Misfire

[andy short]

Hi
I have a Honda blackbird fitted in a single seater race car , I'm having trouble with a misfire which starts at 7200 rpm is at its worst at 8000 rpm ,but then has gone by 9000rpm ,had a rolling road session last weekend and we tried looking at the loggers when it was missing ,but it showed up as being normal ,no trigger loss or anything ,
I'm thinking it must be a hardwear problem after the microsquirt .
I'm using a vw/audi wasted spark coilpack with built in ignition driver and the leads are vw one end and Honda the other [they just screw on] .
has anyone had any problems using this set up and could anyone come up with any ideas what`s causing this ,any help would be greatly received
thanks
Andy

[gboezio]

You may want to post a log and MSQ, so we can check something, if no sync loss, decrease plug gap, this corresponds to max cyl filling on your setup

[PierroMS3]

Hi,

First I would like to thanks you for the MS3 ECU you provide, I really enjoy learning more about engine control with MS3. I'm new to megasquirt but I succeed very quickly to have the engine running, almost at the first try !! So thanks for all the information and the helpfull and interesting manual.

I have a similar problem : Misfire without sync loss. The rpm of misfire can be modified by changing the dwell. The more dwell the less rpm it misfire.

ECU : MS3 / MS3X
code version: 1.3.0
My engine : F4R with intake VVT (from renault clio 3 RS)
Naturally aspirated 2.0 L 4 cylinders, VR sensor 60-2 crank wheel falling edge, poll level for phase determination, check at tooth 4
4 teeth cam wheel rising edge, hall effect sensor.
indirect injection
OEM coil on plug wasted spark with QuadSpark, Spark A and B on MS3X board
Full sequential injection on MS3X board (A,B,C,D)

Composite logger : I only notice that the first tooth after the missing teeth is longer than the other but I also see this phenomena at idle without misfire. I don't know if it's a problem. Do you see something wrong ? I can post another composite logger without misfire in a later post.

In the engine logger, it seems to miss injection, but I'm not sure how to read this file. I understand that this file show overlapping windows, every window separated by symbol "MARK XXX". XXX being the number of the window. Is this correct ?

I tried the following things but without any success or evolution :
- poll level determination at tooth 6, in case of changing phase problem
- change the poll level, just to test
- semi-sequential injection

By playing with the dwell at different rpm and advance, I think I noticed that I have misfire when the coil begin to charge at 72° and 82° before TDC. So taking account my advance table I try to have a dwell table that avoid begin coil charging in those angle by inserting a "jump" in the table. And it works much better I can drive the car around making some other test even beginning tuning my VE table, but I still can feel some misfire around 1900rpm.

On the forum I find other similar case :
http://www.msextra.com/forums/viewtopic ... 25&t=49984
I don't understand how he solved it, if he solved it. Sorry It could be my english understanding

http://www.msextra.com/forums/viewtopic ... 89&t=31619
Maybe not exactly the same problem because, he had sync loss...
He solves his problem by better insulation of the VR cable. I have the OEM wiring harness. If it was an insulation problem, couldn't we see it in the composite logger?

http://www.msextra.com/forums/viewtopic ... 00&start=0
He solve the problem by changing the crank wheel from a 4-1 to a 24-1wheel. But I don't understand what was the problem with the first one.

I will attach my MSQ in the next post because I reached the maximum number attachment.

Andy, did you try changing the dwell ? Can you show composite logger ?

[PierroMS3]

The msq:

[LAV1000]

Most dwell figures are in milli seconds (ms) compare your settings whit the OEM specs of the coils.

[gboezio]

Better start a new thread to get help, this is a different issue than the OP.
But while there, your VR polarity is reversed, swap VR wires and reset 0 degree with a timing light.

[andy short]

Hi
I was looking through the miscosquirt hardwear manual and on page 48 is mentions about fitting a "shunt resistor between the two vr wires to reduce the signal voltage
a 1/4w resistor is sufficient and values in the range of 1k to 10k , 10k is recommended for 60-2 wheels .
so I am using a 12-1 wheel on the blackbird engine and wanted the more technically minded if they can shed some light on this bit !.
is a 10k resistor ok to try ?.
is a "shunt resistor just a normal resistor I can get in maplins or are the special ?.
because of the tooth count ie 12-1 should I be trying a different rating resistor ?.
Many thanks again
Andy

[LAV1000]

Yes they are normal 1/4 watt resistors.
Shunt is the way it is connected to your VR sensor.
They are not expensive postage will be more.
Get a few of the 1kOhm, 4.7kOhm and 10kOhm.
This way you can make up different values.

[andy short]

Thanks for the quick reply ,I have ordered a selection of resistors to try 1k,4.7k,10k,20k,40k,
a question again = if I want to try say 30k can I join a 10k and 20k end to end and this makes it 30k ?
Going back to the trigger wheel being 12-1 any suggestions on a start point ie 10k ? which is what suggested in the manual for 60-2 .?
Thanks again
Andy

[grom_e30]

Thanks for the quick reply ,I have ordered a selection of resistors to try 1k,4.7k,10k,20k,40k,
a question again = if I want to try say 30k can I join a 10k and 20k end to end and this makes it 30k ?
Going back to the trigger wheel being 12-1 any suggestions on a start point ie 10k ? which is what suggested in the manual for 60-2 .?
Thanks again
Andy

the v3 microsquirt already has an internal shunt resistor you just need to connect 2 pads with solder to enable it

[andy short]

Thanks for the info grom ,but I didn't really want to delve into the box itself .
really looking for info as to which resistor to start with the 12-1 wheel ,I have connected up a 10k resistor and going to try that but as it only shows up under load and my next outing is in two weeks time just trying to get as much info as possible !
Thanks again
Andy

[LAV1000]

How and were did you connect the resistor ?

[grom_e30]

Thanks for the info grom ,but I didn't really want to delve into the box itself .
really looking for info as to which resistor to start with the 12-1 wheel ,I have connected up a 10k resistor and going to try that but as it only shows up under load and my next outing is in two weeks time just trying to get as much info as possible !
Thanks again
Andy

i went with the internal on my bike as i was worried that a resistor in the harness may fail due to vibration. 10k is prob a good starting point to try. if you can still start the engine your are prob good. are you actually getting sync loss with rising rpm's??

[andy short]

Thanks again for the quick reply,s
I have mounted the resistor into the loom just before the block connector which goes into the main microsquirt loom I have spliced into each of the vr wires and taken off a spur on each and made up different rated resistors looms which connect into these . I have double heat shrunk all the joints and labelled everything, its also supported in the conduit to combat vibration .
I connected the 10k resister in last night and it started no problems , the only time I can run with the laptop connected is when on the rolling road so its under load which is when the misfire shows up , so making up all the different resistors means I can try at an event during practice .
Thanks
Andy