high compression turbo KA

[2_fast_240]

OK ive asked this question before and some said "dont do it", while others said "yes, but only with a standalone and good tune".

Now, ive been doing some researching and I see no reason why it cant be done with an ecu tune from enthalpy, jwt, efi specialists, etc. Before you flame me, atleast hear me out.

I came across this formula for finding the effective compression.
((boost/14.7) + 1) x compressstion = effective compresstion
It also stated that about 18-19 is the safe limit for effective compression.
So ((10/14.7)+1)x10.5=17.6 ((16/14.7)+1)x8.5=17.8

According to this 10psi on 10.5:1 CR would be just as safe as 16psi on 8.5:1 CR except for one thing. heat.

Compression that comes from boost can be cooled before it enters the cylinders (intercooler, duh), as to where compression achieved from the pistons cannot.

So I could run a water or meth. injection kit to solve that problem.
Then, just install an efi spec. retuned ecu (my choice for turnaround time). Have a good way of monoriting knock, wideband a/f gauge, colder plugs gapped lower, and run 93 octane. Away I drive without having to pull the motor.

Someone please tell me if this makes sense or if im just an idiot. ASAP!!!

And, if I couldnt get away with 93 octane, would octane booster like they sell at autozone make a difference (not sure if that stuff actually works).

[Koopa Troopa]

Why not just run a lower compression and be done with it? With a remapped ECU you're not going to make any decent power anyways so why sacrifice safety to your motor?

[2_fast_240]

Why not just run a lower compression and be done with it? With a remapped ECU you're not going to make any decent power anyways so why sacrifice safety to your motor?

Well, mainly time. Im going back to college in Jan. and would like to have this bia turboed before I do so. If i did this i wouldnt have to pull the motor. And I would want the check the cylinder walls before getting new pistons. So, i would have do that before i can even order them. And if it needs to be bored again, i would have to wait on the machine shop (which took like 4 months last time). And if I do have to bore it again i would have to go .04 over since im already .02 (hello coolant passages).

But, if this would not be safe, I guess ill just pull the motor and do it the right way.

I thought it would be just as safe as low comp. pistons/high(er) boost though. Can you elaborate on why it wouldnt be.

[2_fast_240]

Oh, and as far as power goes, ive only riden in 2 turbocharged cars in my life. So im sure i would be happy with 10psi on a t3/t04e regardless of how conservative the tune is. For now atleast

[Koopa Troopa]

I thought it would be just as safe as low comp. pistons/high(er) boost though. Can you elaborate on why it wouldnt be.


Because nothing on paper ever goes how you want it to.. You could make a safe high comp motor obviously but it'd take time, patience, know how, 2 more motors and more money.

[bo2o]

go with forged piston for the win.
find a new block. there a dime a dozen nowadays.
but u can safely ride on stock internals at 5 to 7 psi. of boost.
but risk blowing your rings. thats the weak point of ka's

as far as tuning if you have it right away then ya you can get away with it. 8 to 9 psi maybe be still facing rings being toast.

[2_fast_240]

go with forged piston for the win.
find a new block. there a dime a dozen nowadays.
but u can safely ride on stock internals at 5 to 7 psi. of boost.
but risk blowing your rings. thats the weak point of ka's

as far as tuning if you have it right away then ya you can get away with it. 8 to 9 psi maybe be still facing rings being toast.

im not talking about stock pistons. I have Supertech 10.5:1 forged pistons.

[Koopa Troopa]

Then buy a thinner headgasket and build a mechha tuned KA24

[gunluvS14]

the key is cylinder pressure, understand the max. cylinder pressure threshold can help you a ton.

[PoorMans180SX]

And you need a professional tune for YOUR car. No send-away aftermarket burn is going to cut it with the delicate balance that would be required.

[2_fast_240]

^^^ I dont understand why it needs a delicate balance. If I just tell them to go way on the safe side and retard timing more than usuall and add more fuel than usuall, it should be ok right?

[orion::S14]

^^^ In theory, yeah.

But you're playing with fire.

Effective compression from boost means NOTHING, per that formula you posted...with respect to the potential for detonation.

You're taking an already detonation-prone motor at 10.5:1...and adding boost.

Yes, it can be done...but the margin of safety goes to NOTHING.

8.5:1 with a bunch of boost still has a margin of safety...your setup will not.

Yes, it can be done. Yes, it is done all the time (turbo S2000's).

But it's NOT recommended.

- Brian

[EDacIouSX]

let me give you a word of advice....

patience is a virtue

Just be patient and do it right later.

[O3DigitalBath]

...I'm not really sure why everyone is so scared and thinks thats such high compression...

Not that I have any experience with a KA-T but in the honda world guys run 11.0 and even higher with boost (like 12psi or more out of 2871's and don't have problems...). Ok, this isn't a honda, but I don't see how he'll have a problem.


I do agree on not having a generic tune tho....not a great idea

[Koopa Troopa]

And I'm sure they swap motors more than I change underwear. I'd rather run a low compression turbo motor and not worry about melting shit or popping something. Replacing something that shouldn't have been replaced is always gay.

[The Riot Hero]

sweet, do it. run a good size turbo and run it on E85. done and big power. will need a good tuning device.

[GSXRJJordan]

If you've already got a built bottom end, you should be ok. 10psi is a lot on a 10.5:1 motor with no oil squirters on the pistons (but running water/methanol injection will help a ton). There's a member on here from San Diego with a nice KA-T tuning shop that burns ECUs... he runs E85 on his KA, and I'm pretty sure he said he was in/near 500whp. I'd talk to him.

[2_fast_240]

Thanks for all the input guys. I think I have come to the conclusion to just swap out pistons though (or maybe mill the ones I have, hmmm). For the hassle of running race gas and having spot on tune, I think it will be easier to just pull the motor. Plus ill be able to turn up boost.

[2ilvia]

According to this 10psi on 10.5:1 CR would be just as safe as 16psi on 8.5:1 CR except for one thing. heat.

if its the same thing, even worse because of heat, then just run 16 psi

[The Riot Hero]

RUN E85!!!!!! itll be awesome with the high compression and you could run high boost too and get the shit at the pump for cheaper than 87. do it

[PoorMans180SX]

^^^ I dont understand why it needs a delicate balance. If I just tell them to go way on the safe side and retard timing more than usuall and add more fuel than usuall, it should be ok right?

Wise man to swap pistons. At the point above^^ you'll be making low power and really bad gas mileage, along with the negative effects on driveablity.

[sideview_180sx]

keep the damn pistons. just run lower boost. you don't need to run 16psi. high comp boosted motors make the same power as low comp motors, by using less boost. if you do run 10.5:1 compression. you could run anywhere from 4-8psi less boost and make just as much power as a 9:1 comp motor. your margin for detonation is thin. however as long as you don't get the piss poor 91 from socal and you are in a state that offers 93up and you run a water injection. the car will be just fine.

this has been discussed on freshalloy many times before.