misfire with fast system & msd dis

[ANSPETE]

I have been hearing about this misfire issue with cars running the fast system & msd dis box together.Was on the dyno today with a turbobuick.It had a misfire that would start anywhere from 5700 to 6250 on up.Sent the fast box back to fast and they made a change to it same problem.Took the msd out of the system problem went away.So on the last pull decied to plug it back in.The car went back to missing at 6250.Now we dont no what to do.So decied to check the switches on the msd box again,all looked fine until we got to the max rpm rev limit.They were all off thinking if there off the rev limiter is off not the case.With them all off its set at 6250.Turned them all on now its set at 10,000 made a pull on the dyno pulled clean all the way to 7300. Then we met our goal 856 rwhp.Made some calls to all the people i know with the problem checked there rev limit switches they were all set at 6250 with the switches off.So i think we solved all the misfire problems we were having here.If anything changes i will let you know.I hope this helps.
Pete Barton

 

[elcato]

Originally posted by ANSPETE
I have been hearing about this misfire issue with cars running the fast system & msd dis box together.Was on the dyno today with a turbobuick.It had a misfire that would start anywhere from 5700 to 6250 on up.Sent the fast box back to fast and they made a change to it same problem.Took the msd out of the system problem went away.So on the last pull decied to plug it back in.The car went back to missing at 6250.Now we dont no what to do.So decied to check the switches on the msd box again,all looked fine until we got to the max rpm rev limit.They were all off thinking if there off the rev limiter is off not the case.With them all off its set at 6250.Turned them all on now its set at 10,000 made a pull on the dyno pulled clean all the way to 7300. Then we met our goal 856 rwhp.Made some calls to all the people i know with the problem checked there rev limit switches they were all set at 6250 with the switches off.So i think we solved all the misfire problems we were having here.If anything changes i will let you know.I hope this helps.
Pete Barton

Could this happen on the regular LS1 coil edist box???

 

[ANSPETE]

Not sure just double check the rev limit switches to make sure their set right.

 

[termn8]

well, I sure am glad to see there is some reasonable resolution to this frustrating problem. It seems like a real simple fix and makes lots of sense. I have previously reviewed a number of posts where members were unhappy with fast and msd's solutions to the problem and several were getting rid of the box and eliminating their two step. I had seen members posts where they were borrowing known "good" boxes for their next meet. Maybe the good boxes were just set up right without setting the switches to limit at 6250??? I went out and found the 4 switches on my box were set in the wrong position, have since reset them and am anxious to get the car on ANS's dyno to see if this has finally solved lots of frustrated members problems. I personnally find it hard to believe with all the boxes that were sent back to msd their techs never caught the last 4 switches in the wrong position or saw that so many members mis-read the set up instructions. I heard talk, there may be some new boxes with knobs and no switches. If this turns out being the solution I'm sure there would be LOTS of happy members with some clearer set up instructions Good luck guys.... I hope this is the ticket!!!

 

[Chuck Leeper]

A suggestion..

termn8 said:
"well, I sure am glad to see there is some reasonable resolution to this frustrating problem. It seems like a real simple fix and makes lots of sense."

I'd not get overly confident that something as simple as a change in sw. settings is the cure.
As I recall, the tests by MSD and FAST led me to believe there's alot more to this than a switch....

 

[termn8]

The box that Pete is referring too was sent back to MSD, was inspected and modified, then returned to the owner. When the box was returned the sw switches were in the same location they were in when the box was sent out to be inspected As we all know... these are both highly respected manufacturers and maybe there really ins't anything wrong with their product, we just might be setting the units up wrong. (I know my switches were in the wrong location..... it's just too cold to take the car to the track.) Maybe when other members check their boxes we'll find out if this theory could be valid.

 

[Chuck Leeper]

?????

Here's about 80 posts on the subject.

http://www.turbobuick.com/forums/showthread.php?s=&postid=733872#post733872

I just talked to some folks, and they've seen no reply to the statement from MSD as to what their position is. [Last I saw was Sept 26th from MSD]

For you "really fast" guys, it may be time to go to a distributor and a 7AL/crank trigger??? [Like Cairns!! ]

One racer I talked to did this, and the car picked up 5mph, no other changes....WOW!!

 

[Chuck Leeper]

??? update??

I sent Spike at MSD an e-mail asking for an update on the problem and what could be done. We'll see where this leads us.

 

[Craig Smith]

Re: Re: misfire with fast system & msd dis

Originally posted by elcato
Could this happen on the regular LS1 coil edist box???

Actually, the eDist isn't part of the equation in this application. A Turbo Buick with a FAST and DIS-4 actually won't use an eDist.

The problem has to do with dwell timing on the EST signal coming out of the FAST and the input debouncer on the DIS-4. However, even in a worst-case scenario, I do not see how the issues we haev identified with MSD could impact a Turbo Buick below 7400 RPM so I am still a little confused as well.

FAST and MSD have basically agreed that we will address this issue together, and I believe this is why Spike hasn't posted anything further on this subject. In the mean time, please be assured that FAST and MSD are working together on not only preventing this in the future but dealing with customers currently having trouble.

 

[DOHC Vobra]

Craig,
Any chance this could cause problems in my case? I'm having a problem where my setup won't pull beyond about 6300RPM, it kind of feels like the ignition is breaking up. I've tried fattening/leaning fuel and retarding/advancing timing with no luck so far. I'm also going to try reducing my plug gap from .035" to .030". I'm running a FAST with an EDIS-8 (waste spark) and MSD-DIS4 on a 4.6L DOHC Mustang.

Best,
Justin

 

[Craig Smith]

On a V8, that's possible. Less time between cylinders at any given RPM so this could be your issue.

 

[DOHC Vobra]

Craig,
Thanks for the reply... that's what I was thinking... I guess I was just wondering if the EDIS-8 was isolating me from that problem, since the FAST is no longer directly controlling the ignition box (and only controls the EDIS)

Justin

 

[John at J&S]

Anyone try adding MSD 8912's between the coil pack and the DIS-4? The 8912's put out a short trigger pulse to the MSD.

 

[Craig Smith]

The 8912 is definitely not a piece you want to use with the FAST system and a DIS-4. The 8912 and the eDist are not compatible.

The purpose of the 8912 is to provide an inductive kick that later OEM computers typically see when the factory coils are triggered. When the computer sees the inductive kickback, it basically uses it as verification that the coil fired. It's part of their misfire detection. However, the load that the coil in the 8912 places on the eDist typically is too much for the eDist to handle.

 

[John at J&S]

OKOK. I was talking about non EDIS installations.

Does the factory coil module cause the MSD to misfire? If so, you could put an 8912 between the coil pack and the DIS.

The 8912 is different from the earlier tach adapters. It has 12v, Gnd, input, and ouput.

The input wire connects to the ignition driver, and provides the high voltage kick back as you described. The output is a short 12v pulse, to trigger the DIS.

I've talked to some tuners using standalones wth the DIS, and they say the dwell time fed to the DIS makes a difference. The output of the 8912 is a standard trigger pulse that the DIS seems to like.

 

[T- Type Tim]

??? update??

I sent Spike at MSD an e-mail asking for an update on the problem and what could be done. We'll see where this leads us.

Did you ever get a response on this matter?
or are we still waiting?

 

[Chuck Leeper]

Never heard...At least I don't think I did.
But that was 21 yrs ago and I'm 85.