high compression pistons
10-29-2009, 11:28 PM
#1
Senior Member
Thread Starter
Join Date: 12-07-07
Location: akron, ohio
Posts: 2,024
Likes: 0
Received 0 Likes
on
0 Posts
high compression pistons
a friend of mine told me that if i got 12:1 pistons that i would have a huge increase in hp, is that true? or am i just retarded
10-29-2009, 11:40 PM
#5
Senior Member
Thread Starter
Join Date: 12-07-07
Location: akron, ohio
Posts: 2,024
Likes: 0
Received 0 Likes
on
0 Posts
actually yes he does, he has a si that he put a turbo on with skunk cams and all this **** and its mid 12s thats why i thought he would know what hes talking about
10-30-2009, 12:21 AM
#8
Senior Member
Yes you can make good power with high compressioned FI car, but be prepared to spend allot of money keeping your car alive. You will need lots and constant tuning, lots of fuel, and race gas is preferred. To run 12:1 you would need to upgrade more than just the pistons. Not something a beginner should attempt.
10-30-2009, 12:29 AM
#10
Correct me if im wrong people. But from what i understand is the higher compression you go the less boost will be needed to obtain the goal HP. For example. Say with a 9.1 compression with a 2.8" pulley and the rest of the stage 2 kit, you will see approx. 250-260hp...at 17~psi
If you go 12.1 you will only require approx 13~psi to hit that same hp. Thats what im gathering from the 370z/G37...our compression ratio is 11.1. On a twin turbo set up the 2-3 guys that have it are only running 7psi of boost and are hitting 465~hp. With the 350z/G35 the ratio is lower i believe and requires around 10-12psi of boost to hit that goal.
Why this is important is because if you are running 2.6" pulley like you said, you will make...what 20psi? with stock pistons...with the 12.1 pistons...your going to blow your engine with those pistons and pulley size. Wither A. go to bigger pulley which is pointless because, like i said above you will make the same hp with stock pistons, smaller pulley then different pistons and bigger pulley which will cost more. So like someone said you will have to upgrade ALOT of the engine to be able to run 2.6 on 12.1.
If you go 12.1 you will only require approx 13~psi to hit that same hp. Thats what im gathering from the 370z/G37...our compression ratio is 11.1. On a twin turbo set up the 2-3 guys that have it are only running 7psi of boost and are hitting 465~hp. With the 350z/G35 the ratio is lower i believe and requires around 10-12psi of boost to hit that goal.
Why this is important is because if you are running 2.6" pulley like you said, you will make...what 20psi? with stock pistons...with the 12.1 pistons...your going to blow your engine with those pistons and pulley size. Wither A. go to bigger pulley which is pointless because, like i said above you will make the same hp with stock pistons, smaller pulley then different pistons and bigger pulley which will cost more. So like someone said you will have to upgrade ALOT of the engine to be able to run 2.6 on 12.1.
10-30-2009, 11:36 AM
#11
Member
Join Date: 02-28-07
Location: Portland, OR
Posts: 334
Likes: 0
Received 0 Likes
on
0 Posts
There are all these rules of thumb with CR. High with NA, low with boost. but what really matters is strong enough components and low enough temps. Increase boost or CR, heat goes up and detonation is more likely. You could have pistons made of diamond and they would't take detonation for very long.
The higher the CR, the faster you'll get your torque though.
I'm running 10:1 with high boost from a turbo. Since I have efficient cooling I get the best of both worlds, full torque by 3800 RPM and no parasitic loss from a supercharger.
12:1 with boost is going to be really hard to cool and keep from detonation in our engines. at that point you have to start running really high octane fuel
The higher the CR, the faster you'll get your torque though.
I'm running 10:1 with high boost from a turbo. Since I have efficient cooling I get the best of both worlds, full torque by 3800 RPM and no parasitic loss from a supercharger.
12:1 with boost is going to be really hard to cool and keep from detonation in our engines. at that point you have to start running really high octane fuel
10-30-2009, 11:51 AM
#12
Senior Member
Join Date: 04-13-09
Location: WI
Posts: 1,450
Likes: 0
Received 0 Likes
on
0 Posts
Like everygody said, if you are going to increase your compression ratio, go to 10:1. 12:1 is too much. If you want to make big power swap a turbo or tvs and lose the stock eaton. If you want to keep the eaton, get your head ported, run a 2.6"pulley, get water/meth, maybe a mild cam, and FIND A GOOD TUNER!
10-30-2009, 12:02 PM
#13
Super Moderator
Platinum Member
iTrader: (16)
There are all these rules of thumb with CR. High with NA, low with boost. but what really matters is strong enough components and low enough temps. Increase boost or CR, heat goes up and detonation is more likely. You could have pistons made of diamond and they would't take detonation for very long.
The higher the CR, the faster you'll get your torque though.
I'm running 10:1 with high boost from a turbo. Since I have efficient cooling I get the best of both worlds, full torque by 3800 RPM and no parasitic loss from a supercharger.
12:1 with boost is going to be really hard to cool and keep from detonation in our engines. at that point you have to start running really high octane fuel
The higher the CR, the faster you'll get your torque though.
I'm running 10:1 with high boost from a turbo. Since I have efficient cooling I get the best of both worlds, full torque by 3800 RPM and no parasitic loss from a supercharger.
12:1 with boost is going to be really hard to cool and keep from detonation in our engines. at that point you have to start running really high octane fuel
simple soultion.... VTEC in the cobalt and your set
10-30-2009, 01:09 PM
#15
Senior Member
Join Date: 10-20-08
Location: Norman, OK
Posts: 1,617
Likes: 0
Received 0 Likes
on
0 Posts
theres ur answer, dont listen to ur friend. go tvs or turbo, not high compression pistons. leave that to the n/a ppl. or else plan to spend a lot of money.
10-30-2009, 01:10 PM
#16
Member
Join Date: 02-28-07
Location: Portland, OR
Posts: 334
Likes: 0
Received 0 Likes
on
0 Posts
10-30-2009, 02:13 PM
#19
Senior Member
Join Date: 10-20-08
Location: Norman, OK
Posts: 1,617
Likes: 0
Received 0 Likes
on
0 Posts
it was a rhetorical response, jesus. he was just saying nothing, not EVEN diamond, could withstand certain detonations. not that there are actual pistons that are made of diamond. he was simply adding to the fact that not even something w/ the hardness of a diamond, let alone metal, could hold against a really high CR and detonation.
10-30-2009, 02:14 PM
#20
Senior Member
Here is a reference to a basic understanding of a/f ratios and forced induction and their relationship to each other. Maybe it will explain better what you would have to do to your engine to raise the compression ratio and also keep the engine in one piece.
http://en.wikipedia.org/wiki/Air-fuel_ratio_meter
http://en.wikipedia.org/wiki/Air-fuel_ratio_meter
10-30-2009, 03:00 PM
#21
Member
Join Date: 02-28-07
Location: Portland, OR
Posts: 334
Likes: 0
Received 0 Likes
on
0 Posts
it was a rhetorical response, jesus. he was just saying nothing, not EVEN diamond, could withstand certain detonations. not that there are actual pistons that are made of diamond. he was simply adding to the fact that not even something w/ the hardness of a diamond, let alone metal, could hold against a really high CR and detonation.
10-30-2009, 03:40 PM
#22
Senior Member
Join Date: 03-12-07
Location: Columbus, Ohio
Posts: 1,586
Likes: 0
Received 0 Likes
on
0 Posts
Correct me if im wrong people. But from what i understand is the higher compression you go the less boost will be needed to obtain the goal HP. For example. Say with a 9.1 compression with a 2.8" pulley and the rest of the stage 2 kit, you will see approx. 250-260hp...at 17~psi
If you go 12.1 you will only require approx 13~psi to hit that same hp. Thats what im gathering from the 370z/G37...our compression ratio is 11.1. On a twin turbo set up the 2-3 guys that have it are only running 7psi of boost and are hitting 465~hp. With the 350z/G35 the ratio is lower i believe and requires around 10-12psi of boost to hit that goal.
Why this is important is because if you are running 2.6" pulley like you said, you will make...what 20psi? with stock pistons...with the 12.1 pistons...your going to blow your engine with those pistons and pulley size. Wither A. go to bigger pulley which is pointless because, like i said above you will make the same hp with stock pistons, smaller pulley then different pistons and bigger pulley which will cost more. So like someone said you will have to upgrade ALOT of the engine to be able to run 2.6 on 12.1.
If you go 12.1 you will only require approx 13~psi to hit that same hp. Thats what im gathering from the 370z/G37...our compression ratio is 11.1. On a twin turbo set up the 2-3 guys that have it are only running 7psi of boost and are hitting 465~hp. With the 350z/G35 the ratio is lower i believe and requires around 10-12psi of boost to hit that goal.
Why this is important is because if you are running 2.6" pulley like you said, you will make...what 20psi? with stock pistons...with the 12.1 pistons...your going to blow your engine with those pistons and pulley size. Wither A. go to bigger pulley which is pointless because, like i said above you will make the same hp with stock pistons, smaller pulley then different pistons and bigger pulley which will cost more. So like someone said you will have to upgrade ALOT of the engine to be able to run 2.6 on 12.1.
10-30-2009, 06:01 PM
#23
Correct me if im wrong people. But from what i understand is the higher compression you go the less boost will be needed to obtain the goal HP. For example. Say with a 9.1 compression with a 2.8" pulley and the rest of the stage 2 kit, you will see approx. 250-260hp...at 17~psi
higher the boost, the lower the CR (to an extent of course)
10-30-2009, 07:27 PM
#24
where your wrong is the amount of boost. You can run 5psi on a high CR. The OP can put in 12:1 CR pistons and run 5psi (on a 4" pulley? lol) and be reliable (assuming proper tuning), but you cant run 15psi (especially from a supercharger) on 12:1 without some detonation happening.
higher the boost, the lower the CR (to an extent of course)
higher the boost, the lower the CR (to an extent of course)
Last edited by Snakes709; 10-30-2009 at 07:27 PM. Reason: Automerged Doublepost
10-31-2009, 04:03 AM
#25
IE, you have an LSJ. You want 400whp with a turbo. You will NOT get there by running 5psi and using any number of CR, however, the opposite is not true. If you use Xpsi and a 9.5:1CR, you can definitely reach that goal