The PERFECT compression ratio?

Is there an optimal compression for all motor honda engines that we should be shooting for? Obviously with a turbo we couldnt be running extremely high compression, but with simply all motor parts (built up or not) does more compression (to a certain point) yield better horsepower numbers?

Whats the max i should be shooting for with a b16a2 or an ls.

are you looking for a daily driver or a track only car ? also are you tlaking aobut running high octane gas ?

the higher the comp ratio the more hp you will get but a comp ratio can only go so high

Im talkin daily driver here. I should have specified that, because that makes a huge difference.

i wouldnt go more than 12:1. but i personally would go 11.5:1 just to be safe

if you go with a gude all motor head the compression I believe for the sohc is 12:1, in my opinion you better always fill up on 94 octane and have an upgraded igntion, wires and all that to be safe. All motor is a very very tough category for us with 4 cylinder motors, dont look for too many results unless u have mucho chavo ta spend...

Originally posted by SmoovSol
if you go with a gude all motor head the compression I believe for the sohc is 12:1, in my opinion you better always fill up on 94 octane and have an upgraded igntion, wires and all that to be safe. All motor is a very very tough category for us with 4 cylinder motors, dont look for too many results unless u have mucho chavo ta spend...
an ex sohc is 9.6:1.....? :huh: 12:1 is up there for a single overhead cam motor.

yeah the ex motor is either 9.2 or 9.6, i believe. a bullfrog head doesnt up your comp ratio, strictly head tuning from what i understand

:frog: i depends on where you live and the air density hear in oklahoma i have a freind that we are runing 12.5:1 on pump 93 oct with out a probom but we have dence air so its up to you :)

if you live in cali, i wouldn't go over 11.5:1. 91 octane is the most we can get at the gas station. or you can run higher compression, but you will have to retard the timing. very important.

I am working on my own stroker at the time, and to avoid knock with 92 octane you shouldnt go any higher then 11.5:1. I personally am gunna run it safe and go 11:1. I have my LS block and the stock rods with the Type R pistons. SO I'd recommend going around 11:1 just to be safe, but then again why not go for the highest possible.

whats the CR for CTR pistons, anyone know? are they 11.1:1?

Originally posted by crxlvr
whats the CR for CTR pistons, anyone know? are they 11.1:1?

Yes on a ctr motor. B16 should be a lil higher? Like 11:4? Somewhere around there.

As for me i'm goin 13:5 cr. I'm gonna be using racing fuel and with some good tuning my car should be a good daily driver. If you don't mind using racing fuel then go 12:5 or higher to produce more power.

According to the engineers at GM (Not that I trust them) all other factors set aside a 17:1 CR produced the most power. Unfortunetly you would have to use 126 octane (eqivlent) methanol to run that comperssion.

Originally posted by mellowboy


Yes on a ctr motor. B16 should be a lil higher? Like 11:4? Somewhere around there.

ok thats nice for my all motor setup, what octane gas should i run, 91 or 93?

Originally posted by crxlvr


ok thats nice for my all motor setup, what octane gas should i run, 91 or 93?

I'd say 93 but i dont think 91 shouldn't do any harm?

i was thinking about getting new pistons, I have a 90 accord (f22a1), rite now stock compression is 8.8, i found pistons that would bring me up to 9.3,, would this give me a decent power boost? if so how much do you think? and also are there any otha mods necessary for new pistons??????????

Originally posted by BIGDOM
i was thinking about getting new pistons, I have a 90 accord (f22a1), rite now stock compression is 8.8, i found pistons that would bring me up to 9.3,, would this give me a decent power boost? if so how much do you think? and also are there any otha mods necessary for new pistons??????????

Are you goin all motor or turbo? IF your goin all motor then go higher compression. LIke 11:5?

Originally posted by mellowboy


I'd say 93 but i dont think 91 shouldn't do any harm?

alright sounds good, no more 87 for me.


and for the accord all motor bump your comp ratio way up, turbo or SC it, then drop it low.

i doesnt hurt your car to run say cam2 because it only has a higher flash point to prevent detonation so i have 10.5:1 cr and i am going to run sunoco94 but fill up at the track with cam2. but i think when you hit 11:1 cr you need atleast 93octane

Originally posted by hybridsol

an ex sohc is 9.6:1.....? :huh: 12:1 is up there for a single overhead cam motor.

Actually 12:1 will work fine as a daily driver if you could get the higher octane I would just go with a 11:1 for daily use. I am going to be putting my Single to a 11:1 compression.

i agree

The compression ratio you can run has more to do with the shape of the dome of the piston than the amount of octane. Also a seriouse problem people have with detonation is using stock injectors and thinking shit will be OK, its not. Think about it like this, any FI works by boosting the CR so in order to make up for the vast amount of airflow we use more fuel to get the right air/fuel mix. Now what do you think Hi CR pitons do? They have more surface on the domes which allows more air to be pulled in, but if you dont have the fuel there to feed them what are you doing? Your running realy lean. I would sugest at least a 1/2 inch fuel rail and 270cc injectors for my DOHC ZC 11.16:1 project... Just to give you an idea. Btw Im also going to be using NOS! LOL! Its all in the tuning. Oh Ill be using 110 Oct as well... Since I only drive my car on the weekends its not to expensive, the 110 just doesent detonate like 91. But thats no excuse to use stock injectors.

thats not true compression ratio is the amount you compress the cylinder volume. it has nothing to do with drawing any air into the engine it is compressing the air thats already in their that much more. Why would it suck more air?? the only problem with detonation is the fuels flash point. the fuel is under such high pressure that after it ignite the unburn fuel is re ignited on the up strock by friction caused by the rings and cylinder wall. that is why you need higher octane. because it has a higher flash point. You dont need bigger injector.

also you are right for forced induction because you are making the airflow more dense so more air = more fuel

Originally posted by redmanjd
thats not true compression ratio is the amount you compress the cylinder volume. it has nothing to do with drawing any air into the engine it is compressing the air thats already in their that much more. Why would it suck more air?? the only problem with detonation is the fuels flash point. the fuel is under such high pressure that after it ignite the unburn fuel is re ignited on the up strock by friction caused by the rings and cylinder wall. that is why you need higher octane. because it has a higher flash point. You dont need bigger injector.


Ditto!:)

Originally posted by redmanjd
thats not true compression ratio is the amount you compress the cylinder volume. it has nothing to do with drawing any air into the engine it is compressing the air thats already in their that much more. Why would it suck more air?? the only problem with detonation is the fuels flash point. the fuel is under such high pressure that after it ignite the unburn fuel is re ignited on the up strock by friction caused by the rings and cylinder wall. that is why you need higher octane. because it has a higher flash point. You dont need bigger injector.

Der der der... Rookie. Look man, if you want to compress MORE you have to have MORE to compress. Dont tell me I dont know what the fuck I'm talkin about, have you ever built a motor? I didnt think so. I have a turbo engine that uses 28.2:1 CR pistons without the 12-14 Psi Im slaming into it.
Pluss if you have higher CR pistons they have more surface on the face which meens they are asking for more fuel/air because they have more surface they draw more. GO ahead and use your 11 to 1 pistons with stock D series injectors then come talk to me after your engine explodes. I have a D16A6 thats runnin 11.2:1 JE pistons right now.

does nyone agree with him???? what no???? dont get mad at me cause i disagree. if a piston has more surface are you have less volume in your cylinger. higher cr doesnt great a higher vacume. 28:1 that the hell the highest i have ever heard of is 18 on 9 sec dragsters what is special about your car. their is no dought you have a high cr turbo but come on.

Its a turbo diesel... ;) No sparkies... Actualy you can run a honda engine just like a diesel and use detonation intsaed of spark. You have to do quite a few mods but it has been done before. And no, just because there is more face on the piston does not meen there is less volume in the Cyl. Hasent anyone taken grade school pyshics in here? Explain to me how there is less room with roller wave pistons, and I'll call you an idiot. There is actualy more room and more face on the pistons or that of equal amount as before. Now Im sure there are some REALY shity companies out there (Such as JE, the pistons Im using in my A6) that dont copensate for the volume of the cyl's when they make there pistons. Now what you get then is realy knarley detonation iether way you look at it. Even with less fuel you will still have detonation. It all realy comes down to your knowledge (Or lack there of) and the knowledge of the company you buy your pistons from. Nuff said.

Seth are you sayin that u have to get bigger injectors if you're goin high compression? Cause my boy have ctr pistons in his b16 without any upgraded fuel and it runs fine.

No, you dont HAVE to have more fuel... But it sure as hell wont make alot more power without more fuel. More fuel = more power to a point. Basicaly if you use more fuel and jump the timing up a notch or two and begin the burn cycle earlier than you will burn more fuel (Which wouldnt do shit if you dont have a higher CR because it wouldnt be verry compressed)

i got you on the deisel they do have high compression. and of cource more fuel always equals more power to a certain extent that is a give.

Originally posted by redmanjd
i got you on the deisel they do have high compression. and of cource more fuel always equals more power to a certain extent that is a give.

Yes, but using less fuel on honda engine with a higher CR promotes detonation... You have less fuel being squished harder VS more fuel being squished harder. What will detonate first? Pluss more fuel = stronger burn even if you arent burning ALL the fuel, your still burning more.

Originally posted by seth 90DX/ZC
The compression ratio you can run has more to do with the shape of the dome of the piston than the amount of octane. Also a seriouse problem people have with detonation is using stock injectors and thinking shit will be OK, its not. Think about it like this, any FI works by boosting the CR so in order to make up for the vast amount of airflow we use more fuel to get the right air/fuel mix. Now what do you think Hi CR pitons do? They have more surface on the domes which allows more air to be pulled in, but if you dont have the fuel there to feed them what are you doing? Your running realy lean. I would sugest at least a 1/2 inch fuel rail and 270cc injectors for my DOHC ZC 11.16:1 project... Just to give you an idea. Btw Im also going to be using NOS! LOL! Its all in the tuning. Oh Ill be using 110 Oct as well... Since I only drive my car on the weekends its not to expensive, the 110 just doesent detonate like 91. But thats no excuse to use stock injectors.
What are you smoking?

Compression ratio is the volume inside the combustion chamber with piston at BDC and valves closed DIVIDED BY the volume when piston is at TDC and valves are closed.

No two ways about it.

Originally posted by seth 90DX/ZC


Der der der... Rookie. Look man, if you want to compress MORE you have to have MORE to compress. Dont tell me I dont know what the fuck I'm talkin about, have you ever built a motor? I didnt think so. I have a turbo engine that uses 28.2:1 CR pistons without the 12-14 Psi Im slaming into it.
Pluss if you have higher CR pistons they have more surface on the face which meens they are asking for more fuel/air because they have more surface they draw more. GO ahead and use your 11 to 1 pistons with stock D series injectors then come talk to me after your engine explodes. I have a D16A6 thats runnin 11.2:1 JE pistons right now.
If you want to compress MORE you just take what you have and force it into a fucking smaller space. You can keep things civil, by the way.

LOL look at this (http://forums.anandtech.com/messageview.cfm?catid=38&threadid=998154)

Thats hella funny. To bad none of you know what your talking about. Why dont you lay it down for me genouse. Make it all make sence for my ignorant little head! BTW faggots, I also have a 69 Mustang GT a 71 BMW, Chevy S10, GMC diesel, and the turbo diesel mercedes Im building, so you can shove your ricer shit right up your already loose faggoty asses! Bitch. Oh my current project (besides my honda) Is droping a 350 into a 47 mercedes my brother owns.... You need to take your one car owning hater asses and get a inline four before you start talkin shit to peeps who probably been workin on cars for alot longer than you. To me an engine is an engine, "There is no replacement for displacement" Bullshit, its called rpm's.