Hi

I dont want to start another thread on hesitaion but i have a question.

When i put pedal to metal in 2nd gear I boost up to the standard 10-11 psi boost spike and settle at 9psi, but at around 3500rpm the engine backs down a bit and then seems to rocket at 4000rpm.

It sometimes does this in 3rd but never 4th or 5th.

Now ive heard that the ecu is specifially designed to do this, to encourage you to change sooner and save the planet? I hear that seats do the same?

The problem never occurs if i accelerate with the car (like i should be!), ie pushing the gas slowy as i accelarate.

No fault codes

Only thing i would say is i see a higher knock voltage on cylinder 2 than 1,3 or 4, but the knock sensor is mounted on cylinder 2 so maybe thats why?

When the instance occurs i see 18 volts of knock on cylinder 2, but no fault code or timing attenuation/retard in vag com.

I swapped over all the injector and ignition coils from this cylinder but made no difference!

Is anybody else aware of this or has something else broken?

I have attached some vagcom data. you can clearly see the drop in torque.

I presume you have done the basics like a throttle body clean?

So did the vac can mod work?

I presume you have done the basics like a throttle body clean?

So did the vac can mod work?

I have done the throttle body clean, yeah my vac can mod still helps..

Is your car still surging? or did you get to the bottom of it?

Yeah fixed it.

New coils and plugs worked a treat.Boost level now rises above the specified level then drops to what it should be,it no longer drops below specified.

N75j instead if f version holds the boost slightly better through the rev range too.

I still havent found an answer to this, but it looks like a few audi tt owners have had simular issues,

I just don't get why it backs off at 3500-4000 rpm, thats where the dip is in my torque plot above, then picks up again! stumped!

found plenty of threads but no answers

any ideas anybody?

You graph is quite hard to read.

This is mine done with vag-com when standard for you to compare if its any help.

ta, thats really helpful

mine seems to be running more torque, which gear did you do it in?

also, does anybody have a graph of standard boost? at the time when my car slows in acceleration, the boost drops, that is the yellow line in the graph i posted, you can see how it peaks then suddenly requests less and less then more as the revs climb.... weared, but it must be a known issue, i found this from an audi with same problem...

http://img482.imageshack.us/img482/1474/boostxw2.jpg

my boost is reacting exactly the same at same rpm although at a lower pressure...

i have similiar problem, will try throttle body clean but what is vac can mod?? new one on me , help

thanks john

ta, thats really helpful

mine seems to be running more torque, which gear did you do it in?

also, does anybody have a graph of standard boost? at the time when my car slows in acceleration, the boost drops, that is the yellow line in the graph i posted, you can see how it peaks then suddenly requests less and less then more as the revs climb.... weared, but it must be a known issue, i found this from an audi with same problem...

http://img482.imageshack.us/img482/1474/boostxw2.jpg

my boost is reacting exactly the same at same rpm although at a lower pressure...

It was a third gear run.

My torque peaked higher than standard,standard being 235nm or 173lb-ft.

I still cannot tell whats happening on the graph you need the figures from block 115.

For the ecu to be requesting less boost than it should could this be a ecu/sensor error?

oK

Here is a new graph.... this is confusing the hell out of me now.... you can see the dip in requested boost (blue)

This was done in 2nd gear and this decrease in boost occured at exactly 3500 rpm, i found it does this in every gear if i plant the throttle.

Even more weared! if i disconnect n75 so running 4psi boost, the requested boost line looks exactly the same, what i mean is it dips at 3500rpm.... this must be the standard map? since this is what its asking for...?

strangly, i always make 240 + Nm at this point, could it be a torque limiter if there is such a thing?

Anybody out there got their standard boost log?

That graph looks crazy.

This isnt even the normal spike,which occurs at the top end of the boost.This is requesting a crazy spike at such low revs.

The only thing i can think of is a map prob.The boost is quite high for a standard car.

Do you know who had the car before you?

You could get an original map flashed back on again,i would not think it would cost much as the mapper should be able to get an original file quite easily and cheaply.

I would imagine the specified boost levels would be set by the map and not the maf etc.If the boost wasn't hitting the target then you would have a mechanical prob.

Looking at the graph i bet you get a hell of a jolt :thumbdwn:

ok have been on the phone to skoda. I asked, is it standard that you get a boost spike then it "retards" then boost comes back in, no they say...

I'm stumped!

its not requesting anything other than normal boost as far as I can see. 1000 mbar is atmospheric pressure so it always starts at 1000 mbar.

I can't think of anything else I haven't checked!

ok have been on the phone to skoda. I asked, is it standard that you get a boost spike then it "retards" then boost comes back in, no they say...

I'm stumped!

its not requesting anything other than normal boost as far as I can see. 1000 mbar is atmospheric pressure so it always starts at 1000 mbar.

I can't think of anything else I haven't checked!

Have i got mixed up, did you take your foot off at the begining of the Graph?

Have i got mixed up, did you take your foot off at the begining of the Graph?

Yep! i took my foot off, i should have removed it!

I just looked at you graph of torque again! i noticed yours does the same thing! at 3500 rpm, the hp levels out before picking up again!

is that normal?

I marked it on the graph below!

Sorry for steeling your graph, too wet to do a run now!

If you look at my graph, in the performance section,under power run with jetex exhaust fitted, you will see the same ie the torque dips @3500. I do not have any hesitation of feel any drop in performance @3500. My previous graph has the same thing @ 3500rpm.Can only think it is a emmissions thing or the valve timing but cant find what revs that occurs at.

If you look at my graph, in the performance section,under power run with jetex exhaust fitted, you will see the same ie the torque dips @3500. I do not have any hesitation of feel any drop in performance @3500. My previous graph has the same thing @ 3500rpm.Can only think it is a emmissions thing or the valve timing but cant find what revs that occurs at.

Hmm.. i cant work out what it is...i thought it might be the vvt, but that runs constantly.

I think i feel it because at the same time my boost dips from say 10-11 psi to 9 psi, i can hear the turbo change pitch and its not as fast as the first "punch" of boost..

hmm, anybody else had the same thing or is it standard?

Have you had the car from new?

Has it to your knowledge been remapped at all?

I have heard of the symptoms you describe with a dodgy remap, one member on here had one that was so bad that you were initially pushed into the seat, then almost thrown forward as the power cut off before going to the max again.

Have you had the car from new?

Has it to your knowledge been remapped at all?

I have heard of the symptoms you describe with a dodgy remap, one member on here had one that was so bad that you were initially pushed into the seat, then almost thrown forward as the power cut off before going to the max again.

mines not been remapped, i havent had the car since new. It only requests standard boost, I just checked out kennys torque graph from the jettex mod, his is the same!

I marked it on the graph below!

Sorry for steeling your graph, too wet to do a run now!

The only blip in my graph was in the torque where it lost 1.5 lb-ft at 2880rpm, the bhp stay nice and smooth throughout with only 0.1 bhp drop where you have circled. I still have all the figures that i used to plot the graph i posted earlier. Maybe the graph is misleading.

I think this is an acceptable loss on a turbo car.

The only blip in my graph was in the torque where it lost 1.5 lb-ft at 2880rpm, the bhp stay nice and smooth throughout with only 0.1 bhp drop where you have circled. I still have all the figures that i used to plot the graph i posted earlier. Maybe the graph is misleading.

I think this is an acceptable loss on a turbo car.

i see where your coming from. either way it seems its standard that it has that blip since mine yours and kennys has it... could it be electronic cam control moving the cams? does anybody know anything about this?

But how can you check if the VVT is working or not?

ok found cause. the oil powerd hydraulic piston which lifts the chain to advance the inlet cam is sticking. I am putting 2 and 2 together here, if its sticking its going to take longer to lift the chain. hence assuming the changeover is at 3500 rpm its taking a little longer than usual.

any thoughts?