Markus

Age old question I know.

the blackbeast is a MY94 WRX Wagon, thus it has got a 220ps engine (what turbo does it have?)

Now and STi engine has 280ps, so exactly what bits are different to give the extra 60ps?

Is it just blueprinted engine parts. eg; con rods, cams, pistons, etc... (lighter/stronger? what does blueprinted really mean)

Lighter/stonger flywheel?

Bigger turbo?

Just curious.

Also, would it be possible to drop the engine from an STi II into the engine bay of the blackbeast? would substantial work need to be done to take it?

Adam M

markus,

your car has a mitsubishi heavy industries td05 (big turbo).

The mechanicals (except the cam profile) will not affect the power output. this is defied by the map. Stronger stuff is just more resilient to boost, so the sti cars can supposedly run a higher boosting map, more agressive ignition timing, and wilder cam profiles.

I am not sure, but I think wagons have a different (higher) compression ratio of 8.5:1, but this may be the stis only, and may be limited to a certain vintage. Bob Rawle will know the answer to this one.

Also I think you could drop the engine from an sti 2 in with ease. Unless I am mistaken, you could also drop in the complete engine (but also turbo) from an sti 3 and 4. Not sure how ignition would work as your car and sti 2 run coil packs but the 3 and 4 are wasted spark.

Regarding engine swapping, the man with the practical and theoretical experience is Pat.

[This message has been edited by Adam M (edited 27 July 2001).]

GavinP

Marcus,

If it is a 220ps model, it is likely to have a compression ratio of 9.0:1. I'm sure Bob said his STi II was 9:0 as well.

The higher the compression ratio, the less boost should be attainable before detonation (in theory).

I would think it would be more cost effective to get your existing engine internals strengthened rather than swapping an entire engine.

Thanks

Gavin

Crusty

I've fitted a STi-3 sedan engine, box & diff into my '93 RA. Just remove the top multi coil and use your old coil packs... new throttle cable, slightly modded wiring and she runs fantastic !! Only downside is that you'll have to change the bonnet to suit the new (larger) intercooler.

THOMO

it would be easier to change the ecu.i have a 93wrx 90%of that year suffer the same problem of juttering when given a hard drive.i went to most places to try and sought it out eventually i was told to change the ecu as this would cure it. my car is excellent now , its smoother faster better response. my first ecu was 240 12 psi . now its 260 14psi with new box + filter its probably a bit more. i would point out that my car went on a rolling road after at high speeds to check for det . it was perfect . obviously you cannot do this with every scoob ,but before i did i asked for previous owners opinions all claiming not a problem . i have done 2000k and up to 155 mph not a problem . if you can give more details of your car i will found out for you. steve bain a bbs member did this two weeks ago, happy with his result he loves me now.

THOMO

sorry the cost} 120+vat +tune

pat

Markus,

You could put an STi III / IV engine in there, but they are all open deck engines, whereas you may have a closed deck engine (MY94 could be made before Oct 1993 and would thus be closed deck). It would not make sense to lose that! What might be a better option is to pull it out the car, pull off the heads, and drop in a set of Cosworth pistons. This will drop the compression to 8.0:1 and will allow the car to run 1.5 bar all day long without breaking a sweat... FWIW, I was getting about 330BHP out of my STi II engine at 1.35 bar; this had forged pistons (STi 8.0:1) but it was open deck, so yours should be stronger. Sadly I broke a rod (NOT, I repeat *NOT* related to the mapping / power I was running). After this swap, the weakest links will be a) the conrods and b) the injectors. Replacing the rods is a major surgery exercise... try to stay within their limits (they start dropping off once you get over about 310 lb/ft, but are a bit unpredictable). Injectors are easy, just get some later 440cc ones

To take advantage of any of these things, you will need a remap, preferably a complete ECU swap...

If you do have the closed deck block, remember that Prodrive used to get 400BHP out of them, but like most teams they had their own interpretation of the rules, and replaced the rods with some which looked pretty standard but were far from it. Tut tut...

Hope this helps... any specific questions about "will X work with Y" just ask... I don't really want to list the whole lot, that would take all week!

Cheers,

Pat.

R19KET

Pat,

Are you suggesting that it's ok to take a '94 car having done XXX miles, and just change the pistons What would the chances be that the bores are in "perfect" condition, and without wear.

Surely if someones going to the trouble of taking the engine out, with a view to strengthening it, to run much more power, the rods should also be replaced, and the block re-bored for the new pistons ???

Are we now saying that the standard rods, and bolts are ok to run 1.5bar ????

I'd also love to see the graphs for the 330bhp run next time you pop over

Mark

mkk33

Thomo,

Can you give more details on the ECU and where to get it please? I have a 93 wrx as well.

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:<HR>Originally posted by THOMO:
<B>it would be easier to change the ecu.i have a 93wrx 90%of that year suffer the same problem of juttering when given a hard drive.i went to most places to try and sought it out eventually i was told to change the ecu as this would cure it. my car is excellent now , its smoother faster better response. my first ecu was 240 12 psi . now its 260 14psi with new box + filter its probably a bit more. i would point out that my car went on a rolling road after at high speeds to check for det . it was perfect . obviously you cannot do this with every scoob ,but before i did i asked for previous owners opinions all claiming not a problem . i have done 2000k and up to 155 mph not a problem . if you can give more details of your car i will found out for you. steve bain a bbs member did this two weeks ago, happy with his result he loves me now.[/quote]

Stephen Cole

A few notes / comments /corrections to previous replies -

As it is a 5 door, it has the smaller TD04 Turbo
(I know as I've got exactly the same 220PS MY94 WRX 5-door)

STi's of the same era (STi 2?) are only 250-260bhp (can't remember exactly, and can't find the FAQ at the moment), not 280bhp
And have different Turbo, ecu, possibly strengthened/blueprinted internals etc etc

Whether early WRX's are closed deck or not is a good question that has come up in the past, and without taking the heads off, there doesn't seem to be a way of telling

Getting slightly more power out of it -
only easy options are
a) bleed valve ...
b) exhaust + filter changes
c) different ecu (Link etc) mapped appropriately
d) different turbo, etc and starts to get too expensive after this
or a replacement engine, but need to ensure correct ecu and wiring etc etc

Realistically would be cheaper to sell it and buy an STi 2/3

Stephen

paulhoubart

StephenC

I've got a MY94 STI V1, 5 door. According to the model codes, the engines rated at 250 BHP.

As for closed/open deck, turbo type etc etc., I get so confused by different people saying different things that I've given up trying to figure out exactly what I've got !

BTW - Anybody else out there with a STI V1 ?

[This message has been edited by paulhoubart (edited 30 July 2001).]

pat

Mark,

I am suggesting that a simple piston swap is OK, on the proviso that the internals are in good condition, ie no scoring / pickup. You know it *IS* possible to re-hone the bores without splitting the block down, IF you are that fussed about it

The trouble with replacing the rods is that it requires splitting the block, and it gets quite expensive. IIRC I was quoted UKP 1800 plus VAT for the labour for splitting and rebuilding a block By contrast, pistons will start at about UKP 440 plus VAT for the set, plus a couple of hours labour to fit, and a new set of head gaskets... much cheaper. Of course if cost is no issue then, of course you'de split it all down!

The standard rods and bolts have been running for quite some time in at least one car that I know of running 1.5 bar....Mine lasted OK at 1.35... yours haven't let go either, and they are ALL standard rods. Also, it has just occured to me that Bob is running similar boost and also his engine seems fine. So while they're not exactly God's Gift to engines, they're not quite made of chocolate either.
You'de be quite welcome to a copy of the 330BHP graph! Is it so hard to believe? I got 297BHP with 380cc injectors on PE's rollers, then after a remap with 440cc injectors I got 330 on the Road Dyno... seems plausible to me. This was with 1.35 bar; my last run at PE made 301BHP at 1.1 bar... it all adds up... in a weird Pat sort of way

Cheers,

Pat.

Markus

Thanks for the info guys.

closed deck eh, now it would be nice to think that the blackbeast has a closed deck.

Think that cosworth pistons might be a nice thing to do, any idea where I would get them from?

Doubt I'll do this until next year, due to a little lack of funds, but at least I know a good first stage.

Plus i've always wanted a Link ECU, so it would be nice to have an excuse to get one, vis a vis "pistons good, but need new ECU for best performance" she might fall for that one, especially if the car is a bit quicker!

R19KET

Pat,

Is it fair to say that when a bore wears, it tends to go oval ? as do the pistons/rings. Even an old engine can retain reasonable compression because pistons/bores wear together. If you go and put new pistons into old bores, you can end up with very poor compression.

Honing won't solve this problem. Out of curiosity, how would they use a honing machine, with the rod still in place. I'm not talking about loosing the odd surface blemish.

Re-Road Dyno figures: you should borrow mine, it consistantly gives higher figures However, Bob R still holds the record with circa 1200bhp, but I'm still trying to beat it

Mark.

pat

Mark,

Yes, the bores will wear oval, however... if you can still see the original honing marks (which you will be able to in a good condition engine) then is it not fair to say that the ovality MUST be less than the depth of the "scoring" produced by the honing process? Since these "scores" are actually VERY shallow, it stands to reason that the ovality must also be very slight.

Remember under normal operation the ring does not touch the bore, there is a miniscule oil film there which prevents it from doing so (and the honing "scoring" gives the oil film something to "cling to"). This is why we use a very thin running in oil, this allows controlled contact between the ring and the bore so the two "mate" and thereby improve the seal. It's why going straight to a fully synthetic is a big no-no... you'de still have fairly "deep" honing which would leak quite badly.

It would be interesting to measure the ovality of the bores on an older block before re-honing... just to quantify the scale of the wear, even if only as an academic exercise.

Having said that, I do agree with your point, and there *IS* more to it than just dropping in a new set of pistons, if you want some sort of reassurance that it will be OK. It's perhaps also worth mentioning that there are NO guarantees on motorsport parts, due to the very nature of their use. Whenever you step outside the realm of the tried-and-tested-to-death operating area the manufacturer intended (and will have spent millions verifying) you're "on your own". You can only be as vigilant as possible (within the constraints of the budget) and try to anticipate problems before they occur, hopefully fitting parts to address these shortcomings.

At the end of the day, it all comes down to budget. In a perfect world we'de all have more money than sense (I fall into that category, but only by virtue of the fact that I have some money, but NO sense so I guess that doesn't count) and could strip the block down, get the best parts money can buy, hire the best engine builder in the country and (hopefully) end up with the best engine money can buy. Sadly there aren't many of us that are willing to spend UKP 1-2k on a decent gearset, let alone spending five figures on an engine

So given a limited budget, and a "vintage" block of reasonable condition, I still think that replacing the cast pistons with forged ones is one of the best "insurance policies" you can buy, and it is cheaper than buying a later (weaker) engine with forged pistons as standard. 1.5 bar is perhaps a bit optimistic on standard rods, if everything else is "OK"... ie if the turbo isn't blowing out gas hotter than the exhaust into the intercooler, and the intercooler is able to get a decent (less than or equal to 40 degrees C) charge temp to the engine. If these conditions cannot be met then the power will be low regardless of boost level. I know a few engines that have lasted well at this level, but these MAY be just lucky... there isn't sufficient data available to say that it will or will not be OK, and there never will be. It's a balance of probabilities at the best of times.

You'de think that after all the millions Subaru have spent that they'de be able to "guarantee" parts, but I bet there are rod failures even on stock cars, just not very many of them. All a game of probabilities.... odds are a rod will be OK, but no guarantees. Can only go on what we know at the time. We know at least one car that has thrown a rod running just over 300BHP/300lb/ft but a few that are OK, based on that miniscule sample, odds are that they will be OK, but we can't see the big picture, so it could be that our little sample is actually completely atypical and that it's actually the case that most let go at that output.

So, Markus, given a similar set of circumstances to yours, *I* would replace the pistons. That doesn't mean that it is the right thing to do. It doesn't mean that it is the best value for money. It doesn't mean that it will work or last. It is just what I consider to be the weakest link at that juncture, very closely followed by the injectors and the intercooler.

I would be very surprised if there was a single Subaru tuner in the world that could give a "definitive" answer, with the possible exception of Prodrive (when winning is the most important thing and cost is virtually immaterial, you have the luxury to destruction test so you can be confident that your rally car won't break... but even they get it wrong sometimes... just the nature of the high performance game).

Re: using a honing machine.... quite easy, just turn the crank so the rod is as far back as possible You'll be able to get past the ring-swept area, which is all that really matters, plus with a little attention to detail you should be able to get all the way down.

Re: road dyno, that run actually read 370BHP, but I have to ignore the end... I dipped the clutch as the car ran out of puff, revs rose "sharply" compared to before hence the peak. The actual peak was about 330-335. The parameters are quite important, and have to be correct, otherwise you get silly readings... I have had mine read in excess of ten thousand BHP, but then like most computer programs it's GIGO, garbage in garbage out... feed it crap and you'll get crap back, feed it sensible figures and you get sensible figures back. To the best of my knowledge the figures I used were correct. I even got the actual temp and air pressure from the MET Office Height above sea level was from GPS (3D). Drivetrain loss based on losses measured on previous rolling road runs (perhaps dodgy).

Cheers,

Pat.