rev range you not only may not gain any HP but you can actually lose it and degrade drivability. Now combine that with the dyno time you'll need to get it close enough it will probably cost you more in the long run to do all the testing and it's mostly trial and error. Ideally if you can pull the gas tank off and get to the fuel pump you may be able to recalibrate the regulator in it for higher pressure like they do on the older SLK230s and C230K sedans. On those cars it's easier because the fuel regulator is seperate and by the fuel rail so easy to get to and it's a cheap fix. I think Upsolute only charges $400 for their chip around here in So Cal.

Still not a bad deal, $350 + $400 for 40+ RWHP.

DCX Engineer

The S-AFC settings can be varied at 500 RPM increments.

I was thinking of using an ODBII data logger to monitor the fuel injectors, MAF signal and O2 Sensor voltages to setup the S-AFC. I have a friend who is upgrading a Stealth Twin Turbo and he suggested this over an ECU upgrade. He likes to tinker with it himself and hates ECU upgrades. He has installed two larger turbos and a boost controller.

Thanks for the input. I look forward to hearing your results once you get Absoluted!

BTW - I didn't know the fuel pressure regulator was located in the fuel tank.

linh

S-AFC will work fine too but it require fine-tune on the dyno after installation.

The post 2000 model fuel pressure regulator are built into the fuel pump. The pre-2000 model fuel pressure regulator are mounted on the fuel rail. Mr. Vaeth are selling this 3.8 bar FPR for only $100. I don't think that there's a need to upgrade the ECU if you install the 3.8 bar FPR. The bad new is that, is only for the pre-2000 model.

Buellwinkle

No, I'm waiting to get GIACed. Mark Cummins got Upsoluted with his Kleemann ring and he's happy with it on his wife's coupe and I hear his A/F ratio is back to normal.

Buellwinkle

Here's the graph of the air fuel ratio where red is with the airfilter and blue is without.