j900ase

Any ideas on this prob. New age 2003 APS fmic, APS 3 1/2 exhaust, APS dump valve, Walbro pump, Injen cold air intake, ECUTEK etc.
Car makes 1.5 bar in 4th 1.6 max, but change to 5th or 6th and boost steadly rises to 1.7 prob more but i back off then.

Thought electronic boost control was fault or pipe split so put new pipe on straight from turbo out to wastegate. (no restrictor)
Still does it, boost slower to build as you would expect but climbs like mad above 4000rpm in 5th and 6th.

Then thought wastegate must be sticking so held it permantly open with mole grips on shaft, still the same boost takes longer to come but hard acceleration in 5th or 6th will still cause massive rise in boost above 4500rpm.

You can here exhaust note differant with waste gate open and you can see shaft moving, so one would assume penny opening (and slower to rise held open so must be closing opening some what.)

Only had massive boost prob since last week, but had fitted open exhaust 4 weeks prior never noticed any prob after fitting exhaust but cant remember really looking too much.

Boost pressure is being measured on Defi BF gauge allways showed correct as far as i know and vacume is reading 0.6 idle 0.8 over run which i belive is about correct.

Any help or ideas Thanks Jase


edited title for differant fault same car etc.

ZEN Performance

The problem is boost creep caused by a combination of the free flowing exhaust, poor flowing turbo wastegate and cold dense air.

The solutions are to either:

Remove the turbo and port the wastegate.
Replace the turbo
Restrict the exhaust

The porting option is going to take around 5 hours of labour including the removal and refitting of the turbo, and all round is likely to the cheapest option. If you were thinking of getting a larger turbo, now might be a good time to consider swapping, but expect to pay the best part of £1000 for a worth replacement.

Paul

Andy.F

Porting job was done within 2 hrs on Wednesday at AWD motorsport when I had a boost creep issue whilst mapping their customers WR1.

OE turbo is good for 330 bhp before you need to consider an upgrade.

Andy

j900ase

O bugger, i thought thats what you would say, been running through many different causes in my head, and thats all i could come up with.

Kind of guessed that in 5th and 6th your in gear so long turbo spins up enough to over come open wastegate and still provides too much boost.

Run out of money at moment so will try noise reducer i got with exhaust ( bung for end ).

Thank you for your very quick and informative response, i will post my results, got a feeling my credit card wont like it though.

Jase.

j900ase

Fitted noise reducer yesterday, spot on know, even trying really hard only goes 1.6bar max for sec then settles down to 1.5bar.

Cant tell if any less power dosent feel like it, rolling road well tell though.

Just got to try and get engine to take some boost at bottom end know, lost when front mount fitted. Capped at 1.0bar till 4000rpm because of compressor stall.

warrenm2

Doesnt the in gear compensation in the remap take care of this?

j900ase

Take care of what?
Over boost in 5th or 6th or boost being held back to 1.0 bar.
Questioned mapper on in gear mapping he said all done in 4th gear and no differant maps for differant gears.

ex-webby

Is this a WRX or STi?

Regards,
Shaun.

GBruce

Hi,

I had this problem on my classic uk turbo, although on a 20g turbo. frequently went to 1.8bar. I got rid of MOST of it by removing the splitter in the cast downpipe bit at turbo joint. May be worth trying though? I just ground it away completely so the mouth of it is similar to the old scoobysport style downpipe. (open neck) it now has a bit of boost creep but nothing like before.

George

j900ase

Shaun its a STI 2003 UK

Referance boost creep, not a prob now noise reducer in. Cant be bothered to take exhaust off again so that will do for know.

Prob i would like help on is with standered top mount, Injen cold air intake, 3" exhuast, sports cat, ECUTEK remap, fuel pump, it made loads of good boost low down, with no hesitation etc. Looking at my boost map 3000rpm 1.3 bar, then fitted APS fmic same map went like mad foot to floor no probs. But when accelerating 2/3 and backing off slightly, car jerked badly like overboost cut.

Went for 3rd remap problem solved by capping boost to 1.0bar till 4000rpm then letting go to 1.50 bar from then on.

Mapper told me it was compressor surge caused by turbo spooling up faster than engine can use air. At this time had sports cat in downpipe, so changed exhuast for open APS 3 1/2" race exhaust in effort to get gasses
through engine quicker.

Now make more power top end but surge/stall worse had remap, boost targets lower to make driveable before 4000rpm.

If fmic causes more lag how come turbo spools up quicker and harder than before in theary would turbo allways be trying too catch up engine with long pipes and huge intercooler to fill up.

ZEN Performance

Surge low down is a seperate problem from the creep, the backoff judder can be reduced severly, there is a thread kicking about dedicated to that very subject. What dump valve are you running? DV choice and setup are important factors in reducing the lift of judder that can come with transient surge.

Paul

j900ase

Hi thanx for your interest.

Aps dual vent BOV fitted.

Looked up many threads could not really find answer, loads of similer symptoms no deffanate fix.

Boost creep no longer problem with fix i have done happy for now with that.

Would like to sort problem with low torque around 3000rpm since fitting fmic,
when i took it to be mapped told problem was compressor stall so boost targets had to be held back 1.0 bar instead of 1.3, hence low torque, no power rush.

Car ok like this to drive but very flat at bottem dosent really get going till 4500rpm+. I kept small turbo in effort to keep quick spool up/fast response but dont seem to have it.

The best way i can describe problem i had before remap to lower boost is....

Driving along road 4th gear on edge of power 3000rpm look to overtake, go for it foot to floor, then you see it is not clear have to back off a bit (not completly) and violant judder and banging, so bad you have too slow right down.

Sometimes you could get it accelerating 2/3 in high gear as it came on strong boost.

Any help...Please...

Andy.F

Your OE turbo will not be entering surge whilst on full throttle at 1.3 bar @ 3000 rpm, your problems are part throttle issues which as Paul has mentioned are mainly due to air backrush across the turbo. The dump valve strategy will be the main player here, killing the turbo response is not the best way to deal with it in my opinion.

Andy

j900ase

Andy,

What should i do? Fit non recerculating dump valve? i.e.vent to atmos,
or fit non vent to atmos i.e.standered one.

Or keep my adjustable, but do i need to soften or harden spring?

(mine is duel vent)

ZEN Performance

The thread I mentioned is here:

http://bbs.scoobynet.co.uk/showthread.php?t=467907

There are some suggestions from various people, myself included, along with feedback from a number of people with similar problems. read and inwardly digest

Paul

j900ase

Yes thanks, allready read that thread, but read it again anyway.

So as soon as i can will soften spring to least pressure and fit 8mm hose to bov
on standered point at moment, may move closer to bov if poss, or tap dedicated hole in manifold close to bov.

One question though... i thought that light spring caused problems with maf reading wrong amount of air in system, or am i reading it all wrong (probley read so much on this my eyes hurt).

Bob Rawle

The aps bov leaks like a seive and so is merely masking the problem, the VF35 (which is what should be on the car) turbo is renowned for boost creep, get the wastegate ported properly and that will fix the problem, a map adjustment to compensate will restore the spool, restricting the boost like that is dulling the cars natural reponse. The factory bov is the best solution and sticking with that and an appropriate fuel and ignition map should sort the jerkiness.

Mark your ecu code does have in gear wastegate compensation but this only has boost compensation which will not help a surge problem. As you know I always set the boost response base line in 5th for a six speeder.

Andy I would disagree, 1.3 bar at 3000 rpm is too soon for the VF35, well on the way to surge at that, better off hitting one bar at that and full boost at 3300 ish. Engine doesn't do much down there in any case.

Bear in mind that you have tight piston to bore clearances and if they are close to minimum you could pick up.

bob

j900ase

Update on bov problem, measured opening vac on my mates car (standerd but same model) then compared with APS .

APS moves slighlty sooner (less vac) but sticks and then needs a lot of vac to open more than a small amount. Took it apart and cleaned it no better, does not leak vac from pipe or piston will hold 30hg for ages.

So fed up with this, ordered Forge recric adjustable valve today 7psi to 35psi 50mm piston. Spoke to Mark Lowe at Forge he said this is what there valve is designed for, i.e. getting rid of high volume of air fast.

Going to start with opening pressure of standered then work more or less from there. Will post results and pressures as soon as.

Thanks everybody for your advise and input Jase.