MSD 7531 slew rate

General Gauges, Wiring, Ignition..

Moderator: John_Heard

Post Reply
Message
Author
User avatar
rsracer
Posts: 20
Joined: Tue Jan 16, 2007 9:07 pm

MSD 7531 slew rate

#1 Post by rsracer » Wed Jan 17, 2007 4:19 pm

Has anyone used it with a nitrous motor and how well does it work?
Is it safe?
Thanks!!!

User avatar
John_Heard
Site Admin
Posts: 5734
Joined: Thu May 12, 2005 11:20 am
Location: Resume Speed, Kansas
Contact:

#2 Post by John_Heard » Thu Jan 18, 2007 1:01 pm

It works but from what I've been told it's real hard on a nitrous motor, you don't want to ride the dots for long. Turbo cars seem to be happy doing it though.

70 nova
Posts: 18
Joined: Thu Jan 18, 2007 6:33 pm
Location: patterson, ny

#3 Post by 70 nova » Fri Jan 19, 2007 7:43 pm

HI GUYS, MY NAME IS ANTHONY,I'M A NEW MEMBER TO THE SITE, BUT I'VE BEEN WATCHING IT FOR A WHILE. I'M KIND OF NEW TO THIS STUFF AS I'M JUST STARTING TO PUT A '70 NOVA TOGETHER WITH MY 7 YEAR OLD SON, AND I JUST WANT TO SAY THAT THERE'S ALOT OF INFO HERE THAT I'M LEARNING ABOUT, THANKS. ABOUT THIS SLEW RATE, I WAS WONDERING ABOUT DOING IT A LOW BUCK WAY, HERE'S HOW IT GOES. LET'S SAY I HAVE A FOGGER THAT IT USE OFF THE TRANSBRAKE, AND A PLATE THAT COMES ON ABOUT 2 SECONDS LATER, AND EACH HAVE A FEW DEGREES OF TIMING RETARD, BUT ON TOP OF THAT I HAVE A FEW MORE DEGREES OF RETARD THAT ALSO COME ON AS SOON AS THE BRAKE IS RELEASED ALONG WITH THE FOGGER AND THE 1ST STEP OF TIMING RETARD, AND MAYBE .75 OF A SECOND THE ADDITIONAL RETARD SWITCHES OFF JUST TO HELP ME GET OFF THE LINE. COULD ANYONE TELL ME IF THIS COULD POSSIBLY WORK, SORRY IF I'M LONG WINDED WITH THIS. THANKS

User avatar
John_Heard
Site Admin
Posts: 5734
Joined: Thu May 12, 2005 11:20 am
Location: Resume Speed, Kansas
Contact:

#4 Post by John_Heard » Fri Jan 19, 2007 9:54 pm

Hi Anthony, welcome to the site.

The Slew rate feature of the MSD 7531 is a simple form of traction control. Ideally it isn't supposed to be activated unless the driveshaft acceleration rate exceeds a predeterminded threshold - like it would if the tires start to spin.

When that happens it activates a rev limiter until the acceleration rate drops back down within the predetermined limits. It's used basically as a "run saver" but shouldn't be used to try to get down the track on every pass - at least with a nitrous motor it shouldn't be used that way.

What you're talking with the multiple retard levels and taking out additional timing to help hook the car up is done quite often. It's a feature you can use in the MSD digital boxes called launch retard which can smoothly bring the timing back whenever you want.

70 nova
Posts: 18
Joined: Thu Jan 18, 2007 6:33 pm
Location: patterson, ny

#5 Post by 70 nova » Fri Jan 19, 2007 10:02 pm

THANKS BEYOND

User avatar
rsracer
Posts: 20
Joined: Tue Jan 16, 2007 9:07 pm

#6 Post by rsracer » Sat Jan 20, 2007 9:56 am

Hey beyond,

How fast is your nova, what size tires do you run?
Is it a heads up car or bracket?

User avatar
John_Heard
Site Admin
Posts: 5734
Joined: Thu May 12, 2005 11:20 am
Location: Resume Speed, Kansas
Contact:

#7 Post by John_Heard » Sat Jan 20, 2007 10:29 am

Last year it was in the 8.70's range on a 28x10.5W tire, I think it had 8.50 something in it with some more work with that same setup. Should be able to improve upon that this year a little bit :twisted:

User avatar
Craig W.
Posts: 1257
Joined: Thu May 12, 2005 11:01 am
Location: Columbia, KY
Contact:

#8 Post by Craig W. » Thu Jan 25, 2007 11:06 pm

Anyone want to share their experience with finding the right settings for the slew rate limiter? I changed over from the 7530 to the 7531 this winter and have no runs on it yet. Being a nitrous motor, I want to stay on the safe side. Thanks.
Craig Watson
2QuickNovas Racing
5.23@131

Sponsors:
AEM Electronics
Carnivore Performance
Rapp Racing
VFN Fiberglass
Fast Shafts

User avatar
rsracer
Posts: 20
Joined: Tue Jan 16, 2007 9:07 pm

#9 Post by rsracer » Fri Jan 26, 2007 5:19 am

Msd has a tech forum that is real good.
Apparently the best way is to go out and make several passes, saving the launch history on every pass. Then you pick the best passes, and can email msd techs and they will help you set up a curve.

Let me know how it works out with nitrous.
Never have run the qtr with the BBC in it, but it runs 5.20's on the plate in the 1/8 th on 28's.
Runs 5.40's on 26 x 10's on a plate.

Post Reply

Who is online

Users browsing this forum: No registered users and 10 guests