Steve E

Hi,

I recently imported a 1996 Legacy GT-B estate from Japan with only 18k miles and a quoted 280bhp.

It is completely stock and apart from some slight piston slap from cold start seems to run fairly ok although fuel consumption would seem a bit heavy at only 20-23mpg even on a run. Is fuel consumption known to be fairly heavy in Subaru turbo's?

Can anyone tell me if it is normal for the twin turbo engine to feel slightly laggy between 3-4k rpm? It pulls ok from 2k rpm and then seems to dip between 3-4k rpm before pulling smoothly to the redline.

Thanks for any comments.

Steve

[Edited by Steve E - 4/18/2002 8:41:12 PM]

john banks

If it is the twin turbo model it sounds like the fabled "valley of death" whilst the second turbo spools up. Apparently exhausts can help a fair bit. But I don't know any more than that about Legacy turbos.

chrisp

Yep I heard they drop off while the second one spools up. I agree making the engine breathe better may reduce some of the lag.

Steve E

Thanks.....

I'm not sure how the single turbo setup compares to the twin turbo setup abd I don't have any owners manual to look into this.

It would appear that a single turbo feeds each bank of cylinders.

It looks like both turbo's spool up at the same?? If one turbo spools followed by the other after 3k rpm, how does the airflow balance across all cylinders?

Is it possible that the first & second stage of boost is actuator controlled?

Is a cat back exhaust system a good way of making the car breath better. Does anyone make a cat bypass exhaust system?

Any further comments would be appreciated.

Steve

PaulHop

Hi,

I think I can remember a while back that there is some sort of earthing mod that can help with this.....

If only search was here

Paul

Jolly Green Monster 2

Might help trying Super unleaded or Optimax which you should really be running a Jap car on anyway..

An exhaust change even just back box might help spool up..

That is a good point about the Turbos.. I had assumed they were just fitted one behind the other in the inlet.... so the exhaust gases at lower speeds spins up the first turbo and then this and the increased exhaust gas flow spools up the second..
but is that the case or are they in parrellel??

JGM

EvoRSX

Twin turbos can be setup sequentially (where they come on in stages) or you can have separate turbos feeding seperate cylinders (in twin turbo Vee engines for example)

The sequential twin turbos are normally put in parralel and there is an actuated valve that controls which turbo the exhaust gases flow to. When this starts to switch across to the bigger turbo, the flow to the small turbo drops and the inital low flow to the bigger turbo isn't enough to generate the same level of boost.
Therefore you get the drop in power that you seem to be experiencing.

One way around this is to try and change the point at which the turbos switch over. Depending upon how the changeover point is set will depend on how easy this is to do.

Andy

BryanC

This may be an absolutely brainless question - but has anyone ever thought of maybe having an electric motor as a "pre-winder" on bigger turbos like this ?

It would spin the turbo up when exhaust gas flow isn't enough - and would cut out when the flow got large enough to take over...

A sort of supercharger just for the turbo ?

Go on - someone explain to me just *how* stupid an idea that is!!

Bry

RichS

Interesting Bry

I'm no a tech guru, but won't the energy required to run the electric motor sap power from the engine, thus negating the advantage?

Nice idea though - hopefully one of our many technical experts will be able to comment.

Rich

john banks

I gather that electrically driven superchargers require massive amounts of power.

BryanC

Rich,

Ultimately, yes it would - but you could run the charge from (for example) a second battery - which is recharged once the current from the elec'y motor is killed as the exhaust gasses supply 'real' boost. Then (I expect) you wouldn't notice the recharge as much...

Or maybe it doesn't even need to be an electric motor - my original "supercharger" name for it might be a better plan - and you could run the spool up off the crank ?

I'm going to cry when someone techy really shoots this down - it's a lovely idea......

Bry

BryanC

I was going to compound my stupidity by saying something along the lines of "yes, but it's not supercharging the engine, just the turbo" - and then I realised that it doesn't make any difference - you're still using electrical current to compress air going into the engine... so it's probably still going to use the same amount of electricity as a standard electrical supercharger....

****.

Oh well - I enjoyed dreaming about it while it lasted... all of ten minutes....

Bry

Floyd

iTrader: (9)

A squirt of Nitros at low-mid revs would do the trick.

F
PS idea from David Vizard!

GavinP

Steve,

There is an article here for a twin-turbo engine transplant into an Impreza which has some information.

MRT do a lot of parts for the Legacy and there is a couple of UK importers around.

Another possible consideration is the fitment of two Dawes MBCs (manual boost controller)...

Thanks

Gavin

[Edited by GavinP - 4/19/2002 12:35:27 PM]

David Lock

Steve,

There is a Legacy group - I think link below will help.

http://groups.yahoo.com/group/legacyb4

David

BryanC

Floyd - I was thinking about NOX too - but then I thought - "No Bryan - you're just being silly now!"

It would do the trick though I suppose....

Bry

EvoRSX

Bryan,
IIRC the Lancia Delta S4 rally cars ran with both a supercharger and turbo and switched between the two once the turbo was up to speed

Andy

Steve E

Thanks for the links...

Just found out that it is a very complicated sequential setup.

Recommendations where to buy cat back exhaust and airfilter would be appreciated.

Steve