: boost vs compresion
07-27-2010, 06:45 PM
right now i'm running 10lbs of boost with 10.2:1 compression. I want to go up to 15lbs of boost. What is the highest compression ratio i would want to go with? and is it ok to just use a thicker head gasket to lower compression when running boost?
07-27-2010, 06:51 PM
listen. the only reason people do really low low low compression ratio's is so they can have a bigger margin of safety. as long as your tuner is good you should be fine. our svtf motors can handle 320whp safely. anything more than that, you are risking it. I suggest getting some piston/rod combo in there and cranking teh boost even higher. lol.
07-27-2010, 06:59 PM
I drive my car everyday and want a little lifespan for my engine. I drive my car kinda hard, I cant help my self I LOVE the sound of the supercharger. I have a 2nd engine to rebuild this winter out of a zx2 and want it to last. All I want is a 300hp everyday driver.
07-27-2010, 07:24 PM
you'll be just fine, don't open up the top end, no need. people push 18 psi all day long on a stock motor (pending turbo choice!)
07-27-2010, 07:25 PM
actually, just realized ur talking about the JRSC. you won't get 300 whp on a JRSC, you need a turbo to do that!
07-27-2010, 07:36 PM
You better have a way of cooling it. Its pointless to push more than 11-12psi without some type of aftercooler. The heat produced will take the hp you would be producing away.
07-27-2010, 07:37 PM
come on 15lbs of boost wont get me 300 or even close to it. I have to try it and ill let you know what it puts out. I'm at about 240hp now.
07-27-2010, 07:42 PM
There is absolutely no way you are at 240 @ 10lbs. The BBK pulley puts it at 9psi and it only pushes 200 with good bolt ons.
07-27-2010, 08:15 PM
Wow I'm an idiot. Didn't notice you had an SVT. My bad. I don't know the numbers for a JRSC'd SVT.
But like I said, anything over 11-12psi won't do anything because of the heat.
07-27-2010, 09:28 PM
psi has nothing to do with it.
its all about RPMs
psi is a messure of pressure (resistance)
switch to a pwsc, and use a 2.4' pulley and a 5.7" ovd pulley and have supporting mods and see what you put out but it turns into a heat factory up top.
you will have better bottom and mid range but up top would be super hot
07-27-2010, 11:23 PM
the JRSC isn't intercooled, so since its not, your talking dangerous territory for the blower, not to mention you'll have to push it way way past redline (the blower) to get there. the only way to make 300 + whp is through a vortec maybe or a turbo. you can try all you want, but u won't get even close. the JRSC kit w/ bbk makes around 220 whp, maybe 240 w/ ORP and proper intake. the ONLY way you will get there w/ a jrsc is nitrous.
07-28-2010, 08:35 AM
A JRSC+BBK isn't going to make 240whp unless it's winter in Canada. [hihi] I made 220whp with a ported head, ported blower, ported manifold, high-flow cat, 3" exhaust, 67mm throttlebody and everything port-matched on a humid 60degree day. That's a lot of work and money for a setup that typically puts out 200-210whp when bolted on. I'm sure with some more work like custom pullies, bigger injectors, COP, bigger MAF housing, bigger TB and water/meth I could probably hit 235whp... MAYBE 240... but it's not a safe setup anymore in my eyes. The limitation is that old 4th-gen Eaton M62... it just can't push that much air without seriously overheating it.
Now, let me make my stance clear: it IS possible to get 300whp with a roots blower safely, I just don't think it's been done on a Zetec engine yet. It will require custom work and more money than a similarly-powered turbo setup would cost, but it can be done.
If you just want a safe 300whp setup without a lot of question marks, go turbo. Modern turbos make more efficient power and more torque than an old roots blower, so there's really no reason not to unless money is a real issue.
By the way, that statement about "winter in Canada" is true... someone dynoed an SVT with JRSC+BBK in Canada during winter and it made something ridiculous like 250whp or so. Just goes to show how much of a difference good cooling can make. [giddy]
Moved to Forced Induction Chat.
08-01-2010, 07:35 PM
I hear what your saying about not getting to 300 with boost. What about that nitrious is that safe with the jrsc? What about higher compression? I'm not worried about heat add an intercooler no problem and i live in michigan we have lots of cold air.
08-01-2010, 07:46 PM
You can have n2o with the jrsc, just tap it into the manifold. Don't run it through the blower.
08-01-2010, 08:14 PM
Also, adding an intercooler would require custom work with the JRSC... there's no provision to add one.
08-01-2010, 08:18 PM
What you need is an AFTERcooler, like water/meth.
08-01-2010, 08:50 PM
won't do anything. you have to cool the IAT's AFTER the blower after the air is compressed.
08-01-2010, 09:24 PM
^Exactly what I said.
08-01-2010, 09:29 PM
Yeah, Tom's turbo kit will get you to 300 no problem and then you'll smoke CaysE [:p]
If you want a tubular manifold and such, Top Speed [:)]