Can someone tell me why more boost with lower compression makes more HP than lower boost and higher compression? Shouldn't I safely be able to make the same power with higher compression. I'm only asking because I wanted to get a inline pro head gasket and arp head studs and boost higher.

BTW the setup is a 95 gsr
rc 440cc
walbro Fuel pump
uberdata
plx wb tuned to 11.8 @ 9psi

 

Forcing air into the motor via turbo,supercharger,etc raises the compression of the motor ..So can you imagine running high compression plus high boost..You would defineatly detonate..

 

It's me again but with a different name....I don't think u understood my Q. I know what ur explaining ...that's the effective compression ratio. BUT what I wanted to know was why there are 400 HP B18C's running stock internals with a thicker headgasket and you don't see any 10:1 compression motors running lower boost making the same power.

 

I was just running 10.5-1 comp je pistons with a fully built motor pushing a sc-61 turbo and melted every piston. and i mean melted. every one says it was detonation... but me and my pops were driving the car when it happened and we know what detonation is and it did not detonate. I was on 15psi the car was making incredible power until it finally gave way. now i'm going to run 9-1 comp wiseco custom pistons.... wish me luck.

 

too much timing sir...


even forged slugs don't like too much timing love.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by not2slo128 &raquo;</TD></TR><TR><TD CLASS="quote">It's me again but with a different name....I don't think u understood my Q. I know what ur explaining ...that's the effective compression ratio. BUT what I wanted to know was why there are 400 HP B18C's running stock internals with a thicker headgasket and you don't see any 10:1 compression motors running lower boost making the same power.</TD></TR></TABLE>

I understand your question.

The answer is simple. The turbo engine, with the same dynamic compression, has more air and fuel in the cylinders than the N/A motor.

Let's say you have some AFR that gives you 1 gram of fuel per 1.8 liters of air. In a 1.8 liter N/A motor, you can, at the very most, get 1 gram of fuel in per cycle. Now you compress the **** out of it. You still have 1 gram of fuel.

Now take a turbo motor. If you make 2 atmospheres of pressure, you should have 2 grams of fuel compressed into the same 1.8 liters of air. Now you compress is half as much as in the N/A engine. You get the same overall compression (well, close to it), but you have twice as much air and fuel.

See?

 

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

..So can you imagine running high compression plus high boost..You would defineatly detonate..</TD></TR></TABLE>

But if you control detonation through tuning than you'll make more power. It's like saying "if you raise you boost from 10 PSI to 15 PSI, you'll detonate"...it's possible, and very likley...but if you control detonation when going from 10psi to 15psi then you'll make more power right?

If I opened up a d-series to make the internals stronger...I'd raise the comrpession to 10.0:1 and run the same bost as I did before.

 

Your correct in your thinking.
The big factor here is pump gas. It has its limits. You can only run so much
effective compression until it becomes unstable. With race gas of course, this is
not so much an issue. A lot of the people here (myself included) like to push
high hp numbers on the street. Lower compression setups simply give more
"room" to work with.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by ssl2k &raquo;</TD></TR><TR><TD CLASS="quote">too much timing sir...


even forged slugs don't like too much timing love.</TD></TR></TABLE>



Tuning is everything. I am getting ready to Turbo a Sleeved b18c1 w/ 11.5:1 JE's in it and poeple think I am crazy and tell me "It's going to blow" but, I'll prove everyone wrong. It has been Done: JG BIG Numbers

 

like was said before high compression is not used because of the limits of pump gas usually.. the higher compression of the pistons isnt enough to over come the difference of that much more boost you are safely able to run while using lower C/R on pump gas.....it might be something like 10:1 at 11psi = 9:1 at 12psi (not real numbers) but the higher compression is less forgiveing with tunning, now why that is? i dont know. thats my take on this but i could be wrong i have no proof just things i have read.

 

Yes, lowering you compression makes it easier to tune...but so does lowering the boost. Wanna get the idea of what compression and boost is really about?... is the answer to 4+6 higher than 7+3?

It's very possible to drop your compression, raise the boost and not get any HP.

There are many reasons to drop the CR to raise boost tough...you can drop your compression, raise the boost ...KEEP THE SAME EFFECTIVE CP as before and gain HP by having the turbo in a better effiency range...or something like that.

((boost psi / 14.7) + 1) x motor compression = effective compression

http://matt3t4.20m.com/photo5.html

 

so i guess i shouldnt pick up these 10.5-1 compression jes for my turbo b16 then eh?

 

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



Tuning is everything. I am getting ready to Turbo a Sleeved b18c1 w/ 11.5:1 JE's in it and poeple think I am crazy and tell me "It's going to blow" but, I'll prove everyone wrong. It has been Done: JG BIG Numbers</TD></TR></TABLE>

And while you're talking about how super awesome your 11.5:1 motor is, and limping around with no boost on pump gas, I'll blow by you, with a reliable 450 to the tire on 94 octane with my 9:1 motor. I see no realistic gains on a street car from higher compression. You saw Boosted Hybrid's test, maybe 3 WHP before boost hits going from 10:1 to 9:1. Do you think ANYBODY here is going to notice 10:1 vs. 9:1? No. If you put anybody here in 2 naturally aspirated B18C5 powered cars, same weight same everything and said tell me which one is 9:1, other than just guessing and having a 50% chance of getting it right there is almost no way you could tell.