Frank_at_Hewitts

Hi Jeff and everyone.
My first tiime here.
I'd like to introduce myself, my name is Frank and I am the electronics/tuner at Hewitt's Marine Performance.
I'd like to thank,Jeff for the opportunity to work on his engine, Dustin at whipple for help relating to the whipple setup, and to Bob at mefiburn for the software.

I am here to try to help elaborate, explain a few points and hopefully, contribute to this board, which ultimately leads to more enjoyable boating!!!

The purpose is to try to increase the level and depth of understanding of these engines.
I apoligize ahead of time as this might be a bit long winded, as I will try to sum things up in one posting.

Relating to the peak HP/TQ numbers, it seems that the whipple kits quoted HP/TQ numbers are pretty close. What I mean by that is I believe they are arrived at using a superflow engine dyno or a similar setup. Paul, who owns Hewitts Marine Performance has said for years and years that his dyno numbers are always low as compared to a superflow. The dyno pull tends to be very fast and short on typical engine dyno's and the fairly rapid ramping/acceleration of the engine creates a 6% buildup of kinetic energy on the dyno and therefore makes the HP/TQ numbers larger by 6%. Paul's Stuska water brake engine dyno can make a slow run and hold the engine at a steady rpm to get the least amount of kinetic energy and therefore a more steady and clearerTQ/HP number.
Even this year, we have had numerous people comment that Paul's numbers are not as high as "so and so", yet they lead races, continously outperform and win.

The fact that I had to throw so much more fuel at the engine, above the fuel maps that the engine came with, and it was running rich to boot, especially , holds a good testament to how much better Paul made the Dart heads flow from as cast. AIRFLOW makes HP. Since this is a supercharger, and therfore a fixed displacment/rpm of air volume, unlike turbo's, the airflow from the supercharger will not increase because of the engine RPM limit. BUT, what this does show is that a high quality engine build, properly done will make the same or more TQ/HP at a lower boost......since the engine consumes more air than before, the boost level has to be lower, the engine is simply more efficient now and therfore less restrictive. A natural and inherent by-product of less boost is less heat and more engine life.

We did all the work, knowing that we were not going to go to a bigger supercharger pulley to bring the boost level back up to the stock whipple kit. The engine will obviously make more power at 6.5-7 psi than at 5 psi.

The HP/TQ numbers of the dyno graph are SAE corrected and are acquired at the start and during the course of the day. SAE corrected, meaning to air temperature, humidity and barometric pressure.

Jeff's 502 BBC reaches ~138 Kpa or 5.3 PSI of boost from 3000 RPM to 5800 RPM.

If the 6% kinetic buildup/increase is placed on the720HP/753 ft-lbs numbers they become 763 HP/ 798 TQ....if a bigger lower pulley was used and brought the boost back up to 6.5 psi, the engine should produce numbers in the 780HP/ 815TQ range on Paul's dyno and 825 HP/ 863 TQ range on the typical superflow dyno......
This engine does use and was tuned using 91 octane pump gas.
Well, thats about it, hope this helps.

Panther

Thanks for the info.

What's interesting is my engines always showed slightly more peak HP/TQ on steady state pulls than full pulls.

Canada Jeff

Thank you for posting Frank, and welcome to the site.

This engine build has educated me big time about supercharged engines. I feel ' 100% piece of mind ' with this engine.

I still have to water test her, but once I do, I'll get you out on her to plug your lapp top in and make sure you like what you see.

Thanx for posting, and again, welcome to the site !

Frank_at_Hewitts

Thanks!
Yep, we'll get together, when everything is sorted and the boat is in the water, then we can hone in on the behavior of the flow of water through the system, and therefore, operating temperatures, in real time and we can then see what we have , and make adjustments, if need be.