Advance curve help...

[English gentleman]

Hi....does anyone have the advance curve figures for the Aircooled net SVDA distributor?
Been searching the net for a while with little success....the Bentley manual isn't really any help.
I've seen a few generic graphs, but I'm not sure how accurate they are. I'm trying to build a base map for Megajolt (MAP). I know the SVDA won't be spot on for my application but I figure it'll be a pretty good place from which to start.

Thanks for any input or advice....all the best for Christmas! As usual it's cold, windy and damp here in the UK, (as opposed to the 'deep and crisp and even'... )

[Bruce.m]

An 009 curve would be enough to get it running. Then you can add the vacuum advance & amend the rpm based advance to optimise the output.

[English gentleman]

Thanks for the reply. I've read mixed reports on using the 009 as a base map, but I'm guessing it's only going to be a temporary measure....part of me wanted to know what Aircooled net had done to tweak their 'SVDA' Dizzys back in the day...

[Piledriver]

Don't limit a programmable ignition to what a mechanical/vacuum setup could physically do.
(other than as a starting place)
Also don't be afraid of vacuum advance... at <85KPA you can get away with murder and the engine will like it.

If it puts out more power with more advance, anywhere, it needed more advance.

The fastest way to cook heads is with too LITTLE advance, like a 009 at cruise RPM/loads.

[Clonebug]

The problem with all the distributor maps is they don't account for engine load...just rpm.

You can adjust your kpa map to anything you desire.

I would start out with an idle of around 8-14 degrees advance and work up from there. put the 100 kpa load at 30-32 degrees at 2700 and up and from 85 kpa and down like Pile said you can bump up the advance till the engine doesn't like it. Blend everything else in between those numbers then test from there.
Best way is to have someone run the computer and change the numbers in the boxes while someone else drives and holds the engine in certain kpa ranges.
You will be able to feel it in the throttle pedal and the way the engine runs whether you have too much or too little.

[English gentleman]

Thanks for the input. If I'm completely honest, I don't know my arse from my elbow...I've no way of knowing how the changes I make to the table are affecting the engine unless it's observable, so I'm guessing it'll have to be done on a dyno.

As things stand, the modifications I've made to the engine will all affect the ideal advance curve...So here is what I was intending to do:

Book some time on a dyno

have the Megajolt/edis installed but not hooked up

run it up with a 'locked out' dizzy, so the dyno operator can figure out the best settings for known RPM stages

have the dyno guy verify the MAP at each stage (load)

extrapolate the data to put into the MJ map

hook the MJ up and see if it's good to go.....


Does this sound like a plan, or is my ignorance even greater than i thought?

[Clonebug]

If you have a fairly stock engine with lower compression it should be quite forgiving on ignition.

I certainly didn't spend a bunch of time on a dyno to set up my map. You can put just about anything in those boxes within reason and as long as it isn't way out of line it will run. Then you can tune from there.
Every engine is different so you just might as well play with it and feel by the seat of your pants and throttle pedal whether the engine likes it or not.
No one can give you the magic numbers to fill those boxes...that is what is the great part about a programmable ignition....you get to have the control.
On a carb engine jetting will affect the timing and timing will effect the AFR. You might have to adjust one and then the other to compensate for that.......if that makes sense.

On my FI I can do both with the computer so it is much easier than with carbs........that's why I'm done with them.......been there...done that...

Post a picture of your current Megajolt map and someone will comment on it.