43 replies to this topic

[NickB787]

I am after some, any one know to buy at the moment? I can find 8.9:1 but 8.5:1

[M3VXT]

Why don't you try wossner(think that how it spelt) pistons. I know a few of the rover turbo guys have been using them with good results. I am sure they do them in 8.5:1

[vocky]

wiseco only list the 8.9:1 or 10:1 pistons

download pdf file

[NickB787]

wiseco only list the 8.9:1 or 10:1 pistons

download pdf file

Explains why I can't find them then!!! cheers mate will try to find the next best

[slindborg]

jesus thats a low CR.... any real reason why you want it that low, or is it using a remapped ECU that cant be forced to do the job properly?

[davep24]

jesus thats a low CR.... any real reason why you want it that low, or is it using a remapped ECU that cant be forced to do the job properly?

supercharging or turbo id guess

[slindborg]

jesus thats a low CR.... any real reason why you want it that low, or is it using a remapped ECU that cant be forced to do the job properly?

supercharging or turbo id guess

the term DUHHHHH springs to mind. I know hes got and S/C and is going for a fruitier S/C build. But an 8.5CR is wayyyy too low imho. I'd sooner run a higher CR (8.9... 0.4 change in CR is a truck load when going down) and control the fuelling and ign properly with a stand alone ecu.

I know tubby and S/C engines behave differently but a friend of mine is building a 500bhp LET (basically VXT) engine and he had it built with something like 8:1 CR and it drove like an utter dog off boost and had mild mapping issues when on boost in that they couldnt get enough air into the engine or acceptable advance in to make best power.

[NickB787]

It's supercharged, the normal way to lower compression on the Courtenays S/C setup is a spacer plate under the head but since I am aiming for 300bhp+ I was going to put new pistons in with my Eagle rods I have.

[slindborg]

dirty dirty spacer plate When I asked on the cobalt forum how they would hit 300bhp (they took this as wheel power lol) I got a list of parts and one of them was 9.0-10:1 pistons.... apparently this works well with their gypsy fuel over there too lol. Might be wise to have a look on the cobaltss and other ecotec forums in the US (unless youve already done this and can aim me somewhere to ram my ramblings lol)

[NickB787]

dirty dirty spacer plate

When I asked on the cobalt forum how they would hit 300bhp (they took this as wheel power lol) I got a list of parts and one of them was 9.0-10:1 pistons.... apparently this works well with their gypsy fuel over there too lol.

Might be wise to have a look on the cobaltss and other ecotec forums in the US (unless youve already done this and can aim me somewhere to ram my ramblings lol)

Know what you mean about spacer plates I don't think they are an issue untill you get into very high bhp/revs, Courtenays and hitec been using them for years with no issues

Been looking on those sites already they are helpful. I need them PDQ. 8.5:1 seems they way to go with the setup it already has and the fuel we run here.

Edited by NickB777, 28 March 2008 - 08:33 AM.

[slindborg]

go here http://www.vauxhall-...rum.com/phpBB2/

PM a user called steveboyslim with what you want. He should be able to help. Failing him, try Stefan on there too.

[NickB787]

go here http://www.vauxhall-...rum.com/phpBB2/

PM a user called steveboyslim with what you want. He should be able to help. Failing him, try Stefan on there too.

[Exmantaa]

In the LSJ ecotec build book, where GM describes the build-up of a 300 HP engine, they even RAISED the standard LSJ 9.0:1 compression to 10.0:1.... I would never go lower than the 9.0:1 in a normal road car. Just make sure you have a cool inlet charge to prevent knock problems. Like Slindborg said, the LSJ is capable of well over 300WHP in standard form. (The SC + inlet manifold is the limiting factor, but you can always change to a twinscrew or the new Harrop TVS SC. And some US guys are working on a proper inlet manifold :-) ) (Anybody know some specs of the Lotus Exige GT3 engine? That is still a 1.8 Toyota with the same (properly watercooled) M62 supercharger and now reaching 261KW!! Would be interresting to know what compression they run...)

[alanoo]

Get the 8.5 ones and fit a LSJ head gasket, it is thinner, it will bring you around 8.8 CR Anything you do... do NOT fit 10:1 CR Wiseco's if you boost. These are NA pistons, that's why they are much lighter than the 8.5 ones. It you want to go 10:1 CR with you supercharger setup, get another brand or get specially made Wiseco's for boost applications

[Exmantaa]

Just FYI...

Nice write-up with pics of a 2,2 build with 8,9 Wiseco pistons: http://cobaltss.net/...ead.php?t=91994

Edited by Exmantaa, 31 March 2008 - 07:28 AM.

[speedster]

NickB, we are chasing the same dragon, 300BHP+. I've 8:9:1's in my supercharged engine. Some have recommenced not to reduced the CR but other's have. Originally dude had my setup earmarked for a high powered turbo application. I can't see why that won't translate in to the high power supercharged arena. The only downside is lower compression means more boost which means there is the potential for more heat generation. My thinking is, as long as I can get the boost and intercooling configuration to run with sustained and efficient cooling I reckon the 8:9:1's will do the trick and offer better longevity. Few questions for you: What diameter pulley are you going run with? Are you going to bolt on the 2-pass intercooler end plate kit? Steve

Edited by speedster, 31 March 2008 - 03:47 PM.

[alanoo]

I think you are missing one key element, you have to do with the M62 efficiency curve If you want to hit 300+ BHP with low compression (let's say 9:1), you will have to get more boost as you said, so a smaller pulley and you will certainly land in an efficiency zone of the M62 were it is so unefficient you'll never be able to cool the intake air enough. I am currently spec'ing my next engine after the NA one (autumn 2009 release), it will be a supercharged LE5/LSJ hybrid with a 380BHP target. CR will be 10.5:1 but not Wiseco (or specially made ones for boost) EDIT : oh and another thing specially for you Steve. Having 8.9 pistons does not mean at all you effectively have 8.9 CR, especially in an hybrid. LSJ/Saab cylinder head gasket are thinner than 2.2 ones. I am not sure the valves have the same big dish on the 2.0 head too

Edited by alanoo, 31 March 2008 - 04:56 PM.

[Winstar]

NickB,

we are chasing the same dragon, 300BHP+.
I've 8:9:1's in my supercharged engine. Some have recommenced not to reduced the CR but other's have. Originally dude had my setup earmarked for a high powered turbo application. I can't see why that won't translate in to the high power supercharged arena. The only downside is lower compression means more boost which means there is the potential for more heat generation. My thinking is, as long as I can get the boost and intercooling configuration to run with sustained and efficient cooling I reckon the 8:9:1's will do the trick and offer better longevity.

Few questions for you:
What diameter pulley are you going run with?
Are you going to bolt on the 2-pass intercooler end plate kit?

Steve

Steve have you already got your sc unit, as mentioned above Harrop have just launched a version of Eatons TVS system to fit the LSJ manifold.

I read a preentation on it a couple of years ago when it was in development it has significanly better thermal efficiency than the std roots blower and IIRC better than Lyshome as well.

I think that for reall power that the way to be going as the CC is only ever going to be able to remove some of the charge heat.

[Exmantaa]

I think you are missing one key element, you have to do with the M62 efficiency curve

If you want to hit 300+ BHP with low compression (let's say 9:1), you will have to get more boost as you said, so a smaller pulley and you will certainly land in an efficiency zone of the M62 were it is so unefficient you'll never be able to cool the intake air enough.

I am currently spec'ing my next engine after the NA one (autumn 2009 release), it will be a supercharged LE5/LSJ hybrid with a 380BHP target.
CR will be 10.5:1 but not Wiseco
(or specially made ones for boost)

That's the nail on the head... The M62 can flow you lots of air IF you keep it in it's efficiency range.. (max 10-12psi) And that is the pressure at the blower outlet!! The LSJ intake manifold is quite restrictive and this will give efficiency problems with higher flows (= HEAT!)
The US guys are at the moment working on a complete new manifold design, but they also ported the standard manifold which significantly improved flow. (Wider laminova slots) Will post a link soon.

(I have a complete LSJ engine waiting, but I'm still figuring out what will be the best solution for my speedster. Personally I think it first should flow (headwork / intake/ exhaust) and rev (valvesprings / balance shaft delete / cams) properly with ~10:1 compression. And then use the M62 to around 10 psi boost and max 15-17000rpm. (The blower that is.)

With well cooled charge temps and some proper tuning... Should be fun enough :-) )

Edited by Exmantaa, 31 March 2008 - 10:20 PM.

[speedster]

Steve have you already got your sc unit, as mentioned above Harrop have just launched a version of Eatons TVS system to fit the LSJ manifold.

I read a preentation on it a couple of years ago when it was in development it has significanly better thermal efficiency than the std roots blower and IIRC better than Lyshome as well.

I think that for reall power that the way to be going as the CC is only ever going to be able to remove some of the charge heat.

Hi Winstar,

Oh...... thats nice! I've got a full SC kit already but might consider this rotor change, it would make good sense to run the TVS on my configuration. Have requested specs and costs from Harrop.

Cheers for the pointer mate