Surging after Remap

[speedsix]

I've posted about this before and thought I'd solved the problem replacing the N75 valve but I'm seeing the same thing again.

Basically, under high load, i.e foot to the floor in a high gear, my boost rises quickly to just over 20psi, drops to 18 and kinda bounces between 18-20 for a moment before settling. If I bring the boost up slowly it's steady.

I don't know if it's anything to be concerned about or if I might have a problem with my guages (autoguage). I'm sure the problem went away, I've just recently made an adjustment with the SPS.

Cheers

Dom

 

[speedsix]

Anyone?

 

[Pabs]

when i had this with my LC i just replaced the n75 as you have done - problem solved.
I'd check on vag-com and see if you have any boost leaks tho....?

 

[speedsix]

It seems to be holding boost fine or did you mean something else in vagcom?

 

[phatchoonz1]

I get exactly the same thing in my Revo'd 210 LCR with an autometer boost gauge, and as you say, it only really happens when the engines really under load - eg. with a few people in the car and the air-con on aswell.
I haven't really had a chance to get much in the way of logs done with vagcom. But keep meaning to and if anyone's got some suggestions of things to log, that'd be cool! I was guessing boost req vs actual and N75 operation?
Keep us posted if you find anything that's causing it though!

 

[Pabs]

It won't be the boost gauge at fault.

It'd be worth logging with vag-com requested vs actual, check for any errors in vag-com, and check on the MAF as well...

When I had this problem, I checked all of the above, and I also checked hoses to n249 and the vac reservoir on top of the engine. I think I also removed and reattached my top intercooler hose, and checked over the TIP. However, nothing looked wrong which is why I changed the n75.

Are you using the standard N75F valve, or are you running a J?

 

[phatchoonz1]

I'm using the standard valve still.

Might go and log a couple of runs now (if the laptops got any charge)!

 

[speedsix]

Sequence of events went as follows,

Set boost down from 8 to 7 with SPS yesterday

Noticed boost was fluctuating under high load. In 4th gear(only when pulling from low revs) and 5th/6th (always) Planting foot at 4000rpm+ in 4th, no problem, same with 1st/2nd/3rd.

Ranted car around for a while, boost got progressively steadier to the point where I can floor it in 5th from low revs and boost is perfectly steady. It's perfect now. Seems to be overboosting as high as 24psi when accelerating hard under load.

 

[speedsix]

Got in the car this morning, boost is fluctuating badly in 5th/6th under load.

Not happy. No idea what to do next, Revo are adament it's not the code (now I'm not so sure) I can't exactly take it to Seat and complain it's not holding 20psi steady when it works fine in stock mode. A regular garage won't have a clue.

 

[daniel_owen_uk]

When you say the boost is fluctuating, can you feel it when driving? Or is it just the gauge that fluctuates?

 

[speedsix]

Yeah you can. It only fluctuates about 2psi either way but you can hear it more than anything, I have a noisy ramair kit and you can hear the intake pitch fluctuate as the boost guage needle bounces.

phatchoons, have you mentioned the problem to Revo atall?

Dom

 

[DPJ]

You really need to log requested v actual with Vag-Com to see what's happening.........

 

[speedsix]

I've done that several times, because it's only sampling 1.5 times a second it all looks comletely normal.

 

[daniel_owen_uk]

Is there a way to change the sample rate? Or is it a limitation of the bus rather than the software?

 

[speedsix]

I've tried the settings that supposedly speed it up but that is as fast as it will go, I assumed it was limited by the bus.

 

[DPJ]

I've done that several times, because it's only sampling 1.5 times a second it all looks comletely normal.

Why don't you post the log up anyway.

 

[speedsix]

My original thread is here..
http://www.seatcupra.net/forums/showthread.php?t=95824

It has some requested/actual boost figures in the thread, this was done before I replaced the valve when I noticed the problem initially. It;s wierd that the boost started smoothing out last night and eventually was perfect only to be bad again this morning.

Getting very frustrated.

 

[speedsix]

Just been out in the car and it's only fluctuating a bit now under high load. Guage rises, hits just over 20 and then drops and 'wobbles' a bit, can hear the pitch change.

On one occaison accelerating from low down in 5th, it held 24psi for a few seconds!!

 

[speedsix]

Just thinking, what would happen if the N75 went on the wrong way round? Can someone describe which way round theres is, i.e which way the metal plate is pointing?

Cheers

 

[flashbsd]

do a battery reset and a throttle body reset, then try again, mine does it if i tweak my map without doing this.

Or your n75 is shagged.