Meth and boost?
Thread Starter
Pro
Joined: Jun 2007
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From: Pensacola Fl
Meth and boost?
I got word from my tuner today that my compression is too high for my boost level and octane. My setup is a forged 390 with ls6 heads, ECS Novi2000 kit, ECS cam; the
compression is 10:1. My pulley setup should make around 18psi and I was planning on running 91 octane and the ECS dual alky kit. I was told that it's too much boost for that
compression level and octane? Is that true? I was informed I will need to run 100 octane and meth in order to safely run that much boost. I was looking for around 850 wheel.
compression is 10:1. My pulley setup should make around 18psi and I was planning on running 91 octane and the ECS dual alky kit. I was told that it's too much boost for that
compression level and octane? Is that true? I was informed I will need to run 100 octane and meth in order to safely run that much boost. I was looking for around 850 wheel.
jobberone
Joined: Aug 2003
Posts: 2,062
Likes: 8
From: Kailua Kona HI
I agree with your tuner. You can run that much boost on 91 octane but you will have to take most of the timing out. You will lose a lot of power and stiull risk your engine to knock. You can run a mixture of 91 octane and 103 unleaded and get to 18-20lbs with the right tune and meth. You will likely be closer to 18 than 20 lbs.
The other option is either massage your heads with larger chambers and/or change your head gasket. And/or change your pistons to a dish.
I don't know if its an option but you can get to your goals a lot easier with 225 heads and on lower boost levels as a result.
If you're not running that much boost right now you may have problems with valve opening unless your spring pressures are high enough. You need at least 150 lbs of spring pressure at that level of boost and preferably 180 to 200 on the intakes.
The other option is either massage your heads with larger chambers and/or change your head gasket. And/or change your pistons to a dish.
I don't know if its an option but you can get to your goals a lot easier with 225 heads and on lower boost levels as a result.
If you're not running that much boost right now you may have problems with valve opening unless your spring pressures are high enough. You need at least 150 lbs of spring pressure at that level of boost and preferably 180 to 200 on the intakes.
Last edited by jobberone; Nov 24, 2010 at 09:30 PM.
Thread Starter
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Joined: Jun 2007
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From: Pensacola Fl
Maybe I can run a restrictor in there, but I am not too sure that I will be able to restrict that much with the blower spinning that fast. I have LS9 head gaskets in there now but I don't think that would change anything. I will have to give ECS a call and see what they suggest.
Tech Contributor
Joined: Apr 2007
Posts: 10,924
Likes: 78
From: Forney Texas
Cylinder pressure is cylinder pressure. You can achieve it with high compression, low boost, low compression, high boost or anything in between. Cylinder pressure is what determines power and what octane tolerance is all about. I feel like you should be able to make around 800rwhp. My reference is Jmoody's car. We built his 403 motor and made 845rwhp on 93, no meth and a very reasonable tune. I'm not going to tell you that I wouldn't be less comfortable tuning on a high compression car with that kind of boost because I would. You would just have to take it slow and walk it in on the timing. Hell, you're only less than 1/2 point higher than me. The ECS car that just went up in smoke only had a few CC's knocked out of the pistons for valve reliefs and was running 20psi boost. It was just too lean. More fuel and it would have lived. That little 347 made 850rwhp.
Melting Slicks
Joined: Jul 2007
Posts: 2,087
Likes: 11
From: Austin TX
Cylinder pressure is cylinder pressure. You can achieve it with high compression, low boost, low compression, high boost or anything in between. Cylinder pressure is what determines power and what octane tolerance is all about. I feel like you should be able to make around 800rwhp. My reference is Jmoody's car. We built his 403 motor and made 845rwhp on 93, no meth and a very reasonable tune. I'm not going to tell you that I wouldn't be less comfortable tuning on a high compression car with that kind of boost because I would. You would just have to take it slow and walk it in on the timing. Hell, you're only less than 1/2 point higher than me. The ECS car that just went up in smoke only had a few CC's knocked out of the pistons for valve reliefs and was running 20psi boost. It was just too lean. More fuel and it would have lived. That little 347 made 850rwhp.
You should be ok running 91 octane with that compression if your tune is spot on
Last edited by golfinz; Nov 25, 2010 at 11:18 AM.
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From: Pensacola Fl
I guess I can change the pulley to be safe, but then I have to swap the pulley whenever I want more boost(lazy). Or I can swap to 317s and lower compression to 9:5:1. I
don't know why, but I just want it to be over 800 all day long. Addicted to HP I guess.
don't know why, but I just want it to be over 800 all day long. Addicted to HP I guess.
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Melting Slicks
Joined: Jul 2007
Posts: 2,087
Likes: 11
From: Austin TX
I like the lower compression idea, especially since your running 91 octane.
jobberone
Joined: Aug 2003
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From: Kailua Kona HI
Thread Starter
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Joined: Jun 2007
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From: Pensacola Fl
I want to do this, but I obviously want to be safe about it. I figure anytime I beat on my car, which isn't often, I would dump a can of torco in it. I just don't see why 91, 100 mix, and meth is still questionable. Should I do 100% or 50/50 mix on the meth? I will have to see about running a restrictor on the Novi to try to lower the boost, but not too sure it will restrict anything with that much boost.
Thread Starter
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Joined: Jun 2007
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From: Pensacola Fl
LQ9, Iron, Callie compstar everything, CP Pistons -15.00cc dish 4.030" bore size 1.200", CH piston set includes Nitrided steel piston ring set, napier 2nd, took that off build sheet. All ARP hardware.
Last edited by PhilsZ51; Nov 26, 2010 at 09:32 PM.
Burning Brakes
Joined: Feb 2004
Posts: 1,130
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From: Camarillo/Oxnard CA
My .02
Run straight meth dual nozzle M15 & M10, tune the car with meth dial on 8, keep timing safe up to peak tq and then ramp a few degrees back in toward the topend. Use the meth to your advantage. Make sure your tuner is experienced enough to feel comfortable doing that.
Make sure you don't have TR6's in there either.
If you really want to limit boost just run a restrictor plate, they work great.
Run straight meth dual nozzle M15 & M10, tune the car with meth dial on 8, keep timing safe up to peak tq and then ramp a few degrees back in toward the topend. Use the meth to your advantage. Make sure your tuner is experienced enough to feel comfortable doing that.
Make sure you don't have TR6's in there either.
If you really want to limit boost just run a restrictor plate, they work great.