BenAWT

Could anybody please help me.

What are the differences between a JDM legacy ('96) GT and the same year GTB.

Is it just the suspension or do the engine outputs and internals differ?

All and any info appreciated, the more detailed the better.

Thanks

bb

As a Legacy TT owner, I stand to be corrected but:

The GT generally refers to the 4door saloon version whereas the GTB is the estate version.

Both versions came with the option (standard in later models) of Bilstein suspension which is where some people get confused thinking the "B" stood for Bilstein.

So in answer to your question, a GT and GTB have a different bodyshell and both could come with or without the Bilstein suspension package so you need to ask more carefully and don't assume a GTB means it automatically has the suspension package. I think most 97-mid 98 versions came with the Bilsteiin package as they tried to sell off the last of the old models and tried to add more equipment standard to make them more desirable.

As far as I know the manual and automatic versions are much more different appart from the 20ps difference. Apparently the manual versions have a stiffer bodyshell / stronger welding which you wouldn't notice visually but it would dynamically feel different.

DuncanG

Its hard to get rock solid info on these cars. FWIW here's my attempt:

The GT-B was introduced for MY97, but a '96 car could be an MY97. The <MY97 twin-turbo GTs have 250ps auto or manual, the MY97 GT has 260ps auto or man and the GT-Bs (MY97+) have 260 auto / 280 manual.

For MY97-98, which seems to be what you're interested in the GT-B (BG5C) has relative to the GT (BG5B):
Bilstein dampers, which are good but don't last forever and are hard to replace,
17x7 wheels which are nice but don't accomodate 4-pot brakes,
possibly (maybe its a later model) larger bore exhaust system with noise reduction flap in the back-box which tends to seize,
the 280ps manual has marginally larger turbos, slightly more boost, slightly more cam duration and sodium filled ex valves to gain the extra 20ps,
its probably more fussy regarding fuel - maybe benefit from octane booster.

The GT and GT-B have the same bodyshell (wagon). The saloon version is the RS. I've never heard of any differences in body-shell welding or strength. The GT is usually much easier and cheaper to insure than the GT-B; eg Liv Vic were ok with the GT but would'nt touch the GT-B at any price, someone else (forget) wanted 50% more for the GT-B.

The tuning possibilities for either are very limited without effectively converting it to an Impreza - there are no easy remaps and the puny turbos are working pretty close to the limit. They are quite rapid in standard form and very stealthy. The brakes are similarily crap on both the GT & GT-B.

Duncan
BG5B MY97 GT

bb

I have a MY98 (last ones before the B4 came out) saloon GT which is twin turbo, automatic with 260ps. The RS is the saloon bodyshell in manual form. 260ps vs 280ps with an extra 500revs before hitting the rev limiter. I am pretty sure that the GT-B is the estate version only, nothing to do with whether they have Bilstein suspension or not.

The info about the stiffer bodyshell is from a friend working at Subaru (HK). Not entirely 100% about that.

But re. the different models, I do have a magazine dedicated to this series of the legacy which lists all the models and specs for the BD/BG legacy over the years it was produced but it's in japanese. I can scan it and send it to you but you need someone to translate it for you. This will probably be useful information for everyone interested in this model of the legacy.

I also have another edition of the magazine dedicated to the >MY98 B4/GTB series of the legacy which I can also scan FYI - again in japanese.

The 17x7s will accommodate the four pots as I have them installed on my car, the standard 2 pots are crap! Unless we're talking about different 17x7s but I do understand that all the UK legacies were imports, so the specs and equipment would be more or less the same as in HK or Japan.

AJbaseBloke

GT-B stands for Bilstein equipped wagon. Only BG5B or C revs. BG and BD from B rev on got a stiffer bodyshell thanks to reinforced shell and a new internal design for the B pillar which really did the biz. Engine was heavily revised, along with a host of other stuff to handle the extra mumbo (250ps pre-face lift). Post facelift = 260ps for autos, 280 for manuals.

Std wheels of this era will NOT fit 4 pots without a spacer or knocking off the Subaru lettering (I tried ).

As mentioned above, they hate bad fuel - once had a numpty servo attndant (yes we are still full service mostly here) fill me with SUL and the car sounded like it was about to die...

I guess I should add that you should go by the model code, and not model year for JDM cars, as model years DID NOT EXIST in Japan back then, so you could get thrown a googly

HTH

BenAWT

Thanks guys.

I'm actually a renault engine tuner and cylinder head specialsit and TBH dont know much about scoobs, kinda dismissed them after taking a impreza round combe . But the Legacy makes a great hack and is surprisingly swift, bar the annoying boost profile lol.

This is my import and was originally sold as a GTB, however after driving and looking into the specs a bit more i realised it might not be, not a major problem, just want to find out what it is. It has no yellow billies and i havent looked very hard for the engine number in the bay. It doesnt have 17's and TBH it doesnt have anything for me to think its a GTB. It would be nice to know the actual engine spec and output, then i can get cracking on what to do to it. Whats the general thing that people do, as i dont know the turbo type and dont have a boost map, i dont know how boost is managed, i dont know what the bhp limits of the std turbos are etc etc.


Thanks again.

p.s i'm not sure about the model code or where to find that info.

p.p.s BB, that info would be great, i'm from HK and should be able to get some jap mates to translate it in semi decent accuracy.

DuncanG

Looks smart, but its definately a GT (BG5A model) and MY<97 ie pre-facelift. So its a 250ps model even if a manual, I believe. A lot of people think all the manuals are 280, but not so. Make sure you insure it as a GT - that could save you a bundle.

Engine tuning is difficult. Your model has a slightly smaller primary turbo which is prone to overspooling leading to failure if you improve the breathing too much or increase boost by using a mechanical boost controller. Don't remove the downpipe cat on the primary (left hand side) or the turbo will tend to overspool. The centre cat can be removed but you might then get boost overshoot and oscillation. That can be fixed by tweaking the boost solenoid restrictor or replacing it with an adjustable pneumatic valve. Do a search for restrictor on here.

The legacyB4 group:
http://autos.groups.yahoo.com/group/legacyb4/
is about the only english language forum for these, but its not very active now. In the files section you'll find EH20.html which give some data on turbos etc.

Probably the best first mod is to improve the brakes. The fronts are the same as the imp of the same year. The rears use a vented disc unlike the imp.

Duncan

PS model code is on the VIN plate: BG5x xxxxxxxx

BenAWT

THanks duncan, i was thinking its a GT and not 280ps.

Insurance is not a problem for GT or GTB, trade insurance lol....only benefit of having your own company specialising in performance engine tuning, but trust me to choose a vehicle and engine which i know nothing about ha ha.

My rear box has fallen apart so its being rebuilt this saturday along with a decat, lucky you told me that info about the primary. The primary is on the nearside right?

Few short questions.

Now, are both turbos on the GTB different, or just the primary?
What is component stength like if i were to use 2 larger turbos?
What sort of result will mild boost increases lead too, either mechanically or via the management. We run our own piggy back ecu system so we can alter fueling/ignition and boosting maps, so long as boost is controlled via the ECU.

again thanks for the decent tech info, nice talking to somebody who isnt a numty.

GTB Limited

Ben,

Have a butchers at my site, lots of info (still need more)

Sometimes removing the centre cat, can make it go flat


Mark
UK Twin Turbo Legacy Register

BenAWT

THanks mark, i did find that site and its got great info.

I am looking for how far people have gone with the twin turbo effort as i know most go the single turbo route.

How exactly does the management control boost and the opening of the valve for the second turbo. ANd why does it take a good 500rpm for the second one to kick in, if it was spinning before why should it take to long to build MAP?

If i only wanted straight GTB spec power what would i need to do? Any other means apart from the turbos, cams?

I'm sure you have all been through this aready, but please humour me.

BenAWT

oh, and the flatness caused by the decat, is that on the GTB only or both GTB and GT?

This is weird, i'm usually the one answering all the questions on other forums lol.

DuncanG

Ben, both turbos on the GT-B are slightly bigger, but its only 1 or 2 mm - they're still small. This lot do upsized turbos but they're expensive:
http://www.power-enterprise.co.jp/ma...spec/index.htm

You should get some useful power increase just by using a MBC along with your piggy-back and accept that the turbo life might be shortened. Don't be too greedy with boost though. If you look at the EJ20.html file you'll see the GT-B runs 750mmHg (1 bar) vs the GTs 600 (0.8 bar). What kind of piggy-back do you use? The differences in cams etc are very minor and not worth the expense of changing - just part of the Subaru fettling process.

For significant mid-range grunt which is sadly lacking on the GTs the simplest way to go is to convert to single turbo. Then you have access to a vast array of stuff developed for the Impreza.

BenAWT

Thanks again duncan.

Personally on my own cars i'm very very lazy as i cant have them off the road for too long. So staying twin tubbed is probably easier, and it would also be quite fun to try and solve the VOD boost drop.

We run the perfect power SMT series of piggy back units.

You wouldnt happen to know the boost management system the legacy uses would you, or how the swith the to second turbo is controlled.

BenAWT

800 quid per turbo!
and one isnt a roller bearing but the same trim spec!???

BenAWT

OH, where is this EJ20.html file?

DuncanG

The EJ20 file is on the legacyB4 group and also on Mark's website, but send me an email (click on DuncanG on the left) and I'll mail it to you along with the aussie B4 technical description which is the best description available on the tt setup (not saying much). I'll be interested to see how you get on with the SMT (Perfect Power?). Someone in oz had good results with one.

The switch to the secondary is not optimal. I did some datalogging and found that when the primary was spooled the excess exhaust was vented through the wastegate instead of being vented to the secondary turbo to help it spool. Best of luck in solving the VOD.

GTB Limited

Ben,

The ECU is JECS.

All boost controlled via the primary actuator, also a soleniod is located behind the wheel arch liner on the LHS frt, for when both are on boost.

HTH

Mark

BenAWT

Right.....were getting somewhere...ta

The SMT7 when it comes out is the one i will try. If its possible i will try control the frequency/amal valve and control the boost reaching the actuator. Does the system use a solenoid etc to control boost passed to the actuator?

The idea of bleeding wastegate flow through to the second turbo is a good idea. It'll take me a while to fabricate a manifold that brings the primary's wastegate flow to the secondary's manifold. But it'll end up costing mega bucks as i'll need the primary turbo to have an external wastegate.....in which case for the work done i might as well follow the single turbo route.

ANd being a cylinder head specialist i would like to carry out a soft chamber conversion in an attempt to curb pre-ig or det whilst being able to run higher ECR's......but like i said, i'm lazy and taking the engine out to get the heads off isnt an idea i'm fond of.

I bought it thinking it would be a daily hack!!! lol

Thanks guys

DuncanG

Ben yhm.

All the hardware for bleeding the primary to the secondary is in place. Your getting a bit ahead of yourself. There are 2 'boost' solenoids both 2-port. One controls the wastegate on the primary as in a normal setup. The other which is also duty-cycle controlled operates the flap-valve in the secondary's up-pipe. That could (and should?) be used as the wategate for the primary in the transition phase; but in my datalogging it doesn't seem to be. That flap-valve is small and ugly - from memory its orifice is only about 22mm diameter and the flow path is not straight. Its probably one of the major restrictions to upgrading the tt setup. There are several other solenoids which are all bipolar (on/off), used for swithing the intercooler valve (2ndry output) and switching pressure sensors etc.

It'll be interesting to see what you make of the cylinder heads which are similar to the Imprezas.

craigdmcd

iTrader: (2)

This is all very interesting reading boys, but pretty soon it is going to be a pain to find as it is lost within scoobynet. Would anyone be interested in a forum dedicated to legacy's?

Craig

Kevin Groat

Bit of advice reqd chaps, I'm after a GTB estate as a winter runaround, my problem is I can only get NUL fuel. I already have an STi v3 that I run on NUL - and before someone tells me that the engine will det/hole piston/expire it has run happily on NUL for 5 yrs 40k miles and doesn't det and is regularly exercised to the redline. How different is the GTB engine/ecu (97 P plate) to the STi3.

BenAWT

I would be yes, but pray it not be something like those horrible free yahoo/MSN sites lol.

BenAWT

Duncan, so your saying that there is already a link from the primary exhaust manifold to the secondary?

The primary solenoid, when you say it works as a normal setup. DO you mean the actuator is controlled in the same manner, or does the solenoid bleed boost to it in some way, as i cant see its used being there in a 'normal' setup.

This up-pipe, what exactly is that?
Does, or is there a way, to pass wastegate exhaust gas through to the secondary manifold?

RE the heads, i would need ot get hold of both an impreza and legacy head, and preferably the different incarnations (WRX/STI/GT/GTB etc etc) to see if there are casting and machining diffs.

Out of interest, is there a subaru computer based workshop manual and parts database?
How long does it take you to get the engine out?

DuncanG

Kevin, I've run my GT on occasion on NUL and get occasional flashes of red on the knock-link. TBH I don't notice a difference in performance. On optimax I still get very occasional flashes of red when going through the transition phase. The GT-B runs a bit more boost so might be more prone to det - who knows.

Ben,
The primary boost solenoid is connected exactly the same as an Impreza with a 2-port sol; ie theres a short hose with an implanted restrictor leading off the primary turbo outlet that goes to a T piece, the opposite branch of the T is connected to the wastegate actuator, and the centre branch of the T leads to the duty controlled boost solenoid which bleeds off pressure to raise the boost under control of the ecu. That controls boost for both the primary and secondary. The ecu normally sets a lower boost level for the primary phase. Some of the earlier models also had a wastegate on the secondary but it was superfluous.

The other duty controlled solenoid modulates the turbo pressure which is fed to the pressure side of the exhaust valve actuator. The vacuum side of the exhaust valve actuator is fed by vacuum from a tank and is switched by a bipolar solenoid. The exhaust valve controls the flow of gas from the ex manifold to the secondary turbo. Its located at the top of the secondary turbo up-pipe; ie the pipe going UP from the manifold to the turbine inlet. This could be used as the primary wastegate for the transition phase. The pipe from the 2ndry compressor outlet to the intercooler incorporates a butterfly valve controlled by vacuum actuator switched by a bipolar solenoid. All this (and more) is controlled by the ecu.

Impreza workshop manuals: http://www.saxonfields.freeserve.co....rkshop_Manuals

If you find one for the Leggy GT let me know

Cylinder heads - Subaru designs might look like they havn't changed for 20 years but you'll soon find that they continually evolve. There are many small differences between different models and years, even when the parts are interchangable.

Duncan

craigdmcd

iTrader: (2)

RE the heads, i would need ot get hold of both an impreza and legacy head, and preferably the different incarnations (WRX/STI/GT/GTB etc etc) to see if there are casting and machining diffs.
I have a set of heads from a MY99 manual GTB (although the inlet valves on No2 port have snapped off after maxing the car for 1min in fifth gear) if you are interested in them. The N/S head of a legacy is different in at least that there is an extra oil drain for the turbo and a water pipe union(both can be machined by any good engineers)

How long does it take you to get the engine out?[/QUOTE]Once you get used to the cars, approx 1.5 hours should get the engine out if you are working on a 2-post ramp, I managed in 2.5 hours on a garage floor with no-one to help me but myself
Very interested if anyone can come up with some cost efficient mods
Craig

BenAWT

If you email/PM me about the heads then dependant on cost we could come to an arrangement.

BenAWT

Thanks for the explanation Dunc.

Was looking it at today as the workshop wasnt very busy. The primary turbo action is fine, just the introduction of the secondary and the opening of the intercooler to the secondary. Now, assuming that the exhaust valve is the only thing hindering the spooling of the 2ndry, we ran through the idea of using the SMT series piggy back ECU and running the freqency valve controller on an amal valve to bleed boost off the to actuator of the valve. Also the valve opens on boost pressure does it not, so running a much softer internal spring to which the primary's low rpm boost is sufficient to overcome the spring.

But still have to consider how the ECU's boost map would handle the removal (hopefuly) of the boost valley. Fueling can be taken care of no problem.

Also, does anybody's elses GT, say in 5th, have pulsing power delivery above 5000rpm. Where the power comes on for say 1-2 secs, dies down a minute bit for the same period, then comes in again. Its not a constant smooth boost.

Oh, and whats the means of increasing boost via the ECU or a chip etc.

DuncanG

Like I said earlier -

AJbaseBloke

Duncan,

I am the one with the SMT - and AVO IC, filter, and exhaust. Circa 315ps @ 39deg ambient. Intakes were stupid high... (btw this is on a BE5B, so has older big bore MAF, intake manifold etc which dates back to the BD/BG era - great for top end, not so great for response). Same mods on BE5D are worth circa 305ps due to smaller bore MAF, intake manifold etc, but response is mucho better.

The SMTs work very well indeed when the tuner knows what they are doing. Mine is going back in for some further tweaks and testing in lower temps, so we'll have to see what the results are (although it looks like 340-ish is going to be the limit of the turbos).

Ben, The boost valley can be tuned out to be a plateau - we've done that. Boost control can get wooly though on those early TTs, esp. without cats. Primaries are well known for self destruction, too (as mentioned). Take a long hard look at the BOV - it is ridiculous really, just a placcy flapper Good results to be had with a decent BOV there.

If you are going to decat - get a better exhaust (centre and tail) IMHO. And get your SMT on it immediately. If tuned properly, there is no reason you can't enjoy some benefits. Just watch the boost, as there is not much headroom in those turbos (as has been said). Of course there is Duncan's way as well.

I've not had much issue with oscillation on my car (which is obviously newer), but I am going to give it a tweak with a boost controller to see if I can get the low end up a bit. Tinkering with the idea of moving the changeover up a bit higher so more gas is flowing, too...

Hope you can spear the dragon with the VoD as it is known to many.

Sorry that there is not much new in my dissertation

Cheers

DuncanG

AJbaseBloke, what parameters are controlled by the SMT? And can they be trimmed both ways, eg can timing be either advanced or retarded? I remember seeing a write-up of your installation but can't remeber where. Could you post a link?

Duncan