andymac

Hi,
I had similar (and I've got a MY98 Terzo). My dealer said that they shouldn't do it, but didn't discount the problem. First I had the hoses flushed, which cured the problem for a while and then at the last service they replaced the waste gate solenoid and only filled the oil up to half way between Min & Max. To date, it's not done it again and I don't feel that there is any less pull.
I'd ask them exactly what they did to cure the problem.

cheers

Andy

Lee

If the turbo was producing too much boost, and the ECU was shutting it down whahey..why not remove the restrictor and fit one of those horrible superchip overboost chips.

The superchips ECU prevents the engine from shutting off when overboost occurs. This would seem to be you main gripe.

So, boost back, lurch gone run on 98RON and you should be OK.

James_Harvey

I recently became the proud owner of an October '98 (99MY) UK Turbo with Prodrive Exhaust system and experienced huge joy at the massive amounts of acceleration on tap.
However, I discovered a problem on filling with Super and taking it for a blast up the Motorway.
Upon reaching 4500 revs (or there abouts) the engine would suddenly loose power.... almost as if I had just hit something... the effect varied between quite gental to an alarming lurch depending on the level of acceleration.

Aha I thought.... this sounds like the clogged wastegate problem listed on the Scooby FAQ, so presented the Dealer ( a Prodrive certified Subaru / Isuzu dealership ) with this info.
They responded by saying that the wastegate problem only happened on older models, and what I was experiencing was "Overboost". The remedy they explained is a restrictor to stop this occuring.

I had this restrictor (boost restrictor?) fitted, the garage stating that the car is now producing the correct levels of boost (can this be verified in any way?) and lo and behold, the problem has gone away. However, the car seems to have lost a fair amount of its low end poke not being as quick off the mark as it used to be, something I found a little dissappointing.

I was wondering if anybody else has experience of these (boost?) restrictors, or has experienced a similar problem (according to the dealer, 40% of UK Turbos experience this.....)?
Was the garage correct in their diagnosis and remedy, or have I been sold a pup and need to get this restrictor removed and do something else to fix the problem.
Could it be that the car is just not set up correctly?

Any comments would be gratefully recieved.

R19KET

The first thing to do,is fit a boost gauge.Then at least you'll know what the car is boosting to.

I suspect they have either changed,or removed the brass restrictor in the hose going from the turbo,to the solenoid.Check to see if it's been removed.The restrictor is usually located about 1" from the solenoid,and you can feel it by squeezing the hose.Squeeze all the way along,just to make sure.

This restrictor controls overboost.The smaller the hole in the restrictor,the more overboost.It's normally about .9mm.No restrictor,very little overboost.It won't effect your boost 'held', just the 'peak'.This is why your car will feel slower low down,and when you floor it to overtake.

Firstly I would check your oil level,and also pull off a hose going to the solenoid,and see if it's oily inside.If it is,ask your dealer to clean the system out,and replace the restrictor.Make sure the oil level is reduced.This will hopfully cure the problem.

If it still happens,mail me off line,and I'll let you know more about sorting the restrictors.

Mark.

stapper

i have not found a restrictor in the hose.
i drive a my99 in the netherlands.
my boost is normaly 0,9 bar
now its is 1.3 bar
i have driving with 2.0 bar then the ecu
shutting the fuel down.
if this restrictor is in the hose 1" from the solenoid its lower the overboost
i have make a bypass in hose by the T from turbo,watgate and solenoid
the bypass is in the hose to the solenoid and
has on the and a Festo airfilter wihtin a 4mm hole
the max boost is 1,3 bar

Dukas

2.0 Bar ????
You must drive your engine crazy

Bob Rawle

Be aware that the mass air meter also is able to trigger an "overboost cut" so I've been told. It may well be that it is not a map sensor/amal valve issue at all. Also check tha map sensor connector is making good contact and does not have any contamination (muck) in it to give misleading readings to the ecu.

Bob

Bob

SteveB

iTrader: (1)

Hi,
Yep, am still trying to sort out my overboost problem (MY97)Started with the cleaning and then more cleaning then fiiting of a restrictor which reduced power dramatically (MAYBE 30BHP)another restrictor fitted that still gave the cut-out problem.The car is due in again on Saturday to hopefully sort it out once and for all.Lets hope that the 5th visit will sort this out ! Will let you know.

Steve.

Imago

Hi James
I think I have got the same problem, did you notice the abrupt power loss when accelerating through the gears ? I only notice a problem in fith gear under full throttle. If it is the overboost sensor then why don't I get a problem through the gears ?
Other than this I have no complaints about performance so I feel uneasy about telling my dealer if he is going to reduce power. I think I will live with it.

SteveB

iTrader: (1)

Imago,
Mine started with cutting out under hard acceleration.Since the last restrictor was fitted the cut out only occurs when under sustained boost like 5th gear on long empty roads or up long hills when the turbo can be heard spinning and a bit more throttle causes a cut out.I've had the car for 2 years and up until 2 months ago has been perfect, so if after my next visit the cut outs have been sorted but power is down, then the car will be back in again !

Steve.

Mike Tuckwood

Been to the East coast today (grim).

In top gear, going up hill, my WRX is boosting to about 1.45bar (kg/cm2) then dropping straight back to between 1.2 bar and 1.35 bar.

On the flat it is boosting off the scale (1.6 bar) to about 1.8 bar but yet again drops back after about 1-2 seconds to 1.35 bar or thereabouts.

The car is chipped, does this sound right?

Mike.

ck

Just had chip fitted and running at 18 psi.
On other posting had negative views with regards to engine reliability.
I know the fuel/timing is not adjusted accordingly but surely this is safer than running 1.5 bar or even 2 bar as mentioned above.
Anyway the extra power is there when needed, i am far from dissapointed, i would not like to take to a track day though.

bob

Had the PE Phase 1 fitted some time ago and the car runs at peak with 18psi and drops to 16-17psi and hold. (superchip)Don't think I would like to run 18psi without fuel and timing adjustments. Before I had PE Phase 1
had overboost problems only in 5th on full throttle at about 3500rpm dealer fitted new type of wastegate solinoid all was OK after.

Bob

Imago

Steve,
Thanks for the info. Looks like I have an overboost problem.
Can somebody please tell me which hose to flush out I have more hoses than you can shake a stick at. Is it the one which goes from the turbo to the solenoid mounted on the wing? This solenoid has another hose which goes to the air filter. If it is I assume I should try cleaning the one which goes to the turbo.
Thanks
Mick

SteveB

iTrader: (1)

Mick,
Took car to dealer today and waited while it was in.I'm told that this is not unheard or in MY97 cars.Subaru have a mod' to fix this that involves the fitment of a restrictor device, the dealer then has to get a set of drills of between .3mm and 1.5mm in .1mm increments, it is then a matter of trial and error to get the right size.My restrictor was expanded today by .1mm and now all seems o.k, fingers crossed.i can't feel any drop in power.
Hope this helps

Steve.

James_Harvey

Had a chat with the dealer about this restrictor device, and sure enough, is is the washer in the hose between the turbo and the solenoid that you mention. There was no device previousely and as you mention, they start as 8mm hole and work up until the PSI is as Subaru Spec.

Interestingly enough, it was a hot few days when this happened, so I would like to remove the restrictor and see if the problem is still there, after flushing the hoses.

How do I identify the correct hose?

SteveB

iTrader: (1)

Hi all,
Did the West Midlands run on Sunday and all seems to be sorted with my car now.Power is still fine as others could probabaly destify to who were there.

Steve

Marky9074

Hello there!

I have a October 98 MY99 and have been actively reading this bbs, since finding out about it whilst rroading a RS T at PE (Would like to keep in touch Essex Boy STIV, who was there at the time! Thanxs for the info!)

I've also had the Subaru UK restrictor put in by Barrets in Canterbury. Firstly a 1.6mm, then a 1.5mm. I was quite horrified after driving all the way back to the Isle of Sheppey, and it still overboosting, that all they were doing was shoving a brass restrictor in, which I could have done myself. Boost was previously averaging 18 psi, now 15 psi peaking at 18.

After an off the cuff talk about this at PE, I was lead to believe that there shouldn't be a restrictor in at all, and that I should bring it in for a look. Which I will probably do soon (on a seismic ship in the North Sea at the mo!).

In short are these restictors correct or not?? Also concerned, that my size, woof woof, is quite a lot larger than others!

Any info from you guys will be greatfully received.

Marky

James_Harvey

Does anyone have contact info for PE?
I would like to get them to check mine over too.

Thanx

Lee

WOW ! Thats some overboost for a MY99 (marky9074) 18, holding at 15 ??

Mine and Paul's MY99 recently dyno'ed were peaking 14 holding 12/13. This is the "correct" figure since the 99 turbo is smaller than the MY98.

You have STi amounts of boost on tap ! Perhaps we should swap restrictors !!

Funnily enough I am looking to change the restrictor as a cheap/undetectable way of obtaining a little extra.

Marky9074

Lee,

Thanks for the info. At least now I know what levels I should be expecting! I guess I shoudn't moan about it then! I think I'll get it down to PE though as soon as I get off this ship. Where are you anyway? Anywhere near Kent? I've got the Digital gauge installed which I had no reason to doubt, have to see.

Marky

Bob Rawle

If the digital guage is an SPA then it will be recording "spikes" which could not be picked up by an analogue guage (with a needle). If an analogue guage was put on Marky's car then it would read alot lower in terms of peak, more in line with the others.

Helps explain the apparant difference in cars.

BTW spikes can be caused by the car knocking.

Bob

James_Harvey

Well, I found and removed the restrictor last night, and sure enough the power has increased.

Interestingly, I took the car for a blast, and there was no cut-out!

I can therefore draw two conclusions:
1. The problem is heat based. The ambient temperature is less now than a month ago.
2. The garage, in addition to adding the restrictor, also cleaned out the Wastegate solenoid and in fact, this was all that needed doing.

I found the restrictor in the small pipe just past the T connector in the pipe from the wastegate. It is a small bullet shaped piece of plastic with roughly (I havnt measured it) a 1mm hole through the middle.

I have kept the restrictor just in case the problem comes back.... but I may also take it to PE, once the phase 2 engine upgrade is out

[This message has been edited by James_Harvey (edited 24-08-1999).]

I think my Scooby is actually '98MY and not 99, the garage said it was '99 when I bought it, but all the pointers are that its a '98 even though it was registered in October '98.

The low rear spoiler and position of dump valve kinda give it away.

[This message has been edited by James_Harvey (edited 25-08-1999).]

Lee

To anyone with good knowledge (Bob!)..

I am of the opinion that if I remove/dabble the restrictor in my MY99 I will gain boost and thus power. This upto the point of overboost cutoff.

I am assuming that the ignition/fuel will be correctly mapped since I am not "confusing" the ECU at all with any daft overboost chips, and the standard ECU should provide correct fuel/ignition for the boost.

Or am I wasting my time ?

Bob Rawle

Lee, could you confirm, or otherwise that the boost control pipework on a MY 99 is a pipe from the turbo to the actuator with a T piece inserted and the T connected to a two port solenoid ?

The ecu does not have infinite capacity to adjust fuel. It will have a map in it that is roughly right but will be able to adjust a limited amount eg +/- 8% (a guess). If you change the boost profile by adjusting the restrictors then its possible that the ecu will hit the end stop of its map. If it does then, for example, the car could locally go very lean. I will admit to tweaking restrictors on my STi in my early days of ownership, not any more though. If you want to do it then take a leaf out of Colin Pierce's book and do it when you can get the fueling checked on a rolling road, by far the safest way. There will be some gains as you can push the boost up more quickly but the ultimate pressure will not change much.

To those who are thinking ... "I could try that" remember that hardly any Impreza is the same in terms of the way it fuels.


Bob

Marky9074

Hello everyone,

Just got back to Uk after six weeks and was distressed that I am now running about 10 psi. I am just about to remove the restictor again. I hate to sound ingnorant, coming from a RS background, but why aren't we using bleed valves instead of restrictors??

Mark

Bob Rawle

Marky there have been several posts debating this issue, its generally considered an unsafe option. I definately think so.

If you search the BBS with key words such as bleed, superchips etc you should pick most of it up.

Bob

Lee

Bob,

I can confirm that on a UK 99 there is a hose from "turbo output/intercooler input" to a T-piece to the diaphragm (actuator?).

The 3rd hose from the t-piece goes off to a denso module along with other hoses (it all gets a bit complicated!!) - I'm assuming this is the solenoid that the ECU controls.

Feeling along the 1st hose there is an object inside just before the T-piece. I'm assuming this is the restrictor.

Now if I've got my understanding correct, boost builds up, the pressure post-turbo goes into this hose and "pushes" against the diaphragm which opens the wastegate at a given level. The 3rd hose off to the solenoid allows the ECU to bleed off pressure to be able to control boost.

I think the restrictor will only have an effect on the initial boost levels, after which boost will return to normal.

I am thinking that boost builds, there is a delay whilst it passes through the restrictor and boost ends up at 14psi on mine. Once the pressure has equalised the boost drops to 12/13.

Reducing the restrictor hole means that it will take longer for the diaphragm to "see" the boost and so initial boost may be greater but once pressure has equalised boost will return to 12/13.

What would seem to be a better idea would be to alter the solenoid behaviour such that pressure is bled-away. Since the solenoid is electrically controlled by the ECU there must be a voltage range or something.

Or am I moving further towards an expensive garage bill

Bob Rawle

Ok so you have it just about right. The size of the hole in the restrictor can be used to change the "delay" in the actuator starting to open (or the amount it opens) which will cause overboost (not boost cut). The ecu will stand this for very short periods without cutting the engine but if its too much or is there for too long then bingo, engine cut. I would still say that if you want to induce overboost to get that "kick in the pants" then it should be done and checked to ensure that there is no knock and that the fueling stays ok. After all you are pushing a big chunk of extra air into the engine in a way and at a place that it is not programmed to receive it. If all is safe then its one way to increase the torque at a single point but, you are right it will do nothing for the ultimate boost value as the pressure will still be applied, just takes a bit longer to get there.

Altering the rate of bleed off is another way but now you are talking about bleed valves. The boost cut will operate for sure if you push the boost too high as a steady value and fueling and timing will definately not match on some cars. The Superchip option is basically this. Clamps the map sensor output to a level that stops the boost cut operating and uses a bleed valve to bump the pressure up. Now you work out what happens if a boost control pipe comes off !! And yes I do know some people who have had pipes blow off. As a matter of interest this can be done for a cost of circa £20. How much is a Superchip conversion ?

Bob


Bob

[This message has been edited by Bob Rawle (edited 27-08-1999).]

Lee

Thanks for that Bob !

so I'm thinking on the right lines then

Does anyone know what level of boost the ECU will "tolerate" before deciding it's too high and cut the fuel ?

I'm going to fit a boost gauge at some point..why do the guides I've read imply T-pieces etc etc when there's a spare plug left on the inlet manifold ? Is this no good ? I would have thought this pressure would be the same as the pre-intercooler pressure ?

To me it seems simple..straight tube from inlet manifold to back of gauge !

---edited bit
Incidentally the same questions seem to keep popping up..what is this part..what does that do..where does this hose go..
I'm in the process of converting my website to Macromedia Flash..what about a drawing of an engine bay where when you hover the mouse over a bit it magnifies it with descriptions etc ?

[This message has been edited by Lee (edited 27-08-1999).]