slew rate

A

Anonymous

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another msd waste. Its only for cars that are perfectly dialed in looking for some starting line control.

but i'm sure somebody will post up how great it is and their friend uses it to get his 4000 horsepower 10" tire car down the track.
 

CutlassRacer

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Helped us win the Drag Radial class at the US Street Nationals in Bradenton earlier this year. :)

I think its pretty cool myself, but not needed until after you science the car out on a perfect track and log a run with zero tire spin.
 
A

Anonymous

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I think it is like an adjustable rev limit to help control starting line power. Seen turbo people use it, but here it is a no-no with nitrous cause of it being a rev-limiter.
 

slow67

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Apr 1, 2007
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Its my understanding that it controls the rate of acceleration by retarding the timing.
 

10secBu

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May 21, 2003
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I haven't used one, but here's my understanding of the MSD digital 7 programmable.

It's got two potential "traction control" functions.

1. timing retard which is fully programmable to amount taken out, how long to bring in 100%, and the agressiveness of the curve.

2. Slew rate. RPM limiting just like the rev limiter only you set a curve which mirrors your engines excelleration rate that way if the tire spins and rpm wants to spike, the limiter will hold it's rate or excelleration.
 

ILLEGAL REGAL

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10secBu said:
I haven't used one, but here's my understanding of the MSD digital 7 programmable.

It's got two potential "traction control" functions.

1. timing retard which is fully programmable to amount taken out, how long to bring in 100%, and the agressiveness of the curve.

2. Slew rate. RPM limiting just like the rev limiter only you set a curve which mirrors your engines excelleration rate that way if the tire spins and rpm wants to spike, the limiter will hold it's rate or excelleration.
I asked about this on yb and pretty much got the same thing out of it.

If I'm correct what you'd do is get a data logger and you can see where you have tire spin. Then in that rpm range you can set a rpm limit and if the tires spin and the rpm's trigger the function it will retard timing to where you set it to and slowly ramp back in at the rate you set to bring traction back and apply power. What does the word "slew" come from or mean in the ignition world?

It sounds very confusing but I think if thats the way it works it's quite cool, but with n2o and your timing retards in that department of the box things will really get tricky. I'll try it.


Todd, you run a logger right? Which one and how expensive does it get just to be able to detect and read tire spin, and that same box can record a wideband also right?
 

10secBu

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May 21, 2003
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ILLEGAL REGAL™ said:
10secBu said:
I haven't used one, but here's my understanding of the MSD digital 7 programmable.

It's got two potential "traction control" functions.

1. timing retard which is fully programmable to amount taken out, how long to bring in 100%, and the agressiveness of the curve.

2. Slew rate. RPM limiting just like the rev limiter only you set a curve which mirrors your engines excelleration rate that way if the tire spins and rpm wants to spike, the limiter will hold it's rate or excelleration.
I asked about this on yb and pretty much got the same thing out of it.

If I'm correct what you'd do is get a data logger and you can see where you have tire spin. Then in that rpm range you can set a rpm limit and if the tires spin and the rpm's trigger the function it will retard timing to where you set it to and slowly ramp back in at the rate you set to bring traction back and apply power. What does the word "slew" come from or mean in the ignition world?

It sounds very confusing but I think if thats the way it works it's quite cool, but with n2o and your timing retards in that department of the box things will really get tricky. I'll try it.


Todd, you run a logger right? Which one and how expensive does it get just to be able to detect and read tire spin, and that same box can record a wideband also right?
I have the basic unit from RPM Performance. http://www.rpmperf.com

I paid $549 last year. It monitors engine & driveshaft rpm as well a battery voltage. It's fully expandable to 12 channels. I later added a WEGOII WBO2 from Daytona Sensors, stocked and sold by Randy at RPM Performance.
 

Excelerater

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you cant slew a nitrous motor or your blow that thing up.......
you can do a gear retard or any retard on a nitrous motor
which is what I am learning to do

MSD does a very poor job with thier software and instructions
not to mention its a VERY old school looking program,afterall
the software is actually over 6 years old when I got my first Dig7
 

CutlassRacer

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None of the cars that I help out with have a data logger. Yeah they are nice, but we have had good success without them. With the Digital 7 you can record your rpm during the run and its pretty easy to see where there is tire spin, especially when you lay the runs over each other and compare a run with no spin vs a run with spin.

We have used the slew rate on an F2 Procharged car that runs 7.70s, a 106mm SBF car that runs 7.80s and a BBC Nitrous car that ran 7.90s before the guy sold it. All of these cars had runs where the "dots" saved them and didnt hurt the engine. All are Drag Radial/Stock Suspension cars.
 
A

Anonymous

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The slew rate was for the pro stockers because they are so exact it will help them go faster because of all the info they have at hand. The way its designed it will only allow you to go as fast as a run you have plotted, before you run so if the track/air is better this run then what? With all of the variables in heads up racing with power adders this becomes a unit that actually will slow you down and not let you find the fastest way down the track. Now if its a true traction control your looking for get one of tobys self learning ones. I might be able to locate a used one if your interested.
 

ILLEGAL REGAL

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I found their site.. does it work as well as they claim? And I'd need the more expensive piece with a crank trigger correct?

How cheap do ya usually see them used because if I had to buy new I can't justify it.
 

CutlassRacer

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Here in FL on these hot summer tracks its practically impossible to get some of these stock suspension cars down the track under full power. My friend Will's BBC/F2 car was "on the dots" for over a second on a few test hits down here and the car still managed to go 5.teens. Getting a car of that nature to repeat should hopefully win him some races. Its been great in testing, time to go racing now :)
 
A

Anonymous

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ILLEGAL REGAL™ said:
I found their site.. does it work as well as they claim? And I'd need the more expensive piece with a crank trigger correct?

How cheap do ya usually see them used because if I had to buy new I can't justify it.
Yes on bracket cars and super class cars they work great.They are just as pricey used.
You don't need one. Ive never used one with nos. You need to dial in a tuneup not look for a bandaid that was designed for something else.
 

DB

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Bigtime said:
ILLEGAL REGAL™ said:
I found their site.. does it work as well as they claim? And I'd need the more expensive piece with a crank trigger correct?

How cheap do ya usually see them used because if I had to buy new I can't justify it.
Yes on bracket cars and super class cars they work great.They are just as pricey used.
You don't need one. Ive never used one with nos. You need to dial in a tuneup not look for a bandaid that was designed for something else.
Ever tried to dial in a tune-up for a small tire car on a 136 degree track??? More than likely the guy in the other lane with the slew rate will beat you to the line......

You still can tune the car to what the track will hold but the "dots" can save your A55. If you have a killer tuneup in the car on a crappy track the MSD still will not stop tire spin. You still have to adjust the slew rate to what you think the track can hold...if your way off you'll still spin.

I usually put the dots far away from what I think the track will hold. I then go back and move them according to the test info. I have used the box on a buddy's car and it worked so well I'm putting it on my own car now as a backup to my usual boost control and timing control.