CyaPussy

iTrader: (1)

A well built 347 head cam etc with d1 15 lbs of boost should make what around 650 rw or is that a low ball number also am not looking to use methonal.

josepy121380

iTrader: (21)

Mine made 680 on 13lbs with some serious belt slip with the meth on but not being used to advance the timing. Cooling purposes only.

The Alchemist

iTrader: (19)

I think it also depends on what your compression ratio is, and how efficient the heads/cam/headers/exhaust setup is. 15psi of boost on a car with stock flowing heads is dramatically different that with a good set of heads.

With that said, I'd expect north of 650 at 15psi of boost.

conan

iTrader: (5)

What they said ^^^

Also what elevation do you live in ? I lost 50rwhp and 40rwtq moving form 900ft to 7,000ft on the same setup @10#'s of boost.

brians91formula

iTrader: (12)

650 - 750 depending on setup i would think

dschmittie1

iTrader: (64)

Wagner, my old stock heads and ls6 intake forged 347 made 670rwhp on 13psi at Keiths dyno with the t56 still in the car. But that was with Meth.

5w20

iTrader: (21)

Thats a very vague question. That's like you asking, "how far can I throw a ball?"

vmapper

iTrader: (8)

Not quite...
You lose hp and tq because your BOOST will DROP as impeller speed is directly in relation to RPM (belt maintains the same relationship) and does NOT change. Your boost drops because per pass of the impeller blade, there is less dense air higher up... so at 'x' impeller rpm, overall less boost is obtained.
You will not have the same boost level at all altitudes on a belt driven system.

You would have the SAME power if you are at 10 psi of boost at 900ft as you would if you had 10psi of boost at 7000 ft. Simply because, 10psi of air has the same amount of O2 regardless of where the air was gathered. (just takes MORE (air volume) at higher altitude to obtain 10psi. This is what turbo setups which are boost controlled (wastegate) experience.

conan

iTrader: (5)

I disagree with this, My boost gauge would read 10#'s when I lived around sea level, boost gauge still reads 10# here at 7,000 ft. Nothing on the set up changed. The power loss comes from the air density with is much less up here where planes fly.

When I drive down to the salt lake vally ( 4,500' - 6,000' ) My boost gauge doesn't read any differant then when I'm driving around in (6,500' - 7,500' )
10#'s of boost @ X elevation is not same as 10#'s at Y elevation.

vmapper

iTrader: (8)

You disagree, because you dont understand. ANd this is not a 'agree' disagree, this is simply how it works.
If your boost stays the same, your not on a belt driven system, or your gauge is crap.


well then. you tell everyone what 10 psi of AIR is comprised of? Last time i checked 10psi of air is made of the same amount of oxygen as 10psi of air.

Unless you are about to explain to the science community that AIR changes composition as elevation changes (which it doesnt - its merely spread apart -less dense), then when you gather 10 pounds per square inch of the stuff.. it contains the SAME amount of oxygen and all the other elements regardless.

Once you pressurize the AIR, all bets are off on the elevation reasoning you have miserably explained.

vmapper

iTrader: (8)

lol.
This is completely wrong.
How can one bottle of compressed AIR have MORE oxygen than another with the same pressure?
simple, you cant.

The Alchemist

iTrader: (19)

Easy. If you compress air that contains 19% oxygen vs. 21% oxygen.

So at higher elevations, the percentage of oxygen can be different.

vmapper

iTrader: (8)

Tisk tisk alchemist.
We are dealing with PRESSURIZED AIR not ambient and missing the entire reasoning.

Let me try to explain this a different way...

Yes, there is 19 % oxygen higher up for a SQUARE AREA OF AIR? -explained a different way in next post (but this may be why there is confusion) why? becuase its less dense... so, to create 101.3kpa or sea level conditions you have to grab even MORE of it volume wise... and when you reach 1 Bar you have what? the same amount of oxygen. Once you have made the higher elevation air 14.7 PSI (which is MSL) you have the SAME % of oxygen...
You are compacting and removing the apart distance between oxygen and other elements.

takes MORE air at higher elevations (more SPACE) to obtain BOOST.. but when you do, it will contain the SAME % of oxygen.

vmapper

iTrader: (8)

Another way to look at it.
The Atmosphere contains elements.
What we are concerned with is the combustible portion, Oxygen.

AIR = Atmosphere contains 20.946% oxygen. (REGARDLESS OF PRESSURE 5 kPa or 5000 kPa)

now at 89 kPA where I live, you will have the oxygen content spread further apart, what we call, density.
At MSL (mean sea level) we have 101.3 kPa, the oxygen is spaced 'THIS' far apart, which is closer than 89 Kpa.

This all makes sense, power is decreased...

Now, I force induct.
Im at 89 kPa, the compressor gathers air and increases Past the ambient 89 (entering boost) to 101.3 kPa.

The compressor has had to gather MORE volume of air to create pressure as the ambient air is of less pressure (density -spread apart, but contains the same oxygen ppm)
But how much oxygen is in that 101.3 Kpa I just made?
Are you suggesting the 101.3kpa I just made contains LESS oxygen than the 101.3 sea level? It doesnt, does that even make sense?. No. More volume of air was used - compressed, to make 101.3.

I dont know how this could me mis-understood.

vmapper

iTrader: (8)

Now for Pullied blowers, In my case, from vancouver to here, its a nice 1.4 psi difference. Guess what? follows the math perfectly. 101.3 kPa - 89 kPa ambient.
And its measurable through my 'accurate' logged 5V output gauge as well as the scans through the Baro sensor.

Bob at brute speed will tell you the same, so will any creditable dyno operator.

conan

iTrader: (5)

Where in any of my posts do you see PSI ?

Every thing I said has #'s of boost. NOT PSI.

You are right, PSI of air pressure is the same at any elevation.

The density of air you are "compressing" is less in high altitude.

vmapper

iTrader: (8)

what does 10#'s mean then?

You were quite clear your gauge reads 10#.
Most gauges we use in vehicles measure PSI, not ATM, kPa or others.

vmapper

iTrader: (8)

And this means?


it takes MORE volume to obtain your desired pressure. Since you are running a BELT driven blower, you cant increase the impeller speed to make up the difference, you then will drop in overall boost.
I've measured it, any reputable blower sales guy, creditable dyno guy or any science guy will tell you this.

Every rotation of the blade will contain Less dense air, as you pointed out. just means, MORE rotations is required to get the same pressure as one would at sea level. But the belt is the reason why you can not as that is the fixed variable in this. The blower can only do x amount of rotations at 6000rpm. (or whatever rpm)

Your power loss is due to less pressure, less boost, not due to atmospheric density and higher elevations having less oxygen in a volume. This oxygen per volume is now increased as you have increased pressure in the manifold, incrasing the oxygen mass. The entire purpose of F.I.
10psi of air from anywhere = contains 'X' amount of oxygen. - this relationship does not change.

This means, if nothing has mechanically changed, your Boost level will have dropped going higher in elevation and directly will affect the amount of oxygen mass ingested per volume.

[WRONG - 10 psi of air has less oxygen if its compressed from 7000' vs 10 psi of air compressed at 800'. - end of wrong.]


If after all these readings, you are still convinced this is not the case, I encourage you to call Procharger or BruteSpeed or do some empirical measurements yourself. (eyeballing a gauge not recommended)
Im trying to help you understand, clearly bad at explaining.

eb02z06

iTrader: (18)

With a good healthy cam, I usually see 630-640 rwhp with 241 heads and a LS6 intake at only 9 psi. This is with a baby Vortech Si-trim.

I8UR4RD

iTrader: (16)

mrdavids car. prob around that boost level. 317 heads, d1, forged 347. made 728