lsvtechatch92

is 10:1 compression to high for pump gas on a piston and rods motor making around 400 whp daily driven....i was told ten to one is really risky pushing close to 400 or more on pump gas.... i need your opinion thanks

1Quikgsr

no compression is not high, is it stock pistons and rods? or aftermarket... im at 11.3 compression

lsvtechatch92

aftermarket

tony413

im guessing your boosting to make 400hp daily. the thing is compression makes heat and the turbo adds heat and heat creates det. and preignition so as long as you get a good tune, cooling system, and engine built properly you will be fine

ham

i made 472hp with 10:1 arias pistons and 93 octane, no issues.

QuarterMileMaster

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by ham &raquo;</TD></TR><TR><TD CLASS="quote">i made 472hp with 10:1 arias pistons and 93 octane, no issues.</TD></TR></TABLE>

My goal down to the T. My motor is built with 10:1 as well. Makes for quick spool. Just be sure to have a good tuner.

agrn93ls

i also run 10.0-.3ish:1 and boost. i like the better low end/spool etc. even though its minor. basically a stock compression forged GSR.

Boostfed

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by agrn93ls &raquo;</TD></TR><TR><TD CLASS="quote">i also run 10.0-.3ish:1 and boost. i like the better low end/spool etc. even though its minor. basically a stock compression forged GSR.</TD></TR></TABLE>


Compression doesn't affect your spool. You have better throttle response and more torque down low but not spooling quicker from compression

raene

I'd love to know how the quench from a set of 9:1 pistons compares to that from a set of 10:1 pistons from the same manufacturer (eg CP). That would determine which I'd prefer to run. Unfortunately I have no way to determine that information

Joseph Davis

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Boostfed.com &raquo;</TD></TR><TR><TD CLASS="quote">Compression doesn't affect your spool. You have better throttle response and more torque down low but not spooling quicker from compression
</TD></TR></TABLE>

That's a contradiction. Better torque is due to better airflow, more airflow means the turbo spools sooner as it's a flow driven pump. Well, which is it?

Tony the Tiger

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Boostfed.com &raquo;</TD></TR><TR><TD CLASS="quote">


Compression doesn't affect your spool. You have better throttle response and more torque down low but not spooling quicker from compression

</TD></TR></TABLE>

It does affect spool, but not the significant amount that everyone hopes for...

Overall, there are tricks to tune the engine for faster spool, and higher compression makes it more effective. More compression needs less timing, yet lesser timing leads to hotter exhaust gases. When you run higher compression, you can still create the same amount of torque (if not, more) yet you can run lesser timing to generate a bit more exhaust temps to give the turbo a kick. This also applies to all the partial boost regions since 1 psi offers more power at a higher compression, and so does 2 psi, 3 psi, and so forth all the way to target boost.

As I've always mentioned, you get guys running 11.0:1 CR with an SC61, or 10.5:1 with a GT42R.. That's pointless. For a responsive and fast spooling setup, every little counts and a well sized turbo is probably the most important part of the puzzle.

Boostfed

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Joseph Davis &raquo;</TD></TR><TR><TD CLASS="quote">

That's a contradiction. Better torque is due to better airflow, more airflow means the turbo spools sooner as it's a flow driven pump. Well, which is it? </TD></TR></TABLE>

OK so whatyou are saying is if I had a 84mm LS/VTEC at 9:1 compression then just swapped the pistons to a 10:1 now my turbo will spool quicker? I don't think so, spool is affected by exhaust size and turbo sizing no compression as far as I have been told. I could be wrong, I am not some super duper MECHANICAL ENGINEER or some dumb redneck who thinsk he knows **** J/K

Throttle response from more compression is due to what higher cylinder pressures? Correct? That is why when you jumo into an NA car with 13:1 compression that **** just jumps when you tap the throttle


Edit:What I think people confuse turbo spooling from higher compression to THROTTLE RESPONSE, you do get better throttle response with higher compression. Anything more complex than this argument and I am lost in space honestly

EARLdaSQUIRREL

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Boostfed.com &raquo;</TD></TR><TR><TD CLASS="quote">

OK so whatyou are saying is if I had a 84mm LS/VTEC at 9:1 compression then just swapped the pistons to a 10:1 now my turbo will spool quicker? I don't think so</TD></TR></TABLE>

more compression gives you more power, more power means more air flow which, which means it will spool the turbo up sooner,

displacement, compression, cams, all come into play with how fast a turbo spools (along with size of turbo)

from what i have seen displacement will spool a turbo up more than any other factor and compression will slightly help

Boostfed

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by coptzer &raquo;</TD></TR><TR><TD CLASS="quote">

more compression gives you more power, more power means more air flow which, which means it will spool the turbo up sooner,

displacement, compression, cams, all come into play with how fast a turbo spools (along with size of turbo)

from what i have seen displacement will spool a turbo up more than any other factor and compression will slightly help</TD></TR></TABLE>


Exhaust size and turbine size are very big contributors to spool .

Runnerdown

more compression does spool the turbo faster. Remember that higher compression is more heat energy. I have gone from 8.5:1 to 10:1 and there was a noticable difference. But like Tony said its not a large amount.

Boostfed

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Runnerdown &raquo;</TD></TR><TR><TD CLASS="quote">more compression does spool the turbo faster. Remember that higher compression is more heat energy. I have gone from 8.5:1 to 10:1 and there was a noticable difference. But like Tony said its not a large amount.</TD></TR></TABLE>


Well to use antilag you must make your tune RICH AND RETARDED like Forrest Gump, when running more compression you will usually be richer and retard timing so what cause it to spool quicker the tune or just the compression?

Again I am not saying I am right, I dunno. WTF do I know? lol I learn from others as others learn from others and teach me and others. If I am stuck on some old bad information that Earl gave back in the day and others agreed to it then damn my thinking has been skewed for the last 3-4 years now on this topic.

2.0tt

if you have a built motor you can push 400whp

QuarterMileMaster

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 2.0tt &raquo;</TD></TR><TR><TD CLASS="quote">if you have a built motor you can push 400whp</TD></TR></TABLE>

wow... revolutionary words... lol

2.0tt

what type of motor meant for forced induction with pistons and rods has a cr of 10:1?

Boostfed

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 2.0tt &raquo;</TD></TR><TR><TD CLASS="quote">what type of motor meant for forced induction with pistons and rods has a cr of 10:1?</TD></TR></TABLE>


Where have you been? Many people do it and even 11:1 CR also

QuarterMileMaster

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Boostfed.com &raquo;</TD></TR><TR><TD CLASS="quote">


Where have you been? Many people do it and even 11:1 CR also </TD></TR></TABLE>

Who knows, he just joined today...

I'm going to do you a favor Mr. 2.0tt, think long and hard before you post a comment because so far you are looking at a future of lots of flaming. FYI.

EARLdaSQUIRREL

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Boostfed.com &raquo;</TD></TR><TR><TD CLASS="quote">
Well to use antilag you must make your tune RICH AND RETARDED like Forrest Gump, when running more compression you will usually be richer and retard timing so what cause it to spool quicker the tune or just the compression?

</TD></TR></TABLE>

why would you run a 10:1 motor richer than a 9:1 motor? you wouldnt....

and timing wouldnt need to be retarded all that much more than a 9;1 motor either... the fact is it will help a motor spool because it will make more power(more air) than a lower compression motor

Runnerdown

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Boostfed.com &raquo;</TD></TR><TR><TD CLASS="quote">


Again I am not saying I am right, I dunno. WTF do I know?

</TD></TR></TABLE>


Its all good. I am hardly a know it all but when it comes to the thermodynamics, it seems to make sense. higher compression is more heat.....nothing else. Heat = energy....it makes more torque and hp. More heat the faster it spools given the turbo and other system parts have stayed the same.

tepid1

Dude.... you are off in your understanding of what compression is and how it affects power.

Not true.

Partially true.... Displacement helps more than compression due to the fact that you can add more fuel to a larger bore than you can a smaller.... thus creating more power. Compression does not affect spool like you think it does.

Higher compression is not more heat energy. There is the same amount of energy in a 10:1 car as there is in a 9:1 car as long as you maintain all the same variables. The 10:1 makes more power, not because of more air, but because is decreases the volume of the area in which the "explosion" occurs which in turn increases piston velocity and yields more power.

Now with the heat aspect....

You are essentially creating more thermal effeciency. The thermal efficiency is a measure of how effectively the engine converts the heat-generating potential of the fuel, when burned with an appropriate amount of air, into mechanical power. In order to appreciate a higher CR you need to also look at the ER, or the expansion ratio as well.

The Expansion Ratio (ER) is what occurs as the piston moves down the bore on the power stroke rather than what happens as it moves up on the compression stroke.

Here is a cool example:



Now so far you should be able to see why more compression makes more power. It is not solely because the charge is squeezed harder and the resulting combustion pressure is increased, but also because the higher expansion ratio allows more energy to be extracted from the original high-pressure charge.

CR and the correct cams go hand in hand. If you don't understand CR then you probibly don't understand the true benefits of a good cam.

So in a nutshell.... raising the CR increases torque, and consequently power, throughout the rpm range. Because raising the CR increases thermal efficiency, it brings about an increase in fuel economy. If a longer duration cam is installed, raising the CR at the same time can be worth considerably more than these two moves considered separately. When the CR is raised, peak combustion pressures are increased. And since cylinder pressure equals torque, that's a good thing. A rule of thumb for typical production engines is that combustion pressure is equal to the CR times 100. This tells us that, from a 10:1 engine, we would expect to see about 1,000 psi of peak combustion pressure.

Joseph Davis

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Boostfed.com &raquo;</TD></TR><TR><TD CLASS="quote">OK so whatyou are saying is if I had a 84mm LS/VTEC at 9:1 compression then just swapped the pistons to a 10:1 now my turbo will spool quicker? I don't think so, spool is affected by exhaust size and turbo sizing no compression as far as I have been told. </TD></TR></TABLE>

Exhaust size and turbo sizing are meant to match up with engine displacement... my criticism is that if the engine is more volumetrically efficient before boost comes in (from raising CR) then it technically displaces more air and acts like a larger engine.

Which isn't the case here, I was just busting your onions.

High CR is less efficient in the low cam area of operation as the engine is fighting itself overcoming suction losses before the intake valve opens. You set the engine up to be more volumetrically efficient in the higher rpms, but any gain from compression is lost in the low rpms/midrange where the turbo spools. All of this can, of course, be altered; I was thinking stock cams for this example and we've all driven cammed cars that had a hell of a lot more midrange before spool... any LS with cams, perfect example.