Can anybody tell me what the normal range is for an STi. Also what would be the absolute maximum safe upper limit? Thanks in advance, Deep.

 

Cheers guys.Any further info from anyone else? I'm still a little confused as to the norm.Darren,sorry I never got back to you about the SS BB but there is a chance my car might need some money spent on it and so d'ont want to make any other expenditures on it until I know for sure. Deep.

 

Deep
I have an STI2 and runs 1.4 bar dropping to 1.2 at the top end . The engine internals are standard .
Dave

 

I'm not too sure that the norm is, but I'm boosting to 18psi in my '95 STi.

Perhaps other STi owners can post their's.

 

I think 18 psi is a bit high for a std STi.
Are you running modded pistons???
Its about 12-15 psi normally isnt it??
Cheers
Darren
MY96 STi

 

Deep,

if you check out the dyno web site you can see standard STi boost values - typically peak at 16-17, hold 15. 12-15 to too low.

How much boost depends on how well you tune your engine - pistons are ok with 'reasonable' limits! But what the hell is reasonable

R

 

My 94 STi Peaks at just below 1.1 bar, and holds just above 1 bar. Scoobymania downpipe was fitted at the same time as boost guage, so I dont know what it should produce normaly.

 

In OZ, Modern Motor magazine did some tests on the version 5 & 6 STI's through APS and found them to run around 15.5 psi max boost under full load using 98 RON Optimax fuel on a day with 26 deg Celsius. They found that weather played the biggest role in turbo performance as they ran less boost on hotter days.

Hope this helps,

WREXY.

[This message has been edited by WREXY (edited 07 May 2001).]

 

Darren

I'm peeking at 18psi, holding at 15. I'm not too sure if the pistons have been changed or not. The car is a Japanese import here in New Zealand. From what I can tell, the forged pistons were an STi option.

I haven't had any problems running at this pressure, but I'm about to put in a Motec (next month). Looking at peaking and holding at 18psi (or as close to it with wastegate creep). 1st gear will be limited to 12psi, the rest will be 18psi.

I notice that Alex is doing around the 1.1 bar region as well, with Big Bear running even more boost

 

Hi all, I hate to butt in but does anyone know what the conversion from Bar to PSI and vise-versa is?

Cheers
Trev.

 

Trev

It's not exact but 1.0 bar is approx 14.5psi.. You should be able to work out the rest from that.

Scoobs

 

Sorry, but I'm a sad (former) engineer.

1 bar = 14.5 psi

1 standard atmosphere = 1.01 bar = 14.7 psi

(normal temperature and pressure etc.)

On amore sensible note, what turbo do you guy have so that you can get that amount of boost?

 

Hi All!

The amount of held boost will be model year dependant, so it really comes down to which STi you have...

IIRC STi / STi II ran 0.9 bar, the STi II about a bar, everything later about 1.1, but I'de need to look it up to be sure.

As for running higher boost, the STi / STi II have an MHI TD-05H turbo with a bespoke (for Subaru) compressor wheel and cover. The standard TD-05 turbo will hold 1.6bar, so this one should do even better... I used to run between 0.9 and 1.4 bar on mine, over 1.3 bar it "screams"

STi III and STi IV run IHI RHF5/VF24 turbochargers which I've yet to see a compressor map for, but they should be good for at least 1.4 bar. Interestingly some of the WRX cars from that era were shipped with VF22 turbos, which will flow more air, should be able to hold 1.5 bar maybe 1.6.

The STi V / VI run a VF28 turbo which is very similar to the VF24, certainly has the same exhaust trim and the compressor cover looks the same, but the compressor wheel may be slightly different, again these should be good for at least 1.4 bar.

The STi VII comes with a VF29 turbo, which essentially a VF28 with a new compressor cover and wheel... suspect this will be good for at least 1.5,

Once you look at after market turbos the sky's the limit... I know of one car running "my" turbo at 1.7 bar and getting 430 BHP, it must just be twiddling it thumbs at 1 bar, LOL Hybrid VF22s are supposed to be good for about 1.8 bar.

But in all this, the most important factor has been overlooked... charge density. Just because a turbo WILL produce a certain amount of boost (ie it's not choking) doesn't mean it's doing so efficiently. It could be imparting a lot of heat to the air, which will mean a less dense charge, hence less air (although it is at a higher pressure) and less power. There is no substitute for good intercooling and a turbo which is matched to the application, so that it is operating efficiently in the area where it is required by the engine

Hope this helps,

Pat.

 

Pat, he has a 98 Typre R

Dan

 

Trev,

that does sound about right for a K plate, it's an early car with an EJ20G engine and TD-05H turbo, they were well under-stressed It is possible that somehow you ended up with a high compression engine even though it is a 4 door, but it would be unusual! Have you compared it to any other cars yet, that will tell you whether a) it is genuiniely going like a rocket or b) you've not driven a scoob before and therefore it feels like it's going like a rocket

The boost does seem about right, assuming it is a 92 car.... it would be "wrong" for anything later than '96 thought.

Cheers,

Pat.

 

Thanks all for the help.

I only have a 4 door WRX on a 92K plate but it goes like a rocket and the boost gauge reads 0.85 bar when I floor it in any gear. so this is approximately 12.325 Psi (240+ BHP?), sound correct for model? Only mods are an unknown Japanese exhaust that came over with the car.

Cheers.
Trev.

 

Cheers Pat.

Well In my job i've driven and wouldn't swap my Scooby for any of these cars:-

Audi TT 230 (only good for pose value)
Volvo C70 T5
Sierra Cosworth 4x4 chipped to 280BHP (owner claims)
Golf V5
Mercedes S80 Exec.
Audi A8 4.2 Quattro
Aston Martin DB7 V12 (Too much Torque, no grip!)
TVR Chimera 5.0L (as passenger only)
Renault Clio 16V (latest version)
+ a few lesser vehicles

Have owned:-
Lancia Delta HF Turbo (chipped to 182 bhp)
Mk2 Golf 8 & 16V.
Peugeot 405 Mi-16 (DO NOT GO NEAR THESE VEHICLES!)
+ a few lesser vehicles

and I can honestly say its the best car I've driven for overall feel, solid comfortness and performance without any real need to try or push it hard.

Haven't driven an STi yet (fuel consumption probably even worse than 22mpg!)but will do sometime.

Trev.

p.s. I don't want to sound big headed I just happen to work in Research and Development for a Car manufacturer and we get to see and drive a lot of cars.

[This message has been edited by tizard99 (edited 14 May 2001).]

 

As Subaru daeler I have a lot of car's whit a turbo pessure from 1,1 a 1,2 bar at the top and i do not have problems.

Hans