MrContro

Hi all,

After you've sorted all the bolt on tuning mods like larger turbo, FMIC, full exhaust system inc. decat, intake, manifold, ECU, boost controller, where do you go from there

How far can you go as far as power/torque on the standard internals assuming you've sorted the fueling and intake temps enough so that detting isn't a problem

If you wanted more power could you just uprate the pistons or would you need to uprate the rods and crank aswell

What generally is the main problems/limitations of the scoob engine that can cause failures

Is it detting - caused by inappropriate fuel, wrong fueling(too lean or rich), too aggressive ignition advance, too high intake temps ?

Pistons - just can't handle the heat from temperatures generated by high boost etc.

Rods - just not upto big power

Crank - just not up to big power

Block(open deck) - just not strong enough

Can anyone offer any information

thanks in advance

Gez

From what i have heard 350bhp and 320lb.ft is about as much as you can go on an STI without internals. After that the rods and crand just cant take the strain. Thats when rebuilds are required ie JE pistons arrow rods etc etc ........ As well as that larger injectors are required to inject more fuel for the power and a replacement ecu to mapp everything correctly. With all that and a nice turbo and front mount intercooler and a nice inductio kit, fuel pump you are leaving 400bhp. As soon as you hit the 400bhp barrier other things start to let go like gearbox, diffs etc. An open deck block doesnt withstand as much power/boost as a closed deck. Some companies in Australia, Japan and the US rebuild engines using closed deck blocks and use 2.5L stroker kits along with another list of parts as long as my arm including rods pistons cranks etc. These beasts can withstand upto 450-500. I remember going on an Aussie Tuning Companies website where there monster was running at 460bhp@the wheels. This was by Toni Regali at Regali racing. A totally mental car. You mentioned running the car rich/lean, this depends on the ecu. The jap imports tend to run slightly lean down low and get richer as power increases but that depends on the Airflow sensor. When the airflow sensor decides to give up (usually due to the fiitning of an induction kit) the car runs v-lean and can lead to a blown engine. Ecu's like Gems and Link dont need the airflow sensor so that eliminates one of the causes of a blown engine. Anyway, i can sit here all night explaining, if you need to know anymore let me know.

Cheers

Gez

Adam M

gez,

when the maf sensor fails the engines dont run lean, they dont run!

the standard ecu detects a fault and the car will take you home in limp home mode until the maf is fixed.

you are righjt in that uprated ecus tend to use map and not maf sensors.

BTW, the standard crank is much stronger than you suggest. IN fact I had only heard of one breaking at 450lbft, but that was a rally car and as such the drivetrain takes much more of a strain when the thing lands.

Dr Drink

Hi,

Gez - thaks for that, is the 350bhp, 320lbft applicable to the WRX too as you said it was rod and crank that may fail, not pistons which I think are the main difference betweeen WRX and STI with regards engine internally, I am nearly at the stage of all bolt ons and soon to have remap, the mapper said he can setup the engine as well as possible without inducing knock, If i'm running optimax + octane booster and all the mods in my previous post how do I know unless I do a poer run that I'm not over stressing the engine power wise

Thanks


Brett

Adam M

even a power run wont tell you what is over stressing the engine as no one knows what they can handle, only how they have performed in the past.

several people have run standard internals sti and non sti at 350bhp and over 320lbft.

You will struggle to get a lot more than that without going for insane boost, which may well require a new turbo anyway (cant remember what you have) .

Dr Drink

Hi

Adam - I have a TD05 turbo. Why do people say scoobs have chocolate internals then, I mean, an escort/sierra cossie needs internal mods to safely get over 350bhp doesn't it ?, and cossies usually run large amounts of boost to achieve this. What is it that makes people say cossie internals for example are loads stronger, is it just that you can be less carefull about fueling and intake temps and just let the engine cope with detting without damage, is this what makes people say they're so strong.

I have no illusions that cossie engines are a stronger than scoob engines but why and even more why if they can only handle similar power increases as scoobs on standard internals.

Please note I am not a cossie expert, I was gonna buy one once and looked into tuning packages from a number of companies and 350/360 seemed their recommended safe level before internal mods would be required.

If you say you need to run big boost to get any more than 350bhp and hence may require a turbo upgrade, then what does adding uprated pistons and rods do to enable you to run high power, is it just that it can handle hotter in cylinder temperatures ?, I thought the main enemy was detting which is caused by hotter in cylinder temps and crap fuel and fuleing which would still happen with uprated pistons and rods etc., is it just that these can handle the stresses of knock ?

Any help would be appreciated

CMA

I'm not an expert Scooby tuner but I have owned four now. I also co-drive a low spec Group A Escort Cosworth rally car.

On the rally car we have to run an air restrictor on the rally car for the rules of 34mm diameter which effectively limits the revs to 5750/6250 rpm as the engine runs out of air otherwise. We also have air injectors to bleed off excess boost at high revs (only needed because of restrictor) and water injection into the intercooler to get the induction temps down. The turbo (Garrett T4) has also been modified with a 360degree bearing and the compressor blades have been machined back to prevent the tips going supersonic in the relatively low pressure air after the restrictor and the associated shockwaves junking the impeller assembly.
Our dyno figures are 285bhp at about 5800rpm and 375lbft torque which if allowed to rev to say 7500 would give in region of 425-450bhp. The internals of the engine are standard Cosworth.... So they can take it. Where we have most problems is drive train and mostly in the gear box due to reverse torque loadings on full boost gear changes and landings and the unwillingness to spend 8000k on a competition 'box.

R19KET

Air injectors have little to do with the restictor, they're just a much better way to control boost, particularly with an external wastegate, and a decent ECU.

Few people use them, because they are expensive, and turbo's with internal wastegates generally won't benifit.

Mark.

MrContro

Thanks guys,

Well one person has experience of cossie internals up to the job, but can anyone else shed some light on the questions I posted earlier, I'm sure it would be beneficial to a number of people, not just myself, alot of people seem to be bolting lots of goodies to their cars and would like to know how far tehy can go with it etc.

By the way I think because the scoob is the tuning flavour of the month so to speak, we get effing ripped off for stuff, have you seen the bargain prices the cossie guys get for similar kit ?, and no manufacturer can say the scoob stuff is specialist items with small demand, everyones gettin one.

anyway could someone please post some experiences of what they have run, and technical info maybe.

Cheers


Brett

R19KET

Brett,

You need to take into account how long the Cossie has been around, compared to the Impreza, and the size of the markets.

Strangely, it's taking an awfully long time for the UK to start REALLY tuning these cars, and for the owners to take the plunge, and go internal, but I guess it's the chicken, and egg story.

You'll find it hard to get a definitive answer, because no one really knows.

We do know that there are quite a few cars running standard internals with circa 350bhp now, and one or two running a little more.

Both the rods, and the pistons, especially the cars with cast pistons, are generally considered the weak link, once you go past circa 350bhp.

The cranks are reputably very strong, and in Aus', even the most powerful cars run stock, but they always replace rods/pistons.

Part of the problem we have, is that because of our engine design, to do anythng internal, means the engine needs to come out. To change the rods means a complete strip down, so most decide to go the whole hog, and replace rods, and pistons.

The only real way to find out just how far you can push your engine, is to try it and see.

Mark.

MrContro

Cheers Mark,

I can uderstand what your saying, but for example what r u running, if you don't want to disclose on the net can you email me details and what you found to work/not work, do you think manifolds work like the HKS one, I've ordered one anyway cos I have heard at least some good things about them but it seems not many people touch the manifold saying its not worth it but it must be, the standard one looks ****e and not just externally lol

Can you recommend a good uprated fuel pump, do I need a Fuel pressure regulator with it ?

Know anywhere that does good prices on pistons and rods and can you recommend any suppliers, and also recommend the make of piston and rod.

How much work is actually involved in fitting these on a scoob ?, could you estimate how much it would cost or how many hours labour it may take obviously not at main dealer rates.

Know anyone whose fitted uprated cams like the HKS ones ?

If you can answer me some of the above I'll shut up and leave everyone alone and i'll post my experiences of boost and power and blow ups over the next few months lol

Cheers again

Brett




Brett

C

I think it's probably best you e-mail Mark about these things to be honest Brett!

He is a valuable source of information who is very helpfull too!

I should imagine he is able to source most if not all the bits & bobs you were talking about and advise you on which way to go.

A lot of the stuff he has been & done himself which helps too.

Chris

David_Wallis

Ill second the fact that he's really helpfull... Id also say that if anybody could spec an impreza engine he could.... His comments on air injectors for example... Only thing is last time I looked at his car he had problems with it.. (problems being there is a fooking turbo the size of a dustbin under the bonnet..)

Oh and Im sure now he has a banner add on the way He will be quite happy to sell you impreza tuning parts...

Incidently mark surely it would be a good thing to disclose your results and engine now??

David

Adam M

Will third that.

mark specced all the parts for my engine too.

I would expect the engine in my car to withstand significnatly more than 500bhp, in fact nearer 600. Mark suggested and pretty much sourced everything on the way there too.

I won't be running anywhere near this kind of power, as my insurance when it is sorted, will probably not allow me to run more than 400, in which case I will be running about 0.7 bar of boost .

Frankly I am too much of a woos to need proper power anyway, so its all wasted on me.


It is worth pointing out that uprated internals can handle higher stresses associated with developing more torque.

At high speed and high torque, the varying forces on the rods means it has to have stronger construction to survive.

Det will kill any petrol engine regardless of how strong. the explosive forces produced through det are much much higher than that experienced during controlled combustion. The pistons need to be uprated to handle the heat and also the greater pressure generated by running higher compression (if you have it) higher boost, and higher temperatures. The amount of energy in the combustion chamber willincrease as you have more fuel burning in more air.

det control is the first thing to sort out if you want longevity and high power. for this you need to consider, ensuring you ahve enough fuel, as running rich lower in cylinder temps. running too rich leads to bore wash which will kill the engine. This is controlled by ensuring good fuel pick up, having a decent fuel pressure reg, and fuel pump/injectors, and mapping the engine properly, all things that mark is the man to talk to about to be honest.


det control is also maintains by reducing charge temps (hence intercooling and cold air induction kits and water spray).

water injection is another route which works well, and should not be mistaken for working by reducing charge temps as that is not its principle aim. It reduces after combustion temps, by wasting combustion energy on boiling water. this allows ingnition to be advanced so that lost power can be more than recouped, or it can be used simply to add safety.

funnily enough this is another area where mark has massive experience both in practical use and in supply.

He is going to need a whole page ad at this rate, dont think a banner is enough.

perhaps an insult might even the balance. He smokes too much and has questionnable taste in alloy wheels!



[Edited by Adam M - 9/25/2002 11:57:02 AM]

David_Wallis

Adam,

Ill second the bit on smoking.. but I like his alloys..

David

SecretAgentMan

...he does smoke alot!

/J

Adam M

so do his tyres, anyone else see the elvington video !

C

I'll third that! (smoking) Lol!

Even manages to put me to shame!

And he has the nerve to call me a tart with my car too!

Chris

SecretAgentMan

You don't want to know what he calls me.

Adam, where's that video?

/J

Adam M

havent got it.

you can buy copies somewhere. it was mentioned in general. sure someone will know about it.

he got a whole little feature and everything.

no pics of the engine bay though or the turbo

Would appear that even needing to reduce his fuelling again and again, his times for the 500m came down about 2 secs. Was still overfuelling by 30%!!! when he got his quickest time. Apparently he ran out of time.

R19KET

You guys may well laugh, but before I knew you all, I didn't need to smoke, or drink, and looked 30 years younger.

Now, having only know you lot for only a short while, I'm a chain smoking alcoholic, with Grey hair, and look like I should have retired years ago !!!!

Mark. Just trying to SURVIVE Subaru owners

dsmawd

Why would the engine internals be a weak link? Aren't they forged pistons and rods? I'm curious as I have recently had an STi Ver. 3 motor installed in my wagon. I was under the impression that the STi cars used forged internals, if that is in fact true, I would think the gearbox would be a limiting factor sooner than engine internals.

- Trent

Adam M

no way.

pistons may be forged, but rods certainly arent.

rods are same in sti as in non sti ie. pants!

rumour has it that sti pistons can handle 1.8 bar, but I would rather be sure hence have JE on order for both engines.

rods are the weakest link I know of.

Gearbox isnt great, but at least when it goes it doesnt take the engine out with it. Plus it can go mroe slowly so you can be aware that you need help. Not so with the engine. snapped rod = £££££££££££

C

excuses, excuses

Chris