I set out to characterize the details about my injectors today. Ran into a bit of a problem with MegaTune and how it interfaces with MegaSquirt. I tried to contact the email that Eric Fahlgren has in the manual, but the address bounces.

I think it is important information that Eric should know, but after sniffing gas all day, I'm not in much of a mood to keep chasing him down. I freely admit that my inexperience and ignorance may be the source of this problem, but I'm posting what I've already written hoping someone might benefit from it and it might get back to someone that can make a difference. Here are the two emails I sent Eric.

Message 1:
I was trying to characterize my high impedance injectors. Set the number of squirts and measure the amount sprayed. Repeat with a different spray amount.

s = milliseconds sprayed
f = nominal flow
m = missed flow due to turn-on/off time
c = cycles sprayed

c(sh-m) = measured volume

The two unknowns are m and h. Do it for several s values and you have a series of equations that you can solve for m and h.

That was my goal. I set s to 80, and the program bailed on me. Said 65 was the highest I could set it to. Unfortunately, from that point on whenever I turn the MS on, I get full fuel flow. I can't turn off the test mode, change it to something else, or switch it to normal. I'm using v2.88E Embedded by B&G as the firmware.

If you have any idea what could be happening, or how I might get back to a starting point I would be so appreciative. Today was going to be my first run of the engine, so I'm a little disappointed right now. I think an ECU jumpered reset might be in order.



Message 2:
I reflashed the MS with the newest version of official firmware. The problem went away.

I tried to continue my characterization tests, but the firmware just got wacky. I couldn't get it to switch out and flow different cycle times or counts. So I gave, declared victory (all injectors are at least flowing), and started to move on to First Engine Start.

The story shouldn't stop here, though. This feature has a very real possibility of adding a LOT of usefulness to MegaTune. Extend it, and call it "Characterize Injectors", or something like that. Show a hardware setup like the one I picture below (you could make some money selling graduated cylinders). Yeah, it is some cheap Harbor Freight clamps holding things together.

Have the software generate some cycles and duration. Run it. Ask the user to tell how much flowed. Immediately run another test with different cycles and duration. Do it four times, just for accuracy, solve each equation against the other three, and average the results for m and f. You now know exactly what the injectors flow, and what to feed in for the turn-on time. You could even have it feed into other maps so that slightly imbalanced injectors are compensated for.

My MS is driving a 13B rotary powered airplane. If you use this idea, it would be nice if you mention that "Ernest Christley smells like gasoline, clear to the highest heavens." 8*)

(I'm a software engineer, and that would look COOL on my resume 8*)




I can chase down and upload the picture of the test apparatus if anyone cares to see it.

 

Unfortunately, I'm not 100% sure how all that works with the standard firmware, as I've never used it!

We do have a test mode in ms2/extra (2.1.0 is the last version that will work with MT though, for the 3.x.x series of firmware, you need TunerStudio).

Ken

 

Didn't read your post. I made up a jig to test about 12 fuel injectors in my backyard.

I used a factory TII S5 secondary rail. A denso fuel pump from a jzx100 chaser. I zip-tied 3 injectors in more permanently and only hot swapped the injector of interest.

I selected based on 'sound and quality of opening clunk', 'cleanness of spray pattern' and then checked my final pair for flow into a jam jar.

 

I think I'm going to switch to ms2/extra 2.1.0 for now, since this Win95 laptop I'm using won't run TunerStudio (I can't find a version of Java). I'll have to open it back up and switch that stupid jumper around one last time, but it should be the last time (barring another firmware corruption). I'm still looking for some release files to see whether the jump from 2 to 3 would be truly useful, or just a feel good move.

Does TunerStudio have a fuel totalizer option. Ed Anderson builds and sells one for a different ECU. It keeps track of the injector pulses and reported fuel flows to show current usage, total usage, etc. It's a trivial implementation, but requires accurate flow numbers. A reasonable test procedure, like I outline above will make the setup a breeze.

If this is not currently available, it will be one of my first contributions after I get everything running correctly.

 

I am not sure if TS currently does that or not. You may want to ask that question over at www.msextra.com's forums in the TS section.

Ken