Issue:
Do my burn out and then back up. Drive forward to stage and then when I go up against the chip to launch, engine will not rev as it has went into safety shut down mode (2000 RPM). I have the safety time set for 8 seconds.
This has happened to me several times, but fortunately only during time trials. I could extend the time but I'm thinking it could still happen if for some reason I was delayed from getting staged past whatever I might have programed.

My thoughts to eliminate is to put a back up button and use a diode on the car to bypass the transbrake activation through normal means.

FYI I am using a K&R Z force if it matters.

Any ideas??

Dave

Generally the Time From Launch Timer (TFLT) will be reset to 0.00 when the TB is re-energized after backing up if the safety run mode has not been activated. Because you have the Safety Rev Limiter set to 2000 you activate this while backing up. The only way to reset is to cycle the ignition OFF / ON.

You need to raise the Safety Rev Limiter. This is easy, but I want to show you what is actually going on in your engine during shut down.

The first pic is a 6 second car that is not firing the ignition during 3.55 seconds of shut down because the Safety Rev Limiter has been activated. That’s fuel going through the engine and not being ignited. Look at the Rev Limit Active for this confirmation.

The second pic is of the same car with the corrected programming.

Below this I cut and pasted what I wrote in my introduction to Grid from the Tips P. 11 on programming Safety Rev Limiter.
https://i.imgur.com/iPh3dkK.jpg

https://i.imgur.com/tvydAOK.jpg


In the REV LIMITER / SETTINGS tabs, the Safety Run-Time uses a default setting of 12.5 seconds. I recommend leaving this setting during initial set-up. The Safety Rev Limiter has a default setting of 2,000 rpm. This value should be raised to 3,500 rpm. The reason for this is that the engine will be rpm limited to this value while shutting down and driving back from the end of the track. To disable this feature, enter an rpm value that is the same or greater than the “Maximum Rev Limiter” setting. To Tune this feature to the best settings, reduce the Safety Run-Time by 0.5 seconds every run, until you see activity in the “Rev Limit Active” channel in Data Acquisition during the run shutdown. When this activity is achieved in the display, return to the previous Safety Run-Time setting. DO NOT use a Safety Run-Time setting “Less Than” your elapsed time plus 1.5 seconds. Example…. A 9.00 et car should not have a finished programmed setting of less than 10.5 seconds in this example. You want the ignition to fire every pulse unlimited during a “normal” shut down.

A good way to tune the Safety Run settings, is after zeroing a Data Acquisition to Launch, open the Engine RPM, Rev Limit Active and Rev Limit RPM. Do an overlay of these three by selecting the box with the two squiggly lines together. The Rev Limit RPM channel is the “Programmed” safety run limits based on time and rpm. From this you should be able to establish safety run time and rpm settings that keeps the engine firing without interruption during shut down, but also is able to stop a runaway condition.

One last suggestion.

In Grid, if you back-up using the TB button and are activating the Launch input, as long as you Do NOT achieve the Safety Rev Limiter RPM setting and the TFLT is running, the TFLT will reset to 0.00 and you will be at Launch RPM setting on starting line.

If you back up, neutral the trans, rev the engine for some reason and achieve the Safety Rev Limiter RPM setting, you have to cycle the ignition OFF/ ON to reset.

One way to avoid problems if wanting to use this Safety Rev Limiter feature and reving the engine after backing up, one needs to add a separate back up button that would need to have a diode attached to isolate it from activating the Launch input and starting the TFLT.

Thanks Mark, looks like you may have found my fault.. I can't remember on the occasions this happened if for some reason I rev'd the engine. That may have been what triggered it going into shut down..

I will reset the RPM to 3500 anyway just to be safe..

Thanks
Dave

Yep, that he said, I dont do the rev the engine to the moon deal after backing up like everyone does, but my safety start rpm is set only about 500 rpm under converter stall so about 6200. My limit is set at 2500 rpm 9 seconds in and never had an issue with no separate back up button.

quote:

Originally posted by Stephen Hughes:
Yep, that he said, I dont do the rev the engine to the moon deal after backing up like everyone does, but my safety start rpm is set only about 500 rpm under converter stall so about 6200. My limit is set at 2500 rpm 9 seconds in and never had an issue with no separate back up button.

I don't remember what I have my safety start rpm is set at at the moment but that will be the first thing I check. I do remember the rpm is at 2000 though. As I said above I don't remember cleaning it out but for some reason I probably did and started the safety shut down.
I'm like you I normally do not rev to clean mine out..

Dave

The Safety Start RPM is another method (other method being TFLT) of starting the Safety Run-Timer.

Example…. You have the Safety Start RPM programmed to 6500 rpm. You do your burnout and achieve 7500 rpm in the burn out. Because you exceeded 6500 rpm the Safety Run-Timer is now running. As long as you do not exceed the Safety Rev Limiter rpm setting after the timer has timed out it can be reset to 0.00 using the Launch input.

After your burnout, you push the TB button to back up, and because it’s tied to the Launch input the Safety Run Timer is reset to 0.00. After backing up and releasing the TB button the Launch input drops low. Because of this the TFLT now starts which re-starts the Safety Run Timer. As long as you do not exceed the Safety Rev Limiter setting the TFLT will again reset to 0.00 when staged and the TB button is again depressed.

Think of it this way. The Safety Run-Timer starts whenever the Safety Run RPM limit is exceeded. The TFLT will start the Safety Run-Timer when Launch input is toggled from ON to OFF. If the Safety Rev Limiter rpm is exceeded when the Safety Run Timer times out, you’ll need to toggle the Ignition ON to OFF to reset.

I hope this better helps you to understand what is going on in this Grid Safety Run programming.
Safety Run-Time 12.5 SEC
Safety Rev Limiter 3500 RPM
Safety Start RPM 6500 RPM

This thread was confusing to me so I called MSD Tech yesterday and was lucky enough to get to speak with Joe Pando.

He explained that the Safety Start RPM value when the Dark Blue Wire initially sees 12 volt is the one of the triggers for the Safety Rev Limiter. If the engine RPM is below the Safety Start RPM, i.e. idle when the transbrake is engaged for reverse, then the Safety Rev Limiter will not be triggered. The other trigger for the Safety Rev Limiter is when the Dark Blue wire sees 12 volt AND the Launch Rev Limiter value is achieved before the Dark Blue wire looses its 12 volt signal.

I guess I need to pull out the MSD Tester and figure it out later.

This message has been edited. Last edited by: Rodney Pryor,

quote:

Originally posted by markemark:
The Safety Start RPM is another method (other method being TFLT) of starting the Safety Run-Timer.

Example…. You have the Safety Start RPM programmed to 6500 rpm. You do your burnout and achieve 7500 rpm in the burn out. Because you exceeded 6500 rpm the Safety Run-Timer is now running. As long as you do not exceed the Safety Rev Limiter rpm setting after the timer has timed out it can be reset to 0.00 using the Launch input.

After your burnout, you push the TB button to back up, and because it’s tied to the Launch input the Safety Run Timer is reset to 0.00. After backing up and releasing the TB button the Launch input drops low. Because of this the TFLT now starts which re-starts the Safety Run Timer. As long as you do not exceed the Safety Rev Limiter setting the TFLT will again reset to 0.00 when staged and the TB button is again depressed.

Think of it this way. The Safety Run-Timer starts whenever the Safety Run RPM limit is exceeded. The TFLT will start the Safety Run-Timer when Launch input is toggled from ON to OFF. If the Safety Rev Limiter rpm is exceeded when the Safety Run Timer times out, you’ll need to toggle the Ignition ON to OFF to reset.

I hope this better helps you to understand what is going on in this Grid Safety Run programming.
Safety Run-Time 12.5 SEC
Safety Rev Limiter 3500 RPM
Safety Start RPM 6500 RPM

Got it Thanks

Dave

quote:

Originally posted by Rodney Pryor:
This thread was confusing to me so I called MSD Tech yesterday and was lucky enough to get to speak with Joe Pando.

He explained that the Safety Start RPM value when the Dark Wire initially sees 12 volt is the one of the triggers for the Safety Rev Limiter. If the engine RPM is below the Safety Start RPM, i.e. idle when the transbrake is engaged for reverse, then the Safety Rev Limiter will not be triggered. The other trigger for the Safety Rev Limiter is when the Dark Blue wire sees 12 volt AND the Launch Rev Limiter value is achieved before the Dark Blue wire looses its 12 volt signal.

I guess I need to pull out the MSD Tester and figure it later.

Rodney, good call to MSD and getting to talk to Joe Pando.

I agree that this is confusing as written, and using an ignition tester would be easiest to confirm actual operation while monitoring in the Gauges Tab of Grid with your laptop attached.

If you do this, please write a review of what you experienced.

Although I believe this is a great feature, I do not use it.