Fluctuating Boost

**s2driveruk** · 27 September 2007, 12:29

checked your vacuum hoses and intake hoses or leaks? Can be really annoying to trace but there is plenty of places a small leak could come from and compromise the boost pressure.

Good luck...

**Animal Mother** · 27 September 2007, 14:29

Cracked exhaust manifold?

**Rusty** · 27 September 2007, 14:47

I had been thinking EM but then decided i was too much money to replace it so it couldn't have gone wrong... will have to have a look!

**Acidburn** · 27 September 2007, 17:14

Good luck with finding the leak, think someone else had this problem with a boost leak thru exhaust manifold recently, possibly big_kev.

**Ws2** · 27 September 2007, 19:32

I have the same with my chipped s2, max boost is 1,5bar and fluctuating from 3200-4000tpm but no hesitation.

Mayby surge?

**newsh** · 27 September 2007, 20:12

Does the boost gauge needle flicker?

**terrybullwon** · 27 September 2007, 20:13

Originally posted by newsh

Does the boost gauge needle flicker?

Andy pm'd me John, its the same as what i had the gauge needle flickers. I never did get to the bottom of it before i took the engine out

**newsh** · 27 September 2007, 21:13

I'm pretty sure mine was either a leak that only leaked at high boost (in other words it didn't leak at all at 1 bar but did above 1.5) I had a leak like this on the small pipe that comes off the IM below the TB and goes to the Carbon Can valve.

Or it was down to a leak at the bottom of the downpipe where it joins the main exhaust.

**Rusty** · 27 September 2007, 21:25

Boost gauge flutters about 0.2 bar total. Haven't had a chance to try a standard ECU since I fixed a boost leak that was responsible for the major fluctutation at the RR back in August. Car pulls like a train with the remap so just have to stick with it for the moment, it'll get worse!

Exhaust wouldn't suprise me, it sounds a bit throaty so could be leaking. It's just the £1k that I'd need to replace the down pipe, fit an RS2 EM and replace all the gaskets, nuts, studs, bolts etc. etc. and then I might as well fit a reconditioned / hybrid turbo whilst I'm at it... etc. etc.

**s2_bo** · 27 September 2007, 23:28

I have the same problem in mine Andy, . It only does it in 4th and 5th though between 3200 and 4200 rpm, During that time the needle flickers like mad up to 1.7 bar and then drops to 1.5 and stays there solid.

I have also tried replacing every bit of hose inc all boost pipes and the Vacuum hoses as well as all the sensors and valves and the WG diaphragm

I have not checked the EM yet though as it sounds like that could be the case.

You can hear the flickering too, its very loud if you have the window down and sounds like its coming from the driver side of the car. (i.e EM)

Keep us postted if you mange to sort it out.

Once thing i did notice is that it doesn't do it if you are above 4K and then let the boost drop and flor it again. Then it just goes straight to full boost. but if your under 3K then if flickers like mad....
If got used to it now though and hope that the RS2 setup and new engine will change all that.
Cheers.
Bo

**HPmuirt** · 27 September 2007, 23:31

Sounds like your Lamda sensor to me

Cheers n

Si

**s2_bo** · 27 September 2007, 23:35

Originally posted by HPmuirt

Sounds like your Lamda sensor to me

Cheers n

Si

Really?

Well i did replace that when i first got the car.
Do you mean as in fumes escaping through the hole where the Lamda connects or just that its broken and taking a bad reading?

Can the Lamda influence the WGFV that much that it would make the WG open and close 10 - 20 times a second?
Also my EGT, which is not wideband stays steady at the top end of optimum during open throttle.

Fluctuating Boost

Fluctuating Boost

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