SonexBuilders.net

After having OK results with lengthening my manifold intake, I'm still not happy with the EGT. Yes, I can run with everything in the green, but not optimally. To keep my highest EGT in the green during cruise, other cylinders have to be too rich.

So, I decided I'd join the fuel injection bandwagon. And so far have purchased the following:

Injectors: IWP023 https://www.ebay.com/itm/113666628635

Speeduino v0.4.3: https://wtmtronics.com/product/speeduino-v0-4-x-pcb/
I was hoping I could get the "Dropbear" version that has 8 injector channels, but that is sold out. Once it's available, I might switch to it if any of my cylinders need individual trimming, but likely won't have to.

Arduino MEGA 2560: https://wtmtronics.com/product/arduino-mega-2560/
The brains of the Speeduino board

Weld-In Fuel Injector Bung for Pico Injectors: https://www.diyautotune.com/product/wel ... injectors/
I bought one of these, and plan to make the other 5 myself.

I still need to figure out what I'm going to use for triggering. The Speeduino has many options including hall effect, distributor wire inductive clamp, and inductive "missing tooth". If I go the inductive route, I'll need to get a $25 VR conditioner.

I'm planning on head heading the injectors like others have done. I'm going to keep my AeroInjector installed as backup, as others have done as well. I think this reduces the risk of EFI failure significantly.

I've also gone through much of the Speeduino code, and could modify it if I wanted to had the PCB board, to allow 8 injector drivers. It only requires 1 $16 chip, and SPI bus wiring.

Still have more buying to do. Any suggestions on sensors, or other comments is appreciated.

In the certified engine world, we use EGT as a tool in controlling Cylinder Head Temperature (CHT). As long as the CHT is within limits, the EGT per se is not relevant. Is it different for the AeroVee? Of course it is desirable for EGTs to be similar for all cylinders but there are other variables relating to the instrumentation, placement of sensors, etc.

I always thought, right or wrong, that EGT's over the limit would burn exhaust valves. If i am incorrect in this assumption, it would be nice to know. The EGTs on my Aerovee are high on takeoff and climb but CHTs are within limits.

I two concerns regarding EGT/Mixture

1. It's likely all of us have heard Mike Busch's leaning presentation, and how EGT doesn't matter as long as CHT are within limits. This may be true, but I have also heard that 1800F is around the temp that the metal in the valves start to change. I don't know if this is weaken, or become brittle, or what.

I talked with Pete at Jabiru years ago, and he didn't have anything good to say about going over the EGT limits. Jabiru seems adamant that EGTs stay below certain limits. I have no idea why there would be a lower limit for >70% power for exhaust valves.

2. I have also read that having the mixture too rich can allow un-evaporated fuel to "wash" oil off the cylinder walls. This doesn't seem good to me.

I'm no expert, so take what I say from that perspective.

Modern fuel-injection is very cool.
I've run the SDSEFII system on a Subaru powered gyroplane as well as my Lyc IO-360 powered Sportsman.
I like being able to tune each cylinder fuel flow fine adjustment. This allows the engine to run LOP at cruise which saves 2 to 3 gph. Depending upon power setting.

As for Max EGT Limits. As far as I know Lycomings don't have published EGT limits. Thus Mike Bush's comments are correct. However several of our smaller engines DO have EGT limits. I believe the published EGT limit for the RevMaster is 1400˚. No doubt it all has to do with what materials are used in the valves and seats. We would do well to respect these limits.

On JabCamit.groups.io I found what seems to explain why Lycomings don’t have EGT limits, but Jabirus do. This seems to be educated speculation, and plausible:

"The issue with the EGT is valve stem temperature. Because Jabiru chose to use little spindly little small diameter valve stems, these are more heavily loaded than thicker ones used in typical aircraft engines (or cars for that matter). Since increased temperature decreases fatigue life, thin valve stems are more vulnerable to reduced fatigue life because of the higher loading (small cross sectional area). Jabiru introduced a leaning setup for the bing that was designed to increase fuel economy (also increased average EGTs). When valves started failing at a higher rate, they withdrew this option. Since Jabiru never really levels with you about why they change things you kind of have to read between the lines, but that’s my take on the situation.”

"the lyco etc have sodium in their thick stems, helps conduct the heat .

Rotax dont seem to have any problem. Jabiru have recently moved (very recently) to the new Nimonic steel valve material. My reading is it is what Rotax use...Not sure of the proportions, where used etc. but the valves have gone from $25 each to $75 each."

lpaaruule wrote:...I talked with Pete at Jabiru years ago, and he didn't have anything good to say about going over the EGT limits....

Interesting. I took the Jabiru maintenance seminar in Shelbyville back in 2016 and at the time, Ben (Pete's son, while Pete was listening) told the class that their recommendation was that 1450 F be the EGT limit, and best to strive for 1350 - 1385 in cruise. This was the only time I can remember writing the numbers down, and I saved my notes. Although in several other conversations with Ben & Pete over the years it was discussed that they liked higher EGT's because it minimized lead buildups, and therefor exhaust gas leakage, and presumably that was net better for the exhaust valve.

My 3300 is at right about 500 hours right now, and I have been fling with a Hackman for the last 300 hours or so and aim for a cruise setting where my highest EGT (typically #5) is just below 1400F, and the others are all over the place, typically 1320-1380. I installed the Hackman right at the same time that I had to accomplish a top end overhaul (at 200 hours!) due to.. lead fowling (failed a compression test). I attest that to living in Denver - and due to the density altitude I fly around all the time at WOT - which is probably below a typical cruse power setting living at sea level. But at WOT the stock Bing would go very rich, EGT's would plummet, and i got bad lead built-up. At least, that is my theory. Rather than re-jet the Bing, I just decided to install the hackman.

Please no one take this as advice - during that 200 hour top-end I took the opportunity with the heads off to put new valves in (and updated my gen 3 to the newer dual-spring design), so my valves only have about ~300 hours on them and I can't attest to any long-term durability. This is still very much an experiment.


Paul - sorry I don't mean to hijack your thread into an EGT discussion. I am also experimenting with the speeduino currently, but not on my Jabiru. I'll be following your project with much interest and feel free to DM me if you want to trade some notes.

Feel free to comment all you want about EGTs, I'm interested in getting as much info and datapoints as I can.

A friend of mine has a 3300 in his Zodiac 601, and he has had to do engine work at 400 hrs. He has the Hacman on his Bing as well. One of his piston rings was so gum'd up that he had to break the rings to get them off, and send the piston out to get media blasted. He had another piston that he was able to change the rings and clean the piston himself. Another cylinder that had a blow-by through the valve guide (burnt oil next to the springs), and he had to send that in to be serviced.

Maybe some of his cylinders were to rich, others too lean. Interestingly enough, he started having a problem with "high" Carbon Monoxide in the cabin. After the engine work was done, the CO levels dropped back to almost nothing.

So keeping cylinders at from burning too rich has advantages beyond lead buildup, and fuel economy.

As far as the discussion with Pete at Jabiru, we were talking about running lean of peak, and if EGT temps mattered. I don't recall specifics regarding temps, but the impression I got was to stay rich of peak.



#EGT #Mixture #CO

lpaaruule wrote:As far as the discussion with Pete at Jabiru, we were talking about running lean of peak, and if EGT temps mattered. I don't recall specifics regarding temps, but the impression I got was to stay rich of peak.

Got it - at the same time I installed a Hackman, I also installed a single wide-band oxygen sensor. I have the stock muffler installed (not Sonex's three-into-one pipes) so it only reads the "average" of all six cylinders. In cruise, I typically end up operating at a lambda of .94~.98 or so. If I go leaner than that, the richer-running cylinders all start exceeding my self-imposed limit of 1400 F. If I go really lean i can get them all back down below the limit temp, but by that time the leaner cylinders are so out of whack that the engine runs rougher. For that reason, I tend to stay just rich of peak.

Individual cylinder oxygen sensors and EFI would do a lot of good on this engine, just a lot of complication to get there.

After a busy summer, I'm finally getting back to the EFI installation.

I ended up buying an 8 channel Speeduino based on the "Dropbear" version from a guy in New Zeeland:

https://kiwiefi.nz/index.php?route=prod ... duct_id=55

So far, I'm impressed with the build quality of the unit, though I have yet to power it up.

I'm installing an O2 sensor on cylinder 1 because the 3 to 1 exhaust is leaky, and I don't want incorrect AFR readings:





I wanted to get the injectors as close as I could to the intake, but in hindsight an extra inch probably wouldn't have hurt, and would have kept me from having to make custom tools to reinstall the intake tubles:


I wondered what the inside of the intake manifold looked like. I was surprised at how black the rear of the manifold was, and wow, that is some serious obstruction in an effort to get even mixture to the cylinders:




I made a Throttle Position Sensor from a linear potentiometer (sound/volume control), and an M3 size rod end and allthread:


Here I am under the engine trying to figure out how I'm going to arrange the fuel filter, pump, fuel rail, and pressure regulator in the smallest area, and the least distance of fuel line exposed to engine heat: