ScoobyJawa

On the way to the Sussex meet today, in 4th gear and as soon as the car hit 5k revs the boost dropped to 0.7kgf/cm (about 0.65bar) on my defi gauge and then a few seconds later went back up again. Car is an MY99.
Coming back home down the dual carriageway I was getting it every single time I hit 5k revs in 4th with my foot to the floor.
I don't think it did it in 5th (only tried once as that means going a bit quick ) Have also noticed it doing it in 3rd but again not quite as bad, possibly to around 0.8, and a pop or bang from the exhaust as it did it (not a backfire!!)

When the engine had cooled down a little it didn't do it the first time but next attempt it came right back.

The peak on my defi is reading just above 1.2(and has done for over a week now, its not changed) and held boost is in 2nd about 1.0 in 3rd about 1.05 to 1.1, in 4th is around 1.1 to 1.15kgf/cm, about 1.15 in 5th. The defi under reads by about .1 I think so I should be way off the fuel cut at 1.25bar (1.27kgf/cm ish on the gauge).

I've been hearing a lot more noise from the dump valve lately (Standard recirc) and wondered if it was possibly leaking air around 5k and thus dropping the boost?

Or any other ideas as to why it might be doing it?

Cheers
Neil

john banks

Any mods? I can't remember if you run a Dawes or not?

ScoobyJawa

Oops Full decat, ITG panel and dawes

john banks

Put it back to std boost control and see what happens then. Remove mods first is the general principle.

ScoobyJawa

Bu99er Knew you were gonna say that

Hopefully give it a bash tomorrow night.......

john banks

You COULD be hitting fuel cut? It is not THAT ferocious? Normally you would hit it a bit lower down the rev range. It seems like you are running a bit close to fuel cut. Before removing the Dawes why not turn it down to 0.9 bar and see what happens.

ScoobyJawa

John,

It is not that ferocious at all - its more like a drop on power for a couple of secs and then back on power. Its nothing at all like the fuel cut that I've been told about and is more like the boost cut that Bob Rawle talked about. Thing is the gauge is the same thats always been on and at PE running with the select monitor 1.1ish equated to just over 15psi that the ecu was seeing, so at 1.15 on the gauge is it possible to be that close to the 1.25bar cut???!?!?!??!

When I went to the dealer I put back the OEM pipework and was still holding 1.0 bar without the dawes so to set it less would be a drop in power from OEM???????

Very strange
Thing is its never done it when setting up with the engine hot and only today after the long run so theres a chance it wouldn't even do it tomorrow if I left it alone!!! I imagine I'll just have to play about some more

john banks

Don't know m8. Holding a genuine 15 PSI would be quite impressive for a standard car. Peaks are another matter. I would just turn it progressively down as far as you need to to see if the problem disappears.

ScoobyJawa

Its always been said that my car was very quick even when standard and also when fitted with the decat......

When I took it back to the dealer (30 miles away) it was peaking about 1.1 and holding about 1.0 on the OEM boost pipework but with the decat and ITG still on..........

Seems a bit weird, What sort of turn increments do you think I should try, 1/4 or 1/8th?

Cheers John

neil.

NB - Scott W has the same setup almost and similar gauge readings in each gear, he's hit the fuel cut on his gauge around 1.35 indicated, but he commented today that I seemed to be noticably pulling away from him. Suspect the gauge must be way out.....

john banks

Try 1/2 a turn to start with but go by the gauge even if there is an offset the relative changes will be about right. Drop it to 0.9 bar and if the problem goes you know it is boost being excessive and then you can turn it up until you get the problem again, then back a bit, but I for one would like to know WHY it it is happening.

ScoobyJawa

Was getting low figures so I upped it half and all seemed ok (having also previously stretched the spring, about 30% longer then release) and increased the bleed to 2.0mm a week ago) but obviously not - perhaps if I reduce by 1/4 that might solve the problem........
Could it be that after stretching the spring over the week its settled a bit and needs a final bit of fine tuning?

What do you mean by WHY it is happening? If I turn the boost down and it goes then thats the problem but do you mean if I turn the boost down and its still there? I suspect if thats the case I may return to OEM setup and look towards and EBC or something like that instead........

john banks

Yes that is what I mean by the "why" question.

ScoobyJawa

Thanks John once again - you are as always very helpful in troubleshooting this sort of thing Cheers mate, much appreciated to have someone to knock ideas/problems around with - especially at 8pm on a Sunday eve

mutant_matt

It sounds to me very much like you're hitting the fuel cut as it's not nearly as violent as it had been described on here when I encountered it for the 1st time last week.

It sounds like the Dawes being set a bit high to me so like John said, just take the Dawes off and see what happens (as this takes all of 5 minutes). If it's still a problem, do you have the OE Turbo out pipe / IC inlet pipe or a Samco (or alike) one? I ask because Stelios (I think) had this problem and it turned out to be a collapsing Turbo hose which he got replaced and cured the prob.

Does sound like the Dawes though.....

Matt

john banks

dodgy dawes try another?

T-uk

check that the Dawes spring and ball are clean,if the cars been serviced recently it may be gunked up.

john banks

No other loose parts. Please note even if you only run standard boost the Dawes should be much quicker low down and at the top end as it flattens the boost curve. Shame it is not working for you and I don't have anything else to suggest.

mutant_matt

Why don't you wind it all the way out so the Dawes is as long as possible and see what happens. I had a prob with mine last week when fitting where on the max unwound setting, I was peaking at 1.3bar ish and getting the fuel cut.

There was a brass washer in it which I took out which dropped the ball about 3mm which should have theoretically reduced the boost a bit but it made it worse (1.6bar). I put the washer back in and cut the spring down in length and now it's great - holding 1.1bar nicely with no fuel cuts.....

Matt

ScoobyJawa

Well I've given up on it for now. Might play again a bit further down the line but thats it for now.

I put the dawes back on one last time tonight and it just wasn't working right at all. I got the peak right down to 1.15 (had been 1.3, then 1.2) but boost control was all over the place. In 3rd it would be about 1.0 up to around 5k revs and then drop straight to 0.8 or just below. In 4th it would boost up to 1.1, drop to 1.0, then up to 1.05, down to 0.9, back up to 1.0/1.05 - basically was all over the place which cannot be good.....

As I said, with the Dawes off it doesn't feel much different, and in fact full boost comes in earlier, with the Dawes it was around 2800ish revs but now its at 2500. Boost holds at 1.0 until about 5.5 to 6k revs and then starts to tail off I think..... There is a small drop in torque with it off and doesn't pull as much from about 5.5k, but I rarely use this in my driving. Mostly town stuff during the week and the odd burn to meets and stuff.
With the dawes on I was getting 17.5mpg Be interesting to see how much it goes up with it off. My car does seem to run very rich though, at PE in Jan with the dawes at 1.5mm bleed and running about 1.1 (just over 15psi on the SM) the figs were 266 and 257torque with 9-10% Co2 which is a fair bit!!!!!

I can say though that this has only become apparant since stretching the spring slightly to try and control boost fluctuation and enlarging the bleed from 1.5 to 2.0mm. Before I did this I had hit a flat spot on a few occasions in 4th but that was when it was still running too high, when it held 1.1 it seemed absolutely fine, although with slight fluctuation as I said.

Its a shame I can't get it right but its now starting to cost silly money in petrol trying to get the setup sorted with all the re-runs in 4th at WOT I'm having to do. Thanks for all the help and advice guys but looks like I'm gonna have to start saving for an EBC or Unichip or similar

T-uk

when you retried the Dawes,did you use new piping?

john banks

Sorry to hear of your trouble. It sounds very much like a dodgy Dawes, but it is such a simple device - it must be a funny spring? If you are anything like me you won't be happy until you get another and get it right. If you had it right once there is no reason it won't be again? Your boost curve being earlier on the standard ECU means the Dawes is definitely not working correctly (I get 18PSI at 2400 RPM with the Dawes). The Dawes should not pass any boost until near target.

Note that the Unichip does not come with a boost controller until they bring out the 3D PID version. And some EBCs give you issues too.

If it is not right for you then fine, but I reckon you are giving up too easily

ScoobyJawa

Nope - same piping thats always been on it, the stuff that came with it. No idea where to get new stuff from.....

I must say - something else that was mentioned to me that would give similar boost was by fitting the pipe from a P1 from the turbo output to the T-piece on the OEM setup (ie P1 restrictor) and that would have the effect of raising boost to about 1.1 but maintaining OEM boost control through the solenoid. Any thoughts on this approach?

john banks

Smaller restrictor from P1 will just give higher peak not higher held - been there done that with a valve on T-uk's car and mine. The closed loop control just puts the boost back to std. A P1 restrictor if the same as the STi is far too small anyway (0.8mm?). Yours is 1.2mm, 1.1mm would probably overboost - tiny change big result.

Another option is a valve off the T-piece. Very smooth, no part throttle issues at all, slower spool up than Dawes, T-uk might give you more comments - he thought it was slower spool up than factory initially, but I think in the end thought not as it was just very smooth, but you can get the same boost as a Dawes. You disconnect the solenoid, and could recirculate the bleed into the intake with a bit of plumbing or vent to atmo.

I don't want to be blinded into only seeing the benefits of an MBC, but it is not like we are all having these issues with them. If we were then scrap the idea and get something better, but as it is why not persist and sort it out?

[Edited by john banks - 3/4/2002 10:11:38 PM]

T-uk

heard about the P1 restrictor change but never tried it,think it will be affected by ambient quite a bit.

ScoobyJawa

lol John - its my bank balance thats giving up at feeding it all this petrol

You are right - I'm like you really and wouldn't be happy until I got another, perhaps scott might let me try using his, and see if the same thing happens.......
I remember you said you ran a different hose, would that have any effect, what sort of places would sell it? Then I could rule out the hosing as the fault. I can't understand though how its so simple its suddenly gone so pear shaped.

I'm also fairly sure that Scotts full boost isn't coming until around 2700/2800 either (we chatted about this earlier) but his seems fine, is there a chance it could be your PPP ecu providing boost that low down?

Was thinking out loud re the chip or EBC, probably wouldn't do that really and just stick with what I've got

Don't really wanna give up - spose its just that Monday feeling - soon be Tuesday though!!

john banks

Sod the bank balance
You bought a Scooby now keep the faith
They don't call me a guru for nothing

I got 3.5mm inside diameter hose from Falkland but I don't really think that is your issue unless the pipe is closing with the acceleration - the inlet to my Dawes is virtually in contact with the turbo outlet with no opportunity for kinkiness Try someone else's Dawes on your car and see the result.

If you want to post your Dawes to me I will check it on my car, but if Scott is near that is an easier option.

T-uk

john fitted a restrictor valve to my car and managed to get the peaks up,but held never changed,the solenoid kicked in and brought it down to standard.

with the valve off the T,I found the car too smooth and thought it was slower.

T-uk

try another bit of hose,I think the Dawes stuff is flimsy rubbish.motor factors such as Halfords should carry new hose.

ScoobyJawa

I'll take a trip down to Halfords tomorrow then and start the testing with some fresh hose too

T-uk

vacuum hose should work.