alpinewhite951

I have searched some old threads about rich a/f ratios, but I still have a few questions. I recently installed an AEM wideband an MBC and 38 mm tial. I also have Autothority chips and stock injectors and stock fuel pressure regulator.
I am planning on getting the Vitesse MAF and new injectors this spring but I want to know if my car is safe to drive until I do.
I am showing 10.9 to 11.1 a/f ratio under full throttle. Is that too rich? I know I should idealy be around 12.5. I am running around 15lbs of boost.
If I raise the boost a little would it raise the A/F to a better level. And if it does will my injectors be at too high of a duty cycle.

blown 944

If you are still running the stock turbo you may (probably) not be running 15 psi at redline. Everything I have read and saw in mine. Those chips run pretty rich. You should be able to lean it down a little by turning the fqs to position 2.

I would also look for boost leaks around the ic couplers (underside)

alpinewhite951

The boost drops off a little at the upper end. I have it set so max boost is 15lb. I think around 5500 rpm. It drops to around 13lb near redline. I live in Pa so I have only driven the car 20-30 miles since i have installed the A/F guage due to the weather. My car does not have a heater.

onspeed

Do you have an aftermarket boost gauge? If not, you should definitely get one before driving the car into boost. The stock gauge will not read above like 14.5psi so there's no way to tell if you're running 15psi and not more.

But if you're positive the MBC is set to 15psi, you'll be fine and the car won't blow up because it's a little rich. There's a good number of people using APE chips (myself included) and their cars aren't self destructing or anything. It's tuned rich to compensate for boost spikes.

Rogue_Ant

For the APE chips, they are designed to run that rich in mid-range... This is to help keep the engine from knocking - which it most likely to knock in peak-torque area, the mid-range.

Also, under full boost 12.5 is definitely too lean on pump fuel. A much more appropriate AFR is mid/high 11s.

alpinewhite951

If I were to turn up the boost a little would that help raise the ratio a little

Darwantae951

I'm no expert by any means, but turning up the boost to "help" AFRs doesn't seem like the most appropriate solution to your problem.

TurboTommy

Autothority's philosophy was lots of timing in the mid range and run 'em rich.
Not saying it's good or bad, but that was their take on it when they started developing chips for the 951.
That being said, I still think it's a tad rich; you're leaving a good bit of power on the table. I definitely feel the car liven up when I go to the low 12s air/fuel.
But, don't go by me; I have a completely different animal and I live on the edge.
Yeah, if you increased boost by 1 or 2 psi, you'd lean it slightly (I think you still have the stock AFM), but still rich enough for safety. And, if you still have the stock turbo, your air flow into the engine in the upper RPMs won't increase by much, and your injector duty cycle should still be acceptable.

TurboTommy

Unfortunately, with a simple burned chip and a stock AFM, adjusting boost vs the fuel mapping on the chip, is really the only way you can do it.
But, what you can also do, (and I think it's simple and effective) is to get an adjustable FPR ($200.00) and you can move the fuel up or down in any increments you want.

Of course, all this is just alot of talk if the OP is going to get a proper MAF in the future.

beebone

Mine is around these figure from 11.3 to 10.9 under full boost, the boost is 1.2 bar. Mine is stock set up with EBC and chiped. No lean spot at all.

beebone

The boost will drop off a bit unless yours are 88 up S model. This is normal for 86-88 model.

alpinewhite951

Thank you for all of the responses. I know the a/f ratio is not exactly where it should be but I will not worry about driving it now.

choinga

too rich is way better than too lean of course...anywhere in the 10's is too rich at WOT...I run at around 11.5 to 11.8 @ WOT.

alpinewhite951

I do not have the money yet to buy the Vistesse MAF so is there anything I can do?

onspeed

Keep it out of boost?

Lol, but really, my car has had autothority chips since 1995 and it hasn't blown up yet. While their tune is rather outdated, it'll get the job done.