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I currently have a set of JE 10:1 compression pistons that I'm debating on using on a my boosted LS/Vtec set up. I'm not sure if I should use these or go to 9:1, or even 8.5:1. I'm looking to get the most power I can from pump gas (93-94 oct), which would lead me to believe that I should go with the 8.5:1, but is there any benifit to going to the higher compression pistons? I've been reading and people say that the higer compression pistons will spool the turbo quicker, but how much quicker? Thanks, RV.

Respect Given Non Takin

The compression ratio, really depends on who is doing the tuning for you. I am currently running a 10.5:1 ratio on my LsVtec setup, I have ran this on my single cam and I had alot of Pep(93 Octane). I had decided to go that route rather than going to a lower compression ratio. The turbo will spool much quicker and you can run less boost, and still get to HP/TQ that you want, with less wear on your engine. Like I said earlier its all about who is doing your tuning for you. There is were you seperate the MEN from the BOYS.. Good luck LsVtec

Rooftop voter

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Thanks. What about the limitations of pump gas with high compression boosted motors? Is it worth dropping the compression to be able to run more boost and make more power? I'm shooting for around 425whp or there abouts.

Respect Given Non Takin

Thanks. What about the limitations of pump gas with high compression boosted motors? Is it worth dropping the compression to be able to run more boost and make more power? I'm shooting for around 425whp or there abouts.

The limitations on pump gas I would say around 350-380, and thats being safe !!

Your tuner would be the Master key in putting the puzzle together. I stress this about the tuner because its as important as you tighten the bolt on the oil pan.. Now some people would say it can go more, but when do it really starts to go bad? after 400HP nope long before that. If you really want to live in that 400HP world step and get some C12 you can live there comfortable, Up until right about 475HP, then you step up C16. Most people will jump straight to C16 and would not see what there looking for. Once you add HP all aspect of the game changes. Why would you want to run more boost? The setup I have will be able to run very close to an honest 25 psi of boost. Why would I need more PSi, when most cars that running 30-32 PSi of boost still isnt beating me, and this REAL TALK.

TheShodan

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Compression ratio will not change your power, it will, however, change your acceleration rate, depending upon the turbocharger used.

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Be using a garret 60-1 .63 AR hotside. Ok, I'm wanting to be able to go higher than that on pump. I'm looking to be able to be around the 425 whp range. I guess, the question is should I do 9:1 or 8.5:1.

TheShodan

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the higher the compression ratio, the better the acceleration rate. But you also want to stay safe with your tuner. NO LOWER THAN 9.0:1

Rooftop voter

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I was thinking 9:1 also, but what does that have to do with accelaration rate? I realize that I would suffer more lag and such, but when getting into boost, shouldn't it still pull like crazy?

reaction360

I've had a high 8compression motor, and 9:1 and now i'm right around 10:1 and its the best motor i've had so far. I think same boost level, a higher compression motor will always feel better n faster. and as stated before, the acceleration will be better and and therefore making the power quicker. I'll never go lower then 9.5-9.7:1 compression again.

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Why would you say it's the best motor you've had? Just curious.

reaction360

power, response. My really low compression motors kinda sucked to drive around on when out of boost. and who realy stays in boost every second when they drive? if you're concerned about tuning and reliability, just go with 9:1. but no lower.

Rooftop voter

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Thanks for your reply. Anyone else? Maybe with some technical info? Thanks Again, RV.

TheShodan

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<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by reaction360 &raquo;</TD></TR><TR><TD CLASS="quote">power, response. My really low compression motors kinda sucked to drive around on when out of boost. and who realy stays in boost every second when they drive? if you're concerned about tuning and reliability, just go with 9:1. but no lower.</TD></TR></TABLE>

This is correct. the acceleration rate increases between gears because the effective compression is already much closer to a level where the turbocharger (the larger ones that honda users typically use) can respond much more quickly. Even drag racers on the professional side use extremely high compression relatively (over 11.0:1 in some cases---remember, they can rebuild their motors at anytime and most likely have additional engines on standby ready to go).

the reason why you see a lot of DSMs and Subarus at 8.5:1 and even lower are for 2 reasons:

1) The factory understands that their car could be at a VARIETY of altitudes, fuels, and other conditions that affect their MAF and computer settings, and want to be reliable at all levels regardless of where the car is sold.

2) the turbos used are typically much smaller, but have an efficiency range at a much different spot than where most honda owners would like below 2PR (pressure ratios) with their static compression lower, using a much smaller turbocharger can still keep the car responsive for the fuel efficiency, consumption, and power that they were designing the car around. Most daily cars look at simply additional torque and power and the lower RPM range, and not in the big 8K + ranges with Honda's VE in mind. On my time attack car, I'm currently at 10.6:1CR, sleeved with upgraded internal components. I'm not going below 9.5:1 ever again myself.


Modified by TheShodan at 11:02 AM 11/2/2008

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Thanks for your in-put. What power numbers are you seeing on pump gas?

TheShodan

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<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Rooftop voter &raquo;</TD></TR><TR><TD CLASS="quote">Thanks for your in-put. What power numbers are you seeing on pump gas?</TD></TR></TABLE>

Well, just remember, that the power capability of the turbocharger is not going to change whether or not you are low or higher compression. But it DOES mean that it will take more pressure (meaning a greater amount of boost to get to the effective compression that you're looking to obtain) to get the same amount of power. On time attack and road race cars, power needed really depends upon the track. Many times you just can't use more than about 300whp on a road race track (the smaller ones in the east coast. as you go south and east, they get larger). But I'd say about 380whp on 14psi, and about 440whp at about 17psi. 18psi + I would use race gas, but since I rarely find the need for a Full tank of race gas, I only use it to keep me safe on a colder day or something like that in case it overshoots once in a while. I'm using an HKS3037S turbocharger (this is slightly smaller in exducer compared to the Garrett GT3076R.

TheShodan

iTrader: (14)

Again 9.0:1 and above is optimal. On simply a 60-1, making sure of course you're using the larger Stage 5 exhaust wheel, and not the standard stage III, 425whp pump gas is very possible.

Here's an example of one person (Mitsuman) with a Silver Surfer turbocharger (60-1 w/ stage 5 wheel) that got about 346whp at less than 12 psi. I'm quite sure 425whp is possible on 93+ octane, but that's about the limit.) His maximum spool is different than the Garrett equivalent because there were some changes made to the housings that are different than Garrett's standard T04S design.

http://smg.photobucket.com/alb...p.flv