Had my latest vRS rolling roaded today, and oh dear.

It made 168bhp and 192lb/ft.

The car has a Motech map, piper cams and 007p.

The guy running the dyno said its really flat at top end, and I've noticed its dropping boost quite badly on the boost gauge, peaks at 26psi and drops to around 12 quite sharply once I accelerate hard.

Does anyone have any ideas what might be causing it? Could it be one of the boost valves or a hose maybe, and whats the easiest way to find out. I've had the car VAGCOM'd this morning and only faults are speed sensor and brakelight sensor (possibly down to the speed sensor error according to the mechanic).

Which boost valves are the worst ones for affecting boost pressure - its got receipts for N75F and N249 around 74k miles (on 89k now)

Really miffed as the car feels a lot faster than 168bhp - would the engine light being on cause any limiting of boost etc as the light wasn't reset?

Any help would be appreciated!!!!

Edited 19 August, 201015 yr by Rob_OctaviavRS

Don't worry about figures from a rolling road, no two rolling roads are the same, you could take that car to another rolling road somewhere else tomorrow and make 210bhp. Mine is standard and made 189bhp on one rolling road and 173bhp on another

26 psi sounds ridiculously high, even Custom Code remaps don't go that high. I'd say running that kind of psi might have ruptured a pipe somewhere.

Erk, I'd personally be looking at the map although checking all of the pipes would be worthwhile. Peaking at 26psi is asking for trouble!

Standard boost is around 9psi and most remaps seem to take it 16-20psi from what I've seen.

I'm a little out of touch but from what I remember the N75F is standard and is meant to be the one to stick with, with the J causing more a boost spike but generally not as smooth. The engine light alone shouldn't reduce the power.

If you have access to vag-com you can map the PSI, so floor it in 3rd from say 2k rpm, would be interesting to see the graph. Maybe get in contact with Motech?

I have Motech calling me back sometime today with info regarding the map.

I did think 26psi is a lot, I had an Escort Cossie about 5 years ago that was only peaking at 25psi and that was 360bhp. The skoda does feel stupidly quick on the pull off as it boosts up to 26psi.

I'm beginning to suspect a pipe, boost valve or the map going tits up maybe.

Not got access to VAGCOM, however I think I know someone who does, so maybe an offer of a drink might help with that!

Sounds like someone could have buggered about with the wastegate actuator pre-load. As by increasing the pre-load, you will get an overboost, which the MAP sensor will pick up on and the ECU will try to kill the boost. Either that or a faulty N75 maybe. But I'd expect an error code from it.

The boost does sound too high. Standard is 10psi, APR Stage 1 is 17psi, Shark Performance Stage 1 is 19psi, and most are in that region.

Could be the map too. Maybe try a decent tuner like Shark for example. I know Motec make some of the best ECU's about, but I've never heard of Motech before! Their website also upsets me! I don't like the stupid names they've given their maps (like the "X Map")!

as above + piper cams????? was this mapped with these as i know the 1.8t doesnt like different cams and ths could be causing issues

26psi is huge and as its spiking will kill theturbo in no time and the ecu will see its to high and tail it off very quickly

Don't worry about figures from a rolling road, no two rolling roads are the same, you could take that car to another rolling road somewhere else tomorrow and make 210bhp. Mine is standard and made 189bhp on one rolling road and 173bhp on another

26 psi sounds ridiculously high, even Custom Code remaps don't go that high. I'd say running that kind of psi might have ruptured a pipe somewhere.

dont worry lol to much down on that one must have a problem lol

i know dyno are not the best but saying dont worry when it should be seeing 215 bhp and didnt even make 170 lol not the best advise again is it :S

I'm just pointing out Clive, for the benefit of other readers, that rolling roads are not the be-all and end-all and will all give different figures. The OP obviously knows there is a problem with the car, and he's been lucky enough to go to a RR where the operator has noticed that as well

Where are you based? I'd personally take it to a specialist, someone like R-Tech and get them to look at it.

26 actual PSI? 1.8 bar?? Got to be a mechanical problem somewhere I reckon but I'd be asking why that level of boost is being allowed without it going into limp mode. The ECU can only read 1.55 bar so boost getting close to that should throw an overboost code. If it doesn't then I would be asking your tuner some questions.

Aye overboost should throw a code and put it into limp. Mine went into overboost once on a RR after fitting the N75J and gave a very poor figure (160bhp ish iirc). Tried it a few minutes later and it never went to limp and gave a good figure.

Edited 19 August, 201015 yr by martziniuk

No overboost codes via VAGCOM just the speed sensor and brake sensor codes (can't remember of the top of my head ATM).

Beginning to wonder if I've bought someone elses problems now.......

....it had a brand new turbo about 2000 miles ago, wonder if thats why it went (apparently the seals went and it was whistling hence it being changed)

Right, I reckon I'm gonna get it booked in at R Tech in a couple of weeks when I'm off work and see what they've got to say, surely worst case its gonna be new sensors/boost valve(s) and another map :(

From everywhere I've looked (including golfgti.co.uk forum as the wife's got a Golf GTi Turbo) their rep is fantastic.

No overboost codes via VAGCOM just the speed sensor and brake sensor codes (can't remember of the top of my head ATM).

Beginning to wonder if I've bought someone elses problems now.......

....it had a brand new turbo about 2000 miles ago, wonder if thats why it went (apparently the seals went and it was whistling hence it being changed)

Right, I reckon I'm gonna get it booked in at R Tech in a couple of weeks when I'm off work and see what they've got to say, surely worst case its gonna be new sensors/boost valve(s) and another map :(

From everywhere I've looked (including golfgti.co.uk forum as the wife's got a Golf GTi Turbo) their rep is fantastic.

I've had my car tuned there and they really seem to know there stuff bud. Keep us posted on what they find.

Will do, gonna book it in for when I've been paid (skint myself buying stuff for it already!)

Hope its not too bloody expensive!!! This car was meant to be a cheaper one than my last one!!!!

what was your last one?

and youve made a mistake coming on here lol, this sight helps you empty you wallet.

I know mate.

good luck gettin it sorted.

what was your last one?

and youve made a mistake coming on here lol, this sight helps you empty you wallet.

I know mate.

good luck gettin it sorted.

It was a BMW 530d M-Sport Auto, nice but fragile as hell!!!!! Can't take the abuse a 26 year old gives it!!!!!

Edited 21 August, 201015 yr by Rob_OctaviavRS

Knowing who writes the software for the motech maps i'd be suprised if it was software related.

Needs looking at in a methodical manner though, get it booked in somewhere.