How much more power?

[N941WR]

A few EI questions:

1) How much more power do you get from using an EI system?

2) Does it make much difference if you have on EI and one mag?

[Bryan Wood]

Here's how it was sold to me. It won't make any more power, but above 6.5k' or so a single EI and one mag will allow you to retain about 4% more of the sea level rated h.p. Duals will net you about 6% more of rated sea level power. Cruise at high altitude with EI adds economy and a greater power retention. How much of this is accurate I don't know but I bought in with this simplistic explanation. I've been happy with it since and the plane runs good and seems to like it too.

Best,

[gmcjetpilot]

Originally Posted by N941WR

A few EI questions:

1) How much more power do you get from using an EI system?

2) Does it make much difference if you have on EI and one mag?

One unit gets you the most advantage and the second a little more. The exact percentage is hard to definitively nail down. The 4% and 6% is possible but not guaranteed.

Gains are more complicated, part brand of EI and engine but more how the pilot flys. Take and economy car for example; if you make jackrabbit starts and always are on the gas or brakes, no in-between, your mileage will suck despite what the EPA milage sticker says.


To realize the percent gains mentioned above (which are near max gains) you would be in cruise at approx 70% or less power. This is where the EI shines, with their spark advance and strong spark. At higher power they have fixed timing like a magneto, but even at higher power with fixed timing, you still enjoy a stronger spark than a magneto, which is very good.

In theory an EI should be more reliable and almost zero maintenance. The down side is they are electronic and require electrical power. The only self sustaining EI is the P-mag. The 4% / 6% mentioned above comes from Lightspeed's website. P-mag does not make any claim of performance gains. However it would be interesting if RV'ers did flight testing between magnetos and all the different brands of EI. I will not say performance is all the same with EI, because they are not, but most buying decisions are because of form, fit and function (aka how its packaged). Technically the Lightspeed III should give the best econ and power. Who knows for sure with out test.

Cafefoundation.org did the only test on EI verses magnetos I know of. They used a Mooney and IO-360 Lyc. The test was with an Electroair EI, both single/mag and dual config's. The Electroair is a fairly representative of an experimental EI, kind of between a Lightspeed and E-mag (report available on their site). They did indeed get some good gains in power and fuel econ. The gains where at the lower power operations like cruise, as I mentioned.

At higher power, even with fixed timing advance, you still get the advantage of a stronger and "fatter" spark (aka longer). Obviously the more gas you burn and not blow out the pipes, the better econ & power. However at higher power with an air-cooled engine we all run full rich anyway (mag or EI), so there is not much or any real fuel econ gain at 100% power. Bottom line, fuel econ requires you move those little black and red knobs judiciously. EI is not automatically going to save you fuel.

You will see a little more power, however the rest of the engine becomes a limiting factor in making more power. EI only can do so much. You need better cams, pipes, induction and basically a whole new head design, combustion chamber shape for example. How much extra max power can you gain? Who knows unless you dyno it. At least (I'm guessing) 1% or 2% on a 180 hp engine, which is almost 4 hp, not bad. I am aware of greater gains claimed. Think of EI as putting a CD player in a 55 Chevy.


The real benefit is easier starting, smoother idle and no points to wear out. Magnetos are still good consider they're design origins date back 50 year old, in principle over a 100 years old, mags have racked up an impressive reliability record, not perfect but very good.

EI has a good reliability record, but you have more wires to connect (even e/p-mag). More wires and connections means more failure points. If you take great care with your EI installation wiring and electrical system design, you'll be fine, i.e., magneto reliability or better. Of course that is why they designed aircraft with two ignitions. If magnetos where 100% reliable, they would not have needed two ignitions. My point is know what you are getting. Its not a panacea.

[gasman]

Originally Posted by gmcjetpilot

One unit gets you the most advantage and the second a little more. The exact percentage is hard to definitively nail down. The 4% and 6% is possible but not guaranteed.

Of course that is why they designed aircraft with two ignitions. If magnetos where 100% reliable, they would not have needed two ignitions. My point is know what you are getting. Its not a panacea.

Two mags are needed to complete the ignition precess. One mag does not have the power to cross that large of a bore. That is why you have a mag drop..

With elec. ign. you will not see a mag drop. One mag and one elec. is the best of both worlds.

[zav6a]

One final advantage - if you intend to run LOP, EI offers higher energy and reduces possibility of lean misfire. Some forms also offer longer duration of spark, reducing lean misfire to yet a greater degree. I have balanced injectors and Electroair and can run outrageously lean without misfire. No fuel econ advantage beyond maybe 50 degrees LOP but it is nice not to have such fine line before the power rolls off and roughness starts. I can descend further from high altitude without richening and have essentially no misfire. When leaning, it does not fall on its face quite so abruptly when overleaning. I don't mind, but my passengers do not like the momentary roughness! I pull the mixture abruptly when entering the cruise state and won't get back to mixture for a minute or two for fine tuning and often find I'm 200 degrees LOP - with no roughness!

[petehowell]

Hi Duane,

When you pull the mixture knob quickly, how do you know how far LOP you are? I have a Dynon EMS and I can go LOP, but I need to go slowly thru the peak range to see where they peak.

I'd love to be able to pull quickly to a GPH setting, but I don't think I get accurate peak info if I do this.

Thanks for your thoughts.

[zav6a]

Pete

I have little table of altitude versus fuel flow where I know I will be significantly lean (50+ degrees) even when it is fairly cold. So, I pull to that number or lower. When I get the time (away from the airport) I then slowly approach peak from the lean side. I also have a table of expected peak numbers at various altitudes (it does not change as much as fuel flow) so I have some idea how far from peak I am, just so I don't waste any time creeping up .1 gpm at a time when I have a full gph to go to peak.

During hard climbs and full power runs down low I run rich of peak and just keep it between 1280 and 1300 EGT. That is at least 150 ROP.

I often fly over 15K so I spend a lot of time fiddling with mixture. Others that bomb around within 3000 feet of sea level don't need to trouble themselves with a lot of this.

[dan]

Originally Posted by petehowell

When you pull the mixture knob quickly, how do you know how far LOP you are? I have a Dynon EMS and I can go LOP, but I need to go slowly thru the peak range to see where they peak.

Find peak from the LEAN side instead.

[petehowell]

I see what you are doing now.

[frankh]

Originally Posted by petehowell

Hi Duane,

When you pull the mixture knob quickly, how do you know how far LOP you are? I have a Dynon EMS and I can go LOP, but I need to go slowly thru the peak range to see where they peak.

I'd love to be able to pull quickly to a GPH setting, but I don't think I get accurate peak info if I do this.

Thanks for your thoughts.

Yes I used to mess around with this but was uncomfortable with how long the richest cylinders were staying in the "detonation zone"...So i sarted finding peak from the lean side as Dan suggested...This works well.

Now I really don't bother unless I'm on a long X country, other wise I take of, get to say 2500ft and yank the mixture till it just quits and screw it back in until it just runs smoothly.

This is now as LOP as you can get...This is how I set the engine up quickly for IFR training and its my usual method now....If I want the ultimate in efficiency I then hit the LEAN button on the Dynon and play with the mixture.

Frank 7a