quote:

Originally posted by 27Keith:
Sorry about digging up this 2 yr old thread, but I was trying to find this exact subject ! My car has been having some consistancy issues that I have traced down to my shift varying 200 rpms. I am shifting off of the yellow wire on the grid. Rpm is set for 7300, i have found shifts as early as 7310 and as late as 7520 ! Thru the racepak voltage graph I can see that the shift is happening when commanded. It varies 200 also. Anyone have any ideas to fix this? In past seasons this has been very consistant.

had a similar issue 20 years ago. Check coil resistance.

The driveshaft graph appears to be good/normal. As for a binding cable, I can see that causing a late shift but not an early one. The Grid review suggestion I will look into when I get home from work but it may be beyond my ability with this stuff. I can check the coil and do have a spare ! Stay tuned for further questions or updates !! Thanks for all the ideas so far.

quote:

Originally posted by 329L:
Without seeing the drive shaft this is all speculation, but the tire might not be hooked.

Bingo! Was going to say the same, wheel speed would do that. Plus G meter.

Get it figured out?

Markemark I am sending you a PM

This was exactly what I was thinking.

quote:

Originally posted by 329L:
Without seeing the drive shaft this is all speculation, but the tire might not be hooked.

I can report that my grid had several hundred runs in the memory. The last 100 or so only had very short recordings. With the racepak I dont use the grid. I did clean it out and have it ready to record on my next trip racing.

quote:

Originally posted by 27Keith:
Markemark I am sending you a PM

I replied

quote:

Originally posted by 27Keith:
I can report that my grid had several hundred runs in the memory. The last 100 or so only had very short recordings. With the racepak I dont use the grid. I did clean it out and have it ready to record on my next trip racing.

My grid has done the same thing before. It's suppose to record over top of oldest run but it messes up every time.

quote:

My grid has done the same thing before. It's suppose to record over top of oldest run but it messes up every time.

The Data Acquisition Overwrite feature in Grid works poorly if at all. For those that do not monitor or maintain I suggest turning the Status to OFF, or installing a larger 8gb SD card, the largest Grid will accept.

When downloading recordings if you select both Transfer and Delete together, it’ll keep your SD card clean for more recordings. The downloaded recording is stored in your laptop Documents MSD file folder and not needed in Grid.

These recordings are not time or date stamped in Grid. They use the present time/ date in your laptop during download. Grid does use a sequence number that is the last 4 digits in the recording file id.

Update,
I was able to clear the grid, change the coil and even installed the wing on the car. I did get 3 runs and got a grid recording on them. What I see is a 20 rpm fluctuation on the shift light thru the grid. This netted me a 50 rpm differance on the actual shift happening. Is this acceptable ? It does seem that the 1st run of the day is the highest shift point which leads me to looking at the shifter/linkage/cable this week.

quote:

Originally posted by 27Keith:
Update,
I was able to clear the grid, change the coil and even installed the wing on the car. I did get 3 runs and got a grid recording on them. What I see is a 20 rpm fluctuation on the shift light thru the grid. This netted me a 50 rpm differance on the actual shift happening. Is this acceptable ? It does seem that the 1st run of the day is the highest shift point which leads me to looking at the shifter/linkage/cable this week.

^^^^^^^ Are you using a crank trigger or a distributor trigger to Grid??

Markemark. Its a crank trigger.

quote:

Originally posted by 27Keith:
Its a crank trigger.

Crank trigger is the most accurate for devices (like Grid) to activate the shift signal at the proper rpm.

In MSD ReView when you are checking the shift rpm of the Shift Light output with the Cursor, are you Expanding (using the zoom in box or thumb wheel on your mouse) to expand the acquisition to the Maximum resolution to set the cursor?? The time period on the bottom should be reading in x.xxxs if you are. If you are Not expanding the acquisition to maximum to set the cursor on the Shift Light, you can/ will be off by 10+ rpms in accuracy.

Here's a simple way to check the actuation of your shift device with the engine off. In Grid Shift Light tab Power-On Test, select ON. Now, every time you cycle the ignition On, it’ll output the Shift Light signal for 3 seconds. If you are using a high amp (40+) electric coil to shift with, it would be wise to turn the ignition off after the shift was executed.

Yes, I am zooming in on the Grid graph to get the most accurate rpm possible.