The last blower motor I built had a static compression ratio of 5.6-1. I was able to run 25 lbs. boost with an 8-71 blower on a 427.
Forced induction question.....
Thread Starter
Drifting
Joined: Sep 2004
Posts: 1,307
Likes: 1
From: Milford Haven Pembrokeshire
Forced induction question.....
If any of the turbo, etc boys out there know...
How much pressure / forced induction does it take for you to notice the difference - not melt the tyres - just notice the difference.
For example - if you took a totally stock used engine - smog or otherwise, you might get some extra bhp with a tune up and maybe a bit of cold ram air.......possibly 10 to 20 bhp. And you would notice that - I should think - it would have more "sparkle "
My question is, with no tune up or any other mod, how much forced induction would it take to create the same amount of sparkle.......I am guessing less than half a psi - am I in the ball park ???
Next question, if you did all the typical mods, heads, headers, manifold etc, and maybe get 100 / 150 / 200 bhp extra, how much forced induction would it take on the same standard engine to gain an equal amount of BHP......once again, as a total guess, I am thinking 12 to 18 psi - am I anywhere near ??
How much pressure / forced induction does it take for you to notice the difference - not melt the tyres - just notice the difference.
For example - if you took a totally stock used engine - smog or otherwise, you might get some extra bhp with a tune up and maybe a bit of cold ram air.......possibly 10 to 20 bhp. And you would notice that - I should think - it would have more "sparkle "
My question is, with no tune up or any other mod, how much forced induction would it take to create the same amount of sparkle.......I am guessing less than half a psi - am I in the ball park ???
Next question, if you did all the typical mods, heads, headers, manifold etc, and maybe get 100 / 150 / 200 bhp extra, how much forced induction would it take on the same standard engine to gain an equal amount of BHP......once again, as a total guess, I am thinking 12 to 18 psi - am I anywhere near ??
Last edited by hensen1954; Jan 4, 2007 at 01:03 PM.
Le Mans Master
Joined: Jul 2005
Posts: 5,752
Likes: 4
From: Austin Texas
In my learning process, doing a supercharged build myself I have seen a general formula that when you double the atmospheric pressure (approx. 15 psi) to 30 psi (15 lbs. boost) you double the n/a horsepower. Another simplistic formula I have seen used is at 15 lbs. of boost: cubic inches X 2 = H.P....FWIW
Le Mans Master
Joined: Jul 2005
Posts: 5,752
Likes: 4
From: Austin Texas
Also, keep in mind that if you drop the compression for your boosted application, the first few pounds of boost will only get you back to where you would have been with an optimized high compression engine. After 2 or 3 lbs. of boost, it's all gravy.
Race Director
Joined: Dec 1999
Posts: 16,945
Likes: 9
and also realize that boost is just a measurement of cramming air flow through a restriction, in this case the supercharger cramming air into the engine w/ the intake path being the restriction. This means that if you have a comparo between 2 engines where 1 is identical but the intake is restrictive, this engine will show higher boost levels for same compr. output, a hotter intake charge and lower power.
Le Mans Master
Joined: Jan 2006
Posts: 6,499
Likes: 137
From: Butler Pa
It will get you back to the original compression, but the air/fuel charge will be larger, which in itself will make the engine run as if it were larger.
Le Mans Master
Joined: Jul 2005
Posts: 5,752
Likes: 4
From: Austin Texas
Le Mans Master
Joined: Jan 2006
Posts: 6,499
Likes: 137
From: Butler Pa
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
2027 Corvette vs The World: Every Model vs Closest Competitor
Joe Kucinski
10 Most Common Corvette Problems of the Last 20 Years!
Joe Kucinski
5 MOST and 5 LEAST Popular Corvette Model Years in History!
Joe Kucinski
2027 Corvette Buyer's Guide: Everything You Need to Know!
Joe Kucinski
10 Things C8 Corvette Owners Hate (But Won't Tell You)
Joe Kucinski
10 Best Corvettes Coming to Barrett-Jackson Palm Beach 2026!
Brett Foote
Every Corvette Grand Sport Explained! (C2, C4, C6, C7, & C8)
Joe Kucinski
Grand Sport & Grand Sport X Launch Alongside All-New 535hp LS6 V8!
Michael S. Palmer
5 Reasons Bad Drivers Crash & 5 Ways to Avoid a Costly Mistake!
Joe Kucinski
Le Mans Master
Joined: Jan 2006
Posts: 6,499
Likes: 137
From: Butler Pa
Thread Starter
Drifting
Joined: Sep 2004
Posts: 1,307
Likes: 1
From: Milford Haven Pembrokeshire
Was seeking accurate knowledge - not intentions..........
And, if you take it a little further - depending on the maths involved.......
if you are seeking as much power as a C3 can handle without a terrific rebuild ( which is about 500 to 700 bhp ) after that you need brakes, diff etc,.. possibly there is a cross-over point when it becomes more cost effective and time effective to force induction the crap out of an un -modified engine rather than force induction a big buck engine.
Have come across this with a certain 4 cylinder euro engine, where you can turbo the crap out of it to produce about 600 ponies ....and it will not last more than about 20k road miles. BUT as a replacement engine from the breakers is only about 150 bucks, just do it again, and again, etc.
And, if you take it a little further - depending on the maths involved.......
if you are seeking as much power as a C3 can handle without a terrific rebuild ( which is about 500 to 700 bhp ) after that you need brakes, diff etc,.. possibly there is a cross-over point when it becomes more cost effective and time effective to force induction the crap out of an un -modified engine rather than force induction a big buck engine.
Have come across this with a certain 4 cylinder euro engine, where you can turbo the crap out of it to produce about 600 ponies ....and it will not last more than about 20k road miles. BUT as a replacement engine from the breakers is only about 150 bucks, just do it again, and again, etc.
Last edited by hensen1954; Jan 4, 2007 at 04:20 PM.
Le Mans Master
Joined: Jul 2005
Posts: 5,752
Likes: 4
From: Austin Texas
Way too many variables. For instance: I called Lunati, Comp Cams and Crane on cam selection for my Pro-Charger build-up. I told them my target was approx. 750 h.p. @ 6,500 rpm. One suggested 256/260 @ .050, the next said 230/236 @ .050, the last said keep what you have now (242/248@.050).
Guessing what power you get for a given boost without much more data to crunch is futile, IMO.
Guessing what power you get for a given boost without much more data to crunch is futile, IMO.
Racer
Joined: Nov 2006
Posts: 412
Likes: 0
From: Arizona
I'm no expert, but you would need more data than just PSI. You need to no what volume; a large "roots type" super charger uses less PSI and more Volume, and the Turbo is the opposite, more PSI and less Volume.
If the information I've given is incorrect please disregard as it's what I was told by a engine builder.
If the information I've given is incorrect please disregard as it's what I was told by a engine builder.