stevo1970

iTrader: (1)

Bugger!

After getting to the bottom of one problem I find there is another. I've just replaced the turbo inlet pipe which cured many of the running problems but I am now aware of a more subtle problem.

The car is fine when off boost at any time, the problems start normally about 15 mins into the journey. Up to this point when the engine is warm it will run fine at any throttle position or boost level. After this time when it been warm for 10 minutes and turbo spool up occurs I can feel can be a little hesitation, just a couple of small instances, but only is 3rd 4th and 5th gear. In 2nd it pulls hardish. In addition as it reaches full boost in top three gears it then holds back as if the ignition is being retarded.

A couple of options spring to mind:

1. The car was a standard UK Turbo when I bought it 5 years ago, I bought all the PPP parts seperatly and fitted them. The car has the standard restrictor pil fitted but has run fine for the last four years.

2. Could the Dump valve have a weak spring that is allowing boost to leak away from the engine thus causing hesitation and poor running. It is the standard recir valve.

Is it possible to check any of the above?

Is it a good idea to remove the DV and run with out one?

Discuss.

TonyBurns

iTrader: (3)

Start by cleaning the boost solenoid, if your symptoms are still there then we shall try something different
I think there is a guide in tech archive on how to clean a boost solenoid.

Tony

Splitpin

Blimey. You're like buses you are. See none for ages and then three come along at once - all number 56's.

When you say "holds back", does the power feel like it's dropping out completely for a fraction, or are we talking a bit of a dulling to acceleration, or what?

Given that we know you fitted a new mass airflow sensor recently while looking at the other problem, the first obvious candidate to rule out is overboost. Have you got a boost gauge? Also, is your exhaust bog standard (or as the PPP would be, standard downpipe with the Prodrive centre and rear box)?

The MY99-00 PPP is supposed to run on the standard 1.2mm restrictor, so if you haven't changed it, on the one hand, that's as it should be. On the other hand, one thing that used to happen a while ago was people after cheap power hikes fitting smaller restrictors to try and get a bit more boost/better spool. If you know you've got a 1.2mm restrictor (i.e. have checked it) ignore the next paragraph.

If you're not sure you have a 1.2mm pill, buy yourself a 1.2mm HSS twist drill from a local engineering supplies place and use it as a gauge. If it passes through your current pill, great. If not, a previous owner fitted a smaller pill - use the drill to open it out, clean the swarf carefully away, refit and see if there's any change to the engine's behaviour.

Think you've already cleaned the boost control solenoid and pipework when going through the previous threads. If you haven't though, do it.

Sometimes the spring in the MY99-00 valve can lose its temper. However, it would have to fail almost completely to cause leakage under boost - you'd be more likely to spot a valve with a weak spring at idle than under hard acceleration. You can give it a fairly unscientific test simply by removing the valve and pushing against it with your finger. It should be firmly shut with the engine off and should require a firm push with your finger or thumb to force it to open.

The other obvious thing to do, as above, is to fit a boost gauge if there isn't already one in the car. If it is overboost, you'll see it straight away. If it isn't, again you'll see it straight away and can move onto investigating other potential causes.

No. Very bad idea.

stevo1970

iTrader: (1)

Right.

The restrictor pill was checked and it is 1.2mm.

The exhaust is a Prodrive backbox, JDM STi 5 Center and standard cat down pipe. One thing I used to run a Magnex center but changed to the STi one just after the trouble started thinking it was causing a problem. Maybe wrong, I might change back to see if it reverts to smooth running.

Dump valve was tested previously and deffinitely needer a firm push to operate the spring.

All boost pipework and solenoid had a good clean a few weeks back.

Plugs 12000 miles old, new fuel filter too.

Its only a subtle problem, its odd that initially all appears well it boost fine then after a while on a jounrey it becomes hesitant at medium revs and at WOT, light throttle is OK at any revs or boost level.

The car was a a Subaru dealer last week and got a clean bill of health on the select monitor.

FB Tuning

iTrader: (30)

If that's not a typo, and the plugs are 12,000 miles old, then i'd be sticking a new set in, gapped to 0.65mm

stevo1970

iTrader: (1)

According to the service book the plugs should be replaced every 24000 miles, why do you thing it will be plugs at 12000?

Splitpin

Without wanting to put words in Richard's mouth, I would suspect that the emphasis is on his entire post. Given what you've said above, and whatever the service book may say about replacement interval, bearing in mind that we don't know

a) What plugs are fitted
b) What condition they're in right now
c) Whether they're properly gapped

...fitting a new set, and taking care to ensure they are gapped correctly, is a perfectly sensible next move.

stevo1970

iTrader: (1)

I got hold of a boost gauge and plumbed it in this morning. On the test run on my private road:

In 4th and 5th from about 2500rmp stamp on the gas boost rises to 1.35 or sometimes 1.4 BAR the settles back at 1.1 (normal for PPP I think) During the 'overboost' stage the car feels hesitant and lumpy but then smooths out at 1.1.

I got my passenger to film it of her phone as we went along, not sure if they will work. Wind on to 50 seconds. 4th and 5th gear acceleration.

http://s30.photobucket.com/albums/c3...t=MOV00261.mp4

Second film, accelerating through the gears up a hill, 2nd, 3rd, 4th and just into 5th before backing off.

http://s30.photobucket.com/albums/c3...t=MOV00262.mp4

It is more obvious what is going on with the boost gauge fitted.

Splitpin

Good move, and there we are then. QED. You have a pronounced overboost problem. And one of that magnitude needs to be fixed PDQ. Try and avoid provoking it in the meantime - gentle application of throttle etc.

I can't read the scale on the boost gauge so will take your numbers as read. You certainly can see the overshoot and oscillation on the video though.

Yeah, not surprised it feels hesitant. It'll pull hard as the boost climbs and overshoots and then, whether as a result of the fuel cut activating, or the ECU pulling loads of wastegate DC, it drops all the way through the target, and then comes back up. Low frequency oscillation.

Right, now you know what it is, you can concentrate on fixing it. Couple of things for you to do/try. First one is to check your boost control pipework/restrictor/solenoid again for oil contamination.

Second is to search my posting history for Simonds1's boost control thread. You'll see me advising him to make a direct link between the compressor bleed outlet and the turbo wastegate. Read that entire passage of the thread as you should try the same thing, for the same reasons, to rule in/out a problem with the physical boost control system and/or a sticky wastegate (or actuator).

stevo1970

iTrader: (1)

I'll research that post now.

One thing that points to an underlying problem with the boost control is that for the last three to four years it has been fine, certainly no pronounsed overboost.

I cleaned to boost solanoid and pipe work again with no change.

stevo1970

iTrader: (1)

Well that was quite a read!

I connected the turbine outlet directly to the wastegate actuator and took the car for a test.

The car pulled to 0.6BAR and stayed there, no overshoot on the gauge in any gear, it pulled smoothly without any jumping or hesitating.

So I guess this means theres a fault in the bost control system. What are my options?

1. ECU - connect everything back up and refit the standard 800 ECU to check the PPP ECU isn't at fault. What is the likelyhood of this?

2. Start drilling out the restrictor pill, this is at 1.2mm as per standard and hasn't been touched apart from being cleaned. Why would this be a factor now whan the car has been fine for 4 years with the Prodrive pack.

3. Replace the boost solanoid, this has had several good cleans with a cleaning solvent with no effect. Could the solvent itself have damaged an internal seal?

4. I'll leave a 4th to the experts who know mare about this than me.

Thanks for your continued help.

stevo1970

iTrader: (1)

Update:

As I have the old standard 800 ECU I thought I would try it to see any difference.

Apart from there obviously being less overall boost, it still overshoots on the gauge by 0.2BAR then settles down to a constant boost, it doesn't reach fuel cut.

As a matter of interest my cheap boost gauge is quite a long way out. With the standard ECU it show a constant of just over 1 BAR and a peak of 1.2-1.3. This can't be right, it does show that my peak with the PPP ECU of 1.3-1.4 is probably over estimated too.

Splitpin

It points in that direction, yes. There'd be nothing wrong with you leaving the direct link on the car for a few days just to see if you notice it doing any weird sh*t (aside from anything else I'm not going to be around here for a few days so won't do any harm).

Moot point now you've tried it, but for what it's worth, the chances of the PPP ECU being "faulty" in such a way that it could cause this problem is minimal to non-existent. If the ECU was "broken" in some way, about the only thing that could fail would be the solenoid driver, in which case you would get boost at consistent actuator pressure - just like you did when you linked the pipes up direct.

Drilling out the restrictor may yet prove the way forward (it was in Kris's case here). However I would not suggest you do this just yet. As you say, the fact that this has suddenly started to occur having been fine previously suggests that something else is at fault. If so, getting into a process of drilling out the restrictor probably won't get you far, as if something else is wrong, it'll probably get worse and you'll be stuck with overboost again.

When you cleaned it, did you do it with the solenoid powered (via ECU test mode or a battery), or just trying to spray into the closed ports? Solvent shouldn't have damaged it (and if it was leaking, you would get underboost, not the reverse) but swapping it out may be something worth trying if you can source another one or know someone else with an MY99-onward Impreza you can borrow one off to test.

As above if you didn't power the solenoid up to clean it, you should do so and spray some more cleaner through. Also make 100% sure the return (the one going from the solenoid back to the inlet pipe) has been cleaned and isn't caught or kinked up on anything - make sure you can blow freely through it.

Also (and there may be a certain amount of repetition here), are you still using the standard Subaru boost pipework, and have you checked it all for splits?


Fuel cut on the standard ECU is 1.22 bar (and 1.35 on the PPP) but the one thing most people don't realise is that boost has to hold over the cut level for one continuous second in order to enable. So you can see peaks going over the red line - but as long as it drops back down quick enough the fuel cut won't activate.

How do you know? The figure of 0.6 bar you got via the direct actuator link is on the high side but not unrealistically so.

How do you know it "can't be right"? Those figures certainly could be from an over-reading gauge, yes. However, they could also be kosher. Holding just over 1 bar on a standard ECU could be a bit of an over-read, or, bearing in mind we know you've got an overboost problem, it could be genuine.

If you want to be certain of the accuracy of your gauge, the easiest way to do it (and one that will help in other ways) is (assuming you have a laptop) to get a diagnostic cable and cross-check your gauge readings with what the ECU is seeing from the MAP sensor. Until/unless you know otherwise, assume what you're seeing from your gauge is pretty accurate. If I were you I'd do that now, as there's no point moving forward until/unless you know you're doing so on an accurate basis.

stevo1970

iTrader: (1)

Update:

I borrowed a mates boost solenoid and it made no difference.

I changed the wast gate actuator with one I had on a spare turbo, again no difference.

I have one glimmer of hope, I mentioned in a previous thread, the original one I think, that the car was fine until about 10-15 minutes into a journey. After a run out tonight I noticed the boost pipework between the turbo and wastegate actuator was quite soft and squidgy where as the long piece to the boost solenoid was much firmer. The soft pipe is grey and looks identicle to the BS pipe. I wonder if this pipe is getting hot over the 10-15 mins (as it is next to the turbo) and loosing its strength to resist internal pressure?

To prove this I need some new boost pipe, is it a Subaru only item?

stevo1970

iTrader: (1)

Final update:

I got a replacement set of turbo to wastegate actuator pipes including the T piece and pill. Just been for a run and we're sorted.

In my previous threads I was looking for a hesitation fault which eventually led to a new turbo intake pipe. During that search I replaced the two hoses as mentioned above with what I thought were replacements from a scrapped Impreza Sport, these were vacuum hoses. It turns out they aren't the same at all and are much weaker and balloon when boost is applied thus giving the boost solenoid a hard time controlling the boost pressure. Anyway it was a problem of my own making which is now sorted.

Car feels great, i'm in love again!

musso2010

Nice result. I wish mine was this simple!