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

[Ryephile]

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!

[fred_boosted]

Originally Posted by RRnold

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

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...

[ryridesmotox]

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.

[Toyota fr-s]

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.

[Dave-ROR]

Originally Posted by Toyota fr-s

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.

[fred_boosted]

Originally Posted by Dave-ROR

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

[Allch Chcar]

Originally Posted by fred_boosted

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?

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.

Originally Posted by Ryephile

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!

^This +1.

Originally Posted by fred_boosted

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

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

[madfast]

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

[fred_boosted]

Originally Posted by Allch Chcar

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.

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

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

[Dave-ROR]

Originally Posted by fred_boosted

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

[Allch Chcar]

Originally Posted by Dave-ROR

Translate the rest of those tech info scans

Yes, please! If you would be so kind Fred_boost.

[ichitaka05]

Originally Posted by RRnold

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

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.

[70NYD]

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

[serialk11r]

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).