low vs. high compression
10-30-2003, 03:28 PM
#1
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low vs. high compression
im pretty sure that lower compression is good for turbos. and that high compression is good for all motor setups but what is good for supercharged engines. low or high. any input would be greatly appreciated.
thanx
thanx
10-30-2003, 03:33 PM
#2
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Re: low vs. high compression (Slomo_civic)
to quote myself from another post: (not to jack, just think it would help the discussion)
I was under the impression that high cr + lower boost is = to low cr + high boost - as far as power and ease of tuning. Or is it only to a certain point? It is just more pressure either way right?
And to answer your question, AFAIK, same for sc as for turbo - after all they both are very similar types of forced induction.
I was under the impression that high cr + lower boost is = to low cr + high boost - as far as power and ease of tuning. Or is it only to a certain point? It is just more pressure either way right?
And to answer your question, AFAIK, same for sc as for turbo - after all they both are very similar types of forced induction.
10-30-2003, 03:44 PM
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Re: low vs. high compression (slashDEVslashNULL)
From what I understand you always make more power with more compression, you really want to run the most compression you can taking into consideration your tuning abilities. Under low compression you have a larger room for error, while tuning while in high compression you'll make more power but there is a not as much room for error in your tune.
10-30-2003, 03:52 PM
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Re: low vs. high compression (beta13)
I agree - but wouldn't you say the same about tuning low cr + high boost? It is the same is it not?<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by beta13 »</TD></TR><TR><TD CLASS="quote">while tuning while in high compression you'll make more power but there is a not as much room for error in your tune.</TD></TR></TABLE>
assuming boost is lower with the high cr setup. If its the same, then obviously the high cr is harder to tune.
assuming boost is lower with the high cr setup. If its the same, then obviously the high cr is harder to tune.
10-30-2003, 04:09 PM
#5
Re: low vs. high compression (slashDEVslashNULL)
high compression may make more power at the same psi level, but you can only boost a certain amount safely. with lower compression, you're making the turbo work, and can also increase hp safely.
oh yeah, SC'n and Turbo'n would have to have similar motor setups.
oh yeah, SC'n and Turbo'n would have to have similar motor setups.
10-30-2003, 04:23 PM
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Re: low vs. high compression (shermanyang)
I guess the bottom line is,
On pump gas, which setup would yield the highest whp?
High CR + lower boost
or
Low CR + high boost
(great tuning on both, same setup except cr and boost)
I used to think they would be the same.
On pump gas, which setup would yield the highest whp?
High CR + lower boost
or
Low CR + high boost
(great tuning on both, same setup except cr and boost)
I used to think they would be the same.
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10-30-2003, 04:53 PM
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Re: low vs. high compression (Muckman)
generally low(er) compression for superchargers due to the in-efficiencies of them, unless you are using an intercooler with it.
It all depends on the setup though, if it was methanol injected, its a totally different story.
It all depends on the setup though, if it was methanol injected, its a totally different story.
10-30-2003, 04:55 PM
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Re: low vs. high compression (lazerus)
I vote for higher cr and lower boost. That way the turbo (I know this is a SC question) will spool more quickly , but in a SC application it will make a stonger motor, thus turning the SC Belt faster and producing boost more quicly.
10-31-2003, 09:03 AM
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Re: (System-7)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by System-7 »</TD></TR><TR><TD CLASS="quote">all the built engines i've seen run low compression. The evo8 runs a compression 8:1, enough said.</TD></TR></TABLE>
Enough said? What size engine is the Evo8, is it at all comparable to a Honda? Have fun making 30HP until boost kicks in with an 8:1 compression.
Enough said? What size engine is the Evo8, is it at all comparable to a Honda? Have fun making 30HP until boost kicks in with an 8:1 compression.
10-31-2003, 11:35 AM
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Re: (System-7)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by System-7 »</TD></TR><TR><TD CLASS="quote">all the built engines i've seen run low compression. The evo8 runs a compression 8:1, enough said.</TD></TR></TABLE>
It's also why the Evo8 has to run 18psi to make 270 hp. I'll be damned it I want to have to run 18psi on my motor to make 270hp.
It's also why the Evo8 has to run 18psi to make 270 hp. I'll be damned it I want to have to run 18psi on my motor to make 270hp.
10-31-2003, 05:57 PM
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Re: low vs. high compression (Slomo_civic)
We are running 10:1 and 28lbs on boost on a fully built GSR block. All you need is enough fuel and good tune and you should be fine. That way when your not boosting you still have decent power.
11-01-2003, 08:48 AM
#17
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Re: low vs. high compression (Rickyh93)
i just switched from an 8.5:1 b16 to a 10:1 gsr motor. The lower compression jsut makes the car feel pig. thats just my opinion though. If you have a good fuel system and a good tuner i would keep compression closest to 10:1 as possible.
11-01-2003, 09:19 AM
#18
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Personaly i would not run high compression on a supercharged motor unless it was intercooled. Air temps in an sc motor are high enough on stock compression when you up the boost over 8 psi making it easily more prone to detonation. This is my own opinon for what its worth.
11-01-2003, 09:29 AM
#19
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does the intercooler on a sc'er work the same as the turbo intercooler. im new to forced induction and am trying to find out all the information i can before i start building my motor
11-01-2003, 09:55 AM
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Re: (Slomo_civic)
It works the same in that it cools the air down, I see a lot of SC guys running air to water. For some reason on a Super charger they call them "After Coolers".
11-04-2003, 11:38 AM
#23
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Re: (Slomo_civic)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Slomo_civic »</TD></TR><TR><TD CLASS="quote">is air to water the best way to cool things down?</TD></TR></TABLE>
not for a street car. on a race car its more feasible.
there are too many things involved on making an water to air, efficant for the street. (im talking from a turbo standpoint)
not for a street car. on a race car its more feasible.
there are too many things involved on making an water to air, efficant for the street. (im talking from a turbo standpoint)
11-04-2003, 12:40 PM
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Evo's have 8.5:1 compression.
Higher compression means the motor is more efficient, and thus will make more power at the same boost level, or the same power at a lower boost level.
This really doesn't matter a lot, lower compression is fine as long as you have the rest of the setup to support more boost.
I wouldn't go much higher than 9:1 on a pumpgas car.
I would run 9:1 if I was building up a car.
If you're bitching about off-boost power, get a turbo that actually spools, or push the damned gas down.
It's not like you're going to have gobs of power down low, no matter what your compression is.
Higher compression means the motor is more efficient, and thus will make more power at the same boost level, or the same power at a lower boost level.
This really doesn't matter a lot, lower compression is fine as long as you have the rest of the setup to support more boost.
I wouldn't go much higher than 9:1 on a pumpgas car.
I would run 9:1 if I was building up a car.
If you're bitching about off-boost power, get a turbo that actually spools, or push the damned gas down.
It's not like you're going to have gobs of power down low, no matter what your compression is.
11-04-2003, 12:55 PM
#25
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Re: (kpt4321)
To me 10 to 1 is fine provided you have some sort of boost retard device in your car. The key to success is tuning. Another thing to keep in mind when building your setup is, what is the maximum octane level at the pumps in your area. I run Sunoco Ultra 94 in my area so that helps me out alot as opposed to some areas that only yeild 91 octane at the pumps. Cause lets face it, race fuel is damn expensive and usually gets thrown in a street car once in a while.