Telephonewire

Have recently purchased a 95 Legacy GT Twin Turbo and am looking for what modifications can be done (within reason) to obtain a bit more power and / or reduce the valley of death (VOD) in the torque curve, also where can I buy the bits or who can do the work.

I have searched the archives but can’t find anything particularly useful.

On a different subject when accelerating hard under full boost the car often feel like it is running out of breath around 5500rpm – 6000rpm at which point I am thinking it’s about time to change up then suddenly another surge of boost / torque comes along and whisks the car up to 6500rpm. What I am trying to say is that even when the boost is up the boost pressure does not always seem to be steady but surges a bit causing erratic acceleration sensations. Is this simply an inherent system effect or might the boost control bits be a bit sticky?

On a different subject again I am getting a burning oil smell coming from the right hand cylinder bank. I am hoping it is coming from a leaky gasket seal on the cam cover rather than a more serious leaky head gasket seal. It’s very difficult to see anything down there especially when the weather is so dark and wet at the moment. Does anyone know if this is the likely problem and if it is a common problem?

Many thanks !

MRK_IV

Hi there

I'm about a month ahead of you as I've just bought a '94 Legacy GT!

It's a difficult beast to tune , but a good starting point would be http://autos.groups.yahoo.com/group/legacyb4/

Exhaust: I've got a Hayward & Scott back-box and de-cat centre pipe so the next logical step will be the down-pipe.
On these it's a Y-shape, with a small Cat on the primary turbo. This has to stay as I've heard removing this will cause the Turbo to over-speed. All the down-pipes I've seen are simply for the secondary turbo although I'm investigating a rumour I heard that HKS do an expansion pipe that replaces the down-pipe after the primary Turbo. A downpipe on the 2nd Turbo will go someway to reducing the 'VOD'.
BTW - Is yours an auto or a manual?
Another thing to look at would be the air filter - I've heard that a performance drop-in can make a marked difference on these cars.
As it's an import, try and run it on 100RON - Optimax + NF Octane booster works for me.

Can't think of much more at the moment - except your power delivery does sound a bit strange - is it always there, or when you put your foot down in that rev range? Apart from 4-4.5K, I have no problems.

MRK_IV

Sorry forgot to add - the burning oil smell: Mine's being fixed on Monday!:
Rocker head gasket, dripping on to a hot exhaust manifold - simple as that. Apparantly, quite common on Porsches

DuncanG

TW, Recommend you fit a boost gauge to see whats going on. I've put in a temporary £30 Racetech until I decide on proper instrumentation package.
In this cold weather I'm finding that I get overboost, ie when secondary spools boost climbs to ~1.1bar (should be 0.9bar) holds that for ~1sec drops to 0.6bar then climbs again & repeats. I'll be experimenting with an adjustable boost restrictor.

Mrk-IV did you go for the Sti wheels?

How about you guys going to the Legacy twin-turbo meet in March (http://www.scoobynet.co.uk/bbs/threa...hreadid=153315)?

BTW mine is '97 GT (BG5B)

Telephonewire

DuncanG

You said "In this cold weather I'm finding that I get overboost, ie when secondary spools boost climbs to ~1.1bar (should be 0.9bar) holds that for ~1sec drops to 0.6bar then climbs again & repeats."

This sounds like what is probably happening to mine, i.e. the boost pressure doing a bit of a roller coaster ! Is this normal ?

Yes, I intend to go to the meet in March if I can get away.

Mine's a manual BG5A (with 17" MY01 wheels!)

MRK_IV

Thanks for the info, and I feel better now I know mine's not the only one with an oil leak!

Is there a cat on the primary down pipe or is it further down stream after the two down pipes come together, I am a little confused?

Also the de-cat centre pipe, won't this cause the car to fail it's MOT? How much do the bit's cost, are they stainless and do you have a telephone number etc.

Many thanks !

DuncanG

Don't know about normal but doesn't seem too unusual, especially if there's been any improvement to the breathing and its cold.

When I got the car a few months ago it had a really restrictive (<2" prob for a NA UK car) back section on the exhaust which was killing power above 5500rpm. I had the local Powerflow exhaust franchise make up a de-catted 3" centre with resonator feeding a 2.5" back section with straight-through box (cost £275). That gave me +30bhp (maybe +10 from oem exhaust), is very quiet and revs well to red-line. Initially there was no overboosting then the weather went cold!

Boost is controlled by a combination of a restrictor in the turbo to w'gate line and an ecu controlled boost solenoid which shunts-off pressure. If the restrictor is too small the pressure in the w'gate control line is slow to respond to the bosst pressure and you overboost. The ecu in defense senses the overboost, closes the boost solenoid and so boost falls to the w'gate crack-point ~0.6bar. The ecu relaxes control and if you are still on wot the cycle can repeat. I've taken up an idea of John Banks to replace the restrictor with an adjustable pneumatic flow-control valve (~£15). Hopefully I'll get the car back on road before end of winter - I'm doing a renovation/upgrade programme on it now.

There is a cat on the primary down-pipe and also in the centre section, so if the centre is de-catted the secondary is also decatted. The accepted wisdom is to leave the primary downpipe + cat well alone to avoid the primary from overspooling. When the secondary & primary are both running there is no active balance to keep the turbo speeds matched and as the primary is designed to spool-up faster (either or both smaller diameter / lower a/r ratio) if they are both de-restricted the primary can overspool (rated max 190,000rpm). At MOT time I might have to disable the secondary.

Hope to see you at meet.

MRK_IV

Hi Duncan - no I didn't - I'm still looking for a set of wheels for track use - it's currently got the 16" BBS forged cross-spokes which I'm more than happy with for road use - especially now I've fitted 205/55/16 Toyos and replaced the god-awful 205/50 Avon ZZ1's. An added bonus (apart from infinitely better cornering, sure-footedness and quiter motorway cruising!) is that my speedo is now only 2mph fast - it was reading 5mph to fast before, throughout the speed range.
Only other mods so far are a set of STi front seats (incredibly comfortable) and an STi carbon front strut brace that's going on Tomorrow.
It's my second car/daily driver/occasional track car, so I don't want to go too overboard!

Probably the most useful mod is the one of got a couple of people looking into at the moment - a UK 5th gear, purely for motorway driving: Forget trying to drive like Miss Daisy, I've yet to get more than 22mpg, with an average hovering at 20. I'm hoping the UK 5th gear will make a huge difference to consumption, specifically on Motorway runs.

GTB Limited

De cat the primary and she goes bang

Has anybody failed their MOT with the centre section de-catted?

The reason I ask, is that I had the car running after an oil change, looking for an oil leak, supries surprise cam cover Whilst underneath, the primary downpipe gets v-hot, but the secondary d-pipe is stone cold.
Is the primary cat good enough to pass an MOT?

Just some food for thought

Mark.

DuncanG

Mrk-IV, keep me posted on your gear change, after having UK Subs this does seem short geared. AFAIK it means changing both front & back diffs - sounds expensive. Do you know what final drive you have - some info I've seen says 4.444, others 4.11?
Mine came with Sti seats, great if your the right shape for them, but I'm not - they're killing me

GTB, a lot of Imprezas get by with one cat so hopefully it'll be ok.

MRK_IV

No worries Duncan.

One of the things I'm looking at apart from the second turbo downpipe replacement is replacing the primary pipe after the Turbo with an "HKS expansion pipe" - I've been told about this, but yet to find it. The other option is replacing the standard primary cat with a 100-cell sports cat...I'l keep you posted.

My main problem at the moment is the spedo conversion - the needle tends to get a little vague at 3-digit speeds, dies completely, somes back, dies completely, triggers the Check light, goesinot limp mode, speedo comes back, check light goes out etc. etc. etc...

GTB Limited

A little bit of subject......

Will the cam cover gaskets on the impreza t fit the legacy tt?

Cheers

mark

Telephonewire

All these different sections of exhaust pipe you are referring to, surely they come in fixed sections and can’t be split down further without having to somehow ‘create’ new joints?

So basically a larger HKS down pipe on the secondary turbo and larger bore HKS pipe from the joint of the two down pipes back. A CAT bypass pipe and decent rear box? Any telephone numbers where I can get these bits? Has anyone done this mod and how much improved drivability and power does it give?

DuncanG, you said ‘If the restrictor is too small the pressure in the w'gate control line is slow to respond to the boost pressure and you overboost’ does this mean than the standard restrictor is not up to the job? If this is common then there must be a relatively common ‘fix’?

On another subject Electrics! My front heated window appears not to work, I have check all the fuses and they are fine but the heater appears not to demist at all, how can I check further. The rear window appears to work a little but no much, any advice on this would be welcomed. I’ve heard some people saying they have heated seats and I assumed they were an option mine did not have, however, whilst scurrying around under the front seats the other day I discovered wires going to both the front seats, are these heated seats? if so I appear to have no button to operate them? Again any advice would be welcome.

DuncanG

TW, Do a search for restrictor, theres loads of threads on it.

Overboost seems to be quite common where folk have put on a less restrictive exhaust (like me) and its exacerbated by the current cold weather which makes the air denser. If you are already getting this problem then maybe you should fix that first before upgrading. Is your car standard? Have you put a boost gauge on yet - without it you can't be sure that you are over-boosting - maybe its something else? A £30 gauge from Rally Design or Demon Tweaks will do well enough.

The common 'fix' to my boost-control problem is to enlarge slightly the restrictor hole (from 1.0 to 1.2mm IIRC). A development of this is to replace the fixed restrictor with an adjustable pneumatic flow-control valve, (from local pneumatics control store) which is what I'm doing.

As I said before I got a centre + back exhaust system custom made by local Powerflow franchise. See www.powerflow.com or is it www.powerflowexhausts.com and www.powerflow.uk.com
Or you can get a system like Mrk-ivs from Hayward & Scott.
I'm not going to touch the down-pipes until I have a better understanding of the twin-turbo system.

I'm not sure that the whole of the front windscreen is heated - I think it might just be the bit under the parked wipers thats heated to unstick them when icy.

Don't know if your seats are meant to be heated, but I know my new Recarros are

Scooby Si

Has any one got a list of which goodies from the Imprezza will fit on a Legacy? ie suspension exhaust wheels?

cheers

Si