I'm sure this question has been asked and/or answered before, but I'm just curious. is the driveshaft counter/sensor (or whatever it is called) illegal to use? I know the nhra rulebook said some sort of msd system was prohibited in all classes expect I think pro mod. I know it really does not matter because no promoters are checking anything. (nhra doesn't even tech anymore I think)

No one is checking anything. It can be all over the rulebook, but no one checks and many racers are in the cooler after they lose, so there isn't much motivation to check the winners.

As long as you can't see it live going down the track.

NHRA does not tech anymore. You may see them spot check belts and safety gear, but that's about it.

I'm honestly not sure about the legality or illegality of drive shaft sensors. As far as I know, as long as there is no active feedback to ignition systems, they are fine if used purely for data collection. I know many guys that use drive shaft data to help tune throttle stops and things of that nature. But it's just recorded data for analyzing, not active changes during a run.

In NHRA racing, a drive shaft sensor is legal anytime a data logger is legal for a given class.

quote:

Originally posted by Larry Scarth:
As long as you can't see it live going down the track.

So having a speedometer is illegal?

quote:

Originally posted by dragkid1990:
I'm sure this question has been asked and/or answered before, but I'm just curious. is the driveshaft counter/sensor (or whatever it is called) illegal to use? I know the nhra rulebook said some sort of msd system was prohibited in all classes expect I think pro mod. I know it really does not matter because no promoters are checking anything. (nhra doesn't even tech anymore I think)

Driveshaft sensors are legal for data acquisition. Anything that can indicate track position in real time to the driver during a pass is prohibited.

The MSD system that you’re thinking of is either the 7531 Digital 7 or the 7761 Advanced RPM
module that plugs into the power grid ignition system. Both of these allow “riding the dots” where the user can program a desired RPM curve and the ignition controls the rate of RPM increase (“slew rate”) in order to produce more consistent time slips.

The 7531 digital 7 is illegal for bracket racing. Obviously the grid is legal, but the 7761 add on is not legal. If a 7761 is plugged into a power grid, it sets an indicator in the software that a 7761 has been plugged in - so if there actually was any tech, they would be able to see it. That indicator stays on for 60 minutes of engine run time after the 7761 was unplugged.

What others wrote prior…. DS sensors Are legal for data collection to be reviewed only after the run.

MSD 7531 does not use a DS sensor for SLEW (rate of acceleration) control. I’ve seen 7531 ignition control in bracket ET cars and never give it a thought that SLEW function is programmed or being used.

so basically, if it's being used to record data during a run its legal. if being used to "control" or run dead on everytime its ilegal.

quote:

Originally posted by markemark:
What others wrote prior…. DS sensors Are legal for data collection to be reviewed only after the run.

MSD 7531 does not use a DS sensor for SLEW (rate of acceleration) control. I’ve seen 7531 ignition control in bracket ET cars and never give it a thought that SLEW function is programmed or being used.

From a technical discussion pov, I’d really like to hear how the resolution really is on slew and if it can be used for uber consistency. I have been a doubter since they came out with slew. It is designed to catch tire spin to rescue run that would otherwise be throw aways. I haven’t seen that the competitive limited tire groups are using the msd version. But I don’t have much exposure to those groups. Can they be so accurate that they can make a car repeat to .005? As I said I have my doubt. And the folks who do know aren’t sayin lol

quote:

Originally posted by Bucky:

quote:

Originally posted by markemark:
What others wrote prior…. DS sensors Are legal for data collection to be reviewed only after the run.

MSD 7531 does not use a DS sensor for SLEW (rate of acceleration) control. I’ve seen 7531 ignition control in bracket ET cars and never give it a thought that SLEW function is programmed or being used.

From a technical discussion pov, I’d really like to hear how the resolution really is on slew and if it can be used for uber consistency. I have been a doubter since they came out with slew. It is designed to catch tire spin to rescue run that would otherwise be throw aways. I haven’t seen that the competitive limited tire groups are using the msd version. But I don’t have much exposure to those groups. Can they be so accurate that they can make a car repeat to .005? As I said I have my doubt. And the folks who do know aren’t sayin lol

These are good questions, but I would approach it from the lens of minimizing effects of weather as opposed to tire spin for bracket racing.

Make a run in “bad air,” and set those dots for future runs. If the air gets good and the car wants to go faster, slew rate will prevent that. But the question remains how well it actually works.

I don't think you're going to get a slew to get you to repeat .005, but if you run a 3 day race (or qualify 2, race the next) it's not going to hurt

Say you're qualifying to run a 7.00 index, It's going to take your 3 day spread from 6.97-7.04 to 6.985 to a 7.025.

Doesn't guarantee a race win, but it sure helps.

This message has been edited. Last edited by: Yellow Ticket,

quote:

Originally posted by 183N:

quote:

Originally posted by Bucky:

quote:

Originally posted by markemark:
What others wrote prior…. DS sensors Are legal for data collection to be reviewed only after the run.

MSD 7531 does not use a DS sensor for SLEW (rate of acceleration) control. I’ve seen 7531 ignition control in bracket ET cars and never give it a thought that SLEW function is programmed or being used.

From a technical discussion pov, I’d really like to hear how the resolution really is on slew and if it can be used for uber consistency. I have been a doubter since they came out with slew. It is designed to catch tire spin to rescue run that would otherwise be throw aways. I haven’t seen that the competitive limited tire groups are using the msd version. But I don’t have much exposure to those groups. Can they be so accurate that they can make a car repeat to .005? As I said I have my doubt. And the folks who do know aren’t sayin lol

These are good questions, but I would approach it from the lens of minimizing effects of weather as opposed to tire spin for bracket racing.

Make a run in “bad air,” and set those dots for future runs. If the air gets good and the car wants to go faster, slew rate will prevent that. But the question remains how well it actually works.

In an unexpected tire spin situation, the only recovery is a blast of nitrous, or a boost "scramble", coupled with a superior reaction time, and good stripe driving skills.

But, to set it up, you make a good run, then plot your rate of acceleration slower than the car is capable of, and ride. That way the system can speed up or slow down the vehicle, to hit the specified time spots.

The original Matty users attracted attention by slowing a car down WAAAYYYYY below capability, and not looking around at the stripe while running dead on.
That system only gave the driver the live display of "too fast" or "too slow" against the target run.

Or you take a 7.00 car and make it run 7.48 in the 1/8 at every track and in any conditions. Summer, fall, mountains, sea level.

They are out there and no one gives them a second look.

quote:

Originally posted by TomR:
Or you take a 7.00 car and make it run 7.48 in the 1/8 at every track and in any conditions. Summer, fall, mountains, sea level.

They are out there and no one gives them a second look.

There was a time when if you had a car that would repeat within .02, you could be King Turd on **** Island.

Funny you should mention repeatability, or same dial in. My car is sitting here with 6.54 on the window and I seldom change it. Last night looking at a picture from 10 years ago and there it was--6.54. One summer at my local track I won the dash for cash 8 times in one summer, never changed my dial in. Now if I ever learn how to hit the tree I may win a race somewhere, MAYBE!

Geeze paint it on there!
I can change what my car runs by .7 using the laptop in a minute. I don’t have all the data to know what it will exactly run after the change though. Lol

quote:

Originally posted by ferndaleflyer:
Funny you should mention repeatability, or same dial in. My car is sitting here with 6.54 on the window and I seldom change it. Last night looking at a picture from 10 years ago and there it was--6.54. One summer at my local track I won the dash for cash 8 times in one summer, never changed my dial in. Now if I ever learn how to hit the tree I may win a race somewhere, MAYBE!

I recently ran across a pair of time slips 21 years apart, within .01 all the way through.