max advance

[dcd]

Hi everybody im just new to MS so i have 2276cc engine 86a web cam 42x37.5 valves i also got msd complete set guys in the forum told that i could lock my distributor and set the timing curve with mega squirt 2 but i dont know where is my maximum advance note my CR is 8.5 to 9 also we have sea level going almost 2000m height thx to any info

[Jadewombat]

Need more information. Is this for drag racing or driving on the street?

[dcd]

its daily drive and the trany 3.88

[Jadewombat]

Locking your distributor for a street car is a very bad idea.

You can use the MS unit to control the distributor and build a 3D map using the MAP sensor readings. A normal distributor uses 2D advance--the engine speeds up and the distributor provides more advance. Using a MAP sensor you are able to control the needs of the engine much better. For example 3000 rpms is NOT the same sitting still as it is launching off the line or going up a hill. The MS will adjust to whatever the needs of the engine are based on temperature, air draw, etc.

I would think you can run a little more aggressive curve than a stock distributor, but not much. I'm sure someone else will chime in here. Example crank-trigger maps, you should not run a map this aggressive with a distributor though:

http://www.shoptalkforums.com/viewtopic.php?t=98618

[Rikard]

Locking your distributor for a street car is a very bad idea.

Why would that be a very bad idea?

You can get the input to MS through the points and then control the spark with MS, right? I guess a better way would be to add a trigger wheel, but I would not call it a very bad idea... or am I missing something?



Rikard

[foreverska]

If you're going to fire through your dizzy locking it is definitely the preferable (some would say only) way of doing it. Locking your dizzy without the MS is a pretty bad idea but that's not what we're talking about.

Now for some reason I feel obligated to say:
There is reportedly visible jitter in this setup. While it will give you control over your curve it is less than accurate in this setup especially triggering via points.

[Max Welton]

Locking your distributor for a street car is a very bad idea.

Why would that be a very bad idea?

You can get the input to MS through the points and then control the spark with MS, right? I guess a better way would be to add a trigger wheel, but I would not call it a very bad idea... or am I missing something?

You aren't missing anything. The only difference between triggering via a trigger-wheel and triggering via points in a locked distributor is spark scatter.

Max

[Jadewombat]

Locking your distributor for a street car is a very bad idea.

Why would that be a very bad idea?

You can get the input to MS through the points and then control the spark with MS, right? I guess a better way would be to add a trigger wheel, but I would not call it a very bad idea... or am I missing something?

You aren't missing anything. The only difference between triggering via a trigger-wheel and triggering via points in a locked distributor is spark scatter.

Max

It's not whether or not you could do this on an engine, my question is why would you keep max advance on a Street car?? For an engine that launches down a dragstrip and only runs a few minutes here and there or in autocross, no problem. Unless you know what you're doing, there is a high possibility of overheating an engine locked-out and they are a bear to start unless you dial in some ignition retard while cranking. To gain what? 1-2hp.

Have any of you ever even driven a race car? Most engines set up for race are just that and almost completely undriveable on the street. It is all ON or all OFF and nothing in between.

[jhoefer]

Locking your distributor for a street car is a very bad idea.

Why would that be a very bad idea?

You can get the input to MS through the points and then control the spark with MS, right? I guess a better way would be to add a trigger wheel, but I would not call it a very bad idea... or am I missing something?

You aren't missing anything. The only difference between triggering via a trigger-wheel and triggering via points in a locked distributor is spark scatter.

Max

It's not whether or not you could do this on an engine, my question is why would you keep max advance on a Street car?? For an engine that launches down a dragstrip and only runs a few minutes here and there or in autocross, no problem. Unless you know what you're doing, there is a high possibility of overheating an engine locked-out and they are a bear to start unless you dial in some ignition retard while cranking. To gain what? 1-2hp.

Have any of you ever even driven a race car? Most engines set up for race are just that and almost completely undriveable on the street. It is all ON or all OFF and nothing in between.

Yes, but we aren't talking about running fixed timing. We are talking about disabling the advance mechanisms in the distributor so we can use the points as a tach input to the ECU. If you leave the advance mechanisms enabled, the ECU will get inaccurate RPM readings and also won't have a fixed starting point relative to TDC on which to base its timing adjustments. The ECU itself fires the coil at the programmed amount of advance compared to the fixed starting point of the tach signal.

[Jadewombat]

I guess I misunderstood then. But yes, seems like a waste of time to fire through the distributor with the scatter. As soon as I went crank-trigger and went for a test drive I could feel the difference right away in the lower gears.

[Steve Arndt]

Some classes of racing require a distributor. This method allows full programmability yet retains the distributor for spark distribution.

[Slow 1200]

I think late FI mexi-beetles have a pointless distributor with no advance (I assume it's controlled by the ECU), which would probably work great in those situations

[miniman82]

Best situation if you must keep the distributor is to use a crank trigger and a single ignition coil, this way you get rid of the scatter and you can still fire to all the cylinders the old fashioned way. My experience with MS and distributor/points is they equal big trouble with noise.

[Piledriver]

I have no measurable scatter on my 36-2-wheel-in-a-009 cobbled together setup...
Firing 4 LS2 coils with it, running fully sequential, using one sensor.

Ditching the points etc is the key.
ACVWs don't inherently have the huge spark scatter issues V8s driving the distributor and oil pump etc via a chain and so forth do.