Hp rating and parasitic drag.

[lots of boats]

When hp rating was standardized by dyno testing at the prop shaft what were the parameters, if any, other than rpm of the engine? What RPM are they tested at and are all the on board systems such alternator load, or air pump load somehow calculated into the hp rating so that when you have motors with electronic or other injection systems, should they be producing the same hp as a carburated engine?

 

[JB]

Re: Hp rating and parasitic drag.

No calculations other than converting torque at the prop shaft to HP based on rpm, LOB. Everything on the engine is there and drawing power normally.

 

[chevyjet]

Re: Hp rating and parasitic drag.

I`d sure like to see a proper independent dyno test on all the new outboards, showing torque and BSFC at all rpm, cause some are way stronger than others with the same rateing.

 

[lots of boats]

Re: Hp rating and parasitic drag.

Hi
I just read a comparison of the optimax, E tec, and TLDI 90's rated hp at wot, they all lost some hp, and were rated at less than 90. This wasn't a very complete test, you will never guess where in the heap the Tohatsu TLDI 90 was buried.

I am still looking for a graph that shows the hp curves of bsph/engines rpm., including the curve for a carbed engine. This is how I would like to compare engine power rating, and to get some idea of the cost of the operating systems. I would also like to see which one has the most grunt at various rpm when a full load is applied to the alternator.

Cheers.

 

[Rancherlee]

Re: Hp rating and parasitic drag.

there really isn't much parasitic drag, an 100 amp alternator on a car sucks less than 2HP at full load on a car engine. I wouldn't think a boat at 20-40amps would draw over 1hp.

 

[JB]

Re: Hp rating and parasitic drag.

Because of tiny differences in manufacturing and assembly not all of a particular model outboard will dyno an identical curve. NMMA allows a +/- 10% range for rating peak HP of production engines. You seem to be savvy enough to know that rated peak HP is of little consequence in real world operation.

I do doubt that alternators are loaded at max amps during the tests.

You are really digging deep in search of some new basis to bad-mouth Tohatsu, aren't you? Not only is it getting old, it is getting annoying.

 

[whitewater90]

Re: Hp rating and parasitic drag.

I do not see why anyone finds this annoying, all these guys are doing is comparing some outboards and sharing ideas about some engines, I also feel the TLDI is a little week for a 90 and i would like to know why just as much as the next guy.

gooday