Originally posted by Peter Campbell
If this is still about HP #- Use the "seat of the pants dyno" With real #s- a 1/4 mile track. Start stock. Do 1/2 hour of off roading- Immediately line up and do three runs. Put on one or the other systems, do another 1/2 hour of off roading, put weight in for the fuel burned/spilled (7 lbs per gallon ) and line up three more times, same driver same truck same day- do not tell the driver what his configuration is. Then the other system. same deal. If you want to get fancy do it again with a pusher pump system no air separation. If the truck started out bone stock with a failing lift pump, the numbers would be good- until you compared with the stock plus pusher. There would be some improvement even with the lift pump working right. The improvement may be very small with a pusher pump ( no air separation ). If the pressure is maintained high enough the air pockets and cavitation should be significantly decreased- not eliminated.
I for one think of the dyno as a measuring device- not the end all. Performance at its job is the real test of machinery. You do not drive dynos you drive vehicles. This was even mentioned in an old DC publication ( that is dodges Direct Connection , not Daimler Chrysler ) About people testing sprint engines with a 440 and quadra bog ( AKA quadrajet), the 440 on dyno did a good 150 HP more than the 383 with a small holly. The 383 with the small holly was faster-on the track- where they raced than on the dyno where the 440 did better. The 3/4 second of bog time and the extra tire spin and loss of traction slowed down the 440 car. How could I loose- my dyno sheet is better.
So shake the fuel ( off road ) and then test on a roadbed ( 1/4 mile). This would test the advetised characteristics of the system.
At work they handle the air entrainment concern with a " head tank " 10 feet above the engine. After the fuel forwarding pumps fill the 150 gallon head tank it can sit quietly and settle. Good for about 1/2 hour of run time. If you have a stationary power plant this works very well. Air pockets do not delay the injection event very much in a 900 RPM machine with a 1050 RPM redline. If you test the vehicle stationary ( not doing its designed job ) then the test does not factor in all the things that need to be tested. For an air filter comparison it is not loosing much accuracy, for a product designed to deal with fuel sloshing it is not testing much at all. Put the entire dyno jet on a shake table, that will properly simulate more of the conditions.
This seems to be common sense- at least to me. But one of the venders got severly flamed for suggesting that maintainig a vehicle stationary by strapping it to a dyno will negate most possible gains froma system designed for fuel slosh concerns, Then got flamed again because the G-tech is a accelerometer derived computer box, and not a real big impressive and expensive skid- when he wanted to test a VEHICLE IN MOTION.
Sorry to those that race thier dyno charts- it is only a measuring tool- with limitations.