Megasquirt Dwell Settings, for those with RUNNING cars!

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11-10-05, 02:28 PM

ddub

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Dwell Settings, for those with RUNNING cars!

Need your dwell settings people.

Looking for someone running MSnS with rotary ignition that can give me the dwell settings they are using for cranking and running. This would really help me out because I am finding some conflicting viewpoints on what dwell settings to run.

So if your rx7 is running with stock coils and doesn't have misfiring, what's your dwell!?

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11-10-05, 02:44 PM

muythaibxr

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I replied to your PM, but since this is a good thing to know, I'll post here too:

Cranking dwell: 6 ms
Running dwell: 2.6 ms
min discharge: 0.5 ms

Tofuball is now daily-driving his car with these settings... His car has the smoothest idle I've seen on almost any engine (you saw the video), and I don't think it misses at all.

Here is a cut 'n paste of the info at msefi.com that shows what the mazda ignitor does with the dwell info sent from the MS:

MS-Dwell Coil Charge Time
[ms] [ms]
1.0 1.0
1.2 1.8
1.5 3.4
1.6 3.8
2.0 4.0
3.0 4.8
4.0 5.6
5.0 6.3
6.0 7.2

** All above at 2000 rpm

Thanks to renns for figuring this stuff out.

Last edited by muythaibxr; 11-10-05 at 02:49 PM.

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11-10-05, 03:34 PM

Jeff20B

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Code:

             Stock VR                           MS ignition
---------------------------------------------------------------------
                                     |  500RPM dwell: 11%, amps: 0.32
                                     |  600RPM dwell: 14%, amps: 0.40
                                     |  700RPM dwell: 16%, amps: 0.46
                                     |  800RPM dwell: 18%, amps: 0.52
                                     |  900RPM dwell: 20%, amps: 0.56
 900RPM dwell: 22%, amps: 3.3 (1.1)  | 1000RPM dwell: 21%, amps: 0.63
2000RPM dwell: 44%, amps: 6.0 (2.0)  | 2000RPM dwell: 43%, amps: 1.25
3000RPM dwell: 56%, amps: 7.4 (2.46) | 3000RPM dwell: 63%, amps: 2.28
4000RPM dwell: 60%, amps: 8.1 (2.7)  | 4000RPM dwell: 59%, amps: 1.95
                                     | 5000RPM dwell: 52%, amps: 1.50
                                     | 6000RPM dwell: 44%, amps: 1.08
                                     | 7000RPM dwell: 39%, amps: 0.80
                                     | 8000RPM dwell: 32%, amps: 0.45
                                     | 9000RPM dwell: 29%, amps: 0.34
                                     | MAX dwell: 65.5%, at 3100RPM, amps: 2.38

Numbers in parenthesis are estimated amperage per coil where 3.3 ÷ 3 = 1.1

Maximum dwell duty never exceeds 60% and max current was about 8.2 amps. Distributor and J-109 stock dwell and current gradually fall as RPMs rise above 4000.

My carbed 13B idles at around 900RPM and I wasn't able to measure dwell or amp load any slower or at cranking speeds.