12:1 compression

I got a question for the high comp people here. I'm planning down the road (in about 6 months when the motor is available) to get an engine swap with a motor that is 2.5L and running 12:1 comp stock and the stock figures is 204hp@6400rpms. And I was wondering with all that compression, what would be the best first step to make some more power or better response? Thanks for any help:)

Start out with the usually intake and exhuast if the fueling is stock and can handle the high compression i wouldnt worry about it but more air=need for mroe fuel so you may need to ugprade your fuel system fpr,injectors,chip etc, i would also deffinatly get some aggressive cams if you want to go all out why dont you port and polish head and port match both manifolds and throttle body there are numerous things you can do

I know there are a ton of things, but I was wondering what would be the best "first" thing to do. Thanks for the info.

what car is it?

it comes stock with 12:1 compression is there anything done to the car modification wize already? if its already a fast car i would do suspension but if its a stock motor and you want strictly more power the first thing i would get deffinatly a nice catback or custom stainless exhuast magnaflow has very nice stainless mufflers and you can get pipes bent at a muffler shop i would go with 2.5" pipeing possibly replace with a high flow cat

then if you want to go from there let me know ;-)

yea it comes stock with 12:1. So exhuast work would be your first bet. Ok coo. Thanks =D

yea id go w the whole intake exhuast headers, expectially on a car w that high of compression, what kind engine is it? are you goin to build it or is it a crate motor?

if its a 22re you (most) likely wont be able to drive that on the street, youd either have to give it a rich/retarded timing tune or run higheroctane gas like leaded fuel

it's a brand new yota motor, 4GR, comes stock with 12:1 compressoin it's a 2.5L V6. It's why I have to wait almost 6 months before I can get one since I have to wait for people to roll their IS250s, lol. But it insures it'll be a low milage motor =D

4gr-fse, me id go with something that could be upgraded easyer like a 2jz, but then again its always nice to be difffrent, if you reallywant a 3gr serires engine go for the 2gr-fse, its in the new is350's and has like 315 hp, that would be NICE to have

yea, I mainly wanted to go small. 2JZ yea gobs more potential. But hangs out long. I didn't want to make a ton of power and I wanted something that wouldn't suck a lot of gas. I'm hopeing for a better weight distribution up front with the 4GR. Should sit much nicer than any inline motor and I'm hoping it's a bit more compact than the 2GR. Basically I wanted the 4GR for, low milage, closer to CG weight distribution, being different, decent power with decent MPG, and with the 12:1 compression I thought I could easily get it to 215~220hp no problem. The rest of my money I want to spend on suspension/brakes/chassie then back to the tranny/drivetrain.

but you gotta remember theres basically no room to inprove on that engine w out rebuilding it w low comp pistons and boosting it

yea, not planing on going any higher than 215~220hp (204hp stock). I want it to still get decent MPG and the rest of my money is on suspension/chassie/brake stuff, then back to drivetrain.

whatever floats your boat

i know you think it's pointless to swap to this motor since it's not powerful to begin with and there is basically no aftermarket support for it. But like you said, whatever floats your boat =D

oh no i like the idea, if your goals are only 10-20 more hp then what the eingine has i think this would be a great engine to have, loads of toraqe, isnt that heavy and would make your fr/rear bias about 50/50 in that car, good choice for your goals, just not a good choice if you want alot of power

yea I'm not much of a drag type guy. I like auto-x or rally-x more. I mean I need power, but I don't need much for what I want to do. I will be gaining 100+hp and 40+tq over my stock motor =D =P

yup and probablyequal the amount of weight it was before, those things are all aluminum, as well as more of a shift of weight to the center of the car, probably putting you around 50

yea that's what I'm hoping =D if you lived down here I'd pay you to do the work

lol yup, you find a place that sells that engine? that would be kinda hard to find

I have hook ups with JDM parts, but the place I want to do my work only uses their parts. If I went the other route I still would have to make it smog legal and that can be a bitch sometimes...

where u livin at in cali? who cares just swap every 2 years, its not that bad...lol

lmao. I live in westminster (the city with lots of Vietnamese people) its in Orange County.

ahhh, that sucks, how far are you from SF

lol, not sure if you find that having lots of viet people sucky or just that I'm in OC. But yea driving up to SF I think is about 7+ hour trip?

hahaha^, taht sucks its about 1 horu south of me, ill be heading down to san jose pretty soon here, how far are you from htere?

but you gotta remember theres basically no room to inprove on that engine w out rebuilding it w low comp pistons and boosting it


I don't understand why you would want low comp pistons. Why not go high comp pistons? Does you think that in all common sense that the high comp pistons would be stronger?

Chances are that if you are building a high performance engine, you will probably use forged pistons whether they or high \ low comp. Low compression means u can boost the holy hell out of it and not risk blowing the damn cyl. head off and also reducing detonation. It all depends on whether u want a boosted or n\a engine. I personnaly like n\a because of the faster throttle response and lower maintinance.

hahaha^, taht sucks its about 1 horu south of me, ill be heading down to san jose pretty soon here, how far are you from htere?


yea, that's closer to me... still about 6+ hours though :p farthest I've ever been up north was I think up to Mamoth mountains, I think took forever, lol.

I don't understand why you would want low comp pistons. Why not go high comp pistons? Does you think that in all common sense that the high comp pistons would be stronger?


like c-tylez said, so you don't blow up the motor, lol. 12:1 compression is nuts. I don't know how much you can boost a motor with that compression, but it couldn't be much at all.

what is a better piston? forged or low compression? Like if i were to sleeve my block, and then get pistions, rods, cams, etc what pistons would i wanna get? low compression? or forged?

You say that with low compression pistons are for boosting the holy hell out of your engine, then whats the point in getting forged?

And wtf is "reducing denotation"?

You can buy low or high compression forged pistons. High comp & low comp. pistons are different in the amount of compression they create on the comp. stroke of the engine. The taller the piston, the higher the comp ratio. Low compression lets moer air\fuel into the combustion chamber therefore allowing for more power to be made from a turbo\supercharger\NO2. detonation is also known as spark knock. where the fuel ignites too quickly( I think).It is very harmful to your engine. Newer engines have knock sensors so they arent as susceptable to it because the ecu knows when knocking occurs and ajusts the fuel\air mixture accordingly. hope this helps. If i'm wrong on any of this the pros on these furums will jump in & let me know:)

lol forged low comps would be better :)
you cant really boost a 12:1 comp motor w/out pulling an assload of tming and dumping a shitload of fuel (that would b epoopy wouldnt it?) doing low comps (i.e. 8.9:1) on that engine w boost would make it alot faster than boosting it at 12:1 beucase you would be able to run a much leaner setup and not have to pull as much timing and you would be able to run more boost due to it dentonating w the high comps

so whats the difference between forged and low comp? the material?

Low comp makes the compression low in the engine then? and those are for high compressed stock engines?

Forged is a way to make pistons, usually forged is an aluminum alloy, to be light weight, strong and heat resistant.

Low compression is a type of piston, other have explain above, but maybe I should try to explain again. With a low compression piston you can dump more air fuel mix that a turbo or super charger will force in. This way the motor is acting like a bigger motor since it's doing the same work that a larger motor would be doing. If you were to use forced induction on a high compression motor it might just predetonate and then break.

there are (really) 2 types of pistons, forged and cast and then theres aluminum, steel and titanium (types of metal), cast means they pour the metal into a dye and that makes the piston, forged means tehres a hardened piece of metal and they cut the piston out of the metal

Oh I guess that makes sense. So it I wanted to turbo my celica I would use low comp pistons it I wanted to put like 20 PSI in there? I would have to sleeve it of course...

I still dont get what would the point of putting a turbo on low comp pistons if you could just use really really high comp pistons and have about the same amount of compression?

there would be less fuel/air. And you can't run 20 psi on a 12:1 compression =P

ok, but if you got the turbo, the turbo will push about 15 psi in there anyways. So whats the difference if the pistons have 12 psi in there + the turbo pumps another 8 psi to make 20 psi.

Am I right, or am I wrong on how this works?

wrong, pistons dont make boost, they have compression, it forces everything into a smaller space, hence its comprssing it. if you had 2 sets of pistons (lets say form arias) one set at 8.9:1 and one at 11.5:1 you woulndt be able to run as much boost (on the same tune/fuel system) on the 11.5:1 pistons w out knocking and dentonating as you would the lower compression ones

and sleeving a block is pointless unless your going to be tearing down and rebuilding the engine frequently (i.e. F1 or nascar) sleeved blocks dont absorbe heat the same way regualr ones do, plus sleeve blocks actually move up and down and traverse w the piston a very little bit (dont kmnow exact fnumbers but if i machened a part in my class and it was .001 off i would failit, and they move alot more than that) i dont know any reputable machieneist that would take a sleeved block over a non-sleeved if it was a street driven/built car unless you planned on rebuiolding it often

Alright, So if i wanted to boost I would have to use the lower comp ones, and probably not sleeve the block?

What if I wanted to put like 20 PSI in there. I would have to sleeve the block because the stock block wouldn't be able to handle it and something would break.

So I would think it would be better to sleeve the block if you want more horsepower instead of risking blowing the block. Right? or is there a different way?(other then not running that much boost)

meh its your choice, i p[ersonally would never have a sleeved block, i dont like it...but most people do

What so different about a sleeved block then normal? Just less reposnse?

sleeved blocks have the sleeves press fit into the block, they can move around in the block even though there press fit in, thats very bad

Oh wow, i didnt think that they moved aorund. that sucks, because it would be nice to get a sleeved block with new pistons, rods, cams, the whole works and then get about 250 shot of nitrous :)

well they do and they dont, when you start getting into high hp they do move, thats why alot of honda guy do block posting and stuff beucase the sleeves will heat up and move around

the sleeves are press fit, press fitting involves heating up or cooling down an object and putting them togeter, then when it goes back to regular heat it presses so hard against the object it is bascially molded togethere, well the cylidar is heated up and therefore everything expands, including the block and the sleeve, allowing it to move

So sooner or later will it move around enough so something actually breaks?

When it moves aorund, what happens? like less torque, low gas mileage? something like that? symptoms?

not really sooner or later, in a stock engine i dont see why it would ever move, and in a properly protected sleeved block it shouldnt move either, but if it can happen, it will happen...diffrent effects, loss of compression manily beuase the sleves can move with the piston, mostly it will destroy your engine