scoobyboy

it's a 2000my turbo with full de-cat induction kit and hks bov. it has been to other garages and has now come to us. before the downpipe cat was replaced it pulled fine as soon as it was de-catted it lost some boost pressure another garage reckoned it was down about 2-3 psi. the restrictor was changed from a 0.9 to 0.8 which gave it back some boost but it now surges under hard acceleration to the point where it makes him feel sea sick! the waste gate starts to open at 7psi which seems a bit low i think and the maf has been done and the o2 sensor is switching.any ideas before i get buried in books and i.m technical.

TonyBurns

iTrader: (3)

When you mean surge do you mean overboost??
I had a problem (well 2 actually) where id decatted my MY00 PPP car, i was getting overboost (surging) in 4th/5th gears, i drilled out the restrictor plug slightly and this cured the problem
The other problem i had wasnt really surging, just loss of boost at 4k rpm, that was just a dirty solenoid. (probably wont have anything to do with the above though).

Tony

The_Judge

What is the boost doing when the surging occurs? If it's changing at the same rate of the surge, I'd put money on it being a sticking wastegate solenoid. If the boost is steady during the surge, sounds more likely to be MAF.

The wastegate is supposed to open at 7psi.

PARTS4U

I am guessing that you have the same problem as my my00
from 2000-5000 the car has a slight surge, boost stays constant ,and you can hear the wast gate opening and shutting ,the car is fitted with full decat +ppp + dawes
any ideas anyone ????????

Jim_B

iTrader: (1)

If this surge is like a sort of power on, power off, power on cycle in the higher gears at about a 1 second interval - then I had this and fixed it by cleaning out the boost solenoid.

The_Judge

PARTS4U,

More likely to be MAF in your case, for 3 reasons.

1. You're using a Dawes, and therefore your wastegate solenoid is out of the equation.

2. Your boost remains constant.

3. It's a MY00, and the MAFs are ****e...

PARTS4U

Thanks judge got a spare at home will try it tonight !!

The_Judge

Dunno whether you've read this thread, might be of interest...

scoobyboy

it's not overboost this is a gentle surging through out the rev range the maf has been changed for a brand new one so i know it's not that and so has the control valve the weird thing is if you take the pipe going to control valve off the 't' piece by the turbo it accelerates normal until over boost kicks in. if i put a bigger restrictor in it loses boost pressure to the point it's only getting about 10psi a standard turbo should have about 13psi.
the waste gate is tight theres no movement in it so i dont think thats knackered starting to get stuck for things to try now

TonyBurns

iTrader: (3)

ECU reset?
Could it be the fuel??

Tony