Compression ratio 12.5:1. Bye-bye Super charger & Turbo build?
 

Also, what about freeing up horsepower in N/A form?

If an intake, and exhaust can get us 220hp i'll be happy with that, but would much prefer 250+hp with FI

Thinner head gaskets will RAISE compression, not lower it.

^ yeah you want a thicker gasket, but realistically it doesnt warrant a very good CR gains or losses.

On that note.. Boxer engines are a bit funky with gaskets

EJ251-Ej255 gaskets are thinner than EJ257 STI headgaskets.. BUT EJ257 gaskets give a HIGHER compression ratio to the same blocks....weird right?

I don't know EJ stuff at all, but what else is different? Or does just changing gaskets increase it?

There's something else involved there because and thinner but otherwise identical gaskets will always increase compression...

Do some research on boosted S2000's. It has been done a thousand times on totally stock engines, with 11.7:1 compression ratio. Results are impressive (420whp @ 12 psi for your typical bolt-on turbo kit using 93 octane, easily 500 with E85). A thicker headgasket is a bad band-aid, if you want to go high boost better build the engine and use lower CR pistons.

The biggest enemies on boosting this car will be:
- DI head (complexity, tuning)
- Space / packaging
- Lead time to having a decent standalone system available

Nice tip!

What about mill the block? Is this safe and not that costly?

A set of after market pistion+rod. But those are just over my budget limit.

I'm considering an used BMW M3 E90/92 now... which is... shame..:(

DI doesn't have any negative effect on boosting anything... At this point the 12.5:1 compression is pretty much the worst thing they could have done. It's going to necessitate one of 2 things... Either Meth/H2O injection or Ethanol or both. But even then I'm guessing that you are only going to be able to run like 8PSI... but you will get good power.

The only good thing about that is... the engine will have a fully forged lower end... It really almost has to... 12.5:1 at 8k rpm or however fast they want to spin this thing... it has to have a forged lower end

Kindly, you are not knowledgeable enough to speak on this subject at all.

STI runs forged cranks and rods factory, if anything id expect this car to have a forged crank since its expected to perform in the upper registries of the RPM range.

You don't have to be a **** about it.

Yes I'm not, just want begin to talk this topic.

And listen to adivces.

Why can't you just say why I'm wrong and tell us how to do thing right?

Just a thought Fred...maybe this might not be the car for you! How about drive it first before deciding if it needs more power. My .02

Milling the head and or the block will also increase compression. You want more room in there instead of less :)

12.5:1 static CR with good DI is not a real problem if you want light boost. A quick calculation tells me that with 93 octane, 10PSIg boost would be plausible for a tuned-to-the-edge-but-still-reliable setup, assuming IAT's are kept rational and the knock control as as good as anything from the past 10 model years.

That said, just because the combustion chamber might be able to handle the BMEP, doesn't meant the piston lands, wrist pins, con-rods, crank, bearings, block, head gasket, or cylinder head can handle the increase in BMEP. There is always a fuse, a weak-link, and it'll take testing, measurement, and trial-and-error to determine what's the weak links are to reliably achieve the power level you're interested in.

Since most tuners have minimal real experience with DI tuning, there will either be an influx of amateur engineering experiments flooding the market, or there will be a slow ramp-up by competent tuners that take the time to do things right [which is rare, especially with an affordable car]. By all means, buyer beware!

Thanks for advice.

I owned a 08 EVO X GSR with all bolt ons tunned with 337 AWHP 338 AWTQ.


Stupid people like me think more HP is better, I know that FT-86 is 1000 lb lighter than EVO. But I love turbo... I want put turbo on everything...

That just my plan, I guess lots people want do turbo buld...

what you might be looking at is a flat or even reverse domed piston depending on what they have in there stock.

Honestly if you are going to do a lower end on this thing, a better option would be to..

a) leaving compression alone and upgrading head gaskets and piston rings... that will allow you to run higher cylinder pressure... oh yea and heavier valve springs...

or----

b) aftermarket subaru sti motor with every option you want, and swap ecu and such.

Is the 12.5:1 CR a fact? I read through the entire post and they were just guessing that was it... Then people took off with that idea. just my 5 cents.

No one translated it.. but it's in the engine specs.. not sure what else it would be honestly.

It is CR... I can type japanese and chinese ... 压縮比

I am very sorry for offending you. I am not very good at disagreeing.

Logically what you said didn't make sense because a thinner headgasket increases compression ratio.

Others could misunderstand what you said and then believe it to be a fact.

^This +1.

Wonderful! It can always come in handy to have someone with your skills! Like today, Aki and Ichitaka were very busy with work.

Personally, I am very happy that the compression is 12.5:1. It is high enough to be even more efficient with E85 yet still be safe for low boost with pump Gasoline. For turbocharging, a lower compression is usually more inline with most tuner's/builder's goals and safer and more reliable. In this case, I think high compression fits better with 90% of the car's purpose otherwise they would have used one of Subaru's turbo motors

12.5 CR means a factory FI option is likely out of the question.

Never mind, I was so excited about the news so...

Glad that I can do some simple translate work for people.

Translate the rest of those tech info scans :)

Yes, please! If you would be so kind Fred_boost. http://allch-chcar.com/saved/bunny.gif

Ditto

Also when did S2k owner stopped them from SC or TC their S2k. Yes, US had 11.7:1 (vs JP was 12 iirc), that's still high comp for boosted car.

diesels are what 17:1? MOST of them are boosted LOL
with petrol, and 12.5:1 you will get low boost but LOTS of power. energy is extracted MORE at a higher comp ratio, so a 10:1 running 10PSI will get more power than a 8:1 running 10PSI ;)

Diesels operate pretty differently, they cannot knock by design as the fuel is injected and burns slowly, instead of all at once (for this reason the diesel cycle is actually less efficient than Otto; effective compression ratio is much worse than the geometric compression because the fuel burns too slow, but since they don't need to worry about knock they just make the CR crazy high to compensate).

A straight up vanilla piston won't cut it, DI piston are typically domed, with a deep asymmetric dish near the fuel injector.

http://i.imgur.com/UoFrF.gif

(pictured: 2JZFSE)

only if they use stratified charge. assuming you can reprogram the ecu to not run stratified charge, a simple piston swap may be enough to lower compression, among other ways...

I think you can't mess with the piston shape with D4-S, they don't use stratified charge but the piston is shaped so the direct injector + port injector create a very even distribution of fuel in the cylinder. If you remove the piston shape, don't expect the performance to stay the same; uneven AFR will promote detonation and poor combustion.

D-4S on the 2GR absolutely uses a version of stratified charge for cold start. PI is used on the intake stroke, and DI is used on the compression stroke. toyota calls this "weak stratified charge".

the dish in the piston has little to do with D-4S, because other cars without D-4S have the dish as well.

Dish is better for combustion. I have seen it on the Honda L series and they used other techniques to raise the compression ratio.

1) Buy a WRX EJ20 turbo motor, wiring harness and ECU for $2000 used
2) Sell your FT86 motor for $2000
3) Profit!

That will most likely be the best thing to do with the car... except I'll keep my stock motor, that way you can put the stock one back in if you ever sell the car and keep your built subie engine

Until the fuel costs catch up :bellyroll:

EDIT: So for people who only want a tiny bump in power, continuing the discussion from the main thread in main forum, 200hp at 7000 is actually pretty pathetic considering what went into this motor. A better exhaust might be able to give a little more and if you don't mind the slight decrease in fuel economy, bigger cams would do some too. 215hp might be realistic considering how the torque is a relatively impressive compared to torque peak 148ft-lb at 7000.

And I am still betting a few years down the road there will be an engine update. I'm not getting a car anytime soon, still in college, but if I'm right I probably will go for said updated FT, well if nothing better comes out.

You forgot labor for installing your new(used) EJ20 turbo motor.

215.... I hope your talking WHP at that number, and even then your forgetting all the other stuff you can do to an NA motor.

EDIT: I was thinking more in the range of 260-280 still staying NA.

Won't happen.

Granted it depends on the block and internals, but it is entirely possible. Throw a really aggressive heads/cam set up on it, plus your headers,intake manifold, throttle body, and other basic bolt on's. I fail to see why you think that its not possible to milk another 60-80 hp out of it.

I'm pretty confident that its a very conservatively tuned motor like most factory production cars.

I've also seen far more aggressive power gains from NA motors, for instance a 99 Formula with a heads/cam/intake/headers pushing 440 whp (305 is stock at crank).

Why do you find it unreasonable to put 280 out of a FR-S / BRZ