"Jim Spanfeller" (awesomeaustinv)
04/01/2020 at 22:12 • Filed to: None
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"Jim Spanfeller" (awesomeaustinv)
04/01/2020 at 22:12 • Filed to: None | 1
| 8 |
It’s a 160 ci two-stroke marine v6 built for boat racing purposes, it revs to 10,500 rpm, it should be making around 400 hp if my facts are correct. Stuffing it in a Miata might take some doing, as I think the exhausts exit out the “top” and the intake is on the “bottom”. But if these guys can stuff a two-stroke marine v8 in a Volvo, then I think the same could be done with this v6 in a Miata:
Man, some of those two-strokes can absolutely rip...
Wrong Wheel Drive (41%)
> Jim Spanfeller
04/01/2020 at 22:44 |
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Marine engines in cars just makes me think of the mazdarati!
RacinBob
> Jim Spanfeller
04/01/2020 at 23:23 |
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One of the challenges is that it is being cooled with 80 degree water. It might be challenging to run it very long at load.
jimz
> Jim Spanfeller
04/01/2020 at 23:27 |
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yes, the intake is at the bottom of the crankcase, and the exhaust dumps into a “chest” inside the vee. Not sure if DI 2 strokes benefit from expansion-tuned exhausts like carbureted ones.
The flywheel is also on the opposite end of the output of the crankshaft.
Distraxi's idea of perfection is a Jagroen
> Jim Spanfeller
04/02/2020 at 00:33 |
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There are ways to deal with a top-exit exhaust:
(also, just to do your head in, the engine in that is a re-inverted inverted aero engine. In its original home (a Tiger Moth) it had the exhaust at the bottom and the crank at the top)
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jimz
> RacinBob
04/02/2020 at 09:27 |
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they still have thermostats and run at 180-200°. you would need to come up with your own water pump, radiator, and fan design but closed loop cooling would still work fine.
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RacinBob
> jimz
04/02/2020 at 15:00 |
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I’ve thought about it for a rac ing application and I think it is harder than you think.
I work in HVAC and f or a radiator, it’s hard to get within 30 degrees of ambient. So lets say 200 degrees water is entering the radiator s o with at 11 0 f air entering at track level , you can cool only to 140 water going to the engine. If the goal is 200 f water, that is 60 degrees rise that the water is taking through the engine .
Now a boat doesn’t have a radiator, it just takes water off the surface and the hotest surface water is 80 f. That 80 f. water g oes to the engine and leaves at 200. So the heat rise for that water is 120 degrees rise. The boat motor temperature rise for a g iven flow is twice that for a car.
So if the heat load is the same, an outboard needs 1/2 the GPM
to cool the same HP auto engine.
That is the question. If you put a radiator closed system on a boat motor, you will need to double flow and therefore the question becomes can you put twice times flow through a boat motor?
I have to wonder because do you notice how compact the head of a 200 hp outboard is? They are tiny. I believe the reason is because they only have to flow 1/2 the amount of water. I think those head might have a hard time flowing more because of that. In otherwords, you may need to put in a water pump capable of making 30 PSI pressure. Not easy. I suspect it explains why you do not see Lemons card and sports racers with outboard engines.
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jimz
> RacinBob
04/02/2020 at 16:12 |
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I have to wonder because do you notice how compa ct the head of a 200 hp outboard is? They are tiny.
they’re tiny because they have no valvetrain. these are two-strokes, the heads are just combustion chambers and a water jacket. Mercury’s four-stroke DOHC cylinder heads look just like the ones on a car.
and an outboard doesn’t just blast cold 70-80°F water at full flow through the powerhead; when you first fire it up the pump down by the drive end sucks up water and fills all the passages in the powerhead. As you get underway it circulates until the water reaches the thermostat regulating temperature, at which point the t-stat opens and starts letting hot water out. Water the t-stat lets out is made up by fresh water. The thermostat will open and close varying amounts to keep the water temp where it needs to be. The important thing is that the thermostat has to restrict the hot water exit and keep some recirculating through the powerhead or else it would run far, far too cold.
I mean, plenty of boats use small block Chevy engines in sterndrives, and they have no problem being cooled by a closed-loop system. They just run the same way; the t-stat keeps water circulating until it needs to open and let some hot water out.
the other limitation outboards have is that they can’t run much cooling system pressure, so the t-stat has to open at a lower temp to prevent the water from boiling.
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RacinBob
> jimz
04/02/2020 at 19:50 |
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Good point about the head size . I guess all of our club big outboards are 2 strokes including the 250 hp,
But I wll say that if the incoming water is 60 degrees warmer, you do need twice the flow throughput in the engine.
. An automotive engine with a closed system is designed with that in mind. A two stroke is not designed for that. Will it be a problem, I am just asking the question.