Compression Question

[1 SICK GT]

just wanted to know how do you determine what compression you should run on a turbo setup

i see so many use different compressions on the same setup


if this helps

my stock compression is 9:2:1

my motor is a 2.5 liter which i might bore to a 2.8

my turbo is a turbonetics ballbearing T-62

[1 SICK GT]

any answers anyone

[Big Baller]

You can run what ever, you want 9.2 is fine for a turbo motor.

[SPOOLIN]

just run stock compression, or run 10.5, just get the fucker tuned and it wont matter

[s13slider®]

^^^ Why in the hell would you want high compression for a turbo set up ? You really need to learn more about cars before giving an input . Ok dude your gonna wanna drop the compression , i would go with 8.5 :1

[SPOOLIN]

dude I know exactly what you can and can not do and most people on this board would agree with me. Im sure baller above can attest, low compression and high compression doesnt mean shit, yeah you dont want 11.5:1 on a high power drag turbo car but there are guys with 12.5:1 turbo setups that are bad ass street cars. Go read more magazines about lowering compression for turbo, ill sit back and keep making my 700hp on my civic. ITS ALL IN TUNING.

[Big Baller]

^^^ Why in the hell would you want high compression for a turbo set up ? You really need to learn more about cars before giving an input . Ok dude your gonna wanna drop the compression , i would go with 8.5 :1

Get ready to learn something...pay real close attention....that shit you have been reading on the internet from those know it all mother fuckers on the forums....IT ISN'T TRUE.

Why would you want high compression ratio with a turbo setup....For off boost response, it spools the turbo quicker.

It also raises the VE of the motor.

YOU NEED TO FUCKING LEARN SOMETHING BEFORE YOU START TELLING PEOPLE WHATS WHAT. FUCK I HATE KNOW IT ALL 16 YEAR OLD KIDS.

[Big Baller]

Cobb tuning runs 11.0 to 1 on their Race motor 30+lbs of boost on a road course. If you have the octane and the tune you can do what ever you want.

Some of the Outlaw Mustangs run crazy high compression ratios with blowers....




IF YOU DONT KNOW......NOW YOU KNOW

[1 SICK GT]

^^^ Why in the hell would you want high compression for a turbo set up ? You really need to learn more about cars before giving an input . Ok dude your gonna wanna drop the compression , i would go with 8.5 :1

well i do not want to drop the compression

either i want to keep the stock compression 9:2:1

or i want to increase it either to 9:5:1 9:7:1 10 but no more than 10:5

just can't decide i only want to buy pistons once if necessary pistons of choice is Ross with Pauter Rods

[Big Baller]

As a general rule a lower compression ratio will allow you to run more boost on pump gas... a higher compression ratio will get you better off boost response and net you more power but you will have to have lots of octane.

youre stock compression ratio should be fine.

Matt

well i do not want to drop the compression

either i want to keep the stock compression 9:2:1

of i want to increase it eiter to 9:5:1 9:7:1 10 but know more than 10:5

just can't decide i only want to buy pistons once if necessary pistons of choice is Ross with Pauter Rods

[Vteckidd]

the norm for most motors now adays is 10:1 for a 500+whp motor that sees the track.

for daily drivers, i would run 9.5:1 because youll mostly be on pump gas, and regardless of what you do, you can get a bad batch of gasoline.

Im a fan of 10:1+ turbo motors, small turbo, big power.

Higher compression will spool the turbo faster, volumetric efficiency increases, the motor is much happier.

Think about it in NA terms as well. Stupid high compression (12.5:1+) for a pump gas motor on the street sucks. you will have to pull so much timing to avoid detonataion that it makes the motor lazy. things arent as crisp, combustion isnt as ideal, etc.

Same way with a Turbo motor with really low compression. Sure its better on pump gas an safer, but youll have to run MORE BOOST to make the same power as a higher compression motor.

So in short, 9.5-9.8 is good for a STREET motor IMO. If your building a semi track/race/street combo, then 10:1-10.5:1 is good.

problem is i dont think most people on this board can pull off high compression turbo motors because they wont spend the money to do it right.

[1 SICK GT]

the norm for most motors now adays is 10:1 for a 500+whp motor that sees the track.

for daily drivers, i would run 9.5:1 because youll mostly be on pump gas, and regardless of what you do, you can get a bad batch of gasoline.

Im a fan of 10:1+ turbo motors, small turbo, big power.

Higher compression will spool the turbo faster, volumetric efficiency increases, the motor is much happier.

Think about it in NA terms as well. Stupid high compression (12.5:1+) for a pump gas motor on the street sucks. you will have to pull so much timing to avoid detonataion that it makes the motor lazy. things arent as crisp, combustion isnt as ideal, etc.

Same way with a Turbo motor with really low compression. Sure its better on pump gas an safer, but youll have to run MORE BOOST to make the same power as a higher compression motor.

So in short, 9.5-9.8 is good for a STREET motor IMO. If your building a semi track/race/street combo, then 10:1-10.5:1 is good.

problem is i dont think most people on this board can pull off high compression turbo motors because they wont spend the money to do it right.

well the car is not a daily driver but it is not a race car either

i would probally only drive it to the track every once in a while and maybe when i come out on the weekends to hang out, other than that the car will be in the garage collecting dust

my hp goal was anything over 600whp and i am not trying to do 600 daily transmission couldn't handle that type of abuse

[Vteckidd]

600whp run 10:1, sleeves

[william_jeff]

the norm for most motors now adays is 10:1 for a 500+whp motor that sees the track.

for daily drivers, i would run 9.5:1 because youll mostly be on pump gas, and regardless of what you do, you can get a bad batch of gasoline.

Im a fan of 10:1+ turbo motors, small turbo, big power.

Higher compression will spool the turbo faster, volumetric efficiency increases, the motor is much happier.

Think about it in NA terms as well. Stupid high compression (12.5:1+) for a pump gas motor on the street sucks. you will have to pull so much timing to avoid detonataion that it makes the motor lazy. things arent as crisp, combustion isnt as ideal, etc.

Same way with a Turbo motor with really low compression. Sure its better on pump gas an safer, but youll have to run MORE BOOST to make the same power as a higher compression motor.

So in short, 9.5-9.8 is good for a STREET motor IMO. If your building a semi track/race/street combo, then 10:1-10.5:1 is good.

problem is i dont think most people on this board can pull off high compression turbo motors because they wont spend the money to do it right.

THIS RIGHT HERE IS SOME PERTINENT INFORMATION RIGHT HERE!!!

thanks for clearing it up helps build insight on my part reps if i can

[morris]

Do not increase your CR, if anything you will want to lower it. I agree that the stock CR is okay as long as you arent going to run extremely high boost.

Those race cars taht were reffered to are running race gas that is why they can get away with the very high cr.

93 octane you want 8.5-9.5 in my opinion

[Vteckidd]

93 octane you want 8.5-9.5 in my opinion

on a honda motor or any 4 cylinder, 8.5 is retarded

[Vuongy_Dong]

^^^yes it is. I would never suggest that CR to anyone.

[IDriveToast]

on a honda motor or any 4 cylinder, 8.5 is retarded

This man speaks the truth. Please listen to him. 9.5-10.5 is the "happy zone".

[Big J]

Lower the CR if you want a slug at part/low throttle, you get more of a light switch effect.......... nothing......wham OMG. In the increased lag you'll put it to the floor just so turbo has a chance to catch up, not fun for a daily driver. You can get away with a less percise tune w/ lower compression, but you'll have a trade off, like shitty drivability.

[Blaze the chemi]

My engine is the B16A which comes stock with 10.2:1. When I rebuilt my engine I choose to install 9.9:1 CR pistons because it would lower the compression just a bit to still have good response while not in boost, but still have good repsonse once I am in boost. I was pushing 12 psi, but soon I'll push 15-20 psi on a much more efficient turbo in the future while still sticking in 93 octane, but a conservative tune of course.

[xbn83]

I use CP 9.8:1 on my GSR build.

[SPOOLIN]

you can run 10.5 and about 450whp on pump generally without a problem. After that, you are pushing the safety zone limits on pump.

[sullen]

well i do not want to drop the compression

so keep stock fucking compression....why did you bother posting this forum or asking that question? if you know what you wanna do, then go fucking do it. 10:1 is fine for a turbo motor. tuning, octane, build.can't run like 40lbs boost....but c'mon, why the hell would you? 2 bar is WAY more than enough for any motor to make ASSLOADS of HP.

[sullen]

spoolin, are you turbo dave?

[1 SICK GT]

so keep stock fucking compression....why did you bother posting this forum or asking that question? if you know what you wanna do, then go fucking do it. 10:1 is fine for a turbo motor. tuning, octane, build.can't run like 40lbs boost....but c'mon, why the hell would you? 2 bar is WAY more than enough for any motor to make ASSLOADS of HP.

because i wanted a dickhead cunt bag like you to say something stupid



my concern was whether to up the compression

[IDriveToast]

spoolin, are you turbo dave?

Spoolin is not turbo dave, Spoolin is Spoolin.

[IDriveToast]

What motor is this BTW? 2.5 Liter? Not many of those around except the QR25. And if you don't want to change anything at all...stock compression will be fine.

You can however up the compression to 10:1 and you response will be better. It's ultimately your decision. Since you're already at higher than 9:1 I would personally up it to 10:1.

Better response will be more productive than 1 or 2 extra pounds of boost.

[SPOOLIN]

Spoolin is not turbo dave, Spoolin is Spoolin.

haha i cant even fabricate a panel to mount something to much less a turbo manifold!

[blackshine007]

What motor is this BTW? 2.5 Liter? Not many of those around except the QR25. And if you don't want to change anything at all...stock compression will be fine.

You can however up the compression to 10:1 and you response will be better. It's ultimately your decision. Since you're already at higher than 9:1 I would personally up it to 10:1.

Better response will be more productive than 1 or 2 extra pounds of boost.

Only motor I know of that 9.2:1 and 2.5L's is the Mazda 2.5L V6 KL. And with a name like 1 sick GT, He's definately driving a Probe GT. I would suggest going over to the Probetalk forums and looking off in the turbo forums. BTW, I think Mr.kidd made a great point. 10:1 comp. is great on a boosted car, but has more of a chance of detonation vs. a lower comp. without the lag time.
http://forums.probetalk.com/
There's a couple of guys there making easily well over 300 hp on not alot of boost. There's one guy there making 540 hp on 19 psi w/ stock crank and block, and turbo cams

[B18c1Turboed]

ill sit back and keep making my 700hp on my civic. .

.........................

[SPOOLIN]

.........................

yes, and you'll sit back with a 800hp show car.

[B18c1Turboed]

yes, and you'll sit back with a 800hp show car.

800+ show car!!!

Plus show car my ass, come see me Drive my show car to Commerce and run it, and then back home friday night!!!

[SPOOLIN]