Dwell observations on the Toyota COP. - Page 2 - Miata Turbo Forum - Boost cars, acquire cats.

Welcome to Miataturbo.net   Members
 


MEGAsquirt A place to collectively sort out this megasquirt gizmo

Reply
 
 
 
LinkBack Thread Tools
Old 02-22-2010, 11:48 AM   #21
Boost Pope
Thread Starter
iTrader: (8)
 
Joe Perez's Avatar
 
Join Date: Sep 2005
Location: Chicago (Over two miles from Wrigley Field. Fuck the Cubs. Fuck them in their smarmy goat-hole.)
Posts: 26,315
Total Cats: 1,913
Default

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.
Joe Perez is offline   Reply With Quote
Old 02-22-2010, 12:09 PM   #22
Moderator
iTrader: (11)
 
sixshooter's Avatar
 
Join Date: Nov 2008
Location: Tampa, Florida
Posts: 15,633
Total Cats: 1,559
Default

Quote:
Originally Posted by Braineack View Post
I'll be dynoing my MS-II unit vs. my MS-I unit on the same spark map on April 10th.
Definitely interested in results of that.
sixshooter is offline   Reply With Quote
Old 02-22-2010, 12:26 PM   #23
Boost Czar
iTrader: (61)
 
Braineack's Avatar
 
Join Date: May 2005
Location: Chantilly, VA
Posts: 72,809
Total Cats: 1,780
Default

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?
Braineack is offline   Reply With Quote
Old 02-22-2010, 12:34 PM   #24
Elite Member
 
Join Date: Jul 2005
Posts: 6,454
Total Cats: 80
Default

Quote:
Originally Posted by Ben View Post
It would need to be scoped. I would imagine, if using the oem power supply to the coils, that you are under dwelling them.
That's what the 10,000 uF capacitors will help.
JasonC SBB is offline   Reply With Quote
Old 02-22-2010, 12:43 PM   #25
Boost Pope
Thread Starter
iTrader: (8)
 
Joe Perez's Avatar
 
Join Date: Sep 2005
Location: Chicago (Over two miles from Wrigley Field. Fuck the Cubs. Fuck them in their smarmy goat-hole.)
Posts: 26,315
Total Cats: 1,913
Default

Quote:
Originally Posted by Ben View Post
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.
And of course, for those of us running in wasted-spark mode, the problem is amplified, as the total draw on the wire supplying the coils is twice what I observed on a single coil. 22 amps is a hell of a lot of current for what I recall to be a 16ga wire. If these cars fell under the purview of the NEC for cabling vs. current, we'd be in violation.
Joe Perez is offline   Reply With Quote
Old 02-22-2010, 12:51 PM   #26
Elite Member
 
Join Date: Jul 2005
Posts: 6,454
Total Cats: 80
Default

The currents are short transients though.
JasonC SBB is offline   Reply With Quote
Old 02-22-2010, 01:05 PM   #27
Boost Pope
Thread Starter
iTrader: (8)
 
Joe Perez's Avatar
 
Join Date: Sep 2005
Location: Chicago (Over two miles from Wrigley Field. Fuck the Cubs. Fuck them in their smarmy goat-hole.)
Posts: 26,315
Total Cats: 1,913
Default

Quote:
Originally Posted by Braineack View Post
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?
Are the two noticeably different?

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.

Quote:
Originally Posted by JasonC SBB View Post
That's what the 10,000 uF capacitors will help.
I should note also that in my setup, there are a pair of 4,700 uf caps in parallel across the coils' supply, located at a point between the old igniter connector and the back of the head.

I wonder if this accounts in some way for the knee in the current profile that I observed in my analysis?
Joe Perez is offline   Reply With Quote
Old 02-22-2010, 01:09 PM   #28
Boost Czar
iTrader: (61)
 
Braineack's Avatar
 
Join Date: May 2005
Location: Chantilly, VA
Posts: 72,809
Total Cats: 1,780
Default

The MS-II default curve is:

Code:
Voltage    Correction
6               500%
8               248%
10              168%
12              128%
14              102%
16              88%
It runs fine and I have my dwell set to 2.5ms. The manual suggests it'll be fine for 99% of users.

Based off Jason's dwell curve, I thought it might be more ideal to go to:

Code:
Voltage    Correction
6               180%
8               160%
10              120%
12              100%
14              86%
16              76%
but it's definitely going to be dwelling less.
Braineack is offline   Reply With Quote
Old 02-22-2010, 01:24 PM   #29
Boost Pope
Thread Starter
iTrader: (8)
 
Joe Perez's Avatar
 
Join Date: Sep 2005
Location: Chicago (Over two miles from Wrigley Field. Fuck the Cubs. Fuck them in their smarmy goat-hole.)
Posts: 26,315
Total Cats: 1,913
Default

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 Perez is offline   Reply With Quote
Old 02-22-2010, 01:29 PM   #30
Elite Member
 
Join Date: Jul 2005
Posts: 6,454
Total Cats: 80
Default

Joe the knee in the current waveform is due to partial saturation of the magnetic core in the coil.
JasonC SBB is offline   Reply With Quote
Old 02-22-2010, 01:29 PM   #31
Boost Czar
iTrader: (61)
 
Braineack's Avatar
 
Join Date: May 2005
Location: Chantilly, VA
Posts: 72,809
Total Cats: 1,780
Default

gotcha chief.
Braineack is offline   Reply With Quote
Old 02-22-2010, 01:42 PM   #32
Boost Pope
Thread Starter
iTrader: (8)
 
Joe Perez's Avatar
 
Join Date: Sep 2005
Location: Chicago (Over two miles from Wrigley Field. Fuck the Cubs. Fuck them in their smarmy goat-hole.)
Posts: 26,315
Total Cats: 1,913
Default

Quote:
Originally Posted by JasonC SBB View Post
Joe the knee in the current waveform is due to partial saturation of the magnetic core in the coil.
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.
Joe Perez is offline   Reply With Quote
Old 02-22-2010, 02:20 PM   #33
Ben
Supporting Vendor
iTrader: (33)
 
Ben's Avatar
 
Join Date: Jul 2006
Location: atlanta-ish
Posts: 12,689
Total Cats: 99
Default

'Tis not an artifact. I'm looking at a trace right now showing the same behavior. Completely different coils on a completely different car.
Ben is offline   Reply With Quote
Old 02-22-2010, 04:52 PM   #34
Elite Member
 
Join Date: Jul 2005
Posts: 6,454
Total Cats: 80
Default

Quote:
Originally Posted by Joe Perez View Post
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.
When a core saturates, inductance drops.
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.
JasonC SBB is offline   Reply With Quote
Old 02-22-2010, 05:30 PM   #35
Boost Pope
Thread Starter
iTrader: (8)
 
Joe Perez's Avatar
 
Join Date: Sep 2005
Location: Chicago (Over two miles from Wrigley Field. Fuck the Cubs. Fuck them in their smarmy goat-hole.)
Posts: 26,315
Total Cats: 1,913
Default

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:



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.
Joe Perez is offline   Reply With Quote
Old 02-22-2010, 05:50 PM   #36
Elite Member
 
Join Date: Jul 2005
Posts: 6,454
Total Cats: 80
Default

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.

Last edited by JasonC SBB; 02-22-2010 at 11:02 PM.
JasonC SBB is offline   Reply With Quote
Old 02-22-2010, 10:47 PM   #37
Boost Czar
iTrader: (61)
 
Braineack's Avatar
 
Join Date: May 2005
Location: Chantilly, VA
Posts: 72,809
Total Cats: 1,780
Default

Quote:
Originally Posted by Zaphod View Post
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.
Attached Files
File Type: msq 2010-01-31_15.47.23.msq (49.4 KB, 143 views)
Braineack is offline   Reply With Quote
Old 02-22-2010, 11:52 PM   #38
Newb
 
Join Date: Aug 2008
Posts: 9
Total Cats: 0
Default

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
hershann is offline   Reply With Quote
Old 02-23-2010, 01:21 AM   #39
Elite Member
 
Join Date: Jul 2005
Posts: 6,454
Total Cats: 80
Default

In my dwell thread, I posted the ideal dwell numbers for the 01 coils. The factory dwell will be slightly shorter than that.
JasonC SBB is offline   Reply With Quote
Old 02-23-2010, 09:02 AM   #40
Newb
 
Join Date: Aug 2008
Posts: 9
Total Cats: 0
Default

Quote:
Originally Posted by JasonC SBB View Post
In my dwell thread, I posted the ideal dwell numbers for the 01 coils. The factory dwell will be slightly shorter than that.
Jason,

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
hershann is offline   Reply With Quote
 
 
Reply

Related Topics
Thread Thread Starter Forum Replies Last Post
Toyota Pickup Engine Swap B.S. Monk Build Threads 24 12-11-2016 03:21 PM
Toyota COP Erat Miata parts for sale/trade 17 02-17-2016 05:22 PM
Bad head gasket or ? shooterschmidty Engine Performance 8 09-30-2015 11:28 PM
Dumb question about crank and cam angle sensors AlwaysBroken Engine Performance 4 09-04-2015 02:35 PM


Thread Tools

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



All times are GMT -4. The time now is 04:10 AM.