Sami951

So, as I've been driving my recently bought 951 around a bit now, it looks like it's getting rather poor MPG... and there's a definite smell of gasoline in the exhaust.

I understand that running a bit rich is the safest option, but I'm thinking this might just be too rich... I'm planning to dyno the car to see if this really is the case or not.

The question is; is there an easy way to do small adjustments to the fuel delivery? The car has stock AFM, unknown set of chips (not stock anyway), stock fuel pressure regulator and stock injectors, as far as I can tell.

I checked the factory manuals and they did describe a screw of some sort in the AFM box that you could use to do something like this, but I didn't completely understand if it only affects idle ratios or throughout the entire rev range...

Edit: also got an LBE, stock boost gauge goes to 2 when pressing hard. Car doesn't have a cat, and browsing thru pet, I don't think it has an O2 sensor either (!?)

pikey7

It will have an O2 sensor, the management system needs one!

Have you tried checking the fuel quality switch? Some sort of 8 position thingy inside the DME? Maybe that can help..... There was some thread on that quite recently (last week???)

I can imagine that the screw in the AFM changes the spring pressure, thus changing the amount of air that gets to the intake. Can't really help on that one though.!

Ski

Sami your car should have an O2 sensor, like pikey7 said, your Motronic system needs it.

The screw on the AFM box is for adjusting CO levels at idle. In the grand scheme of things it will assist very little when your on the boost. Your own advice of getting the car to the dyno and seeing what it is doing is the best thing. Find out what it is doing and go from there. After that if the car is running rich then lean in the upper rpms, give Guru an email,,
<a href="http://www.gururacing.net" target="_blank">www.gururacing.net</a> Right now they have the best chips on the market, from stock to modified, still running AFM or MAP.

Rob

</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica">Originally posted by pikey7:
<strong>It will have an O2 sensor, the management system needs one!</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">I don't think the euro models have one. My nephew's 86 N/A doesn't. The Euro cars run directly from the fuel maps on the DME chip (open loop) all the time.

It might be a good idea to check the fuel pressure, you might have a regulator that is going bad.

Rob

pikey7

</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica">Originally posted by Rob:
<strong>I don't think the euro models have one</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">Mine is a euro model. Must be turbo thing???

Sami951

I think models with a cat have them.. ?

(I haven't really checked if my car has it or not, I just browsed thru PET and it says catless cars didn't come with O2 sensors either)

RJP 951

Sami, you should check the fuel quality switch on the DME and make sure it's in the original factory setting of zero (turning counter-clockwise, it's the first setting). Some of the other settings would have you running rich. Look at Danno's RacerX web site for a good explanation.

Ron

Sami951

Oh yeah, this is actually one thing I'd really love to know more about: is the fuel quality switch strictly a function of DME, ie. it reads a value off the chip and then adds a certain percent to that depending on the switch? Or does the functionality depend on the chips used?

I hope that makes any sense - I'm not very good at explaining stuff

Paul Bloomberg

I've seen a few 951's w/o operating O2 sensors. They run very well making lots of hp.

I personally wouldn't adjust anything on a turbo let alone a turbo running non-stock boost w/o a dyno and someone with experience running the dyno doing the tuning. PISTONS R EXPENSIVE!!
That said.....

The AFM's are like those on the Porsches,BMW's, Toyota's,Mazda's, ect...

The allen screw usually covered by a plug adjusts idle only. (CCW leaner)

The overall mix can be adjusted by removing the black cover pulling back the spring and rotating the black toothed dial (CCW=richer on the 944 n/a)Very small gains on my 944-Spec car 1-2WHP same??? as what I just read in GRM except they leaned it out on a Miata for more power.
Without a dyno w/air fuel reading capabilities, you are taking a shot in the dark and probably couldn't detect the perf. increase or decrease either way.
Paul

Sami951

I'm definately going to put the car in a dyno with a/f reader hooked up, but not until I know how to adjust the amount of fuel in case it indeed is screwed

Olli Snellman

Sami's car is using some after market chips, which they are, i just don't know.Dme switch position with these chips might have something to do with poor fuel consumption.Perhaps you have to check your driving habits as well...Might be too heavy right foot!
I suppose you should change to Guru chips like Tommy,Pete & i.

pete95zhn

Hello Sami!

Should we make a dyno trip together,Im very curious about my car's present hp-figure...also interested in seeing the a/f curve.
There's a place in Juvanmalmi...haven't asked them yet,though.

Pete

Sami951

Pete, you've got mail!

Songz

Strange.. mine is eurospec... with cat but no O2.