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Old 15 October 2004, 08:44   #41
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Quote:
Originally Posted by jwalker
The literature refers to an absorption brake powerhead dyno so I guess they are powerhead figures.
Don't manufacturers quote the power at the prop?

John
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Old 15 October 2004, 09:02   #42
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..if we didn't get the Dyno figure we were expecting for the 'bike we did what any proper engineer would have done....... tried another Dyno...
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Old 15 October 2004, 10:38   #43
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Quote:
Originally Posted by Rogue Wave
getting back to the original question ....then what about a fantum evo
Nice boat and fast. Hull and looks similar to the FALCON and is 2 or 3 times more expenssive. But a good boat nevertheless
Is there a resons that there aren't many of them Fantom Evolutions about? Just asking
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Old 15 October 2004, 10:52   #44
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Been down to the engineers today and we had a flick throufh some data they have from there Dyno measurements and also had some crash lessons on reed valves, cranck shafts and compartion ratios.

The measurements these people do I assume are all at the prop as this dyno thing they have you fit on the prop and they have to submerge the leg in the water tank for that.

Any way you may be interested to know that data that they had from a 150VMax 2-strokes showed 167 bhp and the data from three 200VMax showed three different results 226, 228, 231. In the manuals the manufaturers showed 150bhp and 200bhp respectively.

Quote:
Originally Posted by jwalker
Except for an increase in engine capacity, the only engine modification which will give increased power over the whole of the rev. range is an increase in compression ratio. Generally, mods give extra power at increased engine revs. Note the word 'generally' because this is not necessarily a fixed rule.
On a two strokes engine I was told that this is always the case. More comprestion more power better fuel economy. And to increase compression ration you need to pack the cranck case.
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Old 15 October 2004, 11:31   #45
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Quote:
Originally Posted by Jono
Yanmar "315" engine is only rated at 40 C at the injector. I just wanted to know what a standard operating temperature was in this region...........
As for the outboards, if we take transmission losses into account ........
I dunno about that method of rating. The evapourating diesel will have a cooling effect but the cylinder air temp has to be high enough for combustion when the diesel is injected. Maybe the injectors stay cool but since burning is taking place against the injector, it's difficult to imagine it does.

Volvo recon a loss of 12.9hp through the sterndrive at maximum revs. Given two u/j's and 2 right angle bevel gear sets I would guess at a typical 200hp lower unit absorbing about 6-7-8hp max. Since the losses turn into heat energy, that's still a fekkin lot of heat to dissipate through the casing! About 5 electric fire bars glowing red hot! So, no, the powerhead figures are still at variance with the quoted rating.

-------------

JK, yep the current hp rating for outboard motors is taken at the prop. The figures in the table are independent measurements. Nevertheless, since the lower units losses of the same make and, I would guess, of different makes are similar, it's easy enough to deduct 6 or 7hp from the figures.

-----------

Dirk, could the 300hp rating have been at the drive output and the 315 at the flywheel? Just guessing.
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Old 15 October 2004, 11:39   #46
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Originally Posted by Manos
And to increase compression ration you need to pack the cranck case.
Pardon?

That's the problem with crash courses.

Packing out the crankcase used to be done to increase the charge pressure and, hence, the combustion chamber pressure but it doesn't increase the compression ratio. In modern 2 strokes, there's not much space in the case to pack, but maybe it's still done.
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Old 16 October 2004, 03:59   #47
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Quote:
Originally Posted by John Kennett
there's no way any manufacturer is going to understate the output of their engines . . .
Perhaps for racing? Almost inconceivable though.......

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Old 16 October 2004, 07:11   #48
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John Unfortunately we didn't race due to a serious illness.
Of a mental nature, no doubt.
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Old 16 October 2004, 07:22   #49
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As with all sterndrives, the Yanmar 315 is crank rated, not propeller shaft, so it's only bringing it closer into line with the way OB's have been done since 1985.
Also, a Yanmar has a cooler on the return fuel line (to the tank) presumably to help keep tank and fuel supply temp's nice n low.

If those fig's JW posted are powerhead power outputs, they'd fall fairly well in line with prop ratings for most of them, I can't believe, as JK says, that it's common practice to understate power output, and if they did as far as power/badging, i'm sure they'd get some advertising value from the extra 'free' power.

IMHO
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Old 16 October 2004, 17:22   #50
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Since the late 80's I thought.

Quote:
Originally Posted by John Kennett
Don't manufacturers quote the power at the prop?

John
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