MSD7531 and E85

MSD Digital Ignition Programming & Troubleshooting, Playing with Dots, Slew and other fun toys for traction challanged racers

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The Uncle
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MSD7531 and E85

#1 Post by The Uncle » Mon May 21, 2018 3:49 am

I want to retard the timing at the starting line and then ramp it up to the normal timing.BUT E85 is a special fuel.
Due to the fuel characteristics of E85 is this possible without any problems,OR will it richen up and bad things
could happen?The fuel curve need to follow with less timing and it will go rich.....it was told to me.

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John_Heard
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Re: MSD7531 and E85

#2 Post by John_Heard » Mon May 21, 2018 8:46 am

I really doubt this is any big deal to take a bit of timing out at launch, you could use the Launch Retard feature on the 7531 to do it. Not sure how many degrees you're talking about but I don't really see it having any issues to take out a few degrees of timing out at launch.

The Uncle
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Re: MSD7531 and E85

#3 Post by The Uncle » Mon May 21, 2018 10:17 am

Thanks for the answer,so there will be no issue during the launch retard.
This helps me to launch better....Total timing is 34 degrees.Any ideas how much to retard
and in which time to go back to the original timing?

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Re: MSD7531 and E85

#4 Post by John_Heard » Mon May 21, 2018 11:04 am

There's a lot of questions as far as how much and how long to ramp the retard out.

If the car is hooking ideally use no retard at all.

If the car is just barely hazing the tires at launch, probably only a degree or two for say 1/2 second - just really depends on what it's needing. If it's totally nuking the tires at launch, quite a bit more.

Do remember the way the 7531 works, launch retard is also pulled while you're on the transbrake, so if you pull a lot out it can make the engine a bit hard to get up to launch rev limit. One of the good features they fixed on the new PowerGrid, it has the ability to not do that and only pull the timing after the brake is released.

The Uncle
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Re: MSD7531 and E85

#5 Post by The Uncle » Tue May 22, 2018 12:36 pm

This seems to be a good starting point,cause some of the tracks on which we are running are bad,
so we lost time at the starting line,when we spin the tires instead of making them grip.
Suspension works great with the help of Santhuff Shocks.
We smack the converter not near the stall speed,we run into the converter 1500 under.
I got the tip to this forum from carb guru Mark Whitener.... :thumb:

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