Kingsize K2

Now, I am sure this isn't due to me not being able to change gears properly but if I am driving at full pace, when I engage a higher gear and release the cluth, I get a moment of hesitation for a split second before bang, I'm back on full boost again...

It has been suggested it may be due to my pressure plate not engaging properly. My cluth was recently checked and is it good health.

Any suggestions?

Kingsize K2

Anyone

bruce

iTrader: (5)

Could be slight overboost, what year is your car?, mine does this occasionally, its an MY97WRX with the two port boost solenoid. Would anybody know if this is expected with it and would converting to a 3 port be of any use. Doh more questions than answers --- sorry.

Hakon

Kev,
That will be the vta dump you have NO but seriously hows it running ?
Gervase
Woops, meant to be a wink


[Edited by Hakon - 3/27/2003 7:12:59 PM]

TonyBurns

iTrader: (3)

Its actually called turbo lag

Tony

Andy Hobson

I get this on my MY00 with Tek2.5, full decat and induction kit. It's always been there but I find I can drive around it by giving it more throttle as I lift the clutch. A bit like you would when pulling away from standing only faster. I takes a bit of practice but I now find that most of the time I can get it back on boost pretty much straight away.

Andy.

currymonster

I have an MY 2000 standard part from scoobysport back box. Does exactly the same thing. Just have to be careful when doing full bore changes, slow it down a touch. Will look to DRJ motorsport when clutch change time comes as they supply and fit jap sourced clutches they say are superior to standard. Hopefully that means no judder or the hesitation as you've described,

Cal

TonyBurns

iTrader: (3)

Actually there is no way of driving around turbo lag its due to having the turbo in the first place you do actually get use to driving with it though
The basics are that when you change gear, the gasses get dumped, this spins the turbo down, the new lot of gasses then spin the turbo back up, the gap between spinning down and spinning back up is the lag
Even with the best dv's your going to suffer the same fate, but there are a few tricks Subaru have been working on (the twin scroll thing which keeps gasses coming in quicker so you get less lag).
Smaller turbos dont suffer as much as larger turbos though as the blades take less time to regain momentum, but just enjoy it, the lag then kick is all good fun

Tony

TonyBurns

iTrader: (3)

READ MY POSTS!!!
You may learn something
(and its not the clutches either )

Tony

Kingsize K2

Bruce - car is MY99 STiV. Hoping to get a blinking boost gauge in the next week or so so will be able to tell...

Hakon - lol Am pretty sure it isn't the VTA as I've been out with a Scooby regular who seems to think it isn't the DV.

Tony - pretty sure it isn't Turbo Lag?? I can recognise when I get lag but I think this is definately something more serious...

Andy - won't driving that way wear the clutch quicker?

I can drive around it by not rushing when changing gears under hard accelaration but that kind of defeats the point doesn't it "Great straight line speed but whoops, don't change gear too fast!"

Is a Jap spec STi cluth the answer? Was told a month ago my clutch had half the meat left on it...

Very confused K2

TonyBurns

iTrader: (3)

King,
its definately turbo lag, my scoob suffers exactly from the same thing (acutally all turbo'd scoobs out of the factory suffer the same) its not what people normally refer to as lag (as they dont know what they are talking about ) as they think lag is just when your not in the turbo (which isnt lag as such because you have to have the turbo dumping gasses to get lag, see above for reason for lag).
Its basically, flooring it, hitting 1.2bar, 6k rpm, change up a gear, floor it again, small pause, big kick and off you go

Tony

Kingsize K2

That seems to make sense

So, the solution?? BTW, don't want to hear the words Motec, Gems...

Will a VTA contribute/ help at all? Hakon seems pretty keen for me to lose mine

Bob Rawle

A VTA will cause this, as you change it vents the air from the intake and sends the car rich then instantly lean, the result is you get a flat spot, change back to a recirc and try it then.

Bob

Kingsize K2

First step, lose the VTA then! I will replace it with the standard re-circ and see if that solves the problem.

I'll keep y'all posted. Thanks for the advice

Hakon - seems like you win... for know

Andy.F

I believe this is a fairly common problem on 99/00 cars. John Bank's car does this when I drive it and ****** it through the gears, John has learned to drive it differently, he slips the clutch a little bit between gears and there is no power cut.
It's not turbo lag, I logged it on the AP22 and it is an instantaneous power cut, then back on power, just like someone turned the key off/on.
As Bob says, possibly a weak/rich blip with the fueling when using VTA. John however uses a recirc dump valve, I guess it could still be backrush expansion of air confusing the MAF signal to the ECU.(although it was not detected on deltadash)
As you say, even at full rpm, with a 'slightly' slower shift it doesn't happen, the power is there instantly

Andy

Kingsize K2

Andy - nail on the head

I will try replacing my VTA with the standard re-circ and see if that makes the difference. If it does, I may emigrate to Forge land I may also consider a remap (EcuTek).

Having to adapt the way I drive seems a little "inconvenient" to say the least! I love the car and all if offers and as such I take into account many things, such as warming it up, cooling it down, not dumping the cluth etc, but not being able to change gears quickly because of a glitch is a pain in the glass

After all, this is supposed to be a performance vehicle. Must seriously affect acceleration figures if between each gear you have to pause so as not to upset the car

To be resolved...

TonyBurns

iTrader: (3)

Andy,
Ive watched my boost gauge when doing a change high up in the rev range and that agrees with me that its re building up the boost (thus turbo lag) now if you slip the clutch, all you will do is increase the boost smoother (without a pause because your slipping it) and wear the clutch out
All of the subaru's ive been in, from an MY93 wrx to my own car have suffered exactly the same, its not just down to the MY

Tony

DaveMcC

My MY00 has done this from new - a "feature" according to the dealer. As others have said, learn to drive around it.

Can't see it being turbo lag (unless the scoob has a particularly bad design) as I had a Nissan GTI-R before the scoob and it never did this.

Dave

TonyBurns

iTrader: (3)

You have to think that all turbo's do suffer lag, the higher the boost the quicker the turbo is spinning and when changing the longer the lag (takes time for the turbo to run down/run back up) but yup, it is lag (thus why dta's are not as good as re-circ )

Tony

Andy Hobson

I was hoping my Tek2/2.5 remap may have solved it as it fills in a big lean spot around 2,500 rpm. I have the standard OEM re-circ dump valve so I don't think it can be blamed solely on that. I must admit I'm surprised no one has pin pointed it by now with Delta Dash etc... Any ideas Mr Banks ?

With regard to the clutch I guess it may cause more wear but then you can get an AP organic !

Andy.

TonyBurns

iTrader: (3)

Fact!
All turbo charged cars suffer from lag, cure is simple, dont use a turbo

Tony

JKJ2

Sorry to jump on the end of this thread, but are we saying here that the standard fitment to a '98 Scooby is a recirc DV. I am contemplating changing mine to a Baileys DTA valve, due to erratic idle problems on my PPP car, and was under the impression that the original already fitted was a DTA, I say this as the one in place at the mo is just a black plastic cylinder to the right of the intercooler as you look at the engine, and must be the OE fitted, it's too drab to be anything after-market, but why the loud discharge at gear change if it's recirc. I suspect mine is leaking and possibly not holding boost as I can hear a constant whoosh as the turbo spools up and presumably boost builds, but do get the usual louder whoosh as the DV does its job. My reasoning behind the change apart from the idle problems is that the performance seems to be impaired. Any thoughts welcome.

nom

You'll get the 'woosh' noise on dropping boost if you have an induction kit (rather than the standard box thing) whether it's a DTA or re-circ.
The noise of a BOV giving up is a blowing-over-bottle noise at high boost; constant woosh as the boost builds would be induction again!

TonyBurns

iTrader: (3)

JKJ2,
that could be a MAF sensor problem if your idle is iratic, i would get down to a dealer and see if they can diagnose the problem!

Tony

Andy.F

Tony

This problem, which is particular to 99/00 cars, is NOT turbo lag. That is NOT as in NOTHING LIKE turbo lag
Example - If you take an early car with the same TD04 turbo or even the bigger TD05 'laggy' turbo and drive it the same way you do not get this problem.

Kingsize/Andy John Banks is on holiday until Saturday, he may have more info or even a solution to this

PS Tony It's really really really not turbo lag

Andy

Kingsize K2

Andy,

I have to agree, it isn't lag at all. I know when it comes and slaps me in the face. This ain't it! I have no doubt many cars do suffer from lag, but this problem has developed on my car and was not present when I first had it.

Not that I want to start a fight with Tony or anything

I am soon seeing Dr Bob and hopefully he'll be able to solve my woes

spence7

I agree it aint turbo lag at all....it's more like a momentary fuel cut. Turbo lag is when you're in the turbo range of rpm but you're not flooring it, and when you decide to floor it, the time it takes to reach noticeable levels of boost is turbo lag. It's a smooth progressive regain of power, not straighaway hence the term lag.

The phenomenon eveyone's on about here has the symptoms of an immediate cut to the power - jerky - literally on/off power for literally tenths of a second.

I don't know exactly what it is but I think it's a fuel/boost spike and fuel cut situation. The car literally jerks off (ooer) the power for a split second before raging on.

Only get it in low gears personally !

nom

Lack of transient fuel enrichment (or the correct amount)? Think that's the phrase... when an extra fuel squirt is needed when the throttle is suddenly opened - that thing
Would fit with the leaving-foot-somewhat-down-when-changing-gear getting round the problem as then there's less of a transient...

Andy Hobson

Great ! Thanks for confirming it's not lag guys, similar in some respects but as has been stated it's more severe, like a momentary fuel cut.

Spence7 - can confirm it's most noticable in 2nd / 3rd shiftup and by 4th it's gone.

Nom - I wonder whether an uprated fuel pump / regulator might help. I look forward to hearing from JB on this as it's the only minor niggle I have left with performance (until I decide I need a TD05 front entry / FMIC / ..... of course )

silent running

Worth resurrecting this thread as it seems to be exactly the phenomenon that I've got in my 98 WRX - a momentary off/on hesitation when I suddenly open the throttle. Thinking about it, it may have been there ever since I got the car almost a year ago, and I just learnt to 'drive around it' even though it's an annoying trait which no other car I've ever had (turbocharged or not) has shown.

When I suddenly prod the throttle I can clearly see boost rising the instant I floor it. Then a fraction of second later, the accelerative drive comes in with a bang. I used to have an old 200SX with an auto box and it was kind of similar on a full bore run. But of course the difference was I knew that was the slush box causing the transmission lag, if you could call it anything.

Any ideas? And no it definitely does NOT feel like turbo lag in any way. Unless it's a turbo that can be showing a good 15psi of boost but not actually release any torque into the drivetrain until a tenth of a second later!