MSD Total loss, Programming

[Jameski]

Purchased a second hand single channel digital pn4272 Msd total loss system and its been working great. It was set up a few years back mostly for racing and i think there could be a bit more bottom end from it.

Can anyone help me with the setting of the switches on the back of the unit so that its performing its best for most bottom end power.

2005superjet
b pipe
boyseen rad-valves
stock carbs
13/17 concord 3mm cutback
bored nozzel
pump cone
riva head 35cc domes
msd lotal loss

 

[Matt_E]

Got porting? What's your compression?
Do you want to run pumpgas or race gas?
Do you care about great topend? Do you intend to do lots of WOT runs?

 

[Jameski]

No porting.
185 compression
Pump gas
not that fussed on top end
and i do a few WOT runs.

 

[Matt_E]

Set Revlimit to 8250
Set start retard to 5000
Set final retard off initial to 17 (17 off 29 to end at 12 deg)
Set static timing to 29 degrees

 

[D-Roc]

http://www.msdignition.com/cgi-bin/timingretard.pl?html_link=calculator

It's the RETARD calculator :haha:

 

[D-Roc]

whoa is there an invisible post here somewhere? i got a notice but don't see the post....I must be the RETARD now.

 

[scottie mac]

Set Revlimit to 8250
Set start retard to 5000
Set final retard off initial to 17 (17 off 29 to end at 12 deg)
Set static timing to 29 degrees

Been a while since i have worked on a 4272, but I don't think you can get a full 17 degrees of retard out of a single pickup system. I know you can on a new style dual pick up system.

Also, the 4272 has retard built into the box, make sure you account for this. I think it is 5 degrees or something like that.

Scott

 

[Matt_E]

You are correct, you need to set static timing to +5 of what you actually want.
Example: To get 30 degrees, set it to 35 degrees.

Scott, I think you may be right with the retard. The newer dual channels let you to a total of 30 degrees retard. The older ones may be limited at 15

 

[scottie mac]

Yeah I thought it was something like that. We just replaced Joe's 4272 with a new dual channel set up because we wanted more retard up top. Sucks, his 4272 was all rewired by John at Jetski Solutions, super trick! Probably going to sell it, anyone interested?

Scott

 

[Jameski]

So theres three sets of switches on the back of the panel, what is the correct sequence of ON and OFF positions for them?

I no very little about engine timing guys and any help is much appreciated.

I have a msn manual but its for the newer verson(2 pick-up). Are the switches on the back the same?

 

[Jameski]

If i want to use the Timing retard calculator.

Static Timing: 34 (29deg+5deg because its the old version)?

Retard Begin Speed: 5000

Max Speed Rev-Limit: 8250

Desired Timing: ??????? At Specific RPM:??????

So what values do i add for the Desired timing and At specific RPM ?

 

[Matt_E]

So theres three sets of switches on the back of the panel, what is the correct sequence of ON and OFF positions for them?

I no very little about engine timing guys and any help is much appreciated.

I have a msn manual but its for the newer verson(2 pick-up). Are the switches on the back the same?

You need to call MSD and have them fax the right manual to you. They are very good about that.

The metal coverplate for the switches should have the meaning of all the switches printed on there.

If i want to use the Timing retard calculator.

Static Timing: 34 (29deg+5deg because its the old version)?

NO!!!! Use the real timing. The +5 degrees is just a safety. The actual, real timing is what you use. So if you dial in 34 degrees, 29 degrees is your actual timing.

Desired Timing: ??????? At Specific RPM:??????

So what values do i add for the Desired timing and At specific RPM ?

Without going into too much detail, simply enter the desired final timing at the RPM limit. So, it should be 12 degrees at 8250, or thereabouts.

Alternatively, enter 20 degrees @ 6250 RPM.

 

[Matt_E]

Those switches are for the dual channel module. You need to get the manual for your module, and double-check all those switches.

 

[Jameski]

Only getting back to looking at my msd setting now, but thanks for all the help before.

Iv downloaded the correct manual for my 4272, and iv got the backing plate of the msd.

There is 4 main sets of switches, first is

MAX TIMING which is set to -2

RETARD BEGIN SPEED set to 5000

MAX REV LIMIT set to 8250

MAX SPEED RETARD set at 15


These where set by the previous owner and id like to no if there correct for best bottom end.

How do i find out what my static timing is? and how do i adjust it?

What changes should i make to the switches that are already set?

Thanks guys.