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MG MGA - Mapping a distributor advance curve

In a recent thread by Dominic Clancy, he mentioned that he is about to install a CB Performance Black Box Programmable Timing Control Unit.

This is something that I would like to experiment with on my 1950cc engine following the unexplained head-gasket failure that it suffered last Spring.
I have fitted a set of cooler plugs and reduced the ignition advance a degree or so which should hopefully help to prevent a re-occurrence.

My engine which gives around 140 bhp has a what is marked as an MGB Race Electronic distributor (with no vacuum advance), but it doesn't have a makers mark.

So I wondered if anyone can tell me if it is possible to "Map" the advance curve on my distributor so that I know where to start if I get a Programmable Black Box and also, where could I send it to get this done?

Cheers
Colyn
Colyn Firth

Look for the Aldon Amethist
Dirk
Dirk Van Ussel

yes. send it to the guys at Accuspark. they mapped Mark Hesters twin cam dizzy for him at a much lower price than anyone else offered

or use the table at this link

http://www.mgexp.com/phorum/read.php?1,3269307,page=5

it's also for an MGB 1950 and for the CB unit, but Accuspark is probably better for you as you have their Stealth box
Dominic Clancy

don't forget that for all these boxes you have to disable the advance on the dizzy
Dominic Clancy

Colyn
I to have 1950 engine in my A with a full polished and modified alloy crossflow head twin 1.075 " SU's and a Kent 717 cam I expecting about 125BHP just wondered what cam you have
Regards
David
D M SPEAK

Colyn,

I found the 123 Distributor which Peter Burgess installed on my 1800 engined car extremely effective. The distributor has 6 different advance curves and might be the type fitted to your car

https://www.123ignitionshop.com/gb/aston-martin/36-123GB4RV.html

Regards...John
John Bray

Colin, easy to map your distributor by using a dial back timing light. Just record the advance setting at various rev settings from idle to say 4000 rpm Make sure vacuum line is blocked off.

My modified 1950cc engine (110 hp at the wheels) runing 123 Tune distributor has 27.5 advance at full wack. 10.8:1 compression.
123 Tune distributor lets you set 10 advance settings over the rev range to make your own curve or just copy a curve that is known to work on your type of engine set up. Distributor connected to laptop via mini usb cable to setup make changes. Best done in conjunction with dyno and knock sensor feed back.
Mike
Mike Ellsmore

Thanks Dirk and Dominic.

Dominic, I hadnt forgotten about the Accuspark Stealth unit that you supplied me with, I have just been waiting for the the winter layoff before starting to play around with the ignition.
I admit to being a bit worried about experimenting with mapping the ignition, I suppose it is the thought of it detonating itself to bits that is holding me back.

Thats why I thought if I map my current electronic distributor, then at least it would be a safe-ish starting point.

I will contact Accuspark over the next few days.

John, the distributor (non vacuum advance)that supplied by my engine tuner is unmarked but the box it came in just said "MGB Race".
So even if I did try the 123 dizzy I would still have the present one mapped so that I know what it already has before I could see if the 123 would work on it.
(the rear adjustable lever shocks are still brilliant!)

Dave, my 1950cc engine has a ported cast-iron head with a c/r of 9.3 to 1, it has 36mm exhaust valves and 42.9mm inlets and it runs a Weber 45 DCOE carb on Maniflow manifolds.

It is fitted with a Newman PH1 cam with .270 lift,
this cam has amazed me, it pulls really strongly between 1500 and 6000 rpm. (Apparently I could expect around another 10 bhp if I fitted the next cam up, the PH3, but it would lose a lot of the low down torque it has now and so I will leave it be.)

On Peter Burgess's dyno last year ago he found it produced 140 bhp with almost identical torque and I love it.

I would think you should get at least as much power as mine with your crossflow head and probably much more.

Let us know how it goes when it is finished.

Cheers
Colyn












Colyn Firth

I have the Aldon Amethyst fitted on my Frog. As Dominic says, you disable the action of the weights and set the dizzy to tdc. You can then programme the offset (ie static) and degrees of advance. You can also have a vacuum facility which is programmable.
You need to be able to plug in a laptop to do the programming. You can set up a two position switch (ie "on/off"!) to allow you to swap between two profiles on the fly. Or settle for one setting and a rev limiter.
One downside - make sure you have no major electronic interference under the bonnet, such as wire-core ht leads. It will screw up the signal!
Graeme Williams

This thread was discussed on 17/01/2018

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