Dwell issues (50% dc?) , MSnS-E 029o V3PCB

[snillet]

Here is some other necessary information. We are currently using denso coil on plug units from a honda cbr600f4i. We have swapped out VB921 drivers for IGBT drivers, Fairchild 14N40. We did this as we saw a saw tooth pattern on the R43 with the VB921s, which we presume is because the coils are exceeding the current limit very quickly. The resistance is ~1.5ohms, but the saturation occurs in ~1.3ms.

I´ve noticed that this might happen with the VB921 with "high spec" coils. And i think other people here might see likewise things as you do.....

[Peter Florance]

Dumb question:
Are you using the correct ini file (29o) for Megatune?
I've seen small differences in dwell from setting to scoped value but nothing like you're experiencing
 
 
 
Peter Florance
First Fives.Org - The E12 Registry
1981 Euro BMW 528i w/3.5L & Megasquirt Fuel Injection
1981 US BMW 528i "Repo Car"
http://www.firstfives.org
mailto:peter@firstfives.org (peter@firstfives.org)
ssr# 284
 

From: geoffct [mailto:geoffct@gmail.com]
Sent: Wednesday, April 26, 2006 2:03 AM
To: megasquirt-mss@msefi.com
Subject: Dwell issues (50% dc?) , MSnS-E 029o V3PCB




Hi all,

I am with the University of Michigan Dearborn FSAE. After months of configuiration problems, we are having limited success tuning our engine today. MANY THANKS to Eric Fahlgren for his help.

Here is the current big issue, we have a very funny dwell. Though set to 3ms cranking, 2ms running and 1ms min discharge, at idle our scope across R43, reads ~18ms @ ~8A. So basically our coils are cooking. =-( Any ideas as to why the dwell might be off?? In addition the dwell seemed to correspond to rpm, maintaining a 50% duty cycle.

Here is some other necessary information. We are currently using denso coil on plug units from a honda cbr600f4i. We have swapped out VB921 drivers for IGBT drivers, Fairchild 14N40. We did this as we saw a saw tooth pattern on the R43 with the VB921s, which we presume is because the coils are exceeding the current limit very quickly. The resistance is ~1.5ohms, but the saturation occurs in ~1.3ms.

Some of you may have conversed with another member of the team Dan Gielamonster, and I have discussed with about what he has learned here before.

Yes the ignition is inverted. Anything else please let me know...

Attached is the current settings file.

Thanks in advance.
Geoff



This post is at: http://www.msefi.com/viewtopic.php?p=116613#116613


Posted by email.

[jsmcortina]

I might be mis-interpreting things?? but your trigger teeth look really wacky. The tooth numbers MUST follow in sequence. i.e. as the wheel rotates it has to see trigger A (optionally trigger A return) then trigger B then trigger C etc.

You don't _have_ to have trigger A near zero, it could be say tooth no. 55, but as the wheel rotates, trigger B MUST come next.

Otherwise the dwell calcs will be totally messed up - this is probably what you are seeing.

The VB921 goes into current limit mode once the 7.5A limit is reached and regulates using PWM at say 20kHz (I can just hear it.) You may want to try them again once your dwell is fixed.

Also, 122 teeth is beyond the expected limit of the code. Remind me what physical wheel you have.

The code is set to be 8 cyl, but you have 6 triggers per 360 deg ??
For starters, disable spark E and spark F. Set triggers E,F and their returns to zero.

If this is a 12 tooth wheel then set you number of teeth to 12 and try
trigger A = 2 } swap these plug leads over
trigger B = 5 } from the way you have them now
trigger C = 8 no connection
trigger D = 11 no connection

hope I'm on the right track here.

James

[gielamonster]

James, yes its a 12-1 and yes we have the triggers in wacky order. We knew our measured 171* BTDC for tooth #1 vs. cyl #1 was +/-5 degrees or so. When it started and ran nicely on one cylinder by lousy on the other, we started swapping coil leads and trigger teeth until we had both firing as desired. But obviously if running the trigger teeth out of order causes problems, then thats the first thing we'll fix.

Peter, yes it reads 029o at the top of Megatune while we run it. And I used the .bat to copy the .ini myself, it reported it was sucessful.

James, I also saw the really wacky stuff you're mentioning (tooth 55 assigned to E&F) when I tried to load our .msq from home last night. We definitely haven't set them this way, I don't know if there was just an error in the save or what. Our current spark settings should be identical to this .msq

[Peter Florance]

I think James is on to something; I would follow his advice to it's conclusion.
 
BTW, I was thinking that ODU's FSAE was going to try megasquirt but haven't heard from them in a while
 
 
 

Peter Florance
First Fives.Org - The E12 Registry
1981 Euro BMW 528i w/3.5L & Megasquirt Fuel Injection
1981 US BMW 528i "Repo Car"
http://www.firstfives.org
mailto:peter@firstfives.org (peter@firstfives.org)
ssr# 284
 

-----Original Message-----
From: gielamonster [mailto:gielamonster@hotmail.com]
Sent: Wednesday, April 26, 2006 11:54 AM
To: megasquirt-mss@msefi.com
Subject: Dwell issues (50% dc?) , MSnS-E 029o V3PCB



James, yes its a 12-1 and yes we have the triggers in wacky order. We knew our measured 171* BTDC for tooth #1 vs. cyl #1 was +/-5 degrees or so. When it started and ran nicely on one cylinder by lousy on the other, we started swapping coil leads and trigger teeth until we had both firing as desired. But obviously if running the trigger teeth out of order causes problems, then thats the first thing we'll fix.

Peter, yes it reads 029o at the top of Megatune while we run it. And I used the .bat to copy the .ini myself, it reported it was sucessful.

James, I also saw the really wacky stuff you're mentioning (tooth 55 assigned to E&F) when I tried to load our .msq from home last night. We definitely haven't set them this way, I don't know if there was just an error in the save or what. Our current spark settings should be identical to this .msq



2.7 liters of eVil: '86 Porsche 944 turbo... modified.
UM-D FSAE -> My Success Story Free iPod nano!


This post is at: http://www.msefi.com/viewtopic.php?p=116677#116677

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