beem3r

This is probably the stupidest question(s) to ask. I’m not experienced with forced induction; just want to know from people with experience.

How do you determine if a turbo or a supercharger is better for a car? Only 6-8 psi of boost.
Example: "328i or M3 BMW"

Next question.

In regards to low compression vs. high compression pistons.
I understand the low compression.

For high performance compression pistons + 6psi of boost = engine blow up? Or high performance compression pistons can handle higher compression then regular high compression pistons? I’m lost typing this, if you understand help loll.....

DecentCivicZ6

HIGH compression and turbo on a street car is just asking for a new engine. lol. if you just want a boosted car for DD driving...id go with a super charger...if you want max performance...TURBO. thats how I see it.

DecentCivicZ6

I did see a test done fromsomone cant remember....he ran 10:1 compression and say 15psi... and then 9:1 compression and 15psi..the 10:1 made like 10-15 more hp....BUT it couldnt run as much boost as the 9:1. so in the end...low compression is gonna be better...last longer. But there are alot of 11:1 cr and high boost...ive got a write up on one right beside me. putting down over 700whp, but that calls for race fuel, water/meth injection. all type of shit to prevent detonation

Fabrik8

You should be able to run 6-8 PSI on most stock engines with stock compression.
As for supercharger vs. turbocharger, it's somewhat a matter of personal preference, driving style, and how much power you want. There are pros and cons to both depending on what you're looking for in a power adder.

Fabrik8

Higher compression will always make more power than lower, that's how engines work. Staying in the safety zone is the trick.

beem3r

I see. So if i get an M3 i can run up to 6psi and be in the same zone with a supercharger. i think the compression with the pistons on the m3 is 10:5? or maybe a bit lower.

Fabrik8

Yes... You'll make the same power with either one (turbo, super, etc) at the same boost. You're forcing more air in under a certain pressure, and it doesn't matter how you do it. However, the power bands are different for the two. A s a generalization, superchargers tend to have more low end power, and turbos generally take a little time to spool up. There are a lot of turbo options though, and not very many superchanger units to choose from.
As far as your M3, if it's tuned for 6 PSI without danger then you're fine.
I'd talk to some M3 owners and find out what's out there for your car and what the safe operating area is for a stock engine. The best source of info to start with is people who've been through it already with the same car.

beem3r

cool, thanks for your help man

DecentCivicZ6

same power at same boost level?? http://videos.streetfire.net/video/d...e400eb24ea.htm haha....turbo is 9psi whole rpm...not s/c

Fabrik8

So please explain what power over an RPM range has to do with power at a certain boost level. I'll wait.