JRSC Build
01-10-2009, 04:49 PM
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JRSC Build
Im building a sleeved b20 vtec supercharged motor with water/meth injection. I just dont know what the best Compression ratio would be...I'm thinking 11.5:1-12.0:1. This would a fully built sleeved motor with a ported and lht intercooled supercharger. This would be my second jrsc build...first being a b20 with the m45 lht and water/meth injection at 8.5psi.
What would be the best CR for my build and what are the down sides of to high of a CR?
What would be the best CR for my build and what are the down sides of to high of a CR?
01-10-2009, 07:48 PM
#2
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Re: JRSC Build
The downside to too high a CR is that you'll be knock limited on pump gas, so your tuner will have to pull enough timing to cause power loss to keep the motor alive.
My B22 was knock limited at 11.5 running around 8-9 PSI from an Endyn blower with the LHT intercooler. If I did it again I'd keep it down around 10.5 or so. I never saw any significant gains from water/methanol injection, so I stopped using it. If you ask John at LHT, I believe he usually trecommends no more than 10.5 as well, and he's built even more JRSC setups than I have.
My B22 was knock limited at 11.5 running around 8-9 PSI from an Endyn blower with the LHT intercooler. If I did it again I'd keep it down around 10.5 or so. I never saw any significant gains from water/methanol injection, so I stopped using it. If you ask John at LHT, I believe he usually trecommends no more than 10.5 as well, and he's built even more JRSC setups than I have.
01-10-2009, 08:00 PM
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Re: JRSC Build
The downside to too high a CR is that you'll be knock limited on pump gas, so your tuner will have to pull enough timing to cause power loss to keep the motor alive.
My B22 was knock limited at 11.5 running around 8-9 PSI from an Endyn blower with the LHT intercooler. If I did it again I'd keep it down around 10.5 or so. I never saw any significant gains from water/methanol injection, so I stopped using it. If you ask John at LHT, I believe he usually trecommends no more than 10.5 as well, and he's built even more JRSC setups than I have.
My B22 was knock limited at 11.5 running around 8-9 PSI from an Endyn blower with the LHT intercooler. If I did it again I'd keep it down around 10.5 or so. I never saw any significant gains from water/methanol injection, so I stopped using it. If you ask John at LHT, I believe he usually trecommends no more than 10.5 as well, and he's built even more JRSC setups than I have.
01-10-2009, 08:18 PM
#4
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Re: JRSC Build
There are applications where water/meth will make a huge difference, I've seen blown SBC's that pick up over 30 WHP from it, but Hondas are generally not one of those applications. I wouldn't expect a shop like Stiegemier to know that, as they are mostly about American V8's, but please try it with and without water/meth injection when you have it on the dyno and see. I didn't get much out of it, but who knows, maybe I was doing something wrong?
With a poorted and intercooled M62, you shouldn't be pushing the blower hard enough to see thermal issues My IAT's while running around 300 WHP were only 10-15 degrees above ambient with the LHT setup.
With a poorted and intercooled M62, you shouldn't be pushing the blower hard enough to see thermal issues My IAT's while running around 300 WHP were only 10-15 degrees above ambient with the LHT setup.
01-10-2009, 08:56 PM
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Re: JRSC Build
The downside to too high a CR is that you'll be knock limited on pump gas, so your tuner will have to pull enough timing to cause power loss to keep the motor alive.
My B22 was knock limited at 11.5 running around 8-9 PSI from an Endyn blower with the LHT intercooler.
My B22 was knock limited at 11.5 running around 8-9 PSI from an Endyn blower with the LHT intercooler.
01-10-2009, 10:04 PM
#6
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Re: JRSC Build
It should, but you won't gain significant power from it, so why bother? I guess it depends on your aplication, but I'd rather keep the car streetable on pump gas if I was going to drive it on the street.
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