RPM of small gas engine

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Powerhorse pump requires 5.5 HP engine with 2 7/16in.L, 3/4in. straight keyed shaft, 5/16in.-24 tapped hole and 3 5/8in. bolt circle.

Very similar to the Pacer Pumps I use for high volume applications:

the straight shafts on all the different mounting and drive methods including electric motor drive.

I am quite familiar with pool/spa pumps, have two complete 1-1/2 hp pump/motors and two spare motors > >> Bruce wrote:

Do you know why? Compression, carburation, ignition?

To qualify engines, they take a couple sample engines out of the box (just like they would on the assembly line), put it on the dyno, fire it up, adjust the dyno to the max load it will handle for a 6 hour (full load) break in period. Then they run a full torque vs rpm curve for the engine. Simple math gets you the max hp.

The dyno guys tell me that the B&S Intek 10 HP engine we brought in ran out at 9.4 hp on a "10 HP engine", one of the best that they had seen. My students were fairly shocked that it was that low. The dyno guys said they had seen similar tests running at something like 55%.

Any of the standard things would improve the numbers: bigger jets is probably the first thing on the list since these engines are designed for minimum fuel consumption. The engines we were playing with had fixed jets, no replacement jets available from the mfg. Pretty lean. These engines were used for class racing, no mods allowed. We figured that balancing, slippery oil, and larger jets would have pushed it to an easy 11 hp. Tuned exhaust rather than stock muffler would add another couple ponys.

We didn't try any of the 84 to 85 octane gas we get > >> ...

Needs to be corrected for "standard atmosphere" which is 70F at sea level. At 70F and sea level that 9.4HP "10HP" engine would quite likely excede its rated power.

Actually, premium gas goes not NECESSARILY have lower power density - and up here if you want to guarantee no Ethanol you buy Shell PREMIUM.

MOST fuel vendors in Canada lace the low octane stuff with up to 10% Ethanol. Mixed with 0% premium, you get 5% mid-grade.

MOST small OHV engines actually prefer high-test unleaded fuel, possibly for that reason.

Most 2 stroke (like snowmobile) eng>> >>> ...

Doubt it. The test cell is room temp, elevation is 835 feet.

Not here, many states mandate 10% ethyl alcohol. The Colorado fuel mentioned is only sold at altitudes above 4000 feet, the thin air allows the lower octane in a carburated engine. Doesn't fool a good computer controlled engine with O2 sensors, hence the car mfg recommendations to not use the stuff. But it does improve the power output in low compression, lean jetted small engines.

But the fuel BTU density is such that lower octane fuels have more BTU's per volume, hence make a richer air:fuel mix. The small engines we are talking about have compression ratios around 7.5:1 or 8:1, more than low enough to handle the low octane fuel.

Most snowmobile engines are much higher performance than the typical one lunger 4 cycle lawn or small industrial engine, like or need the high octane.

I think they were refering to 4 cycle engines, to differentiate them from two cycle engines like you'd find in chainsaws and string trimmers... --Glenn Lyford