Performance

[jubsees4]

Hello all - please can someone help me?

Having had the MAF replaced on my 99 S4 a couple of months ago, I've been blown away by the performance and am having a real laugh!

Recently though, I've not been as happy with the performance. Is this because I've got used to it?? Or is there a more sinister reason? I've noticed under hard acceleration that there are "flat spots" throughout the rev range - we're talking unnoticeable by passengers, only me. Anyone else had this experience? The car still seems to fly but I'm just not sure. HELP!! [img]images/graemlins/mad.gif[/img]

[rwoodward]

I had a similar problem, felt the car wasn't as quick as it used to be. Had audi check it out, and sure enough diagnosed a faulty MAF. I agree with your findings that once the unit was replaced the performance came back and I realised what i had been missing!

My brother now has the S4, and he has mentioned that he thinks its flatspotting at 2 points up the rev range too, though I never noticed this - guess its largely down to diving styles as much as anything .. What do others feel?

Ross

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Ex Misano S4 Avant [img]images/graemlins/yellows4.gif[/img]

[fade2grey]

aye.. strange flat spots & feels 'weird' on very light throttle. would the all seeing Vag-com show any errors if the MAF\hoses were goosed?

A

[jubsees4]

Having been out in it this evening, I'm now not sure again!! No flat spots, going like stink (Changed from 3rd to 4th, looked at the speedo and being the wrong side of 100, realised it was getting silly)! But, in a way thats a problem - nothing to compare it to!

The fact that the flat spots aren't noticeable all the time suggests there may be a minor problem somewhere. I've booked it into QST for a checkup next week. The last thing I want is a "Joshie"!! (And whats this about him switching to the dark side???!!!)

[Riz_RS4]

(And whats this about him switching to the dark side???!!!)

BMW M3.... need i say more [img]images/graemlins/piss.gif[/img]

[Dippy]

It's so easy to get used to the performance and then think that something is wrong. However yes there can be problems, which is why a boost gauge and VAG-COM can be useful.

I have also found that performance can vary day-to-day. Cetainly air temperature and humidity can affect it.

Also do consider the effect of the DVs. The recirculation system is really not very good, which is why the engine performs better under harsh acceleration rather than light.

[tartan_rob]

MAF - Does VAG-com diagnose that sensor as faulty, I suspect so?

[jubsees4]

I guess in a way I am concerned that I have started to get used to the performance. The flip side is that I'm also always thinking of possible problems as to why I didn't reach some stupid speed at the top of a hill or why that little t*sser in a Saxo isn't as small a blip in the distance as I thought.... childish really.

The VAG-COM does (in theory) seem like a good idea but me and technical stuff don't get on...... The boost gauge does sound good but so far (reading previous posts) doesn't look too good wedged in an air vent or mounted somewhere obscure out of the way - lets face it, if I wanted out and out performance with a naff interior, a Subaru (spit, spit) would have done just fine!!!!

Rambling on a bit now (just enjoyed Man City going through to the next round of the UEFA Cup!) but I'm not sure that flat spots are a good sign..... are they??!! [img]images/graemlins/confused.gif[/img] [img]images/graemlins/smile.gif[/img]

[Carps]

If you want an integrated boost gauge, check out the OC.T effort - OC.T Tuning boost gauge
A couple of us are planning to give them ago later this year [img]images/graemlins/spineyes.gif[/img]

[jubsees4]

Oh yes, much better. Would consider that....

[fade2grey]

Carps.. does anyone know if the OCT fits the 98 UK spec S4 - I've got an analogue clock in the tacho.. If it does then I'll be interested.

Alex

[Dippy]

I'm sure that total MAF failure would cause a severe problem that you wouldn't need VAG-COM to diagnose!

However the most common problem with the MAF is contamination of the wire (no it is NOT self-cleaning like other brands), such that it reads low. Since the ECU operates on measured boost, it would not detect a low reading of the MAF, but as a result the fuelling might be low. This in itself may be picked up as a lean mixture DTC, but from what I hear of people who have had faulty MAFs, more often it is not: Clearly the ECU has a tolerance level for lean fueling, and if the MAF is such that it is below that level, you'll get no DTC, but the engine won't be running correctly.

Actually I think my car might be in that position now as I've 'felt' that the car is underpowered at the top end. AmD should be investigating it right now. Note that I have no DTCs for lean mixture.

No, flat spots are not good in continuous acceleration (i.e. no gear change). Your only solution is to take the car to a tuning specialist (like wot I have done).

[Carps]

fade2grey:

Best thing would be to drop OC.T a mail and ask them. They seem quite prompt with their responses to questions, in my exeperience.

[tartan_rob]

MAF being Mass air Flow meter??? - excuse my ignorance.

[wazza]

MAF being Mass air Flow meter??? - excuse my ignorance.

Correct [img]images/graemlins/thumbs.gif[/img]