Spanky's Monkey

iTrader: (6)

well since the wife is on board for a zzp sc kit i figured i start planning a build. thing is with the 2.2 blown on stg2 would it be better to go with the 10.1 or 8.9 forged pistons? i understand the lower cr can pack in more boost, but truth be told that's not what i'm looking for, exactly. I plan on meth down the road but i'd like to do to the head, valvetrain and all before i think of playing with the boost. i want stable platform i can continue to build on should the mood suit me as it does now, and it's about damn time.


i don't bullshit with my car and i don't take chances with my investments. so i'm really looking for sound advice and judgement.

SSfamilywagon

iTrader: (2)

From my understanding, yes the lower compression will help with more boost. But with the SC thats not what you really should be after. The higher compression will help with TQ I believe. So 9.5 or 10.1 is good. I think going as low as 8.5 is for really high boost or big power.

At least thats what I remember reading and hearing from other buds. Someone with good knowlegde will chime in soon.

BLKLS

Stick with stock, the lower compression will alow you to run more boost but with the lower compression you have to run higher boost to make up for the lack of compression. If your gonna run stg2 the lower compression may really hurt you daily drivability. Your really may loose a fair amount of power with the 8.9

Maven

iTrader: (1)

Just go with the 10.1 if youre going Wiseco. 8.9 and youre going to be giving up power, and gaining nothing at your level.

erock666

add the 10:1 compression , with 8:9 with the m62 youll never have a big gain , for turbo yes , but with the m62 and the stock compression with a low pulley like 2.5 2.6 and alot of cooling mods youll see around 280 whp

Spanky's Monkey

iTrader: (6)

sweet, that's all i needed to know on that front.

erock666

ya that'll get u decent amount of power but i think when im done building it in april and have her all done i might try twin charge not sure yet still working on saving for a clutch aha

Mr.N00bLaR

iTrader: (7)

Don't people struggle to defeat knock with 2.7/6 on LSJs with almost a point lower CR? got links to anyone running a 2.5 on thier m62 2.2l build?

HunterKiller89

iTrader: (1)

its half a point lower, and thats because of IAT2's not because of compression ratios

Mr.N00bLaR

iTrader: (7)

gotchya on the CR difference. Doesn't IAT play a big role in combustion temp which can cause knock though?

HunterKiller89

iTrader: (1)

a quick breakdown. Roots type superchargers are not meant for high boost applications. They were designed to add 2-8 PSI to an engine and increase its efficiency (in WWII era fighter engines specifically). While they have definitely evolved since then, this basic truth is still true, in that they are extremely efficient at low boost, and lose this efficiency as boost climbs. From the factory, the M62 is pushing about as much boost as it should be to maintain an acceptable efficiency level. Efficiency from a roots blower drops at a geometric rate as boost increases, so each additional PSI starts creating massive amounts of heat and parasitic loss as the boost rises.
(these are not the case for a turbocharger, so lowering your CR for higher HP makes every bit of sense when it comes to turbos)

This is what causes them to knock on high HP applications. Lowering the CR will indeed help control this knock, but you'll still be leaving the SC there robbing larger and larger amounts of power and still have very high combustion chamber temps, and this lower CR will make less power.

If you have a 300whp goal for an M62 (for example), the better way to go about getting there IMO is by using a higher compression ratio and lowering the boost. This gives you a stronger power band and helps keep the supercharger in its efficiency range, which in turn means less parasitic loss from the blower, less heat created, and a more reliable build.

Can you drop CR and up the boost? sure, but you're SC will be robbing more power, and you'll need cooling mods like meth to help control the temps, but it can definitely be done and has been done many times.

If you prefer dropping CR and raising boost, but still want a supercharger, a TVS is a better route, as the TVS series does not lose efficiency at the same rates as a traditional M series SC does when you get into higher boost numbers.

oh, and just so you can have the exact numbers, the LSJ is 9.5:1, the LNF is 9.2:1, the L61/LAP are 10.0:1, and the LE5 is 10.4:1

erock666

hey hunter what pulley are you running safly right now ? i wanna lower my pullie before i build

Fonzi1289

I think he WAS running the 2.8
I think he sold his car

HunterKiller89

iTrader: (1)

i was running a 2.9, but yea, i sold my car. There are at least 2 members off the top of my head running a 2.8 though...should be fine. Just make sure you watch your IDCs

erock666

so hunter how much did u get for your car ?

ipwncivics

Jn2 is running 2.8 if it helps any

HunterKiller89

iTrader: (1)

i dont wanna talk about it

erock666

oh sry =/

Spanky's Monkey

iTrader: (6)

so anyone running sc grind cams?