OK guys, I wanted to know first off the valve to pistion clearance. The next thing I need to know is what is the best compression ratio to use for a supercharger. I am thinking about using 60 over pistions and a headgasket thats .74, but I am not exctly sure. Also is there anything that I can do to the head, as far as getting the compression ratio correct. Any help would be nice as I am taking the motor out tonight and need to know what to have done in the next couple weeks.
http://www.overkillengineeringmotorsports.com/
First - Valve to Piston clearance is something thats measured. My opinion is depends on who does it depends on results (error being the way the indicators are set up). Yes it is a good thing to know, that is the first thing i did when i got my 8.9:1 and my 12.5:1 wiseco pistons. I did not check the factory setup.
Second - the lower the CR the better, alot of guys run the 8.9:1 wiseco pistons that i know of
Third - going .020 .040 .060 overbore shouldnt change your CR, what changes it are a few factors: Pistons are prob #1 (they can easily change it by points) and Valves are a far #2 (they can change it by tenths) and Stroke can change it also, then back to #1 again, checking the valve to piston clearance
When you do check your clearances, you will want to be prob .050 and greater to be safe, In my engine my exaust is .040 and it doesnt really change much when i change the exaust cam timing, but with the intake im at .120 ish, that one will get closer the more i advance the intake cam. I rev to 8000++ and i have -0- engine problems
Hope this helps a little
-Ben
Quote:
the lower the CR the better,
^ was the only part i disagreed with...other than that a wise post
Thats what i heard, with the lower CR you can push more PSI and its easier to tune AFR
-Ben
in a way your right...the lower the CR the easier its going to be to tune afr....but you of all people should know, just cus its EASIER way doesnt make it the BEST way
.. but in the end it all comes down to "what hes trying to do"...like many on this site he posted what needs done..but didnt say what his goal was...that is a VERY vague question when dealing with building an engine...all we REALLY know is that hes putting a supercharger on a 2.4..im assuming the m45..and he didnt say what size pulley or anything...but if that is the case PERSONALLY i suggest a strong 10.1 piston...i dont think id go 60 over though...IIRC 40 was the safe limit..maybe im wrong.
would be nice to know what all else is planned for the build..?? any head work? cams? rods? crank work? ..anything? whats your hp goal?
Cool, I have heard that .60 is a little far. So I will go with .40. For the ratio, would you say 10.1 would be better in the long run than the 9.1? I am going to be running a m62 later on so I want mto build the motor up now so when I put the blower on its good to go.
http://www.overkillengineeringmotorsports.com/
no, the reason HIGH compression is needed on what you want to do is because the m45 (supercharger thats the one you'll be getting, the only one thats made) is small and doesnt provide much air. you need all the help you can get because the s/c literally reaches it's limits and if you want more power, you need higher compression.
id love to see a 10.5:1 CR ld9 with the m45 and a 2.5" pulley on meth.... thatd be interesting...
with boost, i would NEVER go anything more then a Flat top pistion....Now i know thats not a Ratio, so if you can get 10.5:1 with a LD9 and flat tops.. great.
H.O Cams, MP45 blower, Over drive crank pulley, 2.6 charger pulley, Flat tops, and a nice port job on the exhasut side. with all other suporting mods..
should be good for a nice high 13 to mid 13 run, with out the N2O
Chris
'02 Z-24 Supercharged
13.7 @102.45 MPH Third Place, 2007 GMSC Bash SOLD AS OF 01MAR08
There is no bolt on and go way to put an m62 on the ld9, the ld9 sc kit is an m45. Your m45 will not show enough boost that you would need lower compression, even with the smallest pulley you could fit on the m45. Id go with 10:1 pistons, unless you ever have big turbo plans in the future then even stock cr overbore pistons would be fine for the sc.
An overdrive crank pulley would be be great for the m45 setup, you would see more boost without spinning the sc faster so you would have less heat buildup...but good luck finding one. An underdrive crank would see less boost.
You dont want to underdrive your blower
You will want an overdrive or something like MD9 sells, lightened stock size
I will probably either buil a m62 intake manny or maybe use a m45 not sure. But either way I will run a overdrive pulley, I will probably have one made. What would be a good amount to make the over drive pulley from stock, 10%-20%?
http://www.overkillengineeringmotorsports.com/
So is the standard Overdrive Crank Pulley a LD2 pulley?
in theory, you will hit more boost on the smaller numbered size pulleys. the speeds the supercharger up, thus, pumpin more air.
I talked to MD-LD9 about an overdrive pulley. He needs at least 10 people before he can make a batch. That would be a tall order.
I usually see 6-7 psi with my overdrive crank pulley and 2.8" pulley on the SC. I have yet to tap into the 2.7 and 2.6 pullies I have.
Jason
99 Z24 Supercharged
157hp/171tq - NA
190hp/170tq @ 6psi
LD9 for Life
Blwn LD9 wrote:I talked to MD-LD9 about an overdrive pulley. He needs at least 10 people before he can make a batch. That would be a tall order.
I usually see 6-7 psi with my overdrive crank pulley and 2.8" pulley on the SC. I have yet to tap into the 2.7 and 2.6 pullies I have.
I would love to, prolly even buy 2 just to get it going lol but Ive got other plans that doesnt include the sc
my OS crank pulley, and 2.6 charger pulley.... was.... awesome, sounded like a M112 with a 2.8 on a cobra, it was mean.
If i ever get my hands on a 02 4 door Z24, it is so getting that set up on it.
Chris
'02 Z-24 Supercharged
13.7 @102.45 MPH Third Place, 2007 GMSC Bash SOLD AS OF 01MAR08
Quote:
id love to see a 10.5:1 CR ld9 with the m45 and a 2.5" pulley on meth.... thatd be interesting...
Working on it
So far what I have learned during my build is that if you know your going with the GM S/C (M45) then look for Higher compression. The "Safe" and most common route I have seen is 10:1 and usually a .020 overbore(more for maintenance) Plus the over common Eagle rods. This setup appears more common than MR7's
Ill tell you now, there is a lot more to it than you will see to start off with.
..telling ya, flat tops are the way to go....
Chris
'02 Z-24 Supercharged
13.7 @102.45 MPH Third Place, 2007 GMSC Bash SOLD AS OF 01MAR08
I need someone to correct my thinking.....
From my understanding having any disruption on the piston surface can lead to hot spots and detonation. So in theory as Chris suggests wouldn't a flat top be the best no matter what?
