42s Running rich

For anyone following my S-Trim install -- thanks for all the advice to date. So I installed the 42lb injectors, a recalibrated 75mm Bullitt Mass Air and a 255lph high pressure intank fuel pump. I'm scheduled for a dyno chip tune at JMS April 6th, but for now I drove it around the block and it's running very rich at idle and cruise. So rich that the computer kicked a 91 code -- O2 sensor rich fuel condition. Dropped the fuel pressure from 39 to 30# - still rich. The plugs are coated with black soot.

I know the chip will fix all this -- but I was just wondering if the rich condition is typical or expected given these huge 42# injectors, a calibrated Mass Air, a 306 engine, and a stock computer (A9L). I figure so, but thought I'd ask.

yes that is typical. try not to drive the car much either.

Well It may be a little rich at idle but it shouldn't kick any codes out. Are you sure your oxygen sensors are up to snuff? Are you setting the pressure with the line off or on? Have you tried to "clock" your meter? Fan wash?

I'm fishing but everyonce in a while I catch one... :D

installing 42# injectors on a stock tune will run VERY rich at idle and mid throttle, even with a calibrated MAF. driveability will suck also.

rob, did you get a flow sheet with your MAF? if so, bring it with you when you get the car tuned.

Good reassurance.

Set FP with vacuum off and plugged. Experimented with different settings -- 25psi to 30psi -- still very rich. Clocked the MAF, yes. No fan wash possible -- the filter is in a sealed cover with air intake only from the fender and behind the headlight. Cold start is no problem. Funny thing is the cold idle is much improved over the 24lb injectors. But once warmed up it's very rich at idle and cruise. You can smell it in the exhaust, too. The check engine light kicked on during at light throttle cruise and stayed on for about a minute. Once at a stop light it turned off and stayed off. Then the engine stalled a block later at a stop sign. It wouldn't restart until I floored the throttle, like you are supposed to do with a flooded engine, then it started right up. Headed home - it stumbled here and there if the revs got below 1900 -- then have parked it since.

O2 sensors are relatively fresh -- about 2K miles on them. I don't think they are bad. I recall the last time they went south the check engine light was on all the time and code was something like - left AND right O2 sensor out of range - and the car had a much rougher idle and cruise. All the 3923 Autolite plugs are black with soot but not wet.

I did receive a flow sheet with the MAF. I'll be sure to bring it to JMS for the tune. Thanks. I'll also pull and clean all the plugs.

Thanks to all. I'll post the dyno results after the tune on April 6th. Then maybe I can really start enjoying this blower once and for all. Also looking forward to this years' first Southeast SCCA Solo I event at the Gainesville, FL test track at the end of April.

weird, i ran 42s with the stock computer with no problems

same here once i got my C&L straightened out......

I ran 50's with a stock computer and no problems at all....doesn't sound normal to me?

It's gotta be the Pro-M calibration. I understand they set them rich for blowers. As a matter of fact, the meter has scribed on it "42 S/C C".

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Originally Posted by IPPO

It's gotta be the Pro-M calibration. I understand they set them rich for blowers. As a matter of fact, the meter has scribed on it "42 S/C C".

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my meter was a 42 s/c 80 mm pro m

I called JMS about this and they tell me the 42# recalibrated meters they see are rarely, although sometimes, calibrated dead on. He also indicated the Pro-M supercharged meters are typically rich. From what I told him, they believe it's the meter. Bottom line, given the car is operable, they believe there is enough adjustability in the meter/computer to correct the issue with the chip and don't feel it's necessary to send it back to Pro-M for a fix.

For what it's worth I called Pro-M and they told me that the calibration should have been right on the mark. He asked me about my battery relocation to the trunk and if I had a 10 gauage wire from the neg post to the computer wire harness ground on the fender apron next to the selonoid. Yep. Any curves or turns before the MAF? Nope. TPS setting? -- 0.998volts. Good. Fuel pressure? -- okay.

He says their calibration is a little "fat" at the top end only for supercharged applications, unless you are getting a chip. Sometimes a particular application may be off, but the calibration is what it is, there is nothing for them to change or correct if I return it to them. He says when issues like this happens, they burn a custom chip in house or use a MAF adjustable calibrator to correct the issue. He told me about all the parameters the chip can adjust -- something like 2500 in all.

He claims it doesn't happen often, but that it does happen. He felt confident a good chip and dyno tune is all that it needed.

Appreciate the ability to rant and ramble here.