Ben v7

To illustrate the problem and where it is most noticeable...

Full throttle in 2nd over 5,000rpm then go part throttle (about 50%). Engine power drops as you expect before surging suddenly for a split second... all happens very quickly but enough to jolt the whole car and cause a lot of weight transfer - not good when it happens in a corner.

Any ideas what is causing this? I have a two port boost solenoid and was wondering if it might be an issue with not bleeding off the boost quickly enough.

dowser

It is boost related - sounds like your DV is staying closed or blocked off. When did it start happening.

Richard

Ben v7

I've noticed it once or twice before but on the committed drive home last night it was very noticeable... it has the standard re-circ fitted...

jaytc2003

iTrader: (1)

what year of car do you have? If it has a tek management (think thats right) then if you hold it for so long in 2nd you wont get full power. Its a feature of the software

Ben v7

2001 car, EcuTek mapping (Tek 3).

It's not a gentle restriction of power - say like the cut to half boost at an indicated 148mph...

Its a violent jolt where it feels like the boost is cut as you'd expect as you go from 100% to 50% throttle, but then a split second later blips back up to maximum. It feels like the boost has been flicked off and then back on at maximum for a split second before settling down again...

It's not very pleasent and concerned not only with the impact of it doing this should you need to reduce throttle mid corner but also the sudden shock to the transmission and lack of fueling for this boost spike!

It's absolutely fine flat out through the gears with fairly full bore gear changes...

Could this be an issue with the re-circ valve as suggested?

What does it feel like if your 2-port boost soleniod is unable to cope?

Thanks for the help so far and any advice is much appreciated.

Palmo

I have had the exact problem you describe with my car (MY02 v7 WRX). This began to occurr only after a Tek 3 remap (along with several other mods). Like you say, doesn't happen on full throttle, only when lifting to half throttle at about 5200rpm in my case.

Following the remap it did this everytime without fail. I then took the car back to have the map adjusted, and spent almost a full day driving the car while the mapper adjusted things all with little effect to begin with. The car was initially using the standard recirc DV. However, as a test the mapper changed to an aftermarket DV which did seem to improve (but not cure) the situation. The map was then further adjusted until it is now much improved - very ocassionally does it in the right conditions but very rarely. However, I never got an explantion as to why the car was doing it in order to understand the cause of the problem. I have continued to use a dual port aftermarket DV since.

Would be really interested to know if you get to the bottom of this as mine is not 100% cured - probably about 95 - 98% though!

Ben v7

Cheers for the reply Palmo...

I'll raise it with my mapper / garage and if I do get to the bottom of this problem I will let you know.

dowser

What boost are you running? I had this on my old 2.0 when I blanked off the DV - going from WOT to 50% throttle caused an air wave from the turbo stalling to pass MAF in wrong direction and confuse the ECU. It can be used successfully on track to kick the back end out entering corners....but not necessarily what you want for street use

Never heard of new-ages doing it on a stock set-up, but it is possible that (with high enough boost) airflow through the DV is enough to cause a shock wave from turbo impellor to bounce back into MAF. Do you run stock turbo's and TMIC's?

Note that mapping out the problem would likely cause loss of WOT performance if it is a mechanical limitation.

Richard

Ben v7

Richard, it sounds like it could be something like that. Makes sense and explains the varying nature of the problem. The car has the stock TD04 and TMIC running 1.3-1.4 bar. Those were my thoughts exactly on having the problem mapped out.

Palmo

Mine is running lower boost @ approx. 1.25 bar and too has the stock TD04 turbo but is now running an STi 9 TMIC (fitted after mapping and doesn't seem to have made any difference to this problem).

The only thing the mapper referred to - and I may have got this wrong / mixed up - was that it appeared when the car did this 'stutter' a small amount of extra fuel was being supplied for no apparent reason for a split second when lifting to approx. 50% throttle and it was difficult to map around this due to the way the ECU measures the amount of fuel/air going in but does not measure the amount being recirculated (as this should have already being metered). Not sure if this makes sense and if I have got this correct? He also made reference to the fact that it is very possible that there are hidden tables contained within the ECU with access to adjust these not being made available making the situation even more difficult to 'map around'.

My mapper is a well respected guy with a lot of connections in the industry. He made a number of calls (including a call to a friend / connection in Prodrive amongst others, including contacting EcuTek) but no one had heard of this problem before.

Ben v7

Be interesting to know if it is definately the case that excess fuel is being supplied momentarily. My biggest concern was that if it is boost spiking at that point in time without the additional fueling then the engine will be running very lean for that split second. Perhaps it is a question of a parameter that was fine for normal boost being hidden from adjustment... but then why isn't everybody running an aggressive map noticing this effect?

Agreed that this 'surge' can be used to kick the back end out, but not really what I am looking to do in this fashion on the road. Still it is forcing me to drive 'better' as you shouldn't be lifting like this mid corner and it doesn't happen with a normal upshift anyway...

It is noticeable in 3rd usually too, but more pronounced in 2nd as you'd expect.

Palmo

I reckon your comment above about a parameter being fine for normal boost but being hidden from adjustment could be about right? I guess we need some of the top engine mapping guys on here to shed some light. As I say, mine is now much better but not 100% - who is your mapper?

From what my engine mapper told me, there can be quite a few variances between ECU's - even those fitted to the same on the same year, so maybe we're unlucky and have 'problematic ECU's'? Would go some way to explain why everybody running uprated maps are not suffering from the same issue.

Mine sounds like yours in that it is more pronounced in 2nd, but I'd have to say that it is generally more annoying in 3rd because I must seem to lift more from 5000 rpm in 3rd than in second (due to speeds involved). I have a mint series of country roads near where I live and when driving fast it's always 3rd that it shows itself without me particularly looking for it, if you know what I mean.

What model and year is your scoob by the way - mines a MY02 WRX - it is also a 'UK Spec' European Import from Belgium. Would be interesting to know where yours is from?

Ben v7

It's a possibility - definately go do with some 'expert' info around this.

Yes Subaru are always changing the ECU code but when mine was mapped it was flashed with the latest version applicable. Would of thought the hidden tables would of been overwritten anyway.

I generally use 3rd more too but there are a couple of tight bends on a few of my favourite routes that benefit from a change down into 2nd. It is disconcerting when it happens and your already driving in a committed fashion isn't it!

Mine is a very early 2001 UK Spec - one of the first to enter the country. No clues there given yours is a 2002...

Palmo

We certainly could - where are you guys - Andy F / Bob R / Paul B / Pat H.....anyone care to give some advise?


Agreed! Thought it may be along those lines but it seems not! Oh well.

Let me know if you find a definite cause of the problem (I'm fairly sure it's fuel related) and/or a workable solution.

Ben v7

Can no one else shed some light on this?

Andy F / Bob R / Paul B / Pat H - please guys... one of you mapped mine after all.