LEON CR fluttering boost problem

[bentaw]

let us know how that goes when that turns up. I think with the amount of people who have the problem we can rule out the ECU aswell cos surely not all of us have a faulty ECU

 

[richybigman]

I would hope not!

 

[sargey]

im going to join this club too!
mines only in first and second, sometimes in 3rd and the odd ocasion in 6th
revs go up, boost goes up, boost then drops, then goes back up around 2500rpm ish

Mine is:
LC
Induction kit
007P (back up baileys soon standard at mo, possibly Split R or HKS SSQ if it will work)
N249 bypass
and a new N75F

 

[delcac]

Can someone log the N75 duty cycle on Vag Com, block 114 (I think). It should read 95ish all the way, if it drops when the turbo comes on boost or does something weird, I may be able to help.

 

[bentaw]

how will u be able to help if it does do this matey

 

[Pabs]

This is an interesting read.

I used to have this problem, or at least similar. I would watch the needle on my boost gauge go up, hit 20psi, drop to 15psi, rise to 20psi, and up and down a couple of times before holding at about 19psi.

This problem disappeared after i changed my N75 from a standard F to a new standard F valve. The only other thing I did at that time was to unplug and reconnect the MAF.

I never saw this problem again - that was until I changed my Carbonio CAI back for a standard airbox (smoothed) with a k&n panel filter. I changed this about a week ago, and now I have a similar (but not as bad) problem.

I doubt that helps anyone, but I thought I'd mention it anyway.

 

[bentaw]

just adds more confussion to the matter really pabs but it appears it is becomming a bigger problem than first thought in the way that a lot of cars do it

 

[Damo]

You Leon owners aren't alone on this.
Happens on mine too (K03S Ibiza Cupra).
Only does it in 4th or 5th gear. Foot to the floor at anything under 2.5K revs and the boost hits peak, then drops back about 7psi, then creeps back up again. Ive tried changing the N75 valve to a H version which I have lying around and no difference.
Theres a few Ibiza owner's with the same spec cars that also do it.
Still no reason as to why it does it, though, so any info to come out of this thread will be very helpful.

 

[delcac]

how will u be able to help if it does do this matey

When the N75 maxes out the cycles drops as it cannot cope, opening the wastegate till it can control the boost again, hence the rising and falling boost This shows itself as dropping figures in the block above. The only way to over come this is to control the boost spike or you may have a faulty N75.

Mind you this may be utter b******S and has nothing to do with it.

 

[claudefrog]

Unfortunately I have not had a chance to run logs on the n75.. but below find a

pic of a 3rd gear run

and this is a 4th gear run
you can see from between 3000RPM and 5500RPM its really quite bad, and its only like that in 4th 5th and 6th gear

 

[danieltm]

This look the same as mine when i had it on rolling road a few weeks ago. Some days its not too bad then when i think its sorted its back again. My car is NOT revo or remap in any way, i had new DV valve and am running on N75J at the mo. Its better but still not right. What else should i change? i dont mind spending a bit of money as long as i get it sorted.... Someone out there must have the answer???

 

[bentaw]

Delcac i think you might be onto something there with mapped cars especially revo cars that try and extract the most torque out of the engine as possible but then why are there standard cars that do it, unless there is a simliar problem with the same symptoms

 

[richybigman]

I'm booked in at JKM to try the ECU (23rd March) and to get a wheel bearing changed, only done 16,000 miles! If the ECU doesn't sort it my car will be broken for ever!

 

[sportbilly]

Thought I would let you know I think I have found my 'bouncing boost' problem.

After trying 3x N75's I finally got off my arse to check for leaks as this surely could be the only thing left....

Anyway checking pipes etc I noticed the red coloured turbo pipe a little squashed - obvioulsy not put back on at the right angle when the turbo was replaced, so I loosed off to adjust as surely this couldn't be helping anything. I knew this wouldn't be the problem as I had the boost problem before the new turbo was fitted ... anyway whilst altering I noticed a bloody split in the side of the pipe - BINGO! there's the problem.

The annoying part which I will be taking up Monday is why didnt this get seen when the turbo was swapped, surely you would check condition of pipes etc when doing a job like this ....

 

[Scotty_b]

Im going to have to join the club ish! Im over boosting to about 30psi on full boost and ive got the bouncing boost on part throtle between 3psi and 9psi. Ive had my forge actuator off, pipes off the lot! Going for a full strip down and new n75 on sunday and going for a H valve rather than a stock F

 

[sportbilly]

I have a couple of F's going now in the for sale section as I tried one on mine (well 2 actually just to make sure).

 

[Scotty_b]

Ah lovely, dont suppose your local too!

 

[claudefrog]

just tried a n75J valve at the weekend, and wow is all i can say, no limp mode, but what feels like a lot more boost and a lot less spiking, going to try get onto the rollers in the next few weeks to see how the graph is looking now

 

[Banana Man]

Oh this now raises another debate.... which version of N75 should we use.

just tried a n75J valve at the weekend, and wow is all i can say, no limp mode, but what feels like a lot more boost and a lot less spiking, going to try get onto the rollers in the next few weeks to see how the graph is looking now

 

[bentaw]

it does indeed banana man should heavily moddified cars be using the J variant of the N75 valve, problem is there are some cars that are standard and have the same problem or similar one