951pcarguy

My 87 951 (Lindsey Quad MAF, Stage 2 chip, 3" straight through exhaust) is blowing big puffs of black smoke pretty upon full throttle, and I get tons of soot on the rear bumper. The plugs show it's running very rich, with all 4 black after a few weeks of running. Also, I'm only getting about 15mpg, even on the highway.

Any suggestions for where to start? I was thinking of bringing it back to stock by removing the MAF and chip. I've verified the MAF is operating via changing the mapping and dial settings and seeing noticeable differences, but is there a chance this unit is the issue?

Any other suggestions are appreciated.

Jay Ellis
'87 951
Lindsey Quad MAF, Stage 2, 3" SS Exh, Leda Coilovers 650/550

black944 turbo

That is probably a good starting point. Many years ago I had a very similar issue and the best decision I ever made was going back to the afm. I do miss the quicker response of the maf, but don't miss it not holding a tune.

You could always try a different vendors maf kit like a rogue or vitesse. I would suggest staying away from doing a custom chip for your maf, unless the tuner is with you and making adjustments with the car.

bw993

Have you tried tuning the Quad MAF?

I used to own one and it was very easy to tune with a USB cable directly into the MAF, without touching the DME chip.

numbskull

It is very easy to tune the dbx85 once you understand the curve. It's an OK unit even though the sensors need replacement every few years, and you cannot tune live. If given a choice I would go with anything stable you can tune in real time.

Dash01

Have you tried adjusting the DME, if you're still using the stock DME? On my '86 951 (and presumably on your '87) there is a blue switch with various presets to enrichen or lean the mixture.

A car with the low drag coefficient and frontal area of a 951 should be getting about twice the highway mileage.

951pcarguy

Yes, I was able to use the DBX software installed on my laptop and plugged into the mini-USB from the MAF unit, and was able to change the settings (not in real time, of course) and observe pretty significant differences.

I do have the stock DME, so what are the settings on the blue switch for making it leaner?

fejjj

black944 turbo

Be very careful messing with settings unless you have it on a dyno or have at minimum a wide band. My maf kit (same setup) had similar issues and it would not hold a tune. I spent thousands of dollars on dyno time and a custom chip etc... And continued with the issue. That is why I made my suggestion above. I know a lot of people have had some success with these units, but that was not my experience.

951pcarguy

So with different DME and KLR chips, do tuners need to adjust the DME settings to get higher levels of boost, or do the chips alone do the trick?

Also, how do the MAFs work to actually adjust fuel mixture and boost, and what exactly is changing to make it go "out of tune"? Do the sensors inside the MAF unit attached to the cross wires go bad?

I don't have access to a dyno (unless I give SSI about $1000 I figure), so what is a "wide band" and how can I use that instead?

Humboldtgrin

The MAF or AFM has to match the fuel injector size in regards to the tuning of the chip or programming of a aftermarket ECU. Also the fuel pressure has to be adjusted to match the tune. Also if you put a different size turbo on then a retune would be needed. In fact any change with any fuel or air delivery items would have to be tuned to what was changed. So if you put bigger injectors in like 55lbs and the car has a stock AFM and chips then that would cause a rich condition without a tune or chip update. A bigger turbo on all stock items would cause a lean condition if not tuned. If the DME or stand alone ECU doesn't know what items it has to with and there were changes and it doesn't know what it's working with. Then the engine will be out of tune.

Humboldtgrin

Also it could be as simple as your O2 sensor being bad.

black944 turbo

Are you using a power perfect tuner? The problem with that setup is that it can not compensate for weather changes.

I had all the same equipment in my car, never changed injectors or the turbo. It would run great the day it came off the dyno and the next day I would blow black soot everywhere sitting at a traffic light.

951pcarguy

No, I'm just using the Abaco DBX software available from Lindsey, along with the *.DBX files for configuring the MAY settings to the mappings appropriate for my setup.

Can I use Power Perfect with my setup or is that only for a true Engine Management System and not an add-on like the MAF?

raleighBahn

I would go through the sensor troubleshooting guide in the turbo workshop manual with a multimeter (but whatever you do, don't start replacing these ***** nilly or you'll spend a fortune and still not find the problem).

The car (and aftermarket solutions) all take readings from various sensors (water temp sensor, etc) and adjust fuel accordingly. So if you are getting bad inputs, you will get bad outputs all day long.

Imagine if it was freezing outside, but your nervous systen was malfunctioning and you felt hot. You'd be walking around in a t-shirt and shorts and wondering how you caught hypothermia.

shortyboy

i got a vitesse maf sensor i could sell. comes with sensor and connector, youll need to wire it in yourself, but once you buy a custom burned chip from John at Vitesse Racing, he'll help you out with installation.