Overboost - naughty remap?

[Swig]

Hi,

I just bought a 2004 leon tdi 130 se and I'm very happy with it apart from one problem:

If I rev it hard it can end up logging a "overboost condition" in the ECU memory and going into limp home mode. Turning the engine off and on gets the performance back.

It turns out it's been remapped... as it wasn't clear at the time I bought it that it had been remapped the dealership wants to put it right.

The overboost can be caused reliably by revving it over 4.5k or I think by sustained acceleration in motorway driving. When plugged into a diagnostic system it was asking for 1400 or so (not sure of the unit) of boost but getting 2200! (this is with the car sitting still).

Has anyone else had this situation? Is it a poor quality remap?

The mechanic at the dealer is prepared to try and turn down the boost at the actuator - is this a good way to go. They don't have the facility to change the ECU map themselves.

I don't know much about ECU mapping but it looks like a load of tuners using this site do...

Cheers,

Andy

 

[Swig]

...sorry should be in the TDI tuning section. I hadn't found that yet!

 

[mrvavavoom]

i had the same problem with my petrol lc local tuning company went far too aggressive and nearly wrecked my car all sorted now tho

 

[Swig]

yeah, I think someone's gone a bit over the top. All the power appears a bit suddenly - not smooth.

 

[was225]

Hi,

I just bought a 2004 leon tdi 130 se and I'm very happy with it apart from one problem:

If I rev it hard it can end up logging a "overboost condition" in the ECU memory and going into limp home mode. Turning the engine off and on gets the performance back.

It turns out it's been remapped... as it wasn't clear at the time I bought it that it had been remapped the dealership wants to put it right.

The overboost can be caused reliably by revving it over 4.5k or I think by sustained acceleration in motorway driving. When plugged into a diagnostic system it was asking for 1400 or so (not sure of the unit) of boost but getting 2200! (this is with the car sitting still).

Has anyone else had this situation? Is it a poor quality remap?

The mechanic at the dealer is prepared to try and turn down the boost at the actuator - is this a good way to go. They don't have the facility to change the ECU map themselves.

I don't know much about ECU mapping but it looks like a load of tuners using this site do...

Cheers,

Andy

Variale vane turbo fitted on the PD diesel engines, all yoou need to do is seperate the VNT part of the turbo give it a good clean with brake/carb cleaner get rid of the sticky oily residue which makes the vanes stick on turbo causing a overboost fault, remaps are fine ive had one on my PD150 40,000miles still pulls like a train, dealers are fobbing you off.

 

[Swig]

thanks.

is cleaning the turbo a big/unpleasant job?

the guy at the dealers was happy to have the car in their workshop and try to "turn the boost down at the actuator". so far I've been impressed with their willingness to help.

 

[volvic]

"turn the boost down at the actuator"

from what little i know, i dont think that is possible as the vanes control the boost? husbandofstinky,brad1,various jons/jonjays, that guy with a fabia vrs(sorry if i missed out any pros) members will give you a better answer when they see this...

is this a seat dealer? as remapping a car can void warrenty. did they give you a limited parts cover? or was the car purchased as seen?
all a dealer needs to do is flash the ecu with latests software and its a standard car*

*i think!

 

[Swig]

not a seat dealer - an independent. to be fair to him he was on the spot and said he'd look into ways to fix the problem. I just took the car back to them on my lunch break from work to have the fault code read. I've got a 3 month AA warranty.

 

[volvic]

i personally wouldn't let anyone near a VNT turbo (like on yours) unless they had worked on one before.

call up a seat dealer and ask how much to flash the ecu. shouldn't be more than 30mins labour. then bill the garage. but remember you'll lose the extra performance

but as said above remaps if done correctly shouldn't have any problems.

 

[Swig]

Cheers.

I do like the extra performance... very handy for overtaking but if it's causing the overboost problem I'd consider ditching it as you suggest.

Is it normal for a badly done remap cause this sort of problem?

I guess worst case scenario is returning to Seat's original map and then still getting the fault. suppose that would point more clearly to a clogged up turbo. Anyone got any idea how much it'd cost to get the turbo cleaned?

 

[glynnd]

Probably not a bad map as its most likely to be a generic one.
As stated its probably down to the vanes, a company called innotech supply cleaner at about £35 and expect to pay an hour and a half labour to get the turbo cleaned.
Boost cannot be reduced or increased by the actuator. I would get it cleaned before you have it made back to standard.
Glynn

 

[Swig]

Thanks glyn.

Is the difference between requested boost and actual boost (1400 vs 2200 odd) I mentioned normal?

 

[glynnd]

There should be little difference between reqd and actual boost on a well running motor.
2200 versus 1400 is obviously way out.
Glynn

 

[volvic]

its worth reading on how vnt turbos work.

heres a video
http://www.youtube.com/watch?v=Gc2awh0O0Bc

 

[Swig]

thanks glynnd and volvic.

I'll check out that video later. It sounds like a plausible explanation for the overboost.

 

[Husbandofstinky]

from what little i know, i dont think that is possible as the vanes control the boost? brad1,various jons/jonjays, that guy with a fabia vrs(sorry if i missed out any pros) members will give you a better answer when they see this...

Edited for accuracy.



It does sound like a sticky vanes issue and it is a nasty/messy job. I think Glynn may have cleaned his himself before the hybrid went in (correct me if I'm wrong - I know someone did not that many months ago).

In the end it is an issue for the garage to sort out.

The map is a possibility as it could have been butchered by someone. However on a law of averages it is very unlikely.

Fortunately the garage is playing ball and hopefully you'll get your car back soon in order.

 

[Muttley]

The commonest causes of the overboost problem on diesels reported on this forum are sticky VNT vanes and sticky EGR valves.

VNT vanes are spring-loaded in the open position and are pulled closed by the ECU to make the impeller inlet narrower at low revs, when there is less exhaust gas *volume*. Forcing the gas to go through a narrower opening makes it speed up, and this spins the turbo up sufficiently to deliver usable boost. The restriction in the exhaust pipe is more than made up for by the extra power from the turbo boost.

As revs rise the vanes open until at max revs they are open wide. There is no wastegate - the turbo is sized for the max rev condition.

If the car is driven a lot at low revs (commuting in slow traffic, say), the engine produces more soot and the turbo never gets hot enough to burn it off. The soot layer can eventually cause the vanes to stick in the part-open position. Now when the revs rise, the vanes can't open enough and the gas flow goes too high, overspeeding the turbo and so causing overboost.



The EGR system puts some exhaust gas back into the inlet to limit NOx generation. There are many bad side-effects: EGR action is the main cause of soot in the exhaust (and so your sticky VNT vanes) and hot sooty exhaust mixes with oily crankcase vapours in the inlet to form a sticky sludge. This chokes the inlet manifold and eventually causes the EGR to stick open when it should close as revs rise. The stuck-open EGR lets too much exhaust pressure back in to the inlet and causes overboost.

I can bore for England on this topic - so I'll shut up now.

 

[Swig]

Thanks for that. I'm glad people are broadly saying the same thing.

Is there an easy way of diagnosing whether it's the EGR or the VNT vanes?

Anyone with experience of this Innotech cleaning product? - from reading a pdf on the internet it sounds like it makes the VNT job easier.

 

[Muttley]

VNT vanes are the most likely. You could try moving the actuator by hand (with the engine off) to see if it is free or not. Then get someone to switch on and rev the engine while you watch the actuator - but since its under the car you'll want it on axle stands and to be very careful ! Actuator should move from fully open to fully closed as the engine is started up, then open up as the revs rise.

 

[Swig]

Cheers, thanks for your help.