I just want to know who's running them and any problems they are having.

I run meth and have HPT so I think that should cover the basics.

why would you want to raise the compression on your boosted engine?

Throw on some ARP Head Studs and a Cometic Head gasket and you could be making some nice numbers with that blower. nothing wrong with higher compression. dont listen to everyone who says higher compression is bad, it isnt if done right. mild boost + higher compression = more power then them =P

Throw on some ARP Head Studs and a Cometic Head gasket and you could be making some nice numbers with that blower. nothing wrong with higher compression. dont listen to everyone who says higher compression is bad, it isnt if done right. mild boost + higher compression = more power then them =P

well, with 271 hp i'm guessing he's not putting out "mild" boost.

yea. what he said.. if your goal is boost, instead of performance, then lower ratio is what you want.. ive seen a boosted K20 runnin 11 to 1 ratio makin 350+whp on 13 psi. I guess its just easier turnin up the boost with a lower comp. then fine tuning with the higher comp

well I've gone uping the boost, so now I think I want to try something different with low boost. This will help keep the SC in its efficiency range.

well I've gone uping the boost, so now I think I want to try something different with low boost. This will help keep the SC in its efficiency range.

Also understand that you are going to be increasing combustion chamber temperatures by raising the compression. You would also need to fine tune ignition timing depending on how much of an advance it is currently.

You'd also probably want to run richer as well.

You'd be better off going with a more efficient compressor which would yield more power than your supercharger even with higher compression. Another thing to think about, how much air is being delivered into the combustion chamber (talking about your valvetrain) per intake stroke.

Higher octane would be needed as well to avoid knocking.

I think you're really pushing it with that high. Even the J-bodies with the M62 start seeing knocking issues when they reach 3.0" or under.

(Note: The L61 motor is 10.0:1 compression)

Rice eater from the RL forums, has 10.5:1 compression with a 2.6" pulley.

...he has to run a minimum of 100 octane, all the time...

Also understand that you are going to be increasing combustion chamber temperatures by raising the compression. You would also need to fine tune ignition timing depending on how much of an advance it is currently.

you increase this by putting a smaller pulley on too, so I'm sure a 2.5" produces something close to it.

You'd also probably want to run richer as well.

That's no problem, the meth will help here.

You'd be better off going with a more efficient compressor which would yield more power than your supercharger even with higher compression. Another thing to think about, how much air is being delivered into the combustion chamber (talking about your valvetrain) per intake stroke.

Well I can always go TS, but the reason I want to lower the boost on the M62 is because of the efficency, on Eaton's site they don't even have a graph for the stock 12.5psi, so I'm assuming that psi is at it's limit.

since the valve are designed for 9.5:1, I'm assuming there would be plenty of air in and out. I would see this being a problem if I drop the compression.

Higher octane would be needed as well to avoid knocking.

Even in vacuum?

I think you're really pushing it with that high. Even the J-bodies with the M62 start seeing knocking issues when they reach 3.0" or under.

(Note: The L61 motor is 10.0:1 compression)

As long a it doesn't knock during regular driving I am happy.

Rice eater from the RL forums, has 10.5:1 compression with a 2.6" pulley.

...he has to run a minimum of 100 octane, all the time...

oh yea

What's going on with his car anyways?

Mase, if you care about efficiency and you recognize that raising the compression (just for example sakes) will put you in the temperature range of a 2.5" pulley, why go this route? Less boost or more boost, it's overall about the temperature inside the combustion chamber.

You actually COULD knock in vacuum or with very low boost pressure.

As far as running rich, remember the whole issue with having a return-less fuel system...

One last thing

If you have to use Meth Injection on a constant basis to keep temps down, there IS a problem. It should be a helper, not a must have.

I know what you're saying about heat inside the motor.

One of the main reasons I want to go with 10.5:1 is due to the 2.4L. The solstice I tuned made 311RWHP at only 8psi. Now I know they have more displacement, but in comparison to the turbo cobalt which made 323WHP at the front on 18psi, I'm thinking these motors like compression more than boost.

I know what you're saying about heat inside the motor.

One of the main reasons I want to go with 10.5:1 is due to the 2.4L. The solstice I tuned made 311RWHP at only 8psi. Now I know they have more displacement, but in comparison to the turbo cobalt which made 323WHP at the front on 18psi, I'm thinking these motors like compression more than boost.

It's not necessarily of what the engine likes...

You're comparing a Turbocharged Unit to your Supercharger unit. Even with your supercharger staying within it's efficiency range, it does not compare to a properly sized turbocharger as far as how much air (CFM) is being produced AND the parasitic loss that you're having when it comes to turning the supercharger. Displacement defenitley does play an effect as well...there is a slight bore increase over your engine but it's mostly the stroke that's the difference, this means more air and higher VE.

It's hard to really compare 2 setups and try to say that they are slightly similar because even if it was the same engine as yours, you're not going to duplicate it's results.

well I've gone uping the boost, so now I think I want to try something different with low boost. This will help keep the SC in its efficiency range.

If you wanna run low boost, increase ignition timing rather than compression ratio. You'll see larger gains.

People that are running higher comp pistons are doing so because of aggressive cams.

If you wanna run low boost, increase ignition timing rather than compression ratio. You'll see larger gains.

People that are running higher comp pistons are doing so because of aggressive cams.

You make my cam aggressive...grr

My cams are going to be far past aggressive, more like, "WHAT? Your actually gonna drive that on the street!?!?" :D 9.5:1 compression FTMFW!!! 15 psi with a 2.6" pulley FTMFW!!!! Boost/Heat equal to a 2.9" pulley, but the CFM of a 2.6", can't beat that!

are you going to run any other cooling mods or just keep the ones you have

Adding a dry ice box/extra coolant resevior, most likely 3/4 to 1 gallon in capacity. Plus I'm thinkin about a 100 shot of nitrous until I get the twin screw, hey it works for the Cobra guys.

Adding compression and lowering boost will grant you the same power as when you had higher boost and lower compression. The benefits are that your spinning the SC slower which = less parasitic loss, and the roots type you use is less and less efficient the faster you spin it. Turbo's its cool to lower comp, but roots type equipped cars love comp.

10.5 is damn high btw :)

Yeah adding compression and lowering boost will help keep the SC in its best efficiency. However, 10.5:1 is probably gonna be too high to run the car on anything lower then 100 octane.

Wow some people who actually think like i do. I was blasted over at the redline forums because i'm going with SRP 8:1's and a custom whipple at 20psi.

Wow some people who actually think like i do. I was blasted over at the redline forums because i'm going with SRP 8:1's and a custom whipple at 20psi.

Tell me, was the head of the attack on you by chance AlphaJaguar? He TRIED to blast me when I posted about my blower porting! He blasts everyone, and says he has 300 whp with no dyno to prove it.

Tell me, was the head of the attack on you by chance AlphaJaguar? He TRIED to blast me when I posted about my blower porting! He blasts everyone, and says he has 300 whp with no dyno to prove it.

He was one of them trying to tell me that i was "Retarded" for wanting to drop compression that much and i should stick to around stock compression for 20psi of boost. :lol:

One of the reasons why i came over here. Lots of knowledgeable people here.

I was thinking of going 8.8:1 compression...I just haven't found the pistons.

Is That Really Tempe Az I See On Your Location!?!? Shit Man Im From Chandler!!!

I bought 10:5:1 pistons which Rob Archer told me he was going to do before he had to get rid of the car. Now after reading everything and I talked to Todd at Intense I don't know if I want them anymore. Should I sell them or give them a try? I really don't want to run 100 octane. I run only 94 now so I don't really want to go above that. Any advice would be appreciated.

Hey my friend 1ftss is running 10:1 compression pistons and that thing hauls ass now and he is running pumped gas like 93

Wow some people who actually think like i do. I was blasted over at the redline forums because i'm going with SRP 8:1's and a custom whipple at 20psi.

He was one of them trying to tell me that i was "Retarded" for wanting to drop compression that much and i should stick to around stock compression for 20psi of boost. :lol:

One of the reasons why i came over here. Lots of knowledgeable people here.

It was because of way to much of that type of attitude, that I choose to no longer participate on the redlineforums.

Is That Really Tempe Az I See On Your Location!?!? Shit Man Im From Chandler!!!

Blown.. I'm leaving for tempe on thursday.


Hey my friend 1ftss is running 10:1 compression pistons and that thing hauls ass now and he is running pumped gas like 93

How much boost is he running and i imagine he's using the stock eaton. If i tried to run 10:1 and 20psi from a 1.6L whipple on shitty az 91 octane the engine would explode within minutes.

Tell me, was the head of the attack on you by chance AlphaJaguar? He TRIED to blast me when I posted about my blower porting! He blasts everyone, and says he has 300 whp with no dyno to prove it.

lol, your funny

obtw, would you kinda point me in the direction of a post where I say I HAVE 300whp, I'm roundabouts but never said 100% that I was anything beside what my last dyno said and that was with a 2.7", no timing & a 10.4 A/F so me saying I have more than I did then is more than acceptable.

Also, your blower porting is asinine

I try to be.

I bought 10:5:1 pistons which Rob Archer told me he was going to do before he had to get rid of the car. Now after reading everything and I talked to Todd at Intense I don't know if I want them anymore. Should I sell them or give them a try? I really don't want to run 100 octane. I run only 94 now so I don't really want to go above that. Any advice would be appreciated.

You *MAY* be able to get away with 94 octane using 10.5 pictons, but you will have to run stock boost or less to avoid getting knock though.

stick with stock compression or lower and go turbo... best way to make power plain and simple on the these motors.... no arguments about it. Unless you want to stay s/c'd... then well... we've had this argument before.

whats the stock LSJ compression ratio?
:cssNET:

whats the stock LSJ compression ratio?
:cssNET:


I believe 9.5:1

Blown.. I'm leaving for tempe on thursday.




How much boost is he running and i imagine he's using the stock eaton. If i tried to run 10:1 and 20psi from a 1.6L whipple on shitty az 91 octane the engine would explode within minutes.

We dont know he is waiting for it to get tuned so as he does i am sure he will post a thread on here about it

I believe 9.5:1

You are correct. The pistons are a Mahle hypereutectic alloy.

You *MAY* be able to get away with 94 octane using 10.5 pictons, but you will have to run stock boost or less to avoid getting knock though.

You can get away running 14:1 pistons it just depends on how much boost you wanna run.

You can get away running 14:1 pistons it just depends on how much boost you wanna run.

Also timing.

You are going to run into ignition trouble with too much compression. Richer than rich best torque and high compression and you substantially increase your chances of spark issues.

You are correct. The pistons are a Mahle hypereutectic alloy.



You can get away running 14:1 pistons it just depends on how much boost you wanna run.

Which in that case would be zero. Not even race cars use that high compression with boost. The 1450 hp ecotec motor uses 10.8:1 compression and over 50 psi boost. Top fuel motors run a whopping 7.5:1 compression and 45 psi boost!

ALL my mods in my garage....please look before responding..........

sooooooo.... I just got the 10.5:1 with all coating for a good deal... a really good deal ;) .

NOW my problem is I can only get 91 octane. Should I lower my comprerssion? I plan on starting with about 10psi. Then get the fuel and spark right. From there I'll adjust boost/fuel/spark accordingly.

My HG is the last thing to get before the engine goes back together......I could really use the imput....thanks

ALL my mods in my garage....please look before responding..........

sooooooo.... I just got the 10.5:1 with all coating for a good deal... a really good deal ;) .

NOW my problem is I can only get 91 octane. Should I lower my comprerssion? I plan on starting with about 10psi. Then get the fuel and spark right. From there I'll adjust boost/fuel/spark accordingly.

My HG is the last thing to get before the engine goes back together......I could really use the imput....thanks

IMO, you really need to see what the cams you plan on running do for your effective compression and compensate with higher static compression pistons.

If you have too high of an effective compression you may run into spark blowout issues and might have to upgrade your ignition system. I increased my static compressiojn to 10-1 myself and my 272 cams brought my effective compression right back down to stock levels. However, increasing redline to 8k rpms brought forth new spark issues that I have solved by increasing spark dwell time, however its at a cost of significantly decreased coil life span.

All in all, its a pain in the ass no matter what you do. I'm sure no matter what, you can solve the problems with a little bit of tuning.

JBP don't give out there Stage 2 cam specs...... ..what do I do now???

JBP don't give out there Stage 2 cam specs...... ..what do I do now???

Somewhere I saw a few specs listed, maybe in their old group buy thread. Try to call them and bug them, I'm sure they will give them up over the phone.

Here's what I found, everything except the lobe seperation angle, I would probably ignore the secondary intake specs as they are "milder" then the primaries, but I'm no expert in this:

PRIMARY INTAKE
ADV
264* 418L
@.050
209*

SECONDARY INTAKE
ADV
256* 417L
@.050
202*


PRIMARY EXHAUST
ADV
256* 417L
@.050
202*

With 91 octane, you will not be able to run boost. That compression ratio is way way to high for any kind of boost with THAT shitty gas.

Witt.....I think that is for their Stage 1 cams...but IDK.....I'll call them

4-banger......so should I get the .040 HG? That should yeald me around 10.0:1

Lowering compression with the head gasket is never a good idea, because it messes with the quench of the piston and deck. You can do it that way, but you may have problems with knock.

Lowering compression with the head gasket is never a good idea, because it messes with the quench of the piston and deck. You can do it that way, but you may have problems with knock.

and the timing chain

and the timing chain

I don't think an extra .17 inch would do much to the timing chain, but it definatly could as well :confused:

I don't think an extra .17 inch would do much to the timing chain, but it definatly could as well :confused:

I had the .040 on there last time....that's all cometic made at the time. The timing chain fit fine. I don't understand how a thicker HG produces knock. Little info please.

I had the .040 on there last time....that's all cometic made at the time. The timing chain fit fine. I don't understand how a thicker HG produces knock. Little info please.

Some engines have quench style pistons and heads. Ecotecs are not that type. No more than .045" clearance is needed for proper quench, something the Ecotec lacks.

^^ so increasing the HG thickness won't screw up my build? I think I'm going to go with the .040" HG anyways.

This is going to sound dumb but.......I have to ask:

could I add octane booster to increase octane levels so that I can run 10.5:1 w/ a .027"??

^^ so increasing the HG thickness won't screw up my build? I think I'm going to go with the .040" HG anyways.

This is going to sound dumb but.......I have to ask:

could I add octane booster to increase octane levels so that I can run 10.5:1 w/ a .027"??

I guess that would work. You must be rich then :rolleyes:

I guess that would work. You must be rich then :rolleyes:

What do you mean??? The octane booster is like $2-$3 per tank.

You have to buy like 6 or 7 bottles of the stuff to even make a difference. You really think a 8 oz. bottle of 100+ octane is going to make a difference in a 12 gallon tank? Think again.

What would be recommended for 10.0:1 pistons??

You can run pump on 10:1 pistons

Nothing a meth kit with a nice fine mix won't fix. But at that point you might as well run race gas if your that dependent on it.

So your saying my only option with runnning 10.5:1 CR is AT-LEAST 100 octane. This just put a pickle in my build. Now I need to adjust a little.

Do Shiyo Kanaaaaaa

You can run lower octane, but you timing will need to be lowered, and so will your boost.

It isn't worth it though even if your upping compression. You make more power with timing/boost than you will with upping compression.

I know, I know.....I was just hopeing for some type of alternative. I want to keep boost around 10-12psi. I have H/E, Dual pass I/C, Meth Inj.....so I wasn't worring about heat too much.....mainly worring about octane levels......I live in the middle of the Mojave desert; there is only 87 and 91. My goal was to be able to run the balt (w/mods (http://www.cobaltss.net/forums/vbgarage.php?do=view&id=6835)) on pump gas.....I guess it can't be done..............

Now I have to sit down (longer.....) and decide what I want to do.

SOOOOOOO..........I guess my only option is to run 10.0:1 CR and Tune for the best.

Unless I change my pistons.....AGAIN!!

Do you plan on cams at all? A good set of cams with the 10.5s @ that boost lvl would be pretty good. But you will still need to retard the timing a tad probably.

Not enough people run the 10.5s to know what to expect exactly. I think Rice Eater is the only one.

I have JBP Stage 2 Triflow cams.

Somewhere I saw a few specs listed, maybe in their old group buy thread. Try to call them and bug them, I'm sure they will give them up over the phone.

Here's what I found, everything except the lobe seperation angle, I would probably ignore the secondary intake specs as they are "milder" then the primaries, but I'm no expert in this:

PRIMARY INTAKE
ADV
264* 418L
@.050
209*

SECONDARY INTAKE
ADV
256* 417L
@.050
202*


PRIMARY EXHAUST
ADV
256* 417L
@.050
202*

Those are the specs for there stage 2 cams....my bad. Just got an e-mail from them.


BTW I'm going to go with 10.0:1 :thumbsdow I don't have access to 100 octane so my options are limited

Do you plan on cams at all? A good set of cams with the 10.5s @ that boost lvl would be pretty good. But you will still need to retard the timing a tad probably.

Not enough people run the 10.5s to know what to expect exactly. I think Rice Eater is the only one.

Yeah, and he said he runs at least 100 octane all the time.

If you run a port and polished head with a 5 angle valve job and new valves would this make it more realistic to run the 10.5:1. Or does the real problem lie soley in the ingnition timing and Fuel. I ask because I will have that head next week and those pistons. I also have the DR 9.5:1 Pistons. Is there a cam that will change anything with driveability and a lower octane fuel?

You could use a cam with a ton of overlap, that will help bleed off pressure at lower rpm, but it will also consume a HUGE amount of fuel.