Im trying to figure out wat setup to go with on forged internals for a procharger. Its gonna be a dd so im not sure whether to go with High Compression with Low Boost or Low Compression with High Boost. Any ideas?

 

if it were me I'd probably go forged with stock compression pistons

you wont be getting free power like a turbo with the procharger setup so I wouldn't drop the compression personally and going any higher may limit your amount of boost to where you'd have limits on the timing you could run or you'd have to run high octane fuel like 93+ at all times.

 

how about high compression, high boost, and meth injection?

 

Possible on pump gas? i have read something that if your compression exceeds 12.5:1 you will need race fuel to keep from detonation or tune your car to run e85 which is high octane.

 

well the ecotecs seem to like 9.5:1 compression and @20psi, so that's what I"m stayin with for now. but probably drop to 8.5:1 once cams and bigger turbo are ready to go

 

I found this (http://superchargers4less.com/procha...atio_chart.jpg) and according to it at 9.5:1 i would only be able to run about 16psi on pump gas.But its for carbureted engines so probably dont apply to efi.

 

I run over 20psi on pump gas, and I can run up to 25degrees of timing with methanol injection, 15-16 without

 

Does it all depend on if you have control of timing?

 

lol what a procharger.... and a g85

 

Bump........maybe my real question is does lowering cr drop hp that much that at low boost the car will not hardly move? and if i keep it aroun stock cr will it be to much of a hassle to give it the boost? and what setup would be the easiest to get 300 whp?

 

you can run high compression and high boost on pump gas if you know how to tune (but only so far before you push the limits). keep stock compression and dont go crazy with boost, but moderate should be fine.


but the problem is, not boost level. its cfm. if you have a low cfm charger, then you can run alot more boost then a high cfm one

 

If you're going for 300whp then you should build your internals anyway. As long as you're going with boost, you'll probably want to run lower compression pistons

Of course it depends on other things as well. You could stick with stock compression and be able to run a smaller turbo in its efficiency range. It would also give you a faster spool time.

Going with lower compression will allow you to run a bigger turbo at higher boost and make more power, but more than likely it'll take longer for the turbo to spool.

I guess what it comes down to is... what kind of powerband are you looking for. You could reach 300whp going either direction, but do you want a top end monster? Or are you looking to get into boost alot sooner?

Lowering the compression and not going boost would make the car a dog(even more than it already is stock). The way I see it, once you change engine internals, you've already committed to whatever plan you've chosen.

 

low compress, high boost

 

You get more power from Boost and Timing than you do with Upping the compression. Go no higher than stock compression. If you plan on a lot of boost, go lower of course.

 

Im going procharger c-1 1100 cfm's. i know that supercharger builds boost as rpms get higher so if i run low compression its gonna be hard to get my car moving at low rpm's which id like to keep away from.but also id like to run decent boost at high rpms without the need of race fuel as this will be my dd. Is the meth injection, complete control of timing and other options good enough to let me run a FCR of 18.5 Considering going with 9.5:1 and 14 psi max

 

can anyone tell me what cfm is.... can u go high compression and high boost or would that require higher octane fuel or stronger internals?

 

I think 9.5:1 is perfect. thats what im going with. going with a 20psi @ 6500rpm pulley on the procharger with 9.5:1 shouldnt be that much of a dog. i know its not going to have much low end, but you know what, it will be a beast up top. I may even go with a smaller pulley and do the "overspin" effect to build boost faster and bleed it off after a say 20lb's. The vette guys do it, why cant i?

Its how you measure the amount of air thats being pushed by the turbo or supercharger. PSI is irrelevant when it comes to making power. 10psi on a turbo is completely different then 15psi on a procharger. It all comes down to how much air your forcing into the engine. with cfm you can calculate pretty damn close how much power you will produce on an engine.

 

My goal was to go to 10.0:1 with 15 PSI MAX with meth inj. But like someone already said.....You need to know how to tune!!

 

your gonna run a gt2871 right? that should be a sick setup on 10:1. you can also run a higher rev limit.

 

(Cubic Feet per Minute ) in this is related to the flow of the air coming out of the supercharger.

 

Old school rule for blowers was low compression <8.5:1 w/ >15lbs of boost from a large displacement blower was = to increasing the engine's over all displacement by forcing in a greater volume of air/fuel than would be possible with a higher compression ratio of >9.5:1. I don't see why that would be any different today unless there are some emission concerns...

If this holds true for newer cars I would say low compression with a high volume blower w/high boost would be the most desirable combination...

I remember at least three friends that had Weiland 671's huffing small blocks in the mid '80s and every one of them was running around 8:1 compression... I had one friend with an '88 Mustang 5.0 running an R-trim Vortec at 13psi with 8.5:1 compression. That s.o.b flew...

 

Naaaa....My goal was sleeper....I wanted the balt to be a sleeper. I wanted to keep the stock blower....but have the 300+ hp/tq.

 

ohh gotcha. so are you there yet? i havent seen any #'s with 10:1 on the lsj yet. you gonna run a 2.5 pulley w/ meth?

 

Going over 10:1 will also make daily driving with pump gas much more difficult. In this same way, compression levels much under 9:1 will require substantial boost levels to make massive power gains. This would require boost levels that are very demanding of a supercharger. This is truly unnecessary. This isn't to say that the lower compression / higher boost set-up doesn't have a slightly higher potential for power, because it does. A lower compression motor has the ability to contain more volume. This can be an advantage, but is such a minor one that it's not necessarily worth the effort - unless it's for an all out race motor. Even then there are limits for the same reasons as the street / strip motor.

Id like to hear opinions on this.......

 

If you're only worried about hitting 300whp. the stock compression will be fine. But you will need forged internals.

Less compression does allow you to run more boost. In fact if you were to put in lower compression forged internals, you could find yourself running say a 50-60 trim turbo up to 450whp.

Stock compression will take you just as far with forged internals. You won't have to push the same cfms through the motor to make the same power. The way I see it, either way you're going to have to build the motor, might as well go with the stock compression and save yourself some hassle with the f/i end of it.