Metal Props and Electronic Ignition

[mike newall]

Has anyone got any information regarding restrictions placed by the prop manufacturers about running metal c/s props with electronic ignition ? We are not talking high compression or tricked up motor, just electronic such as Electro-Air or P-Mags etc.

[Carlos151]

I?ve got a Hartzell blended airfoil C/S prop on mine. The prop manual shows no restrictions for using electronic ignition.

[pa38112]

Never heard of a concern like this. I?m trying to imagine a difference that the prop would see. The fuel should burn more completely, but I do not think the rate of burn increases with E.I. so I don?t imagine there are torque spikes. -
If anything an E.I. engine will run smoother. What have you heard to make you ask?
I have an O-360-A1A running duel P-mags with a Sensench FP.

[DanH]

And technically, "electronic ignition" has nothing to do with it.

The issue is advanced timing, not the method of generating a spark. A magneto set for advanced timing would net the same result.

It's important to remember, for two reasons. First, there are now multiple EI's available which enable fixed timing or limited advance. Second, an increasing body of evidence says the angle valve engines don't respond to highly increased advance like the parallel valve engines.

[bmarvel]

Originally Posted by DanH

Second, an increasing body of evidence says the angle valve engines don't respond to highly increased advance like the parallel valve engines.

That in itself is ironic, given angle valve engines generally incorporate pendulum absorbers.

Dan:

Not sure what you mean by this. Is the parallel valve more or less forgiving? Please expand a bit on it. I have a P-Mag on one side and Slick mag on the other of the IO-390 in the -14A. My plan is to go to dual P-Mags when the Slick is replaced as I have had zero problems with the P (or the Slick for that matter). Would like to know more about what additional information lies between the lines of your post.

[mike newall]

All good points, well presented.

Our guys seem to have an issue with EI and metal props, I think it may be historic and conservative.

I agree that the method of ignition should make no difference, there has been advice from Hartzell about EI on their props but I don't know how long ago and whether they still apply it.

What I do know is that our dual P-Mag install on our IO-360 has been perfect since 2010, but we are on an MT wood/composite prop which our chaps seem happy with.

We are trying to move forward onto SDS injection/ignition on an IO-540 powered 10. Early days but it will be a lot of work to allow it to be installed. Our lot have a big issue between 2 place and 4 place airplanes which is a historic thing again. Huge advances have been made over here over the last 5 - 10 years, we just need to keep moving forward and satisfying the regulators.

[WAM120RV]

We had this question raised in the UK, the reason given for questioning the set up by the LAA is that they argue that the harmonincs of the crankshaft will be changed.

As a result all applications are treated as what they call prototype modifications, even though similar engines have run for a very long time with the set up. I contacted a number of owners with the same engine, prop as mine and found one with 1000 hours on the set up, with no issues.

Mine being an 0-320 E2A with 8.5/1 pistons, so theoretically a160hp, with two PMags, and at the moment a Sensenich metal FP. A lot of RV and higher performance aeroplanes over here have similar set ups.

[DanH]

Originally Posted by bmarvel

Not sure what you mean by this. Is the parallel valve more or less forgiving? Please expand a bit on it.

Not a question of more or less forgiving. As compared to an parallel valve, the angle valve merely requires less advance to reach optimum performance.

Remember, advance is compensation for finite burn rate. A better combustion chamber and port design (faster burn) requires less advance to result in peak pressure at the optimum point ATDC.

[Full Throttle]

That's what Superior thought when they retarded the spark on the XP-400 angle valve engine from 25 to 20 degrees before top dead center.
Didn't work and they still broke cranks.

[Vansconvert]

I have a hartzell constant speed with dual Lightspeed ignition. I bought the plane from the original builder. Documentation came with the plane from hartzell basically stating there are harmonics at play and for that reason there is a RPM / MP range that is to be avoided.