7 pin HEI still having problems after input mods

Ron Foster · Post by **Ron Foster** » Wed Jun 07, 2006 5:40 pm

long post but need serious help.
MS11 V3.0 software 2.35 GM 8 cylinder dizzy with 7 pin module.

I have been having tach spike issues for months. I followed the posts on the hall input mods and have tried both the MSnS-e mod and the transistor mod.
With the original circuit once hot it would miss and shut off the motor

with the MSns-e mod I got some improvement to where the spikes were random at low rpm up to 3000 rpm no matter where the predictor algorithms were set.( very annoying and not really streetable)

with the transistor mod on the surface seams to be worse than the MSns-e mod very erratic spikes. I have played with the predictor seting and both of the VR pots with no luck

I have also tried 2 alternators, 2 different 7 pin modules, radio shack heavy duty 12v filter, MSD flying magnet vr pick up. running power wire direct to battery.

Please reveiw the attached data log. Need help badly

Thanks
Ron Foster

Bernard Fife · Post by **Bernard Fife** » Wed Jun 07, 2006 6:04 pm

Ron,

I can't see any tach spikes on that image, can you post the actual datalog? It lookls like there are some tach drop-pouts, perhaps... but those appear to be caused by inadvertent accel triggering (from too low a threshold value).

And I don't understand the bit about the "MSD flying magnet vr pick up", I thought you said you were using a 7-pin GM distributor. Maybe you could clarify a bit?

Lance.

Ron Foster · Post by **Ron Foster** » Thu Jun 08, 2006 5:41 am

Lance,

I will post the data log when I get home tonight.

When this data log was made I was in the garage with no load trying to hold it some what steady state. The TPS gage jumps around as well as the acell and decel and dwell.Are thinking I just need to ajust the acell enrichment table? On the general setting page I have most of the setting set at %50.

I was starting to think it was voltage or noise related so I feed the unit direct to the battery with and with out the filter.

As far as the MSD crank trigger, I had read in a post some time ago about the stock VR sensor not having enough amplytude at low rpm so I fabbed up a crank trigger with a MSD 8276 ( 3/4 inch dia ) sensor and feed it into the stock 7 pin. I can swap back and forth in minutes, but both seam to have no positve affect.

Thanks for you input
Ron

jsmcortina · Post by **jsmcortina** » Thu Jun 08, 2006 6:09 am

How good is the grounding? The spikes in the MAT and CLT and (I assume) TPS signal look to be the source of your problems.
As Lance says, I don't see any rpm issues.

Display your TPS signal in the log (instead of TPSAcc). If that is jumping around you WILL have problems.

James

Ron Foster · Post by **Ron Foster** » Thu Jun 08, 2006 5:11 pm

Thanks James and Lance,

I took all of the grounds off of the motor tonight and ran right to the battery and the 12v pos. as well. I have made a data log tonight and it still has noise in it. I increased the tpsdot up to 7 and things smoothed out.

Is it possible that the alternator could be inducing a current into the 5v supply? When I put the turbo on the car I had to move the alternator from the drivers side to the passenger side next to the tp switch, when this was done I did add a sheet metal guard with a ground wire. If this is the case will I have to physically move the switch or some type of electronic filter?

Thanks
Ron

Bernard Fife · Post by **Bernard Fife** » Thu Jun 08, 2006 6:06 pm

Ron,

It's hard for me to comment, since I don't see any tach spikes in your datalog. There is a little bit of noise in your TPS, CLT and MAT singals, but I would say it is no more than is considered normal.

Lance.

krisr · Post by **krisr** » Thu Jun 08, 2006 9:47 pm

Where are the sensors grounded?

I have a little bit of noise in my MAT/CLT/TPS as I grounded to the engine block which is then send through a 2GA to the body shell (trunk mounted battery). Try earthing to the same point as your ECU.