Ignition Mapping

[gav]

Hi all

I do the occasional hill climb and sprint and the rest of the time, my Sprint is used on the road.
I should state at this point that I am reasonable on mechanics but haven't got much of a clue about electrics and electronics.
I am planning to fit the programmable Aldon ignition control unit and am likely to have it set up on the rolling road.
I see from the instructions that I could fit a switch in the cockpit to enable me to switch between two ignition maps.
When I was looking into fuel injection, the three way switch made good sense - you can switch between 3 different performance maps and completely change the characteristics of the power delivery which would have been great. Sadly, financial circumstances mean that I cant afford it so I'm going for the considerably cheaper alternative to sort out my slow speed running. The consensus seems to be that the problem seems to stem from ignition curve issues and that the carbs which are great over 2,500 rpm should be ok at lower revs so long as the ignition curve is sorted out.
My question is - what is the benefit of having two different ignition maps and would I really notice the difference?
I'd be interested in others views.
Thanks in advance
Gavin

[Spyder fan]

Hi Gavin,
Have you downloaded the instructions / software?
Instructions here http://osneyconsulting.com/AmethystInstructions.pdf
software here http://osneyconsulting.com/Resources.htm

from a brief read through, you will need a throttle position sensor (TPS Version Amethyst).

As for having 2 switchable maps, it appears that you lock the advance curve on your existing distributor and then set an electronic mappable advance curve to suit your engine characteristics, therefore you could have an aggressive curve for your hill climbs and a softer less peaky curve for normal road use. I would suggest you couple this together with different jets for competition to allow greater fuelling at higher revs.

It looks a nice system and takes away the chore of altering the advance curve with weights and springs as well as taking the wear and tear issue out of the equation.

A good rolling road session complete with different jet settings for your webers should do the trick.

I run emerald 3d management with jenvey throttle bodies, I don't bother with the switchable mapping as my car is 100% road use, but being able to plug in the laptop and alter the fuelling enrichment on hot or cold starts was a real benefit especially as my engine setup is a one off. Very expensive though!

[AHM]

Gav,

Ignition timing is a 3 dimensional problem and is affected by many variables. Our main variable is throttle position Ie how far open it is. So you may want one map for reliability ie smooth tick over and pick-up at partial throttle opening. And you may want another map one for maximum power with your foot to the floor.

The same goes for Webers, bigger choke for high revs smaller choke for low revs. but you have to take them to bits rather than flicking a switch. Read up on how Webers work. The 2500 rpm that you mention is variable with choke size, below that they 'dribble' the fuel in, so Ignition timing is adjusted for reliability rather than power.

Unless you add sensors (and cost) your black box doesn't know if at 2000 rpm you are pootling in traffic or foot to the floor going up a hill.

Your rolling road session is going to be as much about carb set-up as it is ignition timing so do read-up on how they work (purely mechanical) and decide what you want from them.

[elanman999]

Gavin,

Before I fitted EFI I used to run 3D mapped ignition and carbs. Yes, that in itself is worth doing particularly if your dizzy is worn. Two maps might be useful if you are running a high compression ratio, to enable you to run one map for 97 and the other for 95 octane fuel.
I now have an Emerald and TB's on my +2 which has power, economy (closed loop with Lambda) and low octane maps. But the difference between the 3 power wise can only be seen on the dyno not by driving.
I would not go back to carbs and dizzy now.
Just my take on things.
Cheers
John

[jono]

John,

Which system did you use when you were 3D ignition only? This is what I have installed on my +2 (Megajolt Lite) and I was looking to see if I could scrounge a proper map from someone

Jon

[elanman999]

Jon,
It was an Omex, well have not sold it yet!
I could PM you a spreadsheet of the data and for the emerald if that's any good for you?
Cheers
John

[gav]

Chaps

Not fair - I'd love fuel injection but can't afford it.

Out of curiosity - John why did you leave Omex in preference for Emerald?

Thanks for input to date - further thoughts gratefully received.

Gavin

[elanman999]

Gavin,
Now that's asking me to put it on the line.
I'll PM you.
Cheers,
John

[pauljones]

Happy xmas all.

If you look through my previous posts I put on an ignition Map for a standard 105bhp twincam. This was from a rolling road session. Its a good start if you want to use it as a base.

Its for an emerald equipped twink with twin 40 jenveys.

I have a few more Maps from zetec and duratec engines too if its of any use to anyone.

Paul