Racersky

I can't really find CP Pistons 9:1 88.5mm bore anywhere. Since you were saying that the 8.8:1 with a 88.5 bore can handle more boost but is a bit "laggy" out of boost......How does the CP Piston 9:1 with the same bore do in terms of being laggy? Would the 9:1 piston be more reponsive?

Edit: ALso I forgot to ask this question as well.......if i were to do a similar build to what you described about the dezod bearings would I be buying everything that is listed in the bearing section?

B_Real45

Yes - you need rod bearings, main cap bearings, etc. You should call Paul at Dezod - he can help you plan your build just right.

8.8:1 compared to 9:1 is so close that you probably won't notice a difference.. but I was just saying that the higher the compression ratio, the more responsive the car will be off boost. Ideally I would probably stick with higher like 9.5:1 for a street car that doesn't run too much boost (under 20psi). If I want all out power and run really high boost, the lower compression would be better.

etsnet

iTrader: (2)

You need more boost with lower comp piston to equal the the same power in higher comp piston with the same boost.

Example:
8.8 pistons at 20psi =400whp
9.5 pistons at 20psi =475whp

This is just an example. The higher comp pistons would be better IMO and apparently the scion race cars cuz I believe most if not all are running 9.1 - 9.5.

Just my 2 cents.

B_Real45

Yes that is true - that is why I suggest higher CR for street use. You make more hp on lower boost.

HOWEVER - if you want max HP, you'd want to run lower compression pistons because it'll help fight against detonation when you're running really high boost levels. Race gas can only take you so far.. and if you want to get the max hp without taking out a lot of timing, a lower compression is best.

I'm talking out of the realm of a street car now. We're talking 30+ psi of boost, trying to make the most hp out of a motor. It will be a lot harder to do on higher compression pistons.. not saying it can't be done - it's just a lot harder. The high compression makes it difficult to keep knock levels low - tuning would have to be near perfection.

boosthappy

[/quote]if you want max HP, you'd want to run lower compression pistons because it'll help fight against detonation when you're running really high boost levels. Race gas can only take you so far.. and if you want to get the max hp without taking out a lot of timing, a lower compression is best.

I'm talking out of the realm of a street car now. We're talking 30+ psi of boost, trying to make the most hp out of a motor. It will be a lot harder to do on higher compression pistons.. not saying it can't be done - it's just a lot harder. The high compression makes it difficult to keep knock levels low - tuning would have to be near perfection.[/quote]i was just about to say that not only would you'll be able to run more boost safely you could also be able to run more timing with low comp vs high comp and with more timing it would be natsy out of boost..another thing i here alot of people on here saying 88.5mm bore is what we need to run and any thing more needs to be sleeved i thought .20 over would be fine putting me at a 89mm 2.5L

purevision01

So this is what you do... Get an Eagle stroker kit, sleeve the block, through a gt35r in the mix, with some .40 over pistons which should get the displacement up around 3.0l and run at 8.5 to 1 compression with 35psi... This way you have the power in boost and you have the torque in vac... If the torque isnt good enough and depending on the purpose of the car, you add a gated shot of nitrous with is either rpm or vac dependent and turns off at a predetermined point... and thatll all she wrote... Of course the valve train should be done... total cost will be 8k with machine work and the motor should hold around 8-900 whp...

B_Real45

^^ That setup will have so much stroke - not recommended to run high RPM safely.

purevision01

Tru the recipricating mass will be heavier... But y do you need high rpm if your spooling ur turbo at 2500 and hitting full boost at 3k?

B_Real45

Oh definitely - that's where you need to make your choice.

Go bigger displacement and not that high rpm,

or go higher rpm and have less displacement. I guess this all depends on what you'll be using your car for.

I personally want the higher rpm alternative - or actually, a destroker kit which involves a larger bore and shorter stroke, getting closer to a 1:1 ratio of bore x stroke. Something like a 90mm bore x 90mm stroke - which will give you roughly 2.3L so a minimal decrease in displacement.. but the squared configuration is a bit more desireable for boost applications - plus it'll allow you to run higher rpms (provided you have the valvetrain to support it.)

caveman

Just giving props on this thread, very informative!

Question: How bout us guys piecing together a kit but knowingly will run sub 10psi....how bad would upping the compression be??, and tuning off a FIC...just out of curiosity here...




P.S you guys goin to the BBQ make sure to say hi to a FM tC with a monkey hangin in the back...Ill most likely be taking a bunch of pics, lol...sorry BACK ON TOPIC

B_Real45

I personally think that high compression and lower psi (15psi and under) would be a phenomenal street car. The F/IC is a capable system - so as long as your tuner is good and keeps you away from knocks and pings, high compression + turbo is just gravy.

This would be my way to go if I wanted a low boost street car, with solid reliability (from tune and built internals).

purevision01

Agreed... Displacement is a personal choice... I prefer higher displacement because it spools the turbo faster... You like small displacement bcuz you can wind the crap out of the motor, which I like too but when I think of the possibility of missing a gear at 8000+ ... I get a not so warm feeling, especially as a builder of customer cars. Thats all I need to hear... Im grindin every shift into 2nd and 3rd cuz your tranny is defective... Nooooo, you grind bcuz you rounded the teeth because you cant shift! lol just a lil personal experience.

caveman

haha! thanks for the info...I thought it should be capable but havent fully learned all aspect of compression and such...
Hopefully a strictly 6psi 16g DD/autox lil warrior is on the horizon, .....for now......

purevision01

16g is a pretty small turbo and you will get used to that power quickly... I give you 2 months before you either get a bigger turbo or up the boost... lol I guess thats y God mad boost controllers tho.

B_Real45

Yes.. and to add to the statement that the 16G is small..

Remember that smaller turbos push hotter air at the same psi compared to a larger turbo. So your IATs will be higher - which will need to be accounted for since a higher compression motor will already increase combustion temps..

I would probably stick to a more modern turbo with better flow yet still spools quickly. Something like a GT2860 or something related.

caveman

LOL....yea the reason I am kepping it strictly 6psi for now is because the motor isnt built....I know 2AZs can handle more. But this is me just being me, I'd rather wait to built the block how a want and then up the boost. Which after reading B Reals answer, its kinda got me intrigued, lol..
But you never know wat the future entails right, lol...I could just bump up to the 20g, haha


But...any other bets!?!?!....I got 2 months so far!, lol j/k

caveman

O right, I didnt think about that...well for right now the motor build is pretty much a dream until the actual time comes. I got the turbo and mani for a price basically only a crackhead would refuse, so I went with it thinkin I would just bolt up a pieced together kit for now and then go from there....but this has me thinkin again, lol dam!

B_Real45

Well you'll be fine with that turbo for now. And you'll be fine later if you build your motor - just change it out when you plan on running more psi with a built motor.

caveman

preciate the info...sounds like a plan to me

SoFloTC

iTrader: (3)

hmm so what would ur suggestion be for a person with a built auto tranny? looking to make a street monster pushing about 14-15 psi DD