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Originally Posted by J DAWG
Paolo, what kind of hp increase is normally seen per pound of boost. I know Treynor has put out some equation to determine or speculate what kind of output a car would have at certain boost levels.
Someone previously said this car would be around 33 hp/lb if the car started with 480 hp.
John
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John, the way to calculate the theoretical maximum increase in horsepower is the following: PSI+ 14.7 PSI/ 14.7 PSI = multiplication factor of stock horsepower ASSUMING 100% EFFICIENCY ie no heating up of the air charge, no parasitic power loss to drive the supercharger off the crank/etc......
Another thing to consider here is the fact that there is a decreasing marginal return for each additional # of boost. In simple terms, the 1st # of boost gains you the most with each additional PSI yielding marginally less RWHP than the the one before it.
So any calculation of total RWHP gained divided by the # of PSI is an AVERAGE gain of RWHP/PSI.
Here is a simple example:
@ 14.7 PSI, you would have 14.7 + 14.7/ 14.7 = 29.4/14.7 = 2
In simple terms, this is 2 times the original power output of the engine.
In the real world, this never happens in a supercharged application.( There are certain turbocharged applications where you can actually make MORE than the theoretical maximum)
The most RWHP I have ever seen on a stock engine with cat back is around 440 RWHP.
This 885 RWHP minus 440 RWHP would be a gain of 445 RWHP. (Slightly more than double the power)
Some #'s I can quote for sure would be those of my car.
My car made 500 RWHP and 504 RWTQ in the N/A mode wih 8.5:1 compression.
at 13.5 PSI with {the intake manifold cut in 1/2, polished and ported and welded back together==>added after the initial N/A dyno pulls}, heads, cam, 1.7 T&D roller rockers, being bored .010 over, fuel system to supply the power, 1.75" headers/no cats/side exhaust, and a very large and efficient air-air intercooler, my car made 887.7 RWHP and 864.5 RWTQ.
So 13.5 + 14.7/14.7 = 1.9183673 (theoretical) multiplication factor
Hypothetically, I should have made 1.9183673(500 RWHP) or 959.18 THEORETICAL RWHP and 1.9183673(504 RWTQ) or 966.85 THEORETICAL RWTQ
My car made 887.7 RWHP or 887.7/959.18 which is 92.55% of the theoretical maximum for HP==> This equates to a 7.45% loss in efficiency.
My car made 864.5 RWTQ or 864.5/966.85 which is 89.41% of the theoretical maximum for RWTQ==> This equates to a 10.59% loss in efficiency(Some power to drive the supercharger I would imagine)
{I also just realized I added the intake after the initial 500 RWHP/504 RWTQ so my efficiency might be a tad lower than the #'s I have just listed}
Now back to the matter at hand
Even if '96 GTS's car made 440 RWHP with the stock headers and cat back, the theoretical maximum for RWHP would be 13 + 14.7/ 14.7 = 1.8843537 multiplication factor
So 1.884357 x 440 RWHP = 829 theoretical RWHP
let's say 480 RWTQ
So 480 x 1.884357 = 904 theoretical RWTQ
'96 GTS made 6.75% more than the theoretical maximum for RWHP and 5.973% less than the theoretical maximum for RWTQ.
'96 GTS's car made 34.23 average RWHP/PSI and 28.42 average RWTQ/PSI.
My car only made 28.72 average RWHP/PSI and 26.7 average RWTQ/PSI.
To put this into perspective I believe Smokin V-10 with stock compression, stock heads, 1.7 T&D's, headers/no cats made somewhere around 775 RWHP and 765 RWTQ on 13 PSI. I think his car made somewhere around 460 RWHP and 510 RWTQ in the N/A mode. I could be slightly off on his #'s but the point is clear:
775-460/13 = 24.23 RWHP/PSI 765-510/13 = 19.61 RWTQ/PSI
Another thing to consider here is that the pulley that made 13 PSI on Smokin's car made only 10 PSI on my car.
This means that the headwork and cam on my car make for a larger volume to be filled with the SAME CFM of air from the same blower, crank pulley and supercharger pulley==> So when I have 13.5 PSI, I am surely flowing more air than Smokin at his 13 PSI.
The moral of the story here is that the headwork and certain other modifications INCREASE the volumetric efficiency of the motor.
So stock heads, cam, exhaust manifolds/etc..... are obviously LESS volumetrically efficient than heads that have been polished, ported and have bigger valves, bigger cam, 1.75" primary tube headers/no cats etc.....
I made 4.49 more RWHP/PSI and 7.08 more RWTQ/PSI than Smokin(We both have 1.7 roller rockers)
Now '96 GTS makes 5.51 MORE RWHP and 1.72 MORE RWTQ than me with everything being BONE STOCK is just a little hard to believe.
If I am off base here, somebody please tell me where I am missing the point.
P.S. '96 GTS: I am not trying to be a prick here, I just do not understand how these #'s are possible in the context of what I know about the physical laws of forced induction.
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That don't sound right.. Have you stepped up on the pulley? Also you are running the 2.75pulley which is 2 steps smaller that the one I am running, and i see 12psi with ported heads and headers. RSI tried the 2.75 and they were getting 16psi constantly on highly modded Vipers.. so from you setup you should be seeing 16+ psi. Are you sure you are not giving out all the info on your mods.