T5NYW

iTrader: (4)

Bret,
Cheers for the info I'am not techy minded so nice and simply explaination As some of the previous post went way over my head I'll probably stick to cat back system.

Tony

Pooder

Tony
I will be planning similar mods on my STI when it comes next month and will be very interested to know how you get on. I will probably use power engineering. Anybody care to comment on their service.
Tony have you had any comments from your dealer about warrenty

Dave T-S

BretMan
Not aware of any STi that has shown the CEL problem.

[Edited by Dave T-S - 3/21/2002 5:00:27 PM]

T5NYW

iTrader: (4)

Dave T-s,
I spoke to a nice gent at Powerstation and said. That on the some occassions with Full-decat on an STi7 and cruising down Motorway the CEL may come on. If it does would be £50 to fix and as Brett said the O2 sensor is repoting back cats not working. ECU doesn't use the information from it to calculate fuel ratios.

Pooder,
Just going for Cat back system and my dealer will be fitting them, Warrenty they said if an issue with boost/missing thats that may be attributed to Exhaust they would try an old on to disprove or prove it not so bad if just cat back downpipe many hours and expense

Dave T-S

Well............just been out in the garage and swopped the downpipe for the original one (85 mins start to finish, not bad for doing it with a trolley jack only, no hoist).

Conclusions? Well, it still goes like a rocket, and it *feels* like it might still be overboosting. If it is, it must be due to the up-pipe. The original is sleeved down internally due to the expansion joint in it, and it is a reduction in diameter of 5 or 6mm. It must make a difference to the gasflow to the turbo having a 5 or 6mm bigger bore up pipe in place.

Of course, I could tell for sure what it was boosting if the boost gauges I ordered via TNT overnight delivery had turned up today, but they didn't...

When I get the boost gauge on I shall report again.......

T5NYW

iTrader: (4)

Dave,
85 mins
I was told that charged about 3 hours labour for downpipe not a dealer though. is the up pipe manifold to turbo and down pipe Turbo to last cat???

Tony

Dave T-S

Tony
I think it's three hours labour for up pipe *and* downpipe. Yes, up pipe is manifold to turbo inlet, downpipe (on a MY01/2/STi) is turbo outlet to second cat (cuts out first cat).

[Edited by Dave T-S - 3/22/2002 9:28:36 PM]

LitchfieldImports

After about 3 weeks of hard use the CEL did come one but only after I was cruising very slowly in heavy traffic.

Iain

GRANT

Ian,
Have had a similar problem comes on only while driving slowing around the West End but never on the motorway.
Glad to see your'e enjoying the car.

Cheers

Grant

simakinen

Hello Lads
Am i right in thinking that it is OK to change the exhaust from the front pipe back, leaving the front pipe alone and leaving the rugby ball sized cat in the system for there to be no problems.Maybe this is the best solution for a power gain and Subaru burble at this stage while awaiting the PPP to become available. I also wonder if the PPP will be any good, as it didnt seem to make much difference to earlier modles. Regards, SIMON.

T5NYW

iTrader: (4)

Have heard but only a rumour that Mike at prodrive has nearly got the PPP signed off for the STi7 310 Bhp with a sports cat he has replied on this topic so he might able to give you the defintive answer that's why only went cat back exhaust

Mike have also asked a question in suspension section

Dave T-S

Simon
I'll report when the boost gauge fitted tomorrow.

Tony
PPP imminent, but by the time it is signed off by PD/SUK/in production will probably be 4-6 weeks minimum to be at dealers.

T5NYW

iTrader: (4)

Dave,
Are you getting the genuine Subaru 3 gauge & pod ??? as seen in the new Feb2002 goodie booklet that's got nowt in it for STi7's
and only mentions the new UK300!!!!!!!!!!!!

Tony

Dave T-S

Tony
Nah - I went for the cheapo version - genuine Subaru/Lamco boost gauge only. I work on the basis of need to know only - too busy trying to keep my eyes and the car on the road

Andy W

You are up early Dave!

Andy (watching to see how you get on)

Dave T-S

Righty ho, here we go.......

Fitted boost gauge to both STi's this afternoon.

Carolyn's - now has ScoobySport up pipe, standard downpipe, Scoobysport centre and backbox i.e. front cat still in place, second cat gone.

It is now spiking to only ( 1.5 bar, and holding 1.1 to 1.2 bar in the higher gears.

Mine - absolutely bog standard. Spikes at 1.3 bar and holds 1.1 to 1.15 bar.

I reckon the up pipe is causing the increase in boost on Carolyn's. As mentioned previously it is sleeved down internally by 5mm or so by the expansion joint. My feeling is that the removal of this restriction is allowing the turbo to spin up faster, and this is causing the spiking.

What this needs of course is the good old one fix at a time approach.

I do not believe the ScoobySport centre and backbox can be responsible for the extra boost and I intend to remove the up pipe and put the original back on, and check the boost again. I might also then put the ScoobySport downpipe back on and see what effect this has.

I don't really want to start playing around with restrictors, as I am told by a man that should know that this can cause problems elsewhere.......

mutant_matt

Dave,Can you tell us what these other problems are as off the top of my head I can't think of any?

After all, this is what Prodrive do on the old shape PPP to control the boost after ditching the catted centre etc...???

Matt

russell hayward

It will be interesting to see which exhaust parts are changed on the PPP.

BretMan

Dave T:

We know from RT that just a turbo-back system results in 1.7 Bar spikes, so I guess it must be a combination of the uppipe and downpipe.

Did you put the factory restrictor back on Carolyn's car?

The only downside I can think of for the larger restrictor would be slightly more "damped" boost ramp-up by allowing more wastegate creep, but would that not be offset by the downpipe anyway?

I for one would certainly be interested to know whether a downpipe back system only would cause this...

The more I hear though, the more I think that a boost spike is "supposed" to be there - i.e. designed into the factory boost control and that it is perhaps just the reaction time of the factory control system that causes the "over"spike.

There has been some talk of the factory boost control solenoids (in older models at least) being not that higher quality and being swapped for better ones... I wonder if that might have some effect?

john banks

The lowly 2 port solenoid is not the poor relation everyone says it is. It is a controller issue, and I suspect the same for any other Subaru. A capable controller can work with it quite happily.

Controlling boost spikes with any degree of precision is hard to get right. Certainly fiddling with PID controllers has shown me that the best control integrity comes with a small say 0.5-1 PSI at most boost peak over held. Otherwise the control system is unstable. In different loads and conditions, with different gears, temperatures and engine speeds, especially when combined with breathing mods, overboost spikes are very difficult to regulate from one run to another unless they are small. A 1.5 PSI spike can turn into a 4 PSI spike quite easily, and even these for a short time seem to trigger undesirable responses of fuel cut or instability.

I also don't see the issue of changing the restrictor if the controller will cope better with it. By introducing an exhaust you are effectively changing it anyway and usually increasing the size of it (depending on where it is) is often a good solution.

Dave T-S

I didn't actually change the restrictor in the end on Carolyn's car (although I have now obtained a selection from 1.0 mm through 1.4 mm should I decide to do this ).

It's actually a pain changing them on the STi7 because the restrictor is in the short tube from the T piece to the compressor housing and is half hidden under the dirty great intercooler the 7 has. I *think* you can just about get to it without taking the intercooler off, but will be a nuisance if I do have to.

I want to look into the implications first. Having seen my car spikes to 1.3 bar on a standard exhaust I am now not so sure a 1.5 spike with a modded exhaust is such a big deal. It's not as bad as 1.7. What will be interesting of course is what the PPP spikes to.......

RT

Dave, good news for you. With a cold engine, it should not be a problem to get to the restrictor/T-piece without removing the intercooler.

My mech did it with a hot engine, gloves, needle nose pliers and about 10mins.

RT

May I please request that we add which gear we're in when we mention a boost spike? tks.

1.3bar spike is high for first gear, but "normal" for 4th - I spike to about 1.4bar in 4th. My entire exhaust system is standard.

Dave T-S

RT
Spikes on Carolyn's car to 1.5 bar were in 4th but predominately 5th and 6th - i.e. under most load.

I had thought it was probably *just* about doable to change the restrictor with the I/C in place, need to get hold of a pair of needle nose pliers with angled ends which will probably make it easier. Might just give it a try then - have got hold of some 1.0, 1.05, 1.1, 1.2, 1.25, 1.3 and 1.4mm restrictors, shame not to try them

GRANT

Dave,
On this one I can speak with experience ,it is not to difficult to change the restrictor and have done it without the need of pliers or removing the intercooler.In fact when the car is warm it is easier to do as the pipes are more maliable.


Grant

Dave T-S

Grant

Thanks

Dave

john banks

My burn from doing a Dawes on a MY01 is just about healed now! If the STi is worse with a larger intercooler please wear gloves. It is a nightmare for access compared to MY00. I have also managed to split a hose before by repeatedly changing restrictors before I got a valve. A good way of getting the restrictor out is to use pliers with a rag to protect the hose and gently milk it along. A small screwdriver helps with reintroducing a new restrictor.

RT

Yes, its real easy to split a hose. Suggest you have a standby before doing anything. You don't want to disable the car!

mutant_matt

Just for your info guys, the STi 7 (UK) with PE system that is demo'd on the Ecutek site peaks at 1.26bar and holds 0.98bar.

I will ask Stephen exactly what exhaust this has on and/or any other mods as this seems quite acceptable?

Matt

Dave T-S

Matt

ROTFLMAO

That's less peak and held boost than my bog standard STi7!!!!