crxgsr91

What compression pistons is good with the SC at about 10psi. I would think 10.5 or 11.0:1 would be good (forged of course) for such low boost. So the question is what would the experts suggest?

gitwidit

You don't need a high compression ratio, your not trying to spool a huge turbo. The charge from a roots blower creates high intake temps if you don't have a way to cool it. I think you would be better off staying with a lower compression ratio in the 9's. Throttle response with a JRSC is awesome, lower compression would be ideal and easier to tune.
.03

crxgsr91

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by GITWIDIT &raquo;</TD></TR><TR><TD CLASS="quote">You don't need a high compression ratio, your not trying to spool a huge turbo. The charge from a roots blower creates high intake temps if you don't have a way to cool it. I think you would be better off staying with a lower compression ratio in the 9's. Throttle response with a JRSC is awesome, lower compression would be ideal and easier to tune.
.03</TD></TR></TABLE>

I would think the opposite. The JRSC is limited to the amount of boost therefore power so a lower compression piston would be eaiser to tune and more reliable but would make alot less power.

Rory Breaker

Agreed. I have seen some pretty potent 10.5:1 JRSC setups. I havent seen any 11:1, but I would imagine you would be fine given the right parts and tuning. Its not that huge of a jump.

The thread on a high compression turbo setup going on right now should be of use to some people looking into this.

gitwidit

Doesn't a higher compression ratio have hotter combustion temps? Is it worth daily driving on pump gas? What is the hp gain, maybe 20hp? I'm just guessing.......

Spray some nitrous to make up the difference

11psiTurboSI

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by GITWIDIT &raquo;</TD></TR><TR><TD CLASS="quote">Doesn't a higher compression ratio have hotter combustion temps? Is it worth daily driving on pump gas? What is the hp gain, maybe 20hp? I'm just guessing.......

Spray some nitrous to make up the difference </TD></TR></TABLE>

Not only hotter combustion... but your JRSC creates alot of heat on top of that!

crxgsr91

I agree with what you are both saying but I don't think I am asking that much the ITR has 10.8:1 pistons and they SC it. Sure the temps would be higher but some water injection and good tuning would help.

Anyway this is just an idea after reading about the high compression turbo that would also be a good street/autox/drag setup.

keebler65

yeah i think several of you have it right. you want to keep the boost low since the blower is more efficient in this range. that means a high compression ratio if you want to make abnormal power from it. however, a high compression ratio isn't going to get along with the JRSC unless you use some form of cooling (nitrous, or preferably an intercooler).

MooreBoost

Maybe a low compression piston with a 50 shot?

gitwidit

Running a JRSC @10psi is already prone to pre-detonation due to the adittional heat created by the SC spinning that high of an RPM. Raising the compression ratio doesn't help at this boost level.
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by crxgsr91 &raquo;</TD></TR><TR><TD CLASS="quote">Sure the temps would be higher but some water injection and good tuning would help.</TD></TR></TABLE>
If you want to throw water injection into the equation thats good. IMO though I don't like it because you are "snuffing" the fire, not fixing the root cause. It's easy to reach the point of "diminishing returns" with a JRSC compressing that much air, even with a good tune. Heat ownz you

keebler65

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by GITWIDIT &raquo;</TD></TR><TR><TD CLASS="quote">Running a JRSC @10psi is already prone to pre-detonation due to the adittional heat created by the SC spinning that high of an RPM. Raising the compression ratio doesn't help at this boost level. </TD></TR></TABLE>

my JRSC is currently at 10psi on my 10.2:1 CR stock B16 and i have zero problems with detonation. the setup is not cooled in any way and i run 93 octane.

JR Integra

I have a JRSC at 11 lbs, on 10.5:1 cp pistons, hondata tuned, i was barely able to pull out 200 hp, because they had to tune it so safe to get rid of detonation, the car hauled *** pretty good before hondata but the motor would not have lasted long. I would haVE probably been able to get more hp, with a lower boost!! The car is really fun to drive but for the money it will take to improve it, i am just selling the setup and going turbo.

gitwidit

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by keebler65 &raquo;</TD></TR><TR><TD CLASS="quote">my JRSC is currently at 10psi on my 10.2:1 CR stock B16 and i have zero problems with detonation. the setup is not cooled in any way and i run 93 octane.</TD></TR></TABLE>
Have you ever recorded a 1st-5th gear pull and checked your IAT temps at the manifold? My previous setup would be around 190dg at the end of 4th running 10psi In 5th I would hit 200dg. Maybe it was ventilation or a number of other causes, all setups are different of course. That high of a temp is enough to scare me though

MooreBoost

I made 200whp on a B18C1 with just the blower @ 8psi, no internals, and an FMU.

keebler65

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by GITWIDIT &raquo;</TD></TR><TR><TD CLASS="quote">
Have you ever recorded a 1st-5th gear pull and checked your IAT temps at the manifold? My previous setup would be around 190dg at the end of 4th running 10psi In 5th I would hit 200dg. Maybe it was ventilation or a number of other causes, all setups are different of course. That high of a temp is enough to scare me though </TD></TR></TABLE>

yes, actually, i pay close attention to the temps. i think its probably around 160-180 when fully boosting. however, my above statement was to point out that aside from the high temps, i have zero detonation. maybe it depends on the tune...

JR Integra

when they where tunning my car they found the IAT sensor to be bad, they pulled it out and the end was melted down, they said they had never seen anything like that before. MY old setup with the charger detonated untill the pistons melted.

keebler65

crxgsr91 -

you may also want to post your question on hostboard, because there are a lot of experienced JRSC people with reliable setups. you may have more luck finding the answers you need. here is the link: http://www.hostboard.com/cgi-b...f=110

crxgsr91

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by keebler65 &raquo;</TD></TR><TR><TD CLASS="quote">crxgsr91 -

you may also want to post your question on hostboard, because there are a lot of experienced JRSC people with reliable setups. you may have more luck finding the answers you need. here is the link: http://www.hostboard.com/cgi-b...f=110</TD></TR></TABLE>

Thanks keebler you are always helpful

Muad'Dib

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by JR Integra &raquo;</TD></TR><TR><TD CLASS="quote">when they where tunning my car they found the IAT sensor to be bad, they pulled it out and the end was melted down, they said they had never seen anything like that before. MY old setup with the charger detonated untill the pistons melted.</TD></TR></TABLE>

you mean something like this....?