Fuel injection or electronic ignition

[Toobuilder]

Which brings us back to the electronic ignition. It allows the red knob to act as a throttle. Leave the black knob all the way to the stop and pull back to 150 LOP if you want to go slow. Of course, keeping heat in the engine will become a big problem as your CHT will plummet.

[zav6a]

10inoz

I agree that with fixed timing 10-20 lop at 10k will wring the most crankshaft energy out of a unit fuel burned. I suspect though that with advanced timing, as with EI, the optimal point is a bit leaner. I have yet to find data though. Maybe Tom has some dyno pulls he has not shared?

[RV10inOz]

Originally Posted by Dorfie

David,
Are you saying that once you have established a F/A ratio at any throttle setting (MAP) on the standard Lycoming FI system, changing the throttle position does not affect the ratio at all?
Thanks.
Johan

That would be correct except that is not what happens. In other words in a perfect world a set F/A ratio would remain constant but the FCU's as much as they are pretty good they are not perfectly linear, and lets face it, we are talking about measuring in inches here when miles is more appropriate.

[RV10inOz]

Originally Posted by skylor

REDUCE MANIFOLD PRESSURE?!?!?!

But this violates the whole premise of WOTLOPSOP!!!

Yes shame on me?.off to the naughty corner for even thinking such a thing!

As pointed out above, use RPM and mixture, but when that is not enough, you have to use the throttle!

If you want to fly that slow, by a Cessna 172

[Don at Airflow]

Originally Posted by RV10inOz

That would be correct except that is not what happens. In other words in a perfect world a set F/A ratio would remain constant but the FCU's as much as they are pretty good they are not perfectly linear, and lets face it, we are talking about measuring in inches here when miles is more appropriate.

David,

I have to disagree with you on this comment. As a designer of these products you kind of have to look at the application. Granted we?re not in a laboratory environment here but looking at the change in fuel air ratio with the engine at 55% power and above, with changes in airflow of 20%, the fuel air ratio changes 0.2% to 0.5%. Seriously, you think in operation the engine sees a 0.2% change in fuel air ratio??

I can?t say what our competitors accuracy in fuel air ratio is but I believe from the air box flow testing, dyno testing and field service we have had in the 2000 plus units we built, the accuracy in holding the fuel air ratio correct is close enough for the application we?re in.

Don

[RV10inOz]

Don, read my post again......I am in harmony with you

Read the post from Dorfie down

[SHIPCHIEF]

Operating with Carb Air Heat, or partial carb air heat can increase fuel atomization.
A small reduction in throttle setting will disrupt the airflow after the fuel has entered the airstream, without a great reduction in airflow volume. But the turbulence can change the fuel distribution to the cylinders.
Some combination of the two can even out the notoriously uneven Lycoming exhaust temps, run the engine more smoothly, and allow more leaning.
My T-18 with O-290, Marvel MA-4 and one P-mag responds to carb heat and part throttle particularly well above 6000 ft. I establish the cruise altitude and speed, then apply some carb heat and observe the EGT's change. The difference between EGTs is reduced. The engine 'might' run a little smoother, I then lean a bit more, and/or reduce the throttle. Slowly trying different combinations until I'm satisfied. It works well for a steady cruise configuration, but I resume standard operation approaching the destination when maneuvering and throttle changes are anticipated.
This plane will never receive the big investments in FI or Avionics, simply because I got it to help me get ready for my RV-8. So I'm happy to learn to use it the best I can for the way it is. I went with the Pmag when one mag failed. I've done other cost effective improvements when repairs are indicated, but the RV-8 gets 'the good stuff'.