Problems with my Revo map

[sdmegawuk]

Alright folks,

My Octy RS has a stage 1 Revo map in and i'm starting to have problems with the boost level and i'm looking advice.

When i'm accelarateing hard my car pulls 1.3 bar of boost, but keep accelarating and this drops to 1 bar then increases to1.2 then back to 1 and back up. This carries on until i change gear. I know that 1.3 bar is the boost peak, but when it was first mapped last month, the car used to peak at 1.4 bar and then settle at 1.1bar and just pull hard settled at 1.1bar. Now the boost is just bouncing all over the place. Any ideas???????

Have i got a boost leak????? oh, also my turbo has started to whistle when it gets over 1bar.

Hope this all makes sense, any ideas greatly received.

Cheers
Simon

[DaveH]

New turbo whistling noises would suggest so, have you got access to VAGCOM?

[sdmegawuk]

Ran VAG.com on it today. I've got a N75 valve failure, open circuit vag.com said and N249 mechanical failure. Whatever all that means

[DGW]

What fault codes, ie DTC numbers reported?

[sdmegawuk]

Fault codes: 17608 and 17956

[DaveH]

I believe the n75 and n249 are both control valves, the n75 controls the turbo wastegate and the n249 controls the input to the DV. You need some new ones by the sound of it.

[DGW]

This thread below suggests that a faulty DV may lead to error code 17956 being triggered for the N249. The OEM DV is relatively easy to check for leaks and is cheap to replace (< £25 IIRC). I would try replacing that first.

I came up with the following decodes for those fault codes:

17608 P1200 - Boost Pressure Control Valve (N249); mechanical malfunction
17956 P1548 - Boost pressure Control Valve Open.

[sdmegawuk]

Cheers for that. have ordered a new N75 valve as the DV is a Forge 007 and is ok. Spoke to the chap who mapped the car and he said a new N75 should sort the problem.

[RevoKev]

Just read this post... from your description alone I'd have said it's the N75 valve. That wouldn't always pull up a fault though, it's normally a leak from the DV or vacuum hoses that would pull up the N75 fault... the N249 fault is likely to be a knock on fault although it could actually be the cause of the problem. Hopefully the N75 will sort it. I'd advise resetting the adaptation once the new one's been fitted!

[sdmegawuk]

Thanks for the advice,........Whats is the adaption??? also is it safe to drive the car still, as i have to drive over 400miles next week

[drm_jones]

I have been having similar symptoms to sdmegawuk on my car (although mine is still running the standard map). The boost surging occurred at low(ish) rpm ~ about 2000-3000 and the loud whistling / screeching is most noticable around 2500rpm with approx 50%+ throttle applied (I don't have a boost gauge fitted so I have no idea of the pressure at which this occurs)

I have changed the OEM DV to a Bailey DV30 which seems to have cured the boost surging but it still shrieks like a banshee (although it is less noticable now)

I have VAG-COM'd my car but no fault codes are showing up (I only have the shareware version if this makes any difference) Is the next step to change the N75 valve?

I apologise if this is posted in the wrong forum (as my car is not Revo'd) but it is driving me nuts. Any advice you could give would be much appreciated.

Thanks in advance

[RevoKev]

Adaption/adaptation is really a safety feature of the ECU. It runs adaptive ignition so the ECU will 'learn' based on information from the engine sensors. If your cars got problems then the ECU will 'pull back' and requested levels will be lower. Thus once it's fixed it's best to reset these levels. A throttle body adaptation will do this... disconnect battery, reconnect, prime ignition leave for a minute or so.

David, it sounds like you've got a boost leak or have a collapsing hose rather than a faulty N75 issue... this would be apparant further up the rev range as well, as if you were coming on and off the throttle throughout the rev range. Sounds as though your problem is related to peak boost/load. I'd check all the DV connections. What else have you got on/had done to the car? (other than the cat back and filter?)

[sdmegawuk]

Well, my car is now really f@@ked. So the boost surge is still there, and now the ECU light is on and the bloody car is idling at either 700rpm of 1200rpm , whichever it wants at the traffic lights. Great, what next?

Any ideas anyone? would this idle problem be related to N75 valve? Cheers

[DGW]

Sounds like it could be the N75 if my car is anything to go by. Michael at Jabba took it for a test drive on Tuesday and commented that it was horrible to drive. The boost would rocket up, fall back, then rise again and so on. The N75 was sticking. Cost is around £47 excluding VAT. Apparently this is a common problem with N75s on circa 2002 models.

[sdmegawuk]

that would figure, mines 2002

[daver]

My car had the idle and erratic boost problem before xmas, I bypassed the N249 to no avail, it turned out to be the MAF, changed it and problem was cured

[RevoKev]

Originally Posted by sdmegawuk

Well, my car is now really f@@ked. So the boost surge is still there, and now the ECU light is on and the bloody car is idling at either 700rpm of 1200rpm , whichever it wants at the traffic lights. Great, what next?

Any ideas anyone? would this idle problem be related to N75 valve? Cheers

Have you had the N75 changed yet? Does sound like the cause of your issues... do you know what peak MAF values you're seeing as well? Plug quality?!

[sdmegawuk]

Changed my N75, did'nt make a bit of difference so thats £48 wasted. The MAF is reading excellent. Went to see the REVO guy who mapped the car and he put it on the laptop. So MAF is ok, found a split hose, replaced that. The car is now holding 1 bar of boost so thats good, but the turbo is still whistling like hell. I think the turbo bearings are shot, as the whistle gets less as the car gets louder

[sdmegawuk]

DOH, i mean't the whistle gets less as the car heats up

[RevoKev]

Doesn't sound too healthy!