Yes, I believe Brainey has it right.
I do like the MS2s approach to dwell correction much better than the MS1s, insofar as that it's easily user-configurable. Hacking the code isn't particularly difficult (particularly with MS1, where it's a nice, monolithic package) however I really hate forking software needlessly. A year or two down the road, I (or the new owner of the car) will put new code onto it, forget about the fact that the old code had been manually hacked, and wonder why they're getting misfires all of a sudden. No, I think I'll just stick with my original solution, which is to up-rate the specified dwell. It works fine, introduces the fewest variables, and is easily copied by folks who don't own scopes and don't like to mess with compiling their own code. |
Originally Posted by Braineack
(Post 526619)
I'll be dynoing my MS-II unit vs. my MS-I unit on the same spark map on April 10th.
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So, Joe, do you suggest I stick with the dwell curve that was defaulted, or try the new values based off Jason's optimal dwell curve?
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Originally Posted by Ben
(Post 526560)
It would need to be scoped. I would imagine, if using the oem power supply to the coils, that you are under dwelling them.
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Originally Posted by Ben
(Post 526616)
you're referencing voltage at the ECU for the correction factor, which is a problem because there's less voltage at the coils than at the ECU.
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The currents are short transients though.
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Originally Posted by Braineack
(Post 526656)
So, Joe, do you suggest I stick with the dwell curve that was defaulted, or try the new values based off Jason's optimal dwell curve?
The gist of my findings here are basically that Jason's data is correct insofar as 2.5 ms dwell, with the caveat that, at least in my system, they are correct for whatever supply voltage is actually being encountered at the coils (which I should probably measure), and must not be derated based upon the ECU's observation of system voltage.
Originally Posted by JasonC SBB
(Post 526660)
That's what the 10,000 uF capacitors will help.
I wonder if this accounts in some way for the knee in the current profile that I observed in my analysis? |
The MS-II default curve is:
Code:
Voltage Correction Based off Jason's dwell curve, I thought it might be more ideal to go to: Code:
Voltage Correction |
So far as I can tell, my own observations, Jason's observations, and the MS-II default curve all match up. If you dwell the coil for 2.5ms at what is most likely 12 volts or so (as measured at the coil) you get peak energy.
Since voltage as measured at the ECU is always going to be higher than actual voltage at the coil, I'd suggest sticking with the MS-II default. |
Joe the knee in the current waveform is due to partial saturation of the magnetic core in the coil.
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gotcha chief.
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Originally Posted by JasonC SBB
(Post 526701)
Joe the knee in the current waveform is due to partial saturation of the magnetic core in the coil.
For all I know, it could just be an artifact of my (relatively cheap) current probe. This is the first time I've done this sort of thing with my new Chinese unit as opposed to the $2,500 Tektronix one we have in the lab. |
'Tis not an artifact. I'm looking at a trace right now showing the same behavior. Completely different coils on a completely different car.
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Originally Posted by Joe Perez
(Post 526707)
If that were the case, I'd expect the slew rate to go down, not up.
For all I know, it could just be an artifact of my (relatively cheap) current probe. This is the first time I've done this sort of thing with my new Chinese unit as opposed to the $2,500 Tektronix one we have in the lab. V = L * di/dt For a given applied V, if L goes down, di/dt (rate of change or slope of current) goes up. I get the same exact slope with a $30k setup at work. :D |
Hmmm. Well, I admit that I suck with magnetics. Anything involving Q falls into the realm of FUD so far as I'm concerned. We have a guy here at work who absolutely revels in it, but he frightens me.
Several years ago, I did this exact same test with my then-current setup, involving the stock '90-'93 coils, using the expensive Tek scope from work. Here's what I saw: http://img34.imagefra.me/img/img34/3...lm_3f63c21.gif You can see that the current rise rate is slowing down as primary current increases. Knowing no better, I simply assumed this to be the natural behavior of an ignition coil primary. In this capture, the stock Mitsu igniter is in place, so this may simply be an artifact of that device (a "soft" current limit, as opposed to the Toyota's hard limit) though of course this is only speculation. The leveling-off continued as dwell was increased beyond what's shown in this image, until a knee point was reached which I judged to correspond to the saturation point. |
The reducing slope in the current rise above is due to the primary resistance. Classic L/R waveform. In the Toy COPS, primary resistance appears very low.
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1 Attachment(s)
Originally Posted by Zaphod
(Post 526610)
O.K. - what have you put in your ignition settings in MS2 now. (Pleeeeeease post your msq....)
ok here. i finally remembered. goes in for emissions tomorrow. |
Going slightly off topic here - does anybody know what's the dwell time for the 2001+ stock ECU? Is it the same as the 99/00?
thanks her shann |
In my dwell thread, I posted the ideal dwell numbers for the 01 coils. The factory dwell will be slightly shorter than that.
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Originally Posted by JasonC SBB
(Post 527101)
In my dwell thread, I posted the ideal dwell numbers for the 01 coils. The factory dwell will be slightly shorter than that.
thanks - found it! Looks like the dwell time is just slightly longer than the 99/00, which means I will probably benefit with a dwell reducer circuit for the Toyota COP. her shann |
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