b18sihatch

i have a fulley built block with je 8:2:1 compression pistons.

i was wondering if the lower compression will allow for greater boost pressure numbers (psi) or will this just allow less of a likly hood of detonation? i know the lower compression allows how the lesser likly to cause detonation, but wasnt sure if this lower compression will also allow for more psi numbers than stock pistons. also the block is also sleeved.... i was just curious

RedR

yes u can run more boost, and u will have more lag as well.

DfwBB6

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by RedR &raquo;</TD></TR><TR><TD CLASS="quote">yes u can run more boost, and u will have more lag as well.</TD></TR></TABLE>

true dat!!!there is where u gotta find a balance

Boostfed

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by RedR &raquo;</TD></TR><TR><TD CLASS="quote">yes u can run more boost, and u will have more lag as well.</TD></TR></TABLE>

You will NOT have more lag BUT you will think you are since OFF BOOST response will be unresponsive with a low compression small displacement motor. Exhuast size , cam timing, cams, headwork etc effect spool but not actual compression ratio sir.

Bjorn20

yea lower compression can allow you to go more boost safely. But you have to balance both sides. Sure you can have a real low compression such as an 8:2, and may be able to up the boost. But is that really worth it if it takes a year for the turbo to spool?

In my opinion, 8:2 compression is WAY to LOW for a built motor. But w/e works for your setup.

Boostfed

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Bjorn20 &raquo;</TD></TR><TR><TD CLASS="quote">yea lower compression can allow you to go more boost safely. But you have to balance both sides. Sure you can have a real low compression such as an 8:2, and may be able to up the boost.][b] But is that really worth it if it takes a year for the turbo to spool?[/b

In my opinion, 8:2 compression is WAY to LOW for a built motor. But w/e works for your setup. </TD></TR></TABLE>

Again Compression ratio does not affect turbo spool BUT does affect off boost response

non-VTEC

8.2:1 is not to low.......thats perfect for big boost.....

if i were to build all over again i would go for around 8:1 instead of 9:1+

b18sihatch

well that was what i was asking.

lower boost pressures will yeild you safely to push more boost.

however will it be in my best interest to boost more psi so lag wont become such a issue.

the head is port and polished with a 5 angle valve job.

exhaust i have yet to decide, prolly 3'' open downpipe or turbo back.

i dont want super lag, however since the block has 8:2:1 what kinda psi pressure would be good for the motor and not create so much lag? wouldnt if i ran like 20psi the lag wouldnt so much be there?

whjat im asking is, if i run more psi will the motor be more respondsive to boost? ie: lower lag ect?

BoostedEG6

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by b18sihatch &raquo;</TD></TR><TR><TD CLASS="quote">whjat im asking is, if i run more psi will the motor be more respondsive to boost? ie: lower lag ect?</TD></TR></TABLE>

no, no matter what PSI you run.

93supercoupe

I love hearing that, " lower compression creates more lag"
I just love it.

Turbo-charged

ever driven a 12.5:1 compression turbo car? FUN! off boost power is still good so when the turbo does kick in it feels like there is no "lag". or a 7.x:1 honda motor? they are turdddsss off boost haha.

i can see how people get confused..........but most people who come out and say the comments have not experianced both, they just read the net haha

Boostfed

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 93supercoupe &raquo;</TD></TR><TR><TD CLASS="quote">I love hearing that, " lower compression creates more lag"
I just love it. </TD></TR></TABLE>

You should run an LS tranny because the gears are LONGER and you will stay in boost longer!!! lolololololololololol

To idiots saying that and compression affects lag lol

PH_B16-VTi

If you put 8.1:1 pistons in a car that has original 10:1 ratio and maby 180hp you wil have less hp. Therefor when you are not at Full Throttle or not building boost preasure, you're car will feel much slower. But you can insted run shitload of boost and get a high power car.
Like they say, it depends on what you want. Normaly if you want a street car or daily driver, it's often preferred to have a bit higher compression ratio, like 9'ich so you also get good off boost power. But if you're building drag racing cars and all you need is lots of boost then lower.

Of course this is an example and don't balance your build on my numbers, I'm just talking theory.

/ph

Boostfed

For every point of compression general rule of thumb is 3-5% increase or decrease in power

b18sihatch

so since the compression is lower. and i can run higher boost pressures. what would be a good pressure to have it tuned up to? and then run a boost controller?

also with 8:2:1 compression and a fulley built/sleeved block. what would you say the maximum psi my block could handle/ horsepower it would be able to make?

Turbo-charged

uhhhh most drag cars are running higher compression than on street cars.


dont put 8.x:1 pistons in the car you will hate it. just do 9:1 and tune the thing

b18sihatch

the block is already complete built and done...... i am wanting to tune the motor from 15psi daily 25psi race/track. depending on how the motor and turbo setup responds to the boost and what type of power it makes in those ranges

Turbo-charged

you will be fine at those boost levels if tuned right. hell on my old 9:1 b16 motor when i gave up caring about it i ran 25psi on pump gas for like 30k miles....it never died untill the fuel pump quit working haha.

raene

I agree, drag cars run higher CRs because they can afford to run higher octane because they're not doing 100 km's a day

If I did it again I'd go with lower CR... I'm 9:1 now. There's a lot to be said for having the right piston shape and quench zones but without having all the pistons to play with and see what works right, on my budget, lower CR is safer, and safer at the same level of in-boost power is always good. Who cares about off-boost response, I call it downshifting.

I also see it as we Honda guys like to run big turbos that have good efficiency at high boost. So if you run 8:1 compression ratio, you have to run higher boost - say 18 lbs - which puts the compressor more into its efficiency island than running, for example, 14lbs and making the same power. So the charge is cooler, and you're making the same power, and you can probably get away with lower octane, or even survive a bad tank of gas.

b18sihatch

so at say 15-25psi what kinda numbers am i looking at? i know that alot of other things play a roll in how much power. but say a good turbo kit with the block and those psi levels. im shooting for a safe 300-350whp. im not wanting to go above that right now due to having to upgrade a good ammount to take the 400-450 range. also this is going in a EF so 300-350whp is going to be pretty fast.

thats another thing i was looking to figure out, its easier to figure out the power range with higher compression pistons and a decent ammount of boost. but lower compression and more psi is kinda hard to estimate how much power i would be making