Programming MSD - when should timing be all in?

[Mopar to ya]

I am playing with timing curves for my programmable MSD-6AL-2. I am running my start up timing lower - around 14 degrees. I ramp it up for idle to around 19 degrees, then I am setting all in around 2800 rpm. Any better ideas? Any thoughts or suggestions for when to kick into all in? I'm running a 408 stroker with 12:1 compression. My max timing on race gas is 38 degrees. 93 octane I max out at 34 degrees.

 

[KitCarlson]

I think it was crackedback that said it all, " give it what it needs". You get there by starting as you have, then working up. I look at RPM, manifold pressure (MAP), advance RPM, advance MAP. Then a dyno, or open space where you can safely drive, check out your timing table. Short term loading at a particular RPM, MAP varies with throttle position, hills help increase load. Ping under load is too much, at light load, fluctuations and roughness, is too much vacuum advance.

I looked at the MSD instruction, the timing controls were set up with retard in mind. I think of advance. I was going to have to rethink everthing, with no need for me to ever use one, I did not go further. So I am not good with helping with MSD settings.

 

[Mopar to ya]

You have to think backwards on MSD. You set your total timing and lock the distributor. No centrifugal or mechanical advance. You then retard the timing through the MSD box. It only lets you take away 25 degrees, so if my total timing on race gas is 38 degrees, I can start at 13 degrees, ramp it up at any rpm of my choice for idle, then make any curve I want. I'm looking for thoughts or for knowledgeable ignition guys who might be able to tell me when they think I should be all in.

 

[crackedback]

Is this a new system? If it is, map it the same as your old one if old worked well.

Even though it's working backwards from total to idle, it's still the same settings at the end of the day. Initial, curve, total, the box doing the work instead of springs weight and limiter bushings.

Keep it out of detonation and it's good.

 

[KitCarlson]

I think we are talking about the same thing, but I set my base timing, then 3D table for RPM and MAP adds to that. I use my own timing reference sensors. I can use base timing to start an engine without ECU intervention.

Giving exact timing curves for you is not possible, it varies with your engine combinations, gearing, weight and even fuel mixture. Timing is about centering the combustion pressure where it applies the best beam in stroke. The ignition starts the event, but flame travel speed is based on mixture ratio, quantity, compression, temperature .... My next project will work with that, by measuring combustion event with sparkplug follow-on current. I am in a clean up mode, to finish and sell a few cars to start the project. After that, it will be a race between mental decline and the completion of the system.

 

[Mopar to ya]

I am not running a map sensor, though I certainly could. I have a Mopar Performance MSD-6 right now and I have no idea what the timing curve was. The new programmable unit has a switch wire that I can use to change retards so I can switch between race gas timing and 93 octane timing with the flick of a switch. I guess I'm going to have to play. I am seriously considering welding in a bung and adding an air/fuel ratio sensor as well. I want to get this thing running well.

 

[KitCarlson]

The MAP sensor for advance addition will aid much in drivability, economy and temperature management. RPM only is good for WOT(wide open throttle). At low MAP (high vacuum) more advance is good. Too little advance at cruise, heats the heads and exhaust, and engine compartment leading to unsolvable heat problems. Good running N/A engines burn the fuel in the combustion chamber where it does good.

Using MAP, RPM table lets you go well beyond a mechanical distributor. The OEM mechanical advance and vacuum daspot have tuning limitations because they are independent of each other. A 3D table solves timing control issues, in coast down, and throttle lift at high RPM. It is also possible to tune in rev limit, by retard, keeping ignition active to burn fuel in carb system.