fuel injection and electronic ignition?

How many of you are using fuel injection along with electronic ignitions? Which system seems to work best and is easy to install? I have been looking at the Precision Airmotive Silver Hawk EX system and I would like to get some feedback from anyone using this system. As for the ignition systems I really do not know a lot about them and whether its worth the expense.....

Silver Hawk is the uncertified version of RSA Bendix. Lots of guys use it. I chose Airflow Performance. Their newest servo is zero leakdown so is supposed to reduce hot start flooding without the need of a purge valve. So far mine's working as advertised. Right out of the gate my EGTs are equal through all power settings. Both of those are mechanical injection. There are a few electronic fuel injection systems out there as well. I know a few guys with one of them and they're migrating back to mechanical systems. That's a subjective comment so don't shoot the messenger.

My ignition is dual Pmags. They make the motor go and other than that I don't have much to offer. They're really easy to time, for what that's worth. Carbon Cubs use Lightspeed ignition. They seem to work well. I know Cub guys who've had EFII for a few years and they're moving away from it. Again, subjective based on the guys I know. I have an aerobatics buddy who hates Pmags, but he spins his motor way faster and hotter than me, so pick your pireps, right?

When talking to my aerobatics friend I mentioned being concerned about flooding and hot starts. He told me the new electronic ignitions fired so hot they'll start a flooded engine. I think he's right. I'm still getting to know my engine but I prime whether hot or cold and it starts right up.

stewartb said:

I have an aerobatics buddy who hates Pmags, but he spins his motor way faster and hotter than me, so pick your pireps, right?

When talking to my aerobatics friend I mentioned being concerned about flooding and hot starts. He told me the new electronic ignitions fired so hot they'll start a flooded engine. I think he's right. I'm still getting to know my engine but I prime whether hot or cold and it starts right up.

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That Aerobatic buddy you got is pretty sharp and is right.But when you do miss a start and flood your FI motor, just back it up bout 8 blades mags off full open on throttle And it’ll start right up especially with the duel p-mags !
BTW . That buddy will be back in country shortly .

When he was helping me assemble my plane he offered to fly the first flight if I got too busy. Then he found out I had Pmags and he told me nevermind, fly it myself. Nothing like a shot of confidence from a friend! 8)

stewartb said:

When he was helping me assemble my plane he offered to fly the first flight if I got too busy. Then he found out I had Pmags and he told me nevermind, fly it myself. Nothing like a shot of confidence from a friend! 8)

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That sounds just like our buddy !

cook11 said:

fuel injection and electronic ignition?
How many of you are using fuel injection along with electronic ignitions? Which system seems to work best and is easy to install? I have been looking at the Precision Airmotive Silver Hawk EX system and I would like to get some feedback from anyone using this system. As for the ignition systems I really do not know a lot about them and whether its worth the expense.....

Click to expand...

I'm using a stock Bendix RSA system on an IO-360-B1D (180 hp) which I had overhauled by Airflow Performance due to having sat for 40 years. They modified the nozzles so that their orifice size could be fine tuned to each cylinder. The ignition is dual Pmags with automotive spark plugs which works great, easy to install and is self contained. The combination makes for a very smooth running engine. It starts and stops without the usual O-360 shake and idles smoothly at 450 rpm. If you have experience with Lycoming O-360s, you would not believe this. The Pmags make their own electricity except when at idle, unlike ( as I understand it ) the other electronic systems. This is a plus because you do not want to run out of electricity to your ignition when flying. I did once out over the ocean (don't ask) and the Pmags brought me home. Fuel consumption is 8 gph leaned rich of peak at 22.5"/2400 rpm. It can be leaned until it stops running never finding a rough spot. Just a gradual losing of power. I'm a happy camper with this combination.

stewartb and skywagon8a I appreciate your input regarding your setups. I am now leaning towards the Pmags after reading your information but I will contact Lightspeed Engineering just to get some more information on their product. As for the fuel injection system I am sure I would be going towards the mechanical setups due to the simplicity of the setup. I contacted Precision Airmotive yesterday and they replied promptly to my questions, and I just emailed Airflow Performance. At least I have narrowed down my search just a little bit.....

If you call API you'll probably talk to Don or Kyle, and that's a conversation worth having if you're thinking about FI.

Things you may not have thought about with what you're proposing. You'll need an engine driven diaphragm pump and an electric high pressure pump for FI. You'll be advised to add a fuel filter ahead of the electric pump and to put the electric pump inside the cabin to separate it from heat. I put mine downstream of the gascolator on the firewall and have it inside an enclosure that's cooled by a blast tube off the rear baffle. So far so good. Pmags are also heat sensitive and require individual blast tubes to cool each mag. My buddy I mentioned earlier had Pmags shut down from heat. Known problem, known solution. Blast tube cooling is in the installation instructions. I don't know much about Light Speed but with all the Carbon Cubs out there using it? Finding a pirep should be simple. If you like to fiddle with things there are a couple of programmable-at-the-panel ignition options. I didn't like to fiddle so I passed on those. I just want my engine to run well without me thinking about it. Different preferences, different solutions.

Let me expand upon the Airflow modified Precision nozzles. They have separate inserts which can be removed and exchanged for different sizes. This requires an all cylinder EGT instrument and some flight testing to determine which nozzle needs to have it's size changed. A couple of flight tests seemed to accomplish the deed. I believe that the GAMI nozzles require exchanging the entire nozzle instead of just the insert.

Skywagon, what are your EGTs when leaned to 8gph?

It is unusual to pull mixture out to try to find the lean stumble and not find it. FWIW the spread I get in my EGTs is 25*. I know about the nozzle tuning from API but my injection doesn't appear to need it.

stewart, Your spread of 25* is fantastic don't touch it! I can't come close to that. Perhaps it is the custom build of the engine itself? Mine is just a stock from Lycoming engine. At 8.1 gph, 23"/2370 rpm, 111 mph, EGT/CHT #1-1345/277, #2-1412/306, #3-1386/329, #4-1428/326 This was checked in November so the ambient temps would have been low. Sometimes in the summer when it gets really hot in the high 80s the CHTs will go above 400* I enrich the mixture until the CHT drops below 400*.

I agree that it is unusual to pull mixture out and not find the lean stumble. That is what it does, just slowly losing power. I prefer just to burn the gas and go as fast as is comfortable using the rich side of peak.

My EGTs easily reach into the 1450-1460* range. I don't know what the high limit should be but this plane runs hotter EGTs than I'm used to. Here's a snaphot of my G3X. These temps aren't unusual. I'm enriching to stay below 1400 lately.

I have not seen any temperature limits for EGT. There are exhaust temperature limits for turbocharger inlets which run in the 1650-1750* range. This is to protect the turbocharger components. The EGT limit is whatever the maximum temperature is during the leaning process. That number is an indication of the air/fuel mixture ratio and only becomes a consideration when leaning ROP or LOP as maximum base number from which to adjust the mixture. Lycoming allows running at peak EGT at 75% or less power. Your CHTs are good. I use 400* as my personal limit even though 500* is Lycoming's limit. I found that when running my big Continental for long periods of time in excess of 400* that the cylinders suffer. Thus my personal limit of 400*.

I waver between thoughts. New engine. I don't want to roast it but I don't want to run it too fat, either. All through the build I was focused on oil and cylinder temps. Those worked out very well. I never thought about EGTs. Like I said, they're warmer than what I'm used to.

Do not worry about the EGTs. Especially since they are nowhere near the limits which are in place for the TITs. The answer may just be as simple as the probes being closer to the exhaust valves than in your other planes.

Absolute EGT temps are pretty much meaningless. Tiny variations in the placement of the probes (or variations in the probes themselves) can cause significantly different readings. And unless your exhaust pipes are all four perfectly identical (a virtual impossibility on any airplane I've ever seen), the different curvatures can also cause variations.

What DOES matter is when the EGT peaks for each cylinder, with reference to the other cylinders. Usually, you'll find one cylinder that reaches its peak EGT first – before the others do – because it runs leaner than the others. So that is the cylinder to use when measuring "rich of peak" (ROP) operations (like the "book" figures). When you're operating ROP, you want to be 100% sure that ALL of the cylinders are rich of peak EGT. Using that "leanest" cylinder's EGT ensures that ALL the cylinders are above peak EGT.

There's usually a different cylinder that is the last one to reach peak EGT, and that is the one to use when measuring "lean of peak" (LOP) operations, because it is the "richest" cylinder. Since you're not truly LOP until ALL of the cylinders are running lean of peak EGT, using the richest cylinder for LOP measurements is the right thing to do.

The big thing is to avoid the EGT range where the highest Internal Combustion Pressure occurs. That's typically around 40-50ºF on the rich side of peak (ROP). It's in that area, at high power settings, where your cylinders experience the most stress. If you want them to last longer, either run at 100ºF (plus) ROP, or run them LOP (perhaps 20-50ºF LOP).

All this info comes from the Advanced Pilot Seminar, put on by George Deakin, Walter Atkinson, and George Braly (though George's name is no longer listed on the site: www.advancedpilot.com). Probably the best aviation education course I've ever attended - bar none.

Thanks Jim, You are better at explaining it than I am. I have also noticed on some engines particularly those with a carburetor, that the two hottest cylinders at low altitude will be different cylinders than the two hottest at altitude. I attribute this to the position of the butterfly valve when cruising at low altitude versus wide open up high.

I'm not much of a Mike Busch fan but this article reminds me about a couple of things I used to know. http://www.gami.com/articles/egt_myths.pdf

My concern with my own EGT temp range is more about understanding a new engine. That my temps are 150* higher than what I'm used to? That gets my attention. I suspect it'd get most guys' attention when breaking in a new motor. New instrument package, new fuel injection, new ignition... lots of unfamiliarity.

I agree with everything which Mike Busch says in his article. As long as you can get at least a 100* EGT rise when leaning you have proper mixture control. If you could not achieve at least 100* temp rise then I would question why there seemed to be an inadequate amount of fuel flowing.

Your picture above indicates a happy engine. I just can't figure out how you managed to get .7 hour more on the airframe than the engine.

Mostly system programming time. One number is instrument time and one is engine time. With the battery backup unit I usually turn the instrument on before engine start so the .7 difference will grow.

I like having flat EGT numbers. I worked hard to get there in my 180 so I appreciate not having to work at it in the Cub. I don’t plan to do much LOP cruising but I guess I need to play with it to see how my cylinder peaks compare. Not my priority at the moment.

FWIW, Lycoming’s IO-390 manual says to run 150* rich of peak at 75% power. My engine is a 390 clone so I’ll go with that.

My 100* rise comment wasn't meant for LOP operations. Only as an indication that when running at full rich that it was rich enough. If you were only able to get (to pick a number) 50* rise before peaking then that would be an indication that full power fuel flows were too low.

Can you get at least 100* rise before it starts down? If so it's good.

The Lycoming Operators Manual for the O-360/IO-360 has a chart in it that is titled "Fuel Flow vs Percent Rated Horsepower. The idea of looking for a certain rise in EGT from full rich to peak sounds like a pretty good indicator that I have never come across before. Lycoming's and your concern should be that if an engine is not flowing enough fuel at takeoff power, detonation margins and heat build up are the concerns.

I like what Jim Parker had to say about the value of CHT over EGT. That advanced pilot seminar is one I keep hearing about. But I have not heard anyone yet say that The gurus seem to look not so much at EGT spread when leaning, but at the Fuel Flow Spread between the leanest and the richest cylinder. That is what API is going to target when the tune those injectors. Ideally, You want all your cylinders to reach peak EGT simultaneously irregardless of the each cylinders EGT value. I think a .5 gph spread is ok. 1 gph is not too good.

stewartb and skywagon8a would you guys be able to post some pictures of your fuel injection setup? What brand of engine diaphragm pump, electric fuel pump and fuel filter are you guys using?

Thanks!

Airflow Performance 200A fuel servo attached to a forward facing cold air induction sump.


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Devising an airbox and filter that'll fit in a Cub cowl. Finding airboxes for RVs is easy but they won't fit. Figuring out an alternate air source was fun.

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No idea what the brand of the engine-driven pump is but it's FAA-PMA. This pic was while fitting up a cooling shroud.

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An Airflow Performance electric pump pack on the firewall, also being enclosed in a cooling shroud. No fuel filter for me. The filter is usually upstream of the pump when mounted inside the cabin. My location allowed the pump to be downstream of the gascolater.

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The flow divider. Pretty typical.

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The electric pump is a Weldon #8163-A which is mounted below and outboard of the fuel selector in this photo. This then feeds directly through the firewall to a Steve's gascolator/screen, through an EI fuel flow transducer, then to the engine pump.

The engine driven pump is a Romec gear pump. Whether you use a gear pump or a diaphragm pump will depend on which model engine you have. My engine is a stock Lycoming IO-360-B1D.

I built a SQ2 eight years ago and have about 600 hours on it, BART at aero sport power built my engine, it has the precision silver hawk injection with mags. The hole system has been totally trouble free, hot starts have not been a problem .


I have an electric boost pump, Steve’s gascolator,fuel flow cube, engine driven fuel pump, the mags both have impulse couplers. I plan to change to Emags in the future. The engine is stroked to 375 cu in.with 9:1 compression. At that time Bart did not recommend Emags for cub flying.

cook11 said:

stewartb and skywagon8a would you guys be able to post some pictures of your fuel injection setup? What brand of engine diaphragm pump, electric fuel pump and fuel filter are you guys using?

Thanks!

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fuel pump on engine is same as on a car... old chevy S10 had same, Delco I think... (do not let a used diaphragm pump dry out... sometimes kills the diaphragm in it)

I don't recognize the "AA" logo but you can see FAA-PMA on the support arm.





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Engine fuel pump is not the same as car (5-7psi) Bendix, AFP and precision bendix copys require 25-28 psi, And the v-8 arm don't work albeit similar looking. Just FYI