IO-360 low static RPM

mick · #1 04-10-2009, 07:29 AM

Finally completed my first engine run. What a buzz..
I have run the engine for 30 minutes in-accordance with the instructions from the engine re-builder, a well respected shop here in Australia. My only concern is the static RPM seems low, It will only produce 2000RPM max at WOT. The engine is fitted with a metal Sensenich prop 72 x 85 pitch as sold through Vans. Unfortunately I don't have MAP so are unable to see what the engine is really doing.
Can anyone recall what static RPM is normal for this combination.
I would hope that once the engine has bedded in that the RPM (static) would increase. Is this hopeful thinking?

Cheers
Mick Haynes
VH-ZVR
RV7A IO-360B1E

hevansrv7a · #2 04-10-2009, 10:19 AM

My 180 HP Superior IO-360+ has a cruise prop (Catto) that produces 174 KTAS at 8000 MSL at 2650 rpm and about 2150-2200 static or in a climb. I would expect your prop to give similar results, eventually, as this is just a hair faster than "book" value. Based on that, I'd guess your static is a little low. That said, static means very little, since, the experts say, the blades are stalled anyhow. The first question should be: is it time to worry yet?

steveKs. · #3 04-10-2009, 11:14 AM

Have you confirmed your RPM with another source? Could be that your tach is off.

mick · #4 04-10-2009, 04:34 PM

Quote:

Originally Posted by steveKs.

Have you confirmed your RPM with another source? Could be that your tach is off.

The Tacho is the standard Vans Gage with engine driven transducer. I have not cross checked the readings with another source. What would be the best way to do this ? I could fit another tacho temporarily I suppose.
Is there a way of using an automotive Tacho such as the ones used to tune your car, some are fitted as part of the timing light ?

Mick H

Darylat8750ft · #5 04-10-2009, 05:37 PM

The model airplane people have tachs that are inexpensive and reasonably accurate. Just point them at the prop.
Daryl

Greg Arehart · #6 04-10-2009, 05:40 PM

Mick,

I have basically the same engine and prop, and turn around 2100 on the ground IIRC. With that pitch (cruise), you might expect a bit slower turn than someone with less of a pitch on the prop. Regarding a second tacho, one can buy a fairly cheap one from places like Aircraft Spruce (not sure what equivalent you might have in Oz) that operates on light pulses.

greg

hevansrv7a · #7 04-10-2009, 05:50 PM

You can check it at 1800 or 3600 by running it at night with a fluorescent light illuminating the prop. It will freeze at speeds that are multiples of 60 cycles per second (in the US and Canada, anyhow). You can also use a handheld video camera if it will tell you the shutter speed (standard in the US is 30 frames per second, but many cameras allow you to speed that up.

mick · #8 04-10-2009, 06:30 PM

I should have added more detail about my set up.. It maybe the problem.
I have a IO-360 B1E that has been modified to forward induction, due to the new positioning of the fuel control module I was unable to use the Vans induction fiberglass duct. The end result is a 3" scat tube duct to a standard air cleaner.
Also I am running Mogas 94 octane and set the timing at 23 degrees and not at the recommended 25 degrees. I have found that this model of engine is certificated for 91-94 octane but certified for 100 octane.
I will run the engine without the air cleaner first and then reset the timing to 25 degrees, this way I hope to see if any of this makes any difference.

Thanks for all the input and I will post the results from the next run.

Cheers
Mick Haynes

osxuser · #9 04-14-2009, 11:33 AM

Ditch the scat tubing! If that ever collapses in flight you will loose the engine. You need either sceet (Double wall scat) or a fiberglass duct. I suggest the latter.

As to your problem. I wouldn't doubt that between 94oct and the timing, you could explain 2000 static. The parallel valve should be fine on mogas at 25? provided fuel injection system is compatible with Mogas.

mick · #10 04-14-2009, 09:36 PM

Just an update to the low static RPM that I was getting.
After running the engine for an hour with no change in WOT RPM, I leaned out the mixture just a small amount and the RPM jumped to 2200. Seems it is set to rich.
The only other problem now is an over volt issue, so the alternator is off to be reconditioned.
I agree about the Scat tubing and it is something I will have to fix before first flight.
The IO-360 B1E is certificated for 91-96+ octane so the timing will be adjusted to 25 degrees as the manual specifies. I was erring on the side of caution by setting it at 23 degrees.

Thanks for all the input.

Cheers
Mick Haynes