Boost fluctuation?

TheFiftheElement

Registered User
I appear to have an intermittent issue with some boost fluctuation.

I have tried to make it pretty repeatable (failed) but I would say if I'm sitting around 60/65 in 7th, give it a little bit of right foot so it drops down to 5th/6th and hits @3,200 revs I'm feeling a bit of boost fluctuation. Almost like a subtle stutter/not clean acceleration.

I've had the car checked out (specialist garage - not Audi), hoses/actuator etc. nothing to report (had a smoke test through the system to check for leaks). I've had the car hooked up to a laptop and it's hitting the boost numbers etc.

Standard PFL with a revo stage one map.

The only thing I haven't tried is taking the map off but wondered if anyone had experienced the same issue, or had any suggestions?
 

D0C

Registered User
I appear to have an intermittent issue with some boost fluctuation.

I have tried to make it pretty repeatable (failed) but I would say if I'm sitting around 60/65 in 7th, give it a little bit of right foot so it drops down to 5th/6th and hits @3,200 revs I'm feeling a bit of boost fluctuation. Almost like a subtle stutter/not clean acceleration.

I've had the car checked out (specialist garage - not Audi), hoses/actuator etc. nothing to report (had a smoke test through the system to check for leaks). I've had the car hooked up to a laptop and it's hitting the boost numbers etc.

Standard PFL with a revo stage one map.

The only thing I haven't tried is taking the map off but wondered if anyone had experienced the same issue, or had any suggestions?
Clutch slip possibly. I recall @Leo-RS explaining it better, but in higher gears you are of course in the peak torque band for longer and it puts more strain on the clutches than simply accelerating through the gears. Higher gear at 3000 ish RPM sounds like it could be that. Possibly why MRC and others insist on a DSG tune to increase clamping pressures.
 

TheFiftheElement

Registered User
I had thought about that. I've used manual mode, stuck it in 4th/5th/6th and from low revs given it full throttle - watched the (crappy) boost gauge as I thought that would probably be when full boost would be asked for.

I didn't think about peak torque mind you. The slight shudder on acceleration might just be clutch slip. Hmmm.
 

JWAM

Registered User
Sounds like clutch slip to me too. The other 'feature' these cars have is a sort of crude software anti lag mimic. If you are auto on the box (the fact this happens to you in manual at low rpm at peak torque makes it sound more like clutch slip, especially if you're gunning a wot, mostly full throttle in 3/4th +) and ask for a burst of acceleration the box will shift down, the clutch will stay open and the rpm will hold like a launch control for a fraction to build boost before the clutch clamps and you're off. The first few times it happened to me it caught me out. Throttle position seemed to need a sudden 'prod' to, I guess, 60 per cent plus from a minimal input cruising to trigger it. Happens in d, but more noticible with the box in s and doesn't need kick down to activate. It will also do it if you pull a couple of manual down shifts quickly and hit go. Now I'm expecting it, I quite like it and it adds to the character!
 

TheFiftheElement

Registered User
The description of minimal input cruising to say 60% throttle, with the box changing down (either in auto or with paddles) is exactly the conditions in which the pulsing occurs.

A bit of clutch slip then, I may investigate a TCU/DSG map ..
 

JWAM

Registered User
In that case it could well be the software 'anti lag'

Have a look at this guys video from about 7 min 30 and it explains what I mean. If it's this you're getting it's normal. If not then it's clutch slip.

 

TheFiftheElement

Registered User
I had a watch, I'm pretty sure it's now clutch slip.

I had thought in manual mode, from low revs with a big throttle input would see the revs rise (and no acceleration - as that's my usual clutch slip test) but this feels more like small slip, clamp, small slip, clamp, sort of every 1/2 second or so.

More like a judder ..
 

JWAM

Registered User
Good luck with the tcu map. I'd be interested to hear how it goes and what difference it makes of you go down this route.
 
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