High Compression Turbo
03-29-2009, 02:07 PM
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High Compression Turbo
I am in the market for some 85mm pistons.. I have been doing some research on pistons and the compression, and i have been finding out is eithier i can be running about 9:1 or about 9:8:1 compression.. I am really interested in running 9:8:1 compresion on my ls/vtec car... I think that it is all based on the tuning.. and as long as your motor is built correctly it is going to be ok.. But many people that i have been talking to say that they would never want to run a turbo car with more than 9:5:1 compression.. but i dont see really why..
I am going for about 500whp on my setup... thanks..
I am going for about 500whp on my setup... thanks..
03-29-2009, 02:17 PM
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Re: High Compression Turbo
that is what i am talking about.. i have seen people on here do that.. but i am just scared of denotation.. i am trying to just build it correctly.. but i think that the lower the compression the more boost i am going to need to make the power.. but if my compression was a little higher, i will make more power but i might be starting to run out of fuel if i wanted to run more than 20psi or more on 9:8:1 compression..
03-29-2009, 02:20 PM
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Re: High Compression Turbo
You could do it, just do it on race gas. Most people say 500 whp is a lot of for pump gas and 9:1 compression, let alone 10:1. Use race gas and you shouldn't have any worries. Anyhow, my opinion is just based on research I've done and not practical experiance. I'm sure someone with much more experiance will come along and throw thier two cents for you.
03-29-2009, 02:30 PM
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Re: High Compression Turbo
i totally agree about the power goal.. but ok... i am going to be running water/methonal.. cause i don't see myself running e85 because i would want to run regular gas on low boost and when i want high boost i would it.. and to my understanding.. you can only run regular gas or e85.. not both.. but i can be wrong...
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03-29-2009, 02:39 PM
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Re: High Compression Turbo
From what I've been reading, if your gonna run water/meth, then you should be fine with that compression for what you want. When I was trying to decide weather or not to get some 9:1 pistons or just use the 10:1s I had, I looked on Jeff evans website for info and found a dyno that he did showing the differance between 9:1 and 10:1 pistons. The 10:1 pistons made about 10 whp more than the 9:1s at the same boost level, but as Jeff stated, would restrict the overall power that could be made on pump juice. I'll try and see if I can find the comparison for you.
03-29-2009, 02:49 PM
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Re: High Compression Turbo
From what I've been reading, if your gonna run water/meth, then you should be fine with that compression for what you want. When I was trying to decide weather or not to get some 9:1 pistons or just use the 10:1s I had, I looked on Jeff evans website for info and found a dyno that he did showing the differance between 9:1 and 10:1 pistons. The 10:1 pistons made about 10 whp more than the 9:1s at the same boost level, but as Jeff stated, would restrict the overall power that could be made on pump juice. I'll try and see if I can find the comparison for you.
OK cool.. that would be great, if you could find the comparison... but for the mean time.. i am still lost on what i should do..
03-29-2009, 02:55 PM
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Re: High Compression Turbo
03-29-2009, 02:59 PM
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Re: High Compression Turbo
03-29-2009, 03:00 PM
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Re: High Compression Turbo
This is what Mr. Evans told me when I was trying to decide which pistons.
"Depends on what kind of power you are looking to make on 93 octane. If you are looking for 400whp, 9:1 or 10:1 wont matter much. If you are looking to make 500-550whp on 93 octane 8~9:1 is what you want. Even on race gas only engines i still prefer 9:1 compression. 10:1 is only going to make a small difference in power from 9:1."
Here is the link to my question on his website. Hope this helps you out.
http://forums.evans-tuning.com/viewt...pistons#p28785
"Depends on what kind of power you are looking to make on 93 octane. If you are looking for 400whp, 9:1 or 10:1 wont matter much. If you are looking to make 500-550whp on 93 octane 8~9:1 is what you want. Even on race gas only engines i still prefer 9:1 compression. 10:1 is only going to make a small difference in power from 9:1."
Here is the link to my question on his website. Hope this helps you out.
http://forums.evans-tuning.com/viewt...pistons#p28785
03-29-2009, 03:27 PM
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Re: High Compression Turbo
This is what Mr. Evans told me when I was trying to decide which pistons.
"Depends on what kind of power you are looking to make on 93 octane. If you are looking for 400whp, 9:1 or 10:1 wont matter much. If you are looking to make 500-550whp on 93 octane 8~9:1 is what you want. Even on race gas only engines i still prefer 9:1 compression. 10:1 is only going to make a small difference in power from 9:1."
Here is the link to my question on his website. Hope this helps you out.
http://forums.evans-tuning.com/viewt...pistons#p28785
"Depends on what kind of power you are looking to make on 93 octane. If you are looking for 400whp, 9:1 or 10:1 wont matter much. If you are looking to make 500-550whp on 93 octane 8~9:1 is what you want. Even on race gas only engines i still prefer 9:1 compression. 10:1 is only going to make a small difference in power from 9:1."
Here is the link to my question on his website. Hope this helps you out.
http://forums.evans-tuning.com/viewt...pistons#p28785
that is a great write up up by Mr.Evans.. he does know his stuff. i think i am going to go with 9:1 but i am still open for opionions.
03-29-2009, 03:50 PM
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Re: High Compression Turbo
You could do it, just do it on race gas. Most people say 500 whp is a lot of for pump gas and 9:1 compression, let alone 10:1. Use race gas and you shouldn't have any worries. Anyhow, my opinion is just based on research I've done and not practical experiance. I'm sure someone with much more experiance will come along and throw thier two cents for you.
450 whp has been widely spread as the safe knock limit of pump gas in a turbo B-series in years past on this forum. I can bring that power out, but past ~400 the engine's timing requirement falls off abruptly which is a sign of exceeding the gasoline's ability to cool. Add into the equation the manner in which pump gas is poorly regulated witches' brew and I wouldn't run my motor, or let a friend run his motor, at that power level. Stick to 300-350 whp with a high boost in the ~400 whp range, and only use high boost sparingly.
If you use a fuel with more octane (cooling), then by all means feel free to make more power safely. I like E85 as long as you don't push it's knock limit (it also varies, just like pumpgas), and I loooooooooove c16. All of the local cars that go to the track frequently and run strongly for years are primarily attributable to the owners not cheaping out on the gas they run.
If you do water injection, please do it correctly and set it up as a port injection system. All a single sprayer nozzle in front of the TB does is cause the majority of the water/diluent mix to go down cylinders 1 and 4, leaving the already thermally problematic 2 and 3 cylinders to bake. Water really doesn't like to be distributed evenly by airflow inside of an intake manifold.
03-29-2009, 04:42 PM
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Re: High Compression Turbo
You've nailed it squarely on the head. All the 400+ whp pump gas B-series guys do is trash engines quickly by running at the ragged edge of detonation.
450 whp has been widely spread as the safe knock limit of pump gas in a turbo B-series in years past on this forum. I can bring that power out, but past ~400 the engine's timing requirement falls off abruptly which is a sign of exceeding the gasoline's ability to cool. Add into the equation the manner in which pump gas is poorly regulated witches' brew and I wouldn't run my motor, or let a friend run his motor, at that power level. Stick to 300-350 whp with a high boost in the ~400 whp range, and only use high boost sparingly.
If you use a fuel with more octane (cooling), then by all means feel free to make more power safely. I like E85 as long as you don't push it's knock limit (it also varies, just like pumpgas), and I loooooooooove c16. All of the local cars that go to the track frequently and run strongly for years are primarily attributable to the owners not cheaping out on the gas they run.
If you do water injection, please do it correctly and set it up as a port injection system. All a single sprayer nozzle in front of the TB does is cause the majority of the water/diluent mix to go down cylinders 1 and 4, leaving the already thermally problematic 2 and 3 cylinders to bake. Water really doesn't like to be distributed evenly by airflow inside of an intake manifold.
450 whp has been widely spread as the safe knock limit of pump gas in a turbo B-series in years past on this forum. I can bring that power out, but past ~400 the engine's timing requirement falls off abruptly which is a sign of exceeding the gasoline's ability to cool. Add into the equation the manner in which pump gas is poorly regulated witches' brew and I wouldn't run my motor, or let a friend run his motor, at that power level. Stick to 300-350 whp with a high boost in the ~400 whp range, and only use high boost sparingly.
If you use a fuel with more octane (cooling), then by all means feel free to make more power safely. I like E85 as long as you don't push it's knock limit (it also varies, just like pumpgas), and I loooooooooove c16. All of the local cars that go to the track frequently and run strongly for years are primarily attributable to the owners not cheaping out on the gas they run.
If you do water injection, please do it correctly and set it up as a port injection system. All a single sprayer nozzle in front of the TB does is cause the majority of the water/diluent mix to go down cylinders 1 and 4, leaving the already thermally problematic 2 and 3 cylinders to bake. Water really doesn't like to be distributed evenly by airflow inside of an intake manifold.
03-29-2009, 05:05 PM
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Re: High Compression Turbo
You've nailed it squarely on the head. All the 400+ whp pump gas B-series guys do is trash engines quickly by running at the ragged edge of detonation.
450 whp has been widely spread as the safe knock limit of pump gas in a turbo B-series in years past on this forum. I can bring that power out, but past ~400 the engine's timing requirement falls off abruptly which is a sign of exceeding the gasoline's ability to cool. Add into the equation the manner in which pump gas is poorly regulated witches' brew and I wouldn't run my motor, or let a friend run his motor, at that power level. Stick to 300-350 whp with a high boost in the ~400 whp range, and only use high boost sparingly.
If you use a fuel with more octane (cooling), then by all means feel free to make more power safely. I like E85 as long as you don't push it's knock limit (it also varies, just like pumpgas), and I loooooooooove c16. All of the local cars that go to the track frequently and run strongly for years are primarily attributable to the owners not cheaping out on the gas they run.
If you do water injection, please do it correctly and set it up as a port injection system. All a single sprayer nozzle in front of the TB does is cause the majority of the water/diluent mix to go down cylinders 1 and 4, leaving the already thermally problematic 2 and 3 cylinders to bake. Water really doesn't like to be distributed evenly by airflow inside of an intake manifold.
450 whp has been widely spread as the safe knock limit of pump gas in a turbo B-series in years past on this forum. I can bring that power out, but past ~400 the engine's timing requirement falls off abruptly which is a sign of exceeding the gasoline's ability to cool. Add into the equation the manner in which pump gas is poorly regulated witches' brew and I wouldn't run my motor, or let a friend run his motor, at that power level. Stick to 300-350 whp with a high boost in the ~400 whp range, and only use high boost sparingly.
If you use a fuel with more octane (cooling), then by all means feel free to make more power safely. I like E85 as long as you don't push it's knock limit (it also varies, just like pumpgas), and I loooooooooove c16. All of the local cars that go to the track frequently and run strongly for years are primarily attributable to the owners not cheaping out on the gas they run.
If you do water injection, please do it correctly and set it up as a port injection system. All a single sprayer nozzle in front of the TB does is cause the majority of the water/diluent mix to go down cylinders 1 and 4, leaving the already thermally problematic 2 and 3 cylinders to bake. Water really doesn't like to be distributed evenly by airflow inside of an intake manifold.
03-29-2009, 07:09 PM
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Re: High Compression Turbo
Well, you probably could just run regular 91 or 93 or whatever you can run, then just use the water/meth when you need it. You can be tuned at 25 psi of boost or whatever amount on water meth, and just turn it down when you don't need it . You don't neccisarily need 2 different fuel maps. When you set your boost controler to 15 psi your good to go, and you can turn up the boost when your gonna spray and be fine. This is what I'm planning to do using my apexi AVCR, boosting 15 psi, and having my scramble boost set for 23-25 (whatever amount) psi with water meth.
03-29-2009, 09:56 PM
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Re: High Compression Turbo
I can see a high compression turbo setup for a 350-400 WHP level setup... The off boost throttle response, quicker transient recovery between shifts, etc.. would be worth the extra effort. I loved my old 11.5:1 CR setup, but my build was focused. It had ITB's, a GT28RS (later became GT2871R), 11.5:1 CR, lots of redline, 380-400 WHP and the purpose was to have a killer responsive turbo setup, like the Ferrari F40, Skylines, etc..
For a 500 WHP setup, honestly, when boost kicks in, you can barely use that power in a straight line, let alone trying to ever use it on the street, nailing corners, zipping through traffic, or on a roadcourse. For a 500 WHP setup, there is no point to go with high compression other than wanting to try out some exotic VP import race gas every weekend and blow $$$ when the other guy beside you with 9.0:1 CR can go just as fast on 93 oct.
The only time a high compression turbo setup is nice is when your engine actually spends time at partial boost regions... A medium sized turbo will build 5-10 PSI of boost at midrange, and your throttle can be feathering and modulating during these boosted regions. The higher CR setup will give you amazing response, power and modulation. With a 500 WHP setup, we are expecting a minimum sized GT35R turbo, and really, by the time you see 8-10 PSI, in less than a second, it makes its way to 20 PSI anyway.
For a 500 WHP setup, honestly, when boost kicks in, you can barely use that power in a straight line, let alone trying to ever use it on the street, nailing corners, zipping through traffic, or on a roadcourse. For a 500 WHP setup, there is no point to go with high compression other than wanting to try out some exotic VP import race gas every weekend and blow $$$ when the other guy beside you with 9.0:1 CR can go just as fast on 93 oct.
The only time a high compression turbo setup is nice is when your engine actually spends time at partial boost regions... A medium sized turbo will build 5-10 PSI of boost at midrange, and your throttle can be feathering and modulating during these boosted regions. The higher CR setup will give you amazing response, power and modulation. With a 500 WHP setup, we are expecting a minimum sized GT35R turbo, and really, by the time you see 8-10 PSI, in less than a second, it makes its way to 20 PSI anyway.
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