compression - Performance Forum

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compression
Friday, December 29, 2006 5:19 AM
i want to keep all motor and if i get the 10.5 compression pistons and shave the head, would that get me in the 11's? i don't want to be that high. or should i go lower than stock and get the 9.1 with a shaved head? sorry if stupid question, don't know how much shaving the head would raise the compression.



Nope, it ain't stock.

Re: compression
Friday, December 29, 2006 5:32 AM
personally i think 11s is pretty far goal for an NA engine...if you want 11s youd better start thinking much HIGHER compressions than that..not to mention lots of juice



Re: compression
Friday, December 29, 2006 5:57 AM
11s all motor?

good luck man.. i don't think stock compression will do it unless you spin lots n lots n lots of rpm and use sickly aggressive cams and race gas

on nitrous, i could see a built n/a car hitting 11s (ie. owen stampflee) but with 10.5 cr thats a pretty big limitation you're building into the engine





Re: compression
Friday, December 29, 2006 6:18 AM
I wouldn't shave the head unless you are just leveling it out.

If you want to hit 11's all motor, you are going to need really high compression and a trailer queen (aka some major body lightening). Even then I don't think its possible, high 12's maybe...





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Re: compression
Friday, December 29, 2006 9:14 AM
Easiest way to get high compression on the LD9 is the 086 head swap. I'm with shifted... I believe those that have run 11's (turbocharged) are making power numbers near 400 whp. If you can do that NA you let us know.


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Re: compression
Friday, December 29, 2006 9:48 AM
betonmyz wrote:i want to keep all motor and if i get the 10.5 compression pistons and shave the head, would that get me in the 11's? i don't want to be that high. or should i go lower than stock and get the 9.1 with a shaved head? sorry if stupid question, don't know how much shaving the head would raise the compression.


that alone, no.



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Re: compression
Friday, December 29, 2006 10:07 AM
Im 99.9% sure when he says "into the 11's" he's talking about the comp ratio after he shaves the head with the 10.5 pistons. if you want to keep it all motor or even think about meaybe a little nitrous in the future then I'd swap heads with the 2.3l 086 head. if your doing pistons then you could keep the stock ratio with some valve reliefs and you would still be in the mid 11's.

its pretty cheap setup but you can get a rebuilt head shipped off ebay for around $220
if you don't know the difference's in the two heads I can post some pics up.





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Re: compression
Friday, December 29, 2006 10:11 AM
firebug wrote:Im 99.9% sure when he says "into the 11's" he's talking about the comp ratio after he shaves the head with the 10.5 pistons.


Wow, did I misread. Yeah that makes far more sense.


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"Youth in Asia"...I don't see anything wrong with that.
Re: compression
Friday, December 29, 2006 10:30 AM
yeah i'm sorry if i didn't explain myself better. i heard that having such a high compression as 11:1 was too high for just a daily driven car. i don't want to go that high. my question was should i not even shave anything and just get the 10:1 or shave with a 9:1. i don't wan f/i anytime, and i have nitrous, so i wanna stay a lil higher than stock. sorry again.



Nope, it ain't stock.
Re: compression
Friday, December 29, 2006 11:08 AM
betonmyz wrote:yeah i'm sorry if i didn't explain myself better. i heard that having such a high compression as 11:1 was too high for just a daily driven car. i don't want to go that high.


I think someone lied to you. I believe the celica gt-s has a static compression around 11.5:1. Gilles on here is running 12:1 with ridiculous cams and runs pump gas. Don't worry too much about 11's. I would worry more about your bottom end than compression. You will also have to run premium gasoline (91-93 octane depending on where you live).


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"Youth in Asia"...I don't see anything wrong with that.
Re: compression
Friday, December 29, 2006 8:04 PM
Do yourself a favor and dont shave the head.

If you want to choose the compression, custom order pistons for your application. Most companies will let you choose the compression that you want for about 100$ over thier off the shelf pistons if it isnt a huge difference (+/- 1 point).

If you shve the head you will (eventually) end up having timing chain issues. The tensioner and assembly will be understress, and at worse your timming chain will end up jumping a tooth and you'll bend a valve. This has happened to me before when a shop plained too much off a 2.4 head for me.




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Re: compression
Saturday, December 30, 2006 6:25 AM
^^^that's what i was looking for. thanks everyone for their help. what about shaving the block a lil? any thoughts on that? thanks



Nope, it ain't stock.
Re: compression
Saturday, December 30, 2006 9:47 AM
the 2.4 has something like 9.5:1 compression. with the 086 head it will be rasies up to over 11.
getting 10.5 pistons and the 086 will more than liley shot the compression into the 12 range



Im a Xbox 360 fanboy...and damn proud of it!!
Re: compression
Saturday, December 30, 2006 10:40 AM
Shaving the head or the block end up as the same result. Slack on the timming chain and it's ONLY purpose is to make everything flat. If you do that to raise compression, you're a cheap bastard that shouldn't be working on our engines.

As said above, I'm running 12:1 compression with 94 octane. I do have big cams to help leak some compression.



Gilles
2.3 Ho

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