RX8 dead time + small pulse, controversial results.
#1
RX8 dead time + small pulse, controversial results.
I used the best part of a weekend sniffing fuel vapor while measuring the yellow RX8 injectors. I like to think I did it the proper way:
-Megasquirt in output mode.
-Fuel rail and injectors out of car squirting into bottles, weighing the contents after every set of a specific pulse length.
-I extrapolated (linear regression) the dead time from several pulse lengths between 10ms and 75ms.
I had an adjustable power source which admittedly was sagging just a bit under pulse opening as viewed from my oscilloscope. However, I also did measurements straight from the car battery at ~12.7V with no noticable sag and the results were well inline with the ones done with the power source. I also used the oscilloscope to check megasquirt was actually outputting what I was asking it to.
Results are somewhat controversial. Quite long dead times! I think most are using about half of what I got.
As reference I got 2.85ms@12.7V for the stock Miata 265cc/min injectors.
I also measured small pulse responce. There seems to be a characteristic hump in the output right at the shortest pulses. Same at all voltages.
Output was ~440cc/min at stock fuel rail pressures.
-Megasquirt in output mode.
-Fuel rail and injectors out of car squirting into bottles, weighing the contents after every set of a specific pulse length.
-I extrapolated (linear regression) the dead time from several pulse lengths between 10ms and 75ms.
I had an adjustable power source which admittedly was sagging just a bit under pulse opening as viewed from my oscilloscope. However, I also did measurements straight from the car battery at ~12.7V with no noticable sag and the results were well inline with the ones done with the power source. I also used the oscilloscope to check megasquirt was actually outputting what I was asking it to.
Results are somewhat controversial. Quite long dead times! I think most are using about half of what I got.
As reference I got 2.85ms@12.7V for the stock Miata 265cc/min injectors.
I also measured small pulse responce. There seems to be a characteristic hump in the output right at the shortest pulses. Same at all voltages.
Output was ~440cc/min at stock fuel rail pressures.
#2
Hmm... Maybe the megasquirt was adding the dead time you already had set? Thats the only thing I can think of to make the numbers look that good but be that much higher... There's just no way modern injectors have that much dead time, imo.
I measured one of my yellows at .490 ms @ 13v. (Have a ghetto diy injector test bench, was actually using a basic stamp to drive a tip120, using mineral spirits through a 1.6 fuel rail)
I measured one of my yellows at .490 ms @ 13v. (Have a ghetto diy injector test bench, was actually using a basic stamp to drive a tip120, using mineral spirits through a 1.6 fuel rail)
#4
Hell idk, Not really a hardware guy... I put a diode across the the tip120, but couldn't tell you what kind other than 'a physically large one that was laying around'
Edit: How much does flyback clamping really matter? At this point I'd be pretty happy to be within 25% of correct, lol. It may be worth it to use j-po's voltage curve and my number though since brain contends that the stock ms3 curves are off. I was only able to measure @ 13v since the battery I test with is basically dead (I run a battery charger on it while running the tests, voltage stays pretty consistent but its definitely inelegant.)
Edit: How much does flyback clamping really matter? At this point I'd be pretty happy to be within 25% of correct, lol. It may be worth it to use j-po's voltage curve and my number though since brain contends that the stock ms3 curves are off. I was only able to measure @ 13v since the battery I test with is basically dead (I run a battery charger on it while running the tests, voltage stays pretty consistent but its definitely inelegant.)
#14
BTW, I found this document which is a manual on how to use access tuner for rx8.. It makes me think that they're referencing a map sensor, So in that case does 1 bar = atmospheric = WOT? I'm thinking thats probably what you want to use for a turbo miata w/ rx8 yellows... But then again maybe it'd be better if you had your normal cruise cells optimized? VE values and EGO will adjust for everything else. IDK, either way we only get to pick one row.
http://www.google.com/url?sa=t&sourc...UNgS8g&cad=rja
http://www.google.com/url?sa=t&sourc...UNgS8g&cad=rja
#17
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Memory space at a guess.
Plus MS3 is the new hotness. The devs have stated many times that new features won't be added by them, only bug fixes.
I'm sure they'd welcome you writing it yourself though.
Plus MS3 is the new hotness. The devs have stated many times that new features won't be added by them, only bug fixes.
I'm sure they'd welcome you writing it yourself though.