Vauxhall Owners Forum banner

astra vxr drawing air/no boost

22K views 17 replies 7 participants last post by  scooby-KILLER 
#1 ·
hi all,

wonder if anyone here can shed any light on this,

had my car on the rolling road at the mig day, only made 216.8 max with no boost,

operator says its an engine management fault, the car is drawing in air so to compensate is overfuelling and not boosting,

recently had a new gm turbo fitted by an approved garage and at the same time had my forge recirc valve fitted,

the car has been put on diagnostics and nothing is showing up fault wise, it has now had a smoke test (apparently) and is showing no leaks,

im unsure whether this could be down to the recirc valve not being seated properly or if im going to have to have it underload to try and narrow the fault down as in the words of the mechanics it only seems to be happening under load,


if anyone can help with any info itd be a great help as im starting to get at my wits end with it, :face:
 
See less See more
#4 ·
it wasnt just the one of us that was told this, hence im just repeating what the operator told me,
the problem i have is that after a smoke test, no leaks were found,
yes it probably did boost, very little, so if theres no visible leaks what else could it be?
 
#7 ·
Not that I know of mate, just tests your boost pipes. Which boost guage have you gone for? And just ask questions mate, only way to learn ;) And read other posts, especially on Astra owners club, a lot more zlet & leh problems than on here
 
#12 ·
216bhp and standard is 230? your worring about 14bhp from a 6 year old car? every dyno will read differant, so tomo you may make 230 on someone else dyno.
Did they give you a AFR Print out? may help.
How was everyone else readings? where they all down? where was the car run?
I suspect your chasing something which isent there........
 
#17 ·
Off all the cars that were there, the Z20LET and the two Z20LEH's struggled to make good power. All three were creating boost, just not enough of it. From memory, all three made good torque figures which would suggest they were coming on boost hard and strong, thus creating a big big torque figure however as soon as the overboost had done it's bit, all three were struggling to hold boost to the limiter and hence struggled to make good power. If I remember correctly, James' did something like a bar then dropped down to 0.5bar - or around 14PSi then held around 7PSi whereas a healthy VXR should hit 14PSi and hold around 12PSi.

I wasn't paying attention during the run so can't comment on the AFR ratio but we'll check. Think we'll whip the boost gauge off the Cavalier and plumb it into the VXR and take it a run and see what she's hitting overboost wise and what she's holding. From there, it'll be case of checking for any leaking in the system which could be leaking boost/drawing unmetered air and would certainly cause to to drop boost significantly. It could also be a boost control issue however the boost graph was smooth, not spiking but bypassing the rear and removing the vac box will eliminate those and if need be, I'm sure Coo will let you borrow his front BCS and map sensor to eliminate those. Then again, it may just need one turn on the actuator to help nip the boost level up a bit although it should be set from the factory... but worth checking.

With regards to the rollers and the opperators, I wouldn't question them. The C20LET cars and the NA cars were fine (bar a couple of issues) and of the 3 or 4 standard cars that were there, they all made pretty much bang on standard figures. Personally, I'm going for a boost leak or a boost control issue - the Z20's seem prone to those sort of issues.

To the unit, bring Jaffa Cakes.
 
#18 ·
Dave has hit the nail on the head. My graph started of good/strong then dropped of then steadily struggled. I wasnt doubting beardy's knowledge just more so the fact He said we are chasing something which isn't there and questioned the RR when the mig day was done on better equipment than before and my result was worse than it previously was and there has been no change to my car
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top