monoblade throttle body
12-16-2020, 09:43 AM
#21
Regarding runner length, are the 500 & 525 upper's the same? I just find it odd that most mod the 502 MAG MPI setup, shorten the runner length - I haven't noticed anyone doing this with the 500/525 EFI. Just guessing here, but the the 500/525 EFI runners look longer to me when you consider that the upper intake extends the runner length giving it even longer runners than the 502 MAG where the runners protrude just a bit into the plenum. Of course, I am assuming that the longer the runner length, the more power in the lower rpm range. Am I missing something here?
Last edited by liquidlounge; 12-16-2020 at 09:49 AM.
12-16-2020, 10:16 AM
#22
Registered
Barrett,
I think most guys would jump at an opportunity for a 25 hp gain on a stock motor if it was reasonably priced and relatively easy to obtain, myself included.
Several years ago I was told of a general rule-of-thumb formula for figuring speed gains vs horsepower gains. It is not absolute but seems to be pretty accurate for sport boats: the expected percent gain in speed would be equal to half the percent gain in horsepower. So if you added 25 hp to your HP500, a 5 percent gain, you could expect a 2.5 percent gain in speed. You can obviously use the formula in reverse too. Say you wanted to pickup the speed of your boat by 10 percent, you would have to increase the horsepower by 20 percent.
Hope this helps.
Rich
I think most guys would jump at an opportunity for a 25 hp gain on a stock motor if it was reasonably priced and relatively easy to obtain, myself included.
Several years ago I was told of a general rule-of-thumb formula for figuring speed gains vs horsepower gains. It is not absolute but seems to be pretty accurate for sport boats: the expected percent gain in speed would be equal to half the percent gain in horsepower. So if you added 25 hp to your HP500, a 5 percent gain, you could expect a 2.5 percent gain in speed. You can obviously use the formula in reverse too. Say you wanted to pickup the speed of your boat by 10 percent, you would have to increase the horsepower by 20 percent.
Hope this helps.
Rich
How very close that is in comparison to my old proven theory. 12-13hp typically equates to 1 mph. That’s not x 2 for twins! Hull efficiency, weight, length all play a factor however it’s always been very close from my 24’ singles to 38’ twins.
12-16-2020, 10:48 AM
#23
Registered
Regarding runner length, are the 500 & 525 upper's the same? I just find it odd that most mod the 502 MAG MPI setup, shorten the runner length - I haven't noticed anyone doing this with the 500/525 EFI. Just guessing here, but the the 500/525 EFI runners look longer to me when you consider that the upper intake extends the runner length giving it even longer runners than the 502 MAG where the runners protrude just a bit into the plenum. Of course, I am assuming that the longer the runner length, the more power in the lower rpm range. Am I missing something here?
