yes i realize that at 11.6:1 my compression ratio is really not ideal for forced induction, but i feel that with the right engine management and enough fuel it should be more than possible. after having pulled the engine twice and spent plenty on engine building i really don’t want to pull it apart again to put in some custom pistons. i’m not looking for crazy boost and close to 300whp would be more than enough for me. i have a feeling that a vortech might be more manageable then a turbo, but i want to get the opinion of some people with EXPERIENCE in this. as always i want to stress that i’m not looking for opinions, but facts from experience. if you’re curious about my setup, see the link in my sig.
sup man,
remember its all in the TUNING.
here’s a clip from this book i have…
The next argument that people usually bring up is that a higher compression is bad for turbocharging. Well, if you understand the concept of effective compression, then you should understand that this statement is entirely incorrect. A higher compression engine makes more power in NA form. So, why do you turbo guys think that a lower compression turbo motor makes more power? Does that make any sense when you really think about it? A turbocharger is a power adder? So why deplete power that was there to begin with? The answer I usually get to that is “So I can run more boost!” Well, sorry to rain on your parade, but more boost does not always equal more power. Check out this mathematical example of effective compression:
A motor with a 10.0:1 static CR boosting 10psi
10psi/14.7psi = .68
.68 + 1 = 1.68
1.68 x 10 = 16.8 effective CR
A motor with an 8.5:1 static CR boosting 10psi
10psi/14.7psi = .68
.68 + 1 = 1.68
1.68 x 8.5 = 14.28 effective CR
Now tell me who is going to make more power? The higher CR motor, or the lower CR motor?
So, maybe add more boost to the lower CR motor, right? Wrong…
A motor with an 8.5:1 static CR boosting 13psi
13psi/14.7psi = .88
.88 + 1 = 1.88
1.88 x 8.5 = 15.98 effective CR
Now you see, even adding 3psi of boost, still does not equal the effective CR of the higher compression, lower boost motor.
i don’t know what all the math exactly stands for but…like i said earlier its all in the TUNING. Tune it correctly and you’ll be just fine
what you forgot to take into account in your little math there was sleeve strength. if our engines came with ductile iron sleeves stock, we’d be fine with 10:1 compression. problem is, they don’t.
also, who has more power? 10:1 compression with 10 pounds of boost, or 9:1 compression with 20 pounds of boost?
just remember that if you want to run more than 10 pounds of boost, you DEFINITELY need lower compression. how you lower said compression is entirely up to you.
i highly recommend the forced induction forum at www.honda-tech.com – Vince from Golden Eagle Manufacturing (who built the majority of Ed Bergenholtz’s 9-second honda), Viren from VS Racing (another 9-second honda), and numerous other professional Dyno Tuners, hardcore racers, and engineers post there regularly. If you want to know how the pros do it, wouldn’t it make sense to talk to the pros themselves?
Originally posted by cjsls A motor with an 8.5:1 static CR boosting 13psi
13psi/14.7psi = .88
.88 + 1 = 1.88
1.88 x 8.5 = 15.98 effective CR
Your formula for PR is wrong, its (boost+14.7)/14.7
And effective CR doesnt mean shit unless ur restricted by the amount of boost u can run (i.e. small turbo or rules or something). More psi = more air = bigger boom = more power. At the same boost levels, the higher cr engine will make more power. But wouldnt u rather be able ro run more boost on pump gas and make more power? Its the latest fad that high compression fi is the way to go, i laugh at those people
Originally posted by notecLS
[B]Your formula for PR is wrong, its (boost+14.7)/14.7
And effective CR doesnt mean shit unless ur restricted by the amount of boost u can run (i.e. small turbo or rules or something). More psi = more air = bigger boom = more power. At the same boost levels, the higher cr engine will make more power. But wouldnt u rather be able ro run more boost on pump gas and make more power? Its the latest fad that high compression fi is the way to go, i laugh at those people [/B]
Notec - First of all, what are you doing on this board again?
2nd - they arent HIS formulas, they are from the book he quoted.
3rd - Dont do little tricks to be able to swear.
4th - I dont think you have the right to laugh at anyone. You’re the one that attempted to turn a header into a turbo manifold.
5th - Please leave.
Originally posted by IdntGlwIglisten Notec - First of all, what are you doing on this board again?
2nd - they arent HIS formulas, they are from the book he quoted.
3rd - Dont do little tricks to be able to swear.
4th - I dont think you have the right to laugh at anyone. You’re the one that attempted to turn a header into a turbo manifold.
5th - Please leave.
I didnt attempt, I did do it. And why do you care? Why the hell are you riding my ass for something I did to my car? The header was a FI manifold, i’m sure it will hold up fine. It doesnt hurt performancem, and it doesnt look stupid, so why dog on it? Didnt you ever learn that **** talking is bad? Dont talk to me :squint:
I dont care where he got the formula, I just told him it was wrong. Why are you splitting hairs on stupid shit. i posted somethign constructive, what did you post?
Well look at it this way. High CR w/ low boost is similar to low CR w/ high boost but high boost you will have a lot more air to flow and more potential for power.
The higher the CR the higher the cylinder temp and pressure so your fuel and ignition timing has to be that much more accurate. So a programmable fuel and spark timing is very important for this equation. Also the components will need to be stronger as well. There are also other important factors like type of fuel, atmospheric pressure, ambient temp, type of aftercooling, and most importantly combustion chamber design.
Originally posted by carchitect
[B]Well look at it this way. High CR w/ low boost is similar to low CR w/ high boost but high boost you will have a lot more air to flow and more potential for power.
The higher the CR the higher the cylinder temp and pressure so your fuel and ignition timing has to be that much more accurate. So a programmable fuel and spark timing is very important for this equation. Also the components will need to be stronger as well. There are also other important factors like type of fuel, atmospheric pressure, ambient temp, type of aftercooling, and most importantly combustion chamber design.
Joe [/B]
this is what my theory has always been. highier compression more heat, their should be enough damn heat with the hairdyer, compressed air and FMIC blocking ur radiator. heat:down:
Well the hotter and leaner you run the more your power can be. But your reliability can easily go to sh1t. For a street car reliability is most important. Sacrificing 8% power is like extending the life of a boosted motor by 50%.
If you plan on running this high of a CR. You really should look into having you pistons, valves and combustion chamber coated to reduce the heat transfer to vital engine components.
notec- You should really not open your mouth. I will once again say that you are a boob. Please just read the posts and try to learn and not talk. I still am not sure if you were dumb or trying to make a fool out of yourself because what you were saying is truely idiotic.
i plan on getting a .057" Cometic gead gasket which will reduce my c/r to 10.8:1. also i will run a supercharger if anything; a Vortech kit with aftercooler. if Comptech can provide a bolt on kit for an 11:1 S2000, this can’t be too difficult.
Originally posted by H4-DB1 notec- You should really not open your mouth. I will once again say that you are a boob. Please just read the posts and try to learn and not talk. I still am not sure if you were dumb or trying to make a fool out of yourself because what you were saying is truely idiotic.
You shouldnt judge what I do to my car. Gonna leave it at that :tsk:
If you are building a strictly race only car, you can get away with 10.8 to 1.
Have seen a 85mm ls/vtec 10.8 to 1 @ 38lbs ( granted he had a motec m4 and fully built motor )
Street cars, its pushing it.
Just hope you are happy with a 5-6lbs of boost, and have the money for a standalone to tune it perfectly, and a bunch of 114 for your tank.
man the header as a turbo manifold deal isn’t such a bad idea…i’ve snuck my nose into researching twin turbo V8’s…for some odd reason;), and alot of custom kits are made by turning equal length shorty headers around and extending the pipe. this is partially because the turbo can’t fit right by the block as well as it does on I4’s, but only the high dollar kits have custom manifolds that try to squeeze the turbo right in that mess on V8’s. I don’t see how he’s such an idiot for trying something that has worked for other high performance motors…let him be different AND save money at the same time if it works…don’t bust his balls!
as Blackthought of the Roots said: “Indefinitely go against the grain”.
Hey, this is off topic and all, but I just looked at yer pictures and I noticed you put your VAFC where I was planning on putting mine (eventually). I was wondering what you think of it there and if you’ve had any problems with it being so close to the rearview.
