Quote:
Originally Posted by eschaider
Here is the rationale behind my guess Gary.
To make 100 HP it takes 10 lbs of air per minute or 600 lbs/hr depending on the scale you wish to use. The 7.3L Godzilla displaces 445 cubic inches. At 7600 rpm assuming 100% volumetric efficiency the engine should make a corrected (to STP) 730 HP because it processes 73.0 lbs of air per minute at that rpm and 100% Ve. If you give it and additional 8% for ram tuning you have the 789 HP figure.
The 789 number is probably a result of the short runners tuning at the elevated rpm and enhancing the Ve number because of the ram effect. The video did not say if the power numbers were corrected nor which SAE standard was used for the correction (SAE J1349 or SAE J607) — assuming they were corrected.
J1349 corrects to a temperature of 77˚F and a barometer of 29.31 in Hg. J607 corrects to STP, 60˚F AND 29.92 in Hg. The J607 correction will yield 4% more power than the J1349 correction because of the cooler temperature and higher barometer.
When you boost the engine to 2 atmospheres (~15 psi) you increase the volumetric efficiency by essentially 100%, which should put the power at ~1460 rather than 1580. The reason for the reduction would be the loss of ram tuning in the blower manifold vs the very nice n/a manifold. If the intercooler does its job, you should see the doubling. If the intercooler is really good you can get a little bonus like the ram tubes on the n/a manifold provided but for a different reason.
That's the essential logic behind my guess at the likely power level the engine will produce. One piece that is missing is the power to drive the blower. The new 3.0L Whipples have a new rotor profile that produces a substantial reduction in IAT2 temps (post compressor charge temperature) along with a substantial reduction in the power the compressor consumes compared to earlier designs.
The whisper/guess numbers I have seen on two different cars running the new 3.0L Whipple compressor are 75 to 85 hp to drive the blower. That means whatever the dyno shows the blower has already siphoned off some of that power to supercharge the engine.
The other unknown is the efficiency of the intercooler. The inverted blower positioning and the larger, dual (I believe) intercoolers (one for each cylinder bank) are capable of significantly dropping IAT2 temps to essentially ambient or cooler especially with unlimited cool water in a dyno room. That kind of IC performance can significantly boost indicated hp.
I am quite interested in seeing what the engine actually produces. I find a lot to like in this new Ford engine — especially with a PD blower.
Ed
|
Here is their next video with the engine supercharged. Click here =>
Supercharged Godzilla The dyno measured 1450 HP @7000 rpm which is a whisker down from the 7800 rpm number they used for the n/a version of the engine.
The boost was 2 BAR (2 atmospheres) which should have doubled the power. If you can produce 790 @ 7800 a linear reduction to 7000 would be about 710 HP @ 7000 rpm. Double the mass airflow and you double the power which calls for 1420 HP @ 7000 rpm. The dyno showed 1450 HP. The difference was close enough it is likely atmospheric differences. Additionally at 1450 HP the dyno's margin of error could easily be 15 to 20 Hp. Quite impressive!
I was a bit disappointed when he was asked about compression and he deftly avoided speaking to the actual number he used. I would bet dollars to donuts he reduced the compression from the n/a 12:1 number in the previous test. My guess is he is right around 9:1 which would make sense at that boost level — even intercooled.
All things considered, a very impressive engine!
Ed