Block 32

[flashyg]

Did some Vag checks at a recent meet. None of the cars had errors.

Looked at Block 32 expecting to see minimal trimming but as usual I was wrong, how strange.

After Reading 3 cars in succession these were the varying results.

Idle trims on all around -1 both banks

On 2 cars the trims for mid / full throttle were:
-5 and-7 (millers and 98.6 mtm stage 3) and -4 and -5 (98.6 mrc tuned)

On the 3rd car trims were:
+8 and+10 Dave's (not sure on petrol or state of tune)

Basically mine is squeaky clean and holds perfect pressure so I cant understand why fuel is being trimmed.

Any suggestions or are these readings normal?

Are the positive readings a sign of maf failure?

is + or minus 10% normal tolerances?

the better the fuel the more trimming used?

why are these cars so tricky?

Thanks G.

[JonnyX]

Look ok to me apart from Dave's. That, as you say, looks like it's running
lean. I agree that MAF is the most likely cause although it could also be
causedd by a blocked fuel filter or defective fuel pump.
Most turbo cars run rich on WOT to keep EGT's down hence the -ve numbers.

My car idles around +1 +2 and is a bit lumpy which makes me think I have a vacuum
leak.

HTH

Jon

[shineydave]

mine, as far as i know, is running standard map, no tuning. as for petrol i use the local texeco station but generally put any old crap in it since most of my driving is to work and back.

[flashyg]

Thanks for the info and reassurance.
Any other help re the other questions would be help full in gaining a better understanding.

[shineydave]

so as far as i can see the higher the number the more the mixture is being enriched, is that right? if so that ties in with the fact that i'm a cheapskate and usually bang in 91ron for weekday driving. looks like i'll have to break into the ShineyDave exchequer this weekend and try a tank of optimax. will post the results early next week.

[flashyg]

look forward to hearing back from you.

[JonnyX]

so as far as i can see the higher the number the more the mixture is being enriched, is that right? if so that ties in with the fact that i'm a cheapskate and usually bang in 91ron for weekday driving. looks like i'll have to break into the ShineyDave exchequer this weekend and try a tank of optimax. will post the results early next week.

-ve numbers = rich, +ve = lean.

If you are running low octane you may be dumping extra fuel
to keep the cylinder temps down to stop detonation. You should
be running 95 RON MINIMUM (with reduced performance) even on
a standard S4.

[shineydave]

i generally get around 21-22mpg. going to fill her up tomorrow with optimax then speak to clive about doing a bit of logging. i'm guessing that, based around comments on here, i should see a 10% increase in mpg, i.e, 23-24mpg. FYI i had the MAF out about a month ago and gave it a good clean although it did appear in good condition anyway.

[Uwe@Ross-Tech]

+/- 10% are normally acceptable tolerances. I've seen brand new cars (less than 1000 miles on the clock) with almost 10%.

-Uwe-

[DavidT]

Welcome to rs246 Uwe I shudder to think how many forums you read and contribute to

[flashyg]

a big failte roite from the Irish side to Uwe, Very kind of you to join us.

Thanks for the info.

[shineydave]

just back from MRC who did me a custom re-map. Mihnea found my MAF was dead which was causing the high fuel trims. going like a train now. can't believe the improvement in response above a ton (on a private track of course). the initial trims were slightly better than the ones Gorden took but still over 5 even though i've taken everyones advice and swapped to optimax.

[S2tuner]

Dave, your initial trims were +10 and +13.3%, which is because of the dead MAF. After the remap (but maybe not enough driving) they were -1.5%ish on both banks IIRC.

HTH,

Mihnea

[shineydave]

ahhhhhhhhhhhhhhhhh..........i thought u'd said they were just over 5, in any case the car is hugely improved, the kick when you stamp on the peddle above 100 is so addictive it'd be rude not to. in fact i think that should be your new slogan.

MRC Tuning.......It'd be rude not to

it's got quite a ring to it i think

[CliveH]

I'm running +0.6 and -0.2 at idle and -7.0 and -6.3 at mid revs. Tesco's 97, Millers 5W40, MRC Stage2 (RS4 exhaust and gutted downpipes).

I like the slogan Dave - MRC Tuning, it would be rude not to...