OK, I need some advice from a turbo expert. Looking into a "strange" configuration for an experimental engine, between a 2.2 and a 2.5 engine. Now, the engine spec should provide large dollops of torque, and has been tested at some scary levels of BHP - my question is, what turbo should I specify ? I'm looking for around 600-700BHP, so the turbo needs to be able to handle boosts up to and beyond 2 bar - I believe the GT series of turbo can get close to this, but what I don't want is something that needs beyond 3500-4000 RPM before I start getting some boost.

Can I also ask, before people start telling me that "you can't get that sort of power from a Subaru engine", or "the engine will blow up long before you reach that", the engine spec will more than handle this level of power. I'm more interested in high power turbo characteristics, which provide more torque vs BHP, what spec compressors etc etc I should be considering.



Paul Houbart
Gecko Motorsport

 

YHM

 

Ta - so do you !

 

GT35/42 or Turbonetics Twhatever

See here for an easy to digest list of Garret GT series.

External wastegate.

Plenty'O'boost, 2+ bar held

Head work and cams/springs

850 -> 1000/cc injectors depending on fuel pressure (or 8x staged in batches of 4)

3"+ exhaust tapering to turbo exhuast housing diameter (the 'Pat' spec exhaust springs to mind).

Management that doesn't use a MAF sensor OR a fecking big MAF sensor (custom ones available from US)

Others will I'm sure have their own views.

 

Pavlo -

Thanks for that, most useful. What should I be considering on the turbo spec regards boost behaviour ? Thinking in terms of boost vs revs graph, looking for something that isn't too peaky, and I want to keep the torquey nature of the engine as it stands.

 

A good place to look is Ray Hall Turbos:
http://www.turbofast.com.au/welcome.html

Their prices are really good compared to the guys in the USA.
They have a great GT35 turbo that is rated to about 700hp
comp a/r .70 trim 56
exhaust a/r 1.06 trim 84 on a T3 flange, so the spool up is really fast.



We're going to get 700hp out of the new turbo EJ2.5 engine with this turbo.

hope this helps,
Jerry

 

Jerry, see my link above

Paul,

You need to speak to mark he has practical experience of such turbos. His is LARGE, and a bit laggy, but not too large for 650 hp.

Worth bearing in mind that the 2.5 engine has more torque off boost anyway, and although not at FULL boost, even a little boost on these engines/turbos goes a very long way.

paul

[Edited by Pavlo - 2/13/2003 2:41:50 PM]

 

a little bit too small.. good for about 600..





David

 

Hi,

go for twinturbo!

thomas

 

But even the big power Skylines dump the twin turbo's for a single turbo.

Andy

 

Andy > not all of them

 

I would stick with single, it works.

Twin turbos can have balance problems when trying for high boost.

Paul

 

This is a serious question... How do you intend to keep the heads on and the block halves togther at that torque/power?
I know from experience that at that sort of load this can prove to be the limiting factor on the flat 4.

 

ScoobyRacer -

The engine spec I'm considering has been tested previously at 850BHP, so handling 600-700 should be no problem. Virtually every part of the block is upgraded, including the valve train. Oh, and it's not based on the EJ20 block, FYI.

 

Head lift can be sorted by stud conversion..

Block splitting I havent heard of... but I havent actually split a block yet..

David

 

Fair enough. I'm also running 14mm head stud conversion on an EJ20 without problems but I'm not running that sort of power.
I was just thinking back to the mid 90's to when we ran Per Eklunds rallycross engine, that was an EJ20 running 625bhp@3bar boost and lifting heads/cracking blocks were the limiting factor...just a thought thats all...

 

LOL ....what in the world are you guys going to do with all that power ???

Seriously though, can that car be driven daily with that type of power or is the gearbox, clutch, lag, gas usage ridiculous ?

What type of quarter mile speed could you get from a Scoob doing over 600 bhp.... under 10 secs ?

Cheers,
Ray

PS: You are all nutters ....and I like it

 

Scooby Racer - I won't be running anywhere near 3 bar, probably 2 bar max. The engine could take more, and has been tested at 37PSI, but as I mentioned earlier, I'm not after a peaky engine.

Well, the gearbox and clutch will need some "slight" modifications ! Lag wise, it should be no worse then a highly tuned EJ20 engine, the engine spec I'm considering has lots of torque. Gas usage, well I'm planning on having several different maps to run different power levels, so while driving on public roads it tuned down to a sensible level (maybe 450-500? ), but when on the track/drag strip/rolling road I switch to the high power map. Diffs are an unknown at the moment, and one element I'm trying to figure out at the moment. Could be troublesome, I agree.

Well, there's only one way to find out !

As an aside, this ain't cheap : I've reached £10,000 before even speccing the diff's and ECU, so wether it happens or not is another matter. Basically, given a known engine spec I'm trying to cost up what else would need upgrading, to arrive at a final figure.

Anybody fancy lending me £15k ?

 

Paul

Some little clues throughout your posts lead me to believe you have been talking to Ron in the US ?

Andy

 

Who?

 

WOW!! thats a lot of money do pay, so you are looking at about $25,000 USD for everything!

I got a complete running 700hp EJ25 for less than $10,000usd (minus the drivetrain)

A 700+hp WRX will run low 10's in the 1/4. thats the fastest in the US now. But those guys are going crazy with the mods now. They'll be in mid 9's soon

A 700+hp WRX in Australia will run high 9's

 

You should really hook into using the new semi-decked turbo EJ25 engines (same block on the new North American STi). They cost only about $1500usd. Then use EJ20 heads. These 2 combos are good for 700hp. It will save u a lot on the engine work.

Jerry

[Edited by jerry hong - 2/15/2003 1:19:47 AM]

 

Jerry,

errr - well you can do that - but won't the EJ20 heads will need plenty of work to achieve the power levels you are talking about - they are designed to flow well on an EJ20 - BUT the EJ25 needs 25% more airflow. So if that is what you mean then sorry if I misunderstood.

Scooby Racer,

I remember reading an article as to why Per Eklund changed from Scoobs to Saabs. He said with the Scoob his engine builder worked 6.5 days per week and never had a holiday. With the Saab he was lucky if the engine builder needed to work 2 days a week.

However that was with an EJ20 - considerably more power can be gained with slightly larger engines.


In terms of budget - in my experience the engine is not the expensive bit - of my budget, probably less than 40% of the outlay is for the engine itself - and this is because I am having some very specialist work done on it. It could easily have been half what I am paying. The big budget stuff is drivetrain, ECU and ancilliaries for fueling etc.


In terms of results, the world record holders for the Scoobies lie with cars prepped by the Rigoli brothers - to touch ten seconds you need a car that is running around 500bhp at the wheels, is geared specifically for a quarter, and is superlightened. To break ten seconds they have had to revert to using a computer controlled autobox (although that was the other brother).

Rannoch

[Edited by Rannoch - 2/15/2003 10:36:12 AM]

 

Dave,

EJ20 heads can flow more, just increase the flow velocity.

(for the benefit of anyone else reading)
I think Stephen measured a 10% increase with his headwork. But comparing a std MY95 head to modified MY00 head the difference was more like 15% at max cam lift. The subaru WRC cars use reduced port areas (don't know how) to increase gas speed, so I think a modified EJ20 head should be up to the job of flowing a sensible amount of air for an EJ25.

As far as the block mods go, I have found some very nice liners. They can go down to a 0.75mm wall thickness if you like. Available in MMC too, with ceramic (of sorts) coating.

I still like the idea of using the EJ25 block, and it's cast in place liners, even if they are ceramic coated.

Scoobyracer, having the block splitting is something I had not considered, worth bearing in mind. I take it you work for ProDrive?

Onwards and upwards!

Paul

 

Paul,

I agree - was merely highlighting the need to do the headwork - as you may get choke in the ports.

For the WRC cars - they dont need a lot of gasflow at high revs as the restrictor kills them anyway. What they need is best gas speed to get the outrageous torque levels that they aspire to.

Rannoch

 

The EJ20 heads flow great up to 600hp. The Rigoli's were using stock heads before to get mid 10's in the 1/4.
The problem with the new TURBO EJ25 heads is that is has a VTEC system on them. And not many tuners have had the chance to experiment with them. I'm sure the new TURBO EJ25 heads flow great, but the problem is that no one has tested them yet, and there are aftermarket cams for them. The 2.5 STi won't be out until late this year. I was just referring to the topic of having an engine NOW! and not in a year or two. I have from personal experience to say the the new EJ25 engines are much improved from the old versions. For years people have been putting EJ20 heads on EJ25 blocks.

I know that building a race engine isn't cheap, and cutting corners isn't an option.

And i do know some people in Canada are blowing the blocks apart.

Jerry

 

Jerry,

I think the main thing against turbo EJ25 heads is availability. I've yet to see any specs either, so no proof that they have larger valves and ports. In fact, do we know that they are any difference from the the EJ20 Sti8 heads?

Cost is the other factor. Most people want to either use there own heads, or cheap used ones from an EJ20, which are easy to get hold of.

Paul

 

Pavlo,

Thats what i'm saying too.. I agree with you. A good combination is using an EJ25 block, with EJ20 heads. And this combo is good for 600hp, without any re-work of the heads. I wasn't recomending using the EJ25's heads, but rather the block. It is already semi-decked, so no work of the blocks are needed.

Heres my engine:
-2003 NEW semi-decked (stock) Turbo EJ25 block
-Rigoli rods, Rigoli 100mm pistons, stock crank
-1999 EJ20 heads, huge 272 degree cams, upgraded springs, titanium retainers, Sti valves, Rigoli bored 850cc injectors
-Microtech ECU
-Ray Hall 700hp GT35 turbo
-Rigoli full dog box tranny

and all the usuall stuff to keep it all together

 

Jerry,

Are the new 2.5 turbo blocks already available in the US?

Mark.

 

Jerry,

So why are Oz horses quicker than US horses?

Also I thought the Rigoli cars that are getting low tens only have around 500bhp ATW.......does this mean they have a 200bhp+ drivetrain loss - seems quite high!

Also what are you using for boost control?

Rannoch

[Edited by Rannoch - 2/16/2003 12:24:37 PM]