Bumped my boost up today...fuel question.

[Hotwheelsjr]

So, I bumped my boost from stock to 9 psi today. I'm running a T67, 50mm WG, 550cc inj, and a Lexus MAF on a stock ECU...and a Walbro 255 and some off brand AFPR. The bottom end was built with forged parts.

At full boost my AFR stuck steady around 10 (measured with a AEM wideband), so I'm getting plenty of fuel. I'm not running any type of piggy back, so my question is, am I safe? With an AFR of 10 - 10.5 at full boost and no pinging, I'm assuming I'm good. I just recently mounted a GM 3 BAR MAP and IAT in prep for a AEM stand alone, but they're not wired up yet and the AEM is still sitting new in the box. Once the AEM is in I plan to have it dyno tuned with 18-20 psi...I'm not going to blow this thing up at 9 psi and no piggy back, am I? I'm kinda new to boost, so please excuse my ignorance.

THANKS!

 

[gsxr141]

i think you might be too rich. there was another thread about this, and from what i understand... too rich is bad.

 

[90mkiiisupra400hp]

IMHO 10 is to low I wouldn't run it like that. I have mine right at 11.5 at full boost, IIRC running it that low and there is a chance of washing the cylinders, someone else may want to chime in on this.

 

[Hotwheelsjr]

Ya -- I figured 10 was pretty rich...I was looking at it as I'd much rather be rich than lean. Until I get AEM EMS into it, I'm without any type of fuel controller. Any way to pull fuel under boost without a piggy back? Pull the vacuum line from my AFPR?

 

[SPOOLINLUST]

IMO I wouldn't pull the vac line because that may lean it out to much, the purpose of that line is to reference the boost and raise the fuel pressure per pound of boost. You may be able to turn the pressure on the FPR down a little or raise the boost a little to get it to around 11 at least.

 

[Turbo Habanero]

Ok so i am in the same boat as you Hotwheels and yes this is to rich.

You run risk of washing the cylinders. You can try lowering your fuel pressure to help lean it out a bit but you really wan this thing closer to 11.5afrs

In between 11 and 11.5 is a safe point.

When i was using a piggy back i aimed for

2500rpm to 4500rpm 11.8-11.9 AFR's and 4500rpm to 6500rpm i aimed for 11.4-11.5 AFR's but i would never risk going any leaner then these numbers.

 

[Hotwheelsjr]

Cool -- thanks all. With plans to drop AEM into it, I am not going to waste my time on a SAFC-II, so I guess I'll try dropping my AFPR some and see what happens...for now.

 

[IndigoMKII]

Be careful with running too rich. What most people mean by saying richer is safer is by like 11 to 11.5, not 10.0 because you risk cylinder wash and ruining your oil. I believe Habanero has gone through cylinder wash before so ask him what gas does to your oil while your engine is still running.

 

[suprarx7nut]

Not sure what would make it run that rich. The stock fuel system should support a good, clean tune well beyond 9psi. I just got an AEM wideband and at ~10 psi it'll go about 11 at WOT. Does it hover around stoich (14.5-14.7) at idle and cruise?

 

[IndigoMKII]

So, I bumped my boost from stock to 9 psi today. I'm running a T67, 50mm WG, 550cc inj, and a Lexus MAF on a stock ECU...and a Walbro 255 and some off brand AFPR. I'm not running any type of piggy back

Not sure what would make it run that rich. The stock fuel system should support a good, clean tune well beyond 9psi. I just got an AEM wideband and at ~10 psi it'll go about 11 at WOT. Does it hover around stoich (14.5-14.7) at idle and cruise?

He has plenty of fuel for what he has, problem is he has no means of telling the ecu he's running too much fuel.

He's running a lex afm with 550's which also makes the car run rich without a means to tune it out.

 

[Hotwheelsjr]

He has plenty of fuel for what he has, problem is he has no means of telling the ecu he's running too much fuel.

He's running a lex afm with 550's which also makes the car run rich without a means to tune it out.

Yep...what he said. At idle I'm at 17.5ish and at cruise it'll run around 16. I was actually running for a while with my boost controller as low as it could go (5-6 psi) and my AFR was around 12 at WOT. Now that I've bumped my boost, I'm seeing sub 11. This just gives me motivation to get my AEM installed and tuned.

 

[SPOOLINLUST]

Careful with the AEM, if you use the start up tune they give you, mine had the FP trigger set at 0 RPM so as soon as the key turned on the pump wood keep running it actually made the motor sound like it was growning! Result was hydro locked motor and washed the cylinders so now it smokes. The method of tuning with your setup IS the boost controller and FP.

 

[Hotwheelsjr]

Thanks much.

 

[SPOOLINLUST]

No prob.