Boost makes more power than compression does. You won't change much either way going from 8.5:1 to 9:1. I don't trust much of what some of these "tuners" claim.

The general consensus is that you run enough compression to keep throttle response "snappy" (8.5-9.0) and let boost make the power. Building a 12:1 motor and trying to put boost through it isn't going to work out very well. (I'm exaggerating a bit)

 

Damn I must have not turned on instant email notification. Well, JJ has been pretty upfront about what he is doing to motors over on nloc. Might wanna ask him a couple of questions off the boards.

My honest opinion is that if you go from 8.4:1 to about 9.1:1 then all you would have to do is lower the boost, say from 6#'s to 4#'s, and take some timing out, add a touch of fuel and you should be good. Or get it on the dyno again and let someone tune it for it.

 

Well, I know that Dave's (Screaming01L) truck is turning 10's on I think he said 15 psi out of a KB. I know he's got stage III's in everything, so I'm not sure how much of a difference that makes.

Yeah, I'd thought about all that. I was just thinking along the lines of maybe you could meet somewhere in the middle, say like you wouldn't have to run as much boost to make the same power, etc..

I dunno, like I've said, I know N/A motors up, down and all around, but I don't know a lot about forced induction yet. I'm still pretty new to this game.

 

I am still in the planning stages of my engine build, but I may end up going with a bit higher compression, and less boost with more nitrous.

 

What about my set up?
L33 is 9.9:1 CR and I am going to FI w/Radix.

What if I added AFR 205 Heads (mega $$) ??

 

I'll throw out some numbers here... and this is on a pump gas configuration, no nitrous. Obviously if you're going to sacrifice street power for race power, this may not apply.

Let's say you have an 8.5:1 motor and you've got it tuned perfectly for 10 psi. EVERYTHING remains the same except the pistons which you install to change the compression ratio to 9:1. You will have to lower the boost to ~8 psi to run the same amount of timing as before. The rule of thumb is that each full point of compression is worth about 2% increase in hp. So, you get a 1% power increase from compression, but you lose roughly 10% because you can't run as much boost.

 

I'm in the same boat

i know a guy that is a nitrous guru and severl people that have excessivly fast N/A cars but no one with a lot of experiance in forced induction

 

I think you also have to look at the type of blower being used. If the blower has no trouble breathing to 20psi and you only plan on running 10psi and it is very efficient (IE very low heat) then going low compression and upping the boost some would be good.

Now take a small blower that starts to really heat things up after 7psi then going higher compression and keeping boost low would be a better option IMO.

That is what I'm doing anyway since the Radix maxes at about 10-11psi and really kicks in the heat at that point. Its working well so far but I need to change my cam, retune after the 90mm TB and see what it can do. Ohh and keep my pressure steady. My peak HP was on 4.8psi

 

Hey Rob, i can get a good deal on Manley Rods and Pistons. Let me know on here, or SVTP if interested.

 

It'll probably be end of summer before I can start getting parts together, but I will keep that in mind bro.