Engine Rpm

johnfireball · Post by **johnfireball** » Sun Apr 13, 2008 9:14 pm

Hi all,
my engine was set to run at 3000rpm probably on a genset. There is a wired adjustment screw for setting. Would It do any harm to up the rpm another 600 or 700revs? I assume it was made to run all day at 3000 non stop whereas in the bike it will be subject to varying loads. I plan on a second tank with a changeover valve for the veggie oil and believe this must be preheated. Would a fuel pipe coiled around the exhaust suffice? Its a direct injected engine.
Thanks John

oldbmw · Post by **oldbmw** » Sun Apr 13, 2008 11:04 pm

It is my belief all those stationary engines will be happy at 3000 or 3600 rpm. The reason I say this is because for a generator (alternator if you need to be precise) in Europe the motor needs to run at 3000 rpm to make the 50hz waveform required. In USA ( not the small town near Tokyo ) alternators have to run at 3600rpm to make the 60Hz they use. There is no sense in making two different motors so similar, so it will be down to max revs setting on the govenor.

Also as small engines are often used in place of electric motors the same situation applies. European motors run at 3000 rpm ( two coil) Usa ones at 3600 rpm.

oilburner · Post by **oilburner** » Sun Apr 13, 2008 11:11 pm

If my suspicion is correct, the 3000 vs 3600 is to accommodate 50 Hz vs 60Hz AC generators. If your engine is available in either RPM range, you should be able to increase max RPM, but you might also have to change the injection pump timing - I believe there are different shims for this purpose for each engine.

Thinking out loud here - I wonder how long the the engine would run before blowing up if the max RPM was bumped up to 4000 (assuming the valves didn't float first).. Of course the cast flywheel would have to be exchanged for a machined one. The downside to an engine with fixed timing is that increasing the timing for 4000 rpm (outside design specs) would probably result in degraded low speed performance i.e. even more smoke, rougher idle overheating etc.

Post by **Fiddler** » Tue Apr 15, 2008 7:18 pm

John,

I followed this advice with my industrial diesel engine which was rated at 3000rpm. Adjusted the govenor and set it at 3600. No ill effects so far, seems to run as well as before, maybe timing is factory set as a compromise between the two on some engines?

Mark

johnfireball · Post by **johnfireball** » Tue Apr 15, 2008 8:30 pm

Thanks all for the vote of confidence I will be turning up the rpm.Any ideas on running the veggie oil?
John.

Darren · Post by **Darren** » Thu Apr 17, 2008 3:06 pm

Unless your engine is indirect injection (or a VW group Tdi) you will need two tanks one for diesel fuel for starting until the engine is warm then switch to veg for the bulk of your journey before switching back to diesel for a few miles before you shut down so that the injection pump, injection lines and injector are all full of diesel ready for the next start.

Indirect injection engines and VW group Tdi engines require modifications for reliable operation.

johnfireball · Post by **johnfireball** » Thu Apr 17, 2008 9:12 pm

Hi Darren,
What about preheating? my engine is direct injected.
John.

Darren · Post by **Darren** » Thu Apr 17, 2008 9:51 pm

Hello John,

I might consider it if the whole engine especially injector and the fuel in he injector was pre heated before starting.

Cold starts are the time when all the bad things happen.

The cold oil is thicker and has a higher surface tension so does not inject correctly. Instead of a nice fine mist the injected fuel will consist of much larger droplets that will travel further and not ignite or burn as quickly or as completely

Add that to the cold metal of the engine that takes heat from the air as it is compressed degrading combustion - the cold metal of the injector which will tend to cause part burnt fuel to stick to it and your looking at trouble - may take a while - maybe not.

Poor combustion = much more unburnt fuel. This fuel will cause deposits on injectors. Deposits in the ring lands and get past the rings into the engine oil which eventually will turn to jelly when cold.

Deposits on the injector cause degraded fuel injection and deposits in the ring lands will eventually cause lower compression and thus lower temperatures in the combustion chamber leading to further degraded combustion.

Best if everything is hot before you start to run on vegetable oil. Some engines with combustion chamber glow plugs can be reliably started in ambient temperatures that donot regularly get below freezing.

This is the way I understand it.

Best

Darren