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SDS EFI RV6A Video Project

rv6ejguy

Well Known Member
I've been talking about this for some time and we are finally able to start this thread.

The intention is document the process of tuning our EFI on a Lycoming 360 in photos and regular videos. The test subject is a 6A rebuilt by friends Ralph Inkster and Howard Brekke. The aircraft is located just up the street from us.



This morning was a big milestone with the first engine start and setting the initial ignition timing. Engine idle was excellent down to 650 rpm on the base settings, just turning the mixture knob slightly.

I'll be putting together a video on YouTube tonight and post the link here.

The plan is to post a new video roughly every 7-14 days as we progress through initial mapping on ground runs to first flight, air tuning and performance testing eventually. I'm hoping this will be helpful and informative for people considering or already installing/ using SDS EFI. Stay tuned.

I started a new web page for this project too: http://www.sdsefi.com/projectrv6a.htm
 
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you mentioned a mixture knob. Is the mixture knob basically setting a target A/F ratio electronically?
 
The mixture knob trims whatever injector pulse the ECU is delivering at the time. You can go +/- 50% from the 12 O'clock (0% trim) position.

Most folks will use this to manually lean once cruise power is set and for running LOP.
 
Running 100LL. Open loop is the only option.
Will be using the O2 sensor for tuning only.

I haven't been a member of the 'Gerry Can' toting gang since I finished the Turbo Subie 7, 10 years ago, we needed to run Premium Shell in that one. This 6A is meant to be a cross country machine so will use commonly available fuel.

Maybe in 10, 20 or 30 years\... when ever they finish their endless UL testing, we'll throw the switch.
 
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So running open loop at that point?

Correct. Leaded avgas reduces O2 sensor life substantially in many cases so that limits our ability to reliably use closed loop feedback control. Swift unleaded 94 avgas is becoming available in more places across the US which is a good start. https://swiftfuels.com/ul94-map/

While the present SDS already has closed loop control software, it targets stoich (near peak EGT) so is not usually used in aviation applications.

The next gen ECU will have more sophisticated closed loop capability as unleaded avgas comes into more widespread use in the future. Some places in Europe have pretty good UL avgas availability already.

We do think it will be a few more years before there is a "universal" unleaded avgas in North America. The FAA PAPI program evaluating UL avgas was recently put on hold for more study on the fuel formulations and their impact on operations. That probably wasn't what most people wanted to hear but at least Swift took the initiative a few years back and started selling their blend.

This RV6A will eventually help us develop and test new closed loop control software for the EM-6 ECU under development now.
 
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Part 3

This is a basic introduction on using the PC data logging feature to tune the SDS EFI system on the ground. After many painful editing tribulations, I was finally able to get this rendered in an H.264 format today.

https://youtu.be/nzeYz1xpu-Q

We'll work on Part 4 after Reno and this will describe more in depth on how to interpret the data logging results and make changes with the programmer.
 
It Flies!

Ralph has finally been getting some flights in on the EFI 6A lately and has some interesting things to report on fuel trim. Hopefully we can resume the video series on this when the hours are flown off.
 
This engine has a standard Lycoming sump with vertical induction. Ralph has about 5 hours of flight time on the plane now and has found a total of 12% trim is required on 2 cylinders. 0, 0, -5 and +7. EGTs align nicely with this setting at 2500 rpm cruise but as you change rpm, the trim amounts change as other people have noted as well.
 
This brings up a question for me. Which is the best way to utilize the trimming function, trim for EGT or CHT?

It seems CHT might be a better indication of engine balance. There is no sensor variance as the CHT probes are all installed in the same location where as EGT could be prone to variances from the install process.

Any thoughts on how that might effect engine performance?
 
The thought is that there is no way to know whether the cooling airflow is equal to each jug so there is not much point in balancing to equal CHTs initially.

Equal numerical value EGTs may not indicate equal AFRs, the only way we can tell that is if they all peak at the same time as this indicates near stoich on all. So IMO, the best way to trim is to get all cylinder to peak at the same time. Then we can look at CHTs and start trying to get those more equal with baffle and deflector changes.

Note though that if the cylinders are trimmed differently, this means unequal airflow in and/or perhaps differences in exhaust scavenging and likely that each cylinder is producing a different amount of hp and therefore heat. Different primary exhaust tube lengths or intake runner lengths can explain some of this. Ralph did notice that trim amounts changed with a change in rpm and this is expected with big differences in intake and exhaust tube lengths as the pressure waves take longer or shorter times to reach each end.

Therefore the best you can do with what you have is to trim so all cylinders peak simultaneously and then go after getting the CHTs equal with lots of tries at baffling alterations followed by more testing.
 
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Interesting point about the peak of EGT. I guess the actual numerical value of the EGT is useless as long as they cylinders reach peak temperature together. Ill give that a shot. Thanks.
 
Ralph is past the halfway point on the 25 hour flyoff. Hopefully soon we'll be able to shoot some more videos when we get some decent weather.
 
Ralph has the C of A now for the aircraft. We've just finished a whole month of very cold weather where not much flying could be done. Hoping in a few more days that will moderate and we can continue on doing some more testing and videos.
 
Fast 6A

I haven't updated this thread lately. Ralph and I are always busy. Ralph flew the plane to Osh and has quite a few hours on it now, using it as his aerial transportation around the province. Last month, he had a jug go bad. That's changed now and he'd been breaking in the replacement at high power.

With a standard 360 and fixed pitch metal prop, he's getting 180 KTAS on this thing with a bit of throttle left (limiting to 2700 rpm). Pretty darn impressive. I'm hoping to get flying with him soon to shoot some more video. The weather has turned cold he this weekend but we should get some reasonable weather in October to continue.

We'll try to do some 3 way GPS runs to verify what he's been seeing has been accurate.

The SDS EFI doesn't seem to be hurting performance at this point.
 
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