8.5 to 1 pistons....and low end power
#1
8.5 to 1 pistons....and low end power
I cooked my #4 cyl. Now I have to decide if I want 8.5 or 9.0 or 9.5 to 1 pistons . How much will low end power be hurt going with 8.5 pistons be compared with 9.5 ? I have a Vortech and with lower compression I can run my smallest pulley [2.87] and be close to 12lb's of boost at redline . So which pistons do you think would be best ?....Bill
#2
Re: 8.5 to 1 pistons....and low end power
Originally posted by booger
I have a Vortech and with lower compression I can run my smallest pulley [2.87] and be close to 12lb's of boost at redline . So which pistons do you think would be best ?....Bill
I have a Vortech and with lower compression I can run my smallest pulley [2.87] and be close to 12lb's of boost at redline . So which pistons do you think would be best ?....Bill
Peter
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I hope I don't get to that point for a while, but comparing it to the 300ZX I would rather have lower boost but better low end power.
A question for Peter or anyone else, what would be the highest boost with 9.5 CR?
A question for Peter or anyone else, what would be the highest boost with 9.5 CR?
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In my uneducated (relating to compression and boost) opinion, with the SC, I don't think I would go lower than 9.5 or 9.0.
With tt's, I think 8.5 would be great because you can just turn up the boost in the low end to compensate, but with the Vortech boost building from about 3k up, I would be worried that between 1k and 3k there wouldn't be any power with 8.5 to one compression.
That's funny you asked booger, 'cause I was pondering this exact dilemma on my way to work today.
With tt's, I think 8.5 would be great because you can just turn up the boost in the low end to compensate, but with the Vortech boost building from about 3k up, I would be worried that between 1k and 3k there wouldn't be any power with 8.5 to one compression.
That's funny you asked booger, 'cause I was pondering this exact dilemma on my way to work today.
#5
Originally posted by westpak
A question for Peter or anyone else, what would be the highest boost with 9.5 CR?
A question for Peter or anyone else, what would be the highest boost with 9.5 CR?
Both items are critical to the positive pressure strategy you can utilise safely.
Peter
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Originally posted by APS
What fuel octane do you have available in your state, it's not possible to answer this question accurately without knowing the fuel octane you use and what means you have to map the ignition timing.
Both items are critical to the positive pressure strategy you can utilise safely.
Peter
APS
What fuel octane do you have available in your state, it's not possible to answer this question accurately without knowing the fuel octane you use and what means you have to map the ignition timing.
Both items are critical to the positive pressure strategy you can utilise safely.
Peter
APS
#7
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I would go 9.5:1 9.0 at the lowest. Like previous poster said, the SC power is more linear than the TT, so if you go too low, you'll have a gutless bottom end. You'll need to retard timing regardless....I think 15 degrees is a bit too much. Tuning with 91 octane fuel is always a bit tricky...but I dont think you'll be happy with 8.5:1 on an SC...you will loose about 25%-30% of your TRQ at the bottom end, and wont be able to compensate by raising boost, ala TT.
Even with my TT, I went with 9.0:1, since my goal is roughly 500-550whp max.
Even with my TT, I went with 9.0:1, since my goal is roughly 500-550whp max.
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#8
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Originally posted by APS
What fuel octane do you have available in your state, it's not possible to answer this question accurately without knowing the fuel octane you use and what means you have to map the ignition timing.
Both items are critical to the positive pressure strategy you can utilise safely.
Peter
APS
What fuel octane do you have available in your state, it's not possible to answer this question accurately without knowing the fuel octane you use and what means you have to map the ignition timing.
Both items are critical to the positive pressure strategy you can utilise safely.
Peter
APS
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Hey tig, is your engine build finished?
It would be nice to see a torque curve on some of these different compression ratios.
I'm not glad that people have blown their engines, but I'm glad that I'm not the first. Now I can see how well these different builds work so I no what to get when I finally blow mine.
It would be nice to see a torque curve on some of these different compression ratios.
I'm not glad that people have blown their engines, but I'm glad that I'm not the first. Now I can see how well these different builds work so I no what to get when I finally blow mine.
#13
Originally posted by westpak
93 Octane and JS Safeguard
93 Octane and JS Safeguard
This will also depend on how efficient the air to air intercooler system performs.................the better the intercooling (colder charge air temperature) the easier it will be to achieve a safe and powerful state of engine tune.
Peter
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People have thrown rods or broken pistons with a supercharger? Was the supercharged aircooled or watercooled? You might want to save your money and just infest in some good tuning for 2 hours. Just get a water/methanol injection kit for $200-$300 that way you can run more timing by keeping the intake charge cooler.
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Originally posted by APS
I'd aim for a static comp ratio of 9.5 to 1 for 93 octane fuel and you should be able to map turbo boost pressure to around 9 to 10 psi safely with a good/safe ignition timing map.
This will also depend on how efficient the air to air intercooler system performs.................the better the intercooling (colder charge air temperature) the easier it will be to achieve a safe and powerful state of engine tune.
Peter
APS
I'd aim for a static comp ratio of 9.5 to 1 for 93 octane fuel and you should be able to map turbo boost pressure to around 9 to 10 psi safely with a good/safe ignition timing map.
This will also depend on how efficient the air to air intercooler system performs.................the better the intercooling (colder charge air temperature) the easier it will be to achieve a safe and powerful state of engine tune.
Peter
APS
Of course, I understand if the answers aren't here yet, but this is the real question I've been looking at since you annouced your kit.
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