BDR on carbs - how much control do I need of the ignition advance

[Gridgway]

In parallel to my efforts to get sparks for my BDR and in contemplating what to do if I can't get the Lucas ignition to work, I'm wondering how much control I need of the ignition advance curve?

Few of the aftermarket units (Lumenition etc) seem to give any control.  I assume its linear advance from about 1,000 rpm to a max at somewhere like 3,500 rpm of something like 35 degrees advance?

Something like the 123ignition allows either pre-selected maps or you can build a map based on vacuum and revs (3D presumably).

Anyone got any experience or views?  Thanks!

[OldAndrewE]

The Lumenition I have in my Xflow just replaces the points and condenser in the distributor.  The advance is still controlled by the springs and weights in the distributor - different springs are available to vary the rate of advance.  Max advance is determined by what is built in (usually marked somewhere on the cam piece which is what the weights and springs move).  

Might also be worth giving these people a call H&H Ignition Solutions I use one of their electronic ignition systems in my Mini and it has been good. As far as I know they are ex Lucas people who set up their own business

[Gridgway]

Excellent, thanks Andrew, very useful.

ETA looks like they repair stuff too, so could be the immediate answer to the no sparks issue!

[OldAndrewE]

"could be the immediate answer to the no sparks issue!"  I am sure they could Graham.  Bit of a trek from Epsom but I would imagine that after talking to them you could parcel it up and send to them for testing and repair

[paul_w]

although most DCOE set ups run with just the springs and weights clockwork advance, in theory some of the carbs/inlets have vacuum ports and if you take vacuum off all the ports and into a suitable plenum (to avoid the pulsing you get if you just take it from one runner) then you can run vacuum advance. Not many people seem to have much success with it though.

I've been thinking about mapped ignition for my BDR, since it's on 45s and is reasonably cammy, and a clockwork advance can only ever be right for maximum cylinder filling at full throttle - the rest of the time it will be retarded from the ideal timing, which means worse fuel economy, running hotter, worse part-throttle response (though probably helps create the over-run popping!). How much worse is debatable, but I was chatting to someone at the Ricketts Racing Lotus day on Saturday who found his 155bhp crossflow was much more flexible when he switched to mapped ignition, and fuel consumption went from high 20s to low 30s mpg. Depends how you use your car, but I'm tempted - after driving it the length of France I'm definitely on cruise or part throttle a lot more than I'm flat out, and high-octane fuel isn't cheap these days...

[Gridgway]

Thanks Paul, so you know what mapped ignition they used?

And agree, the idea of setting up vacuum is not that appealing

[oilyhands]

I've run a number of carbed engines on mapped ignition and the change in drivability is very marked. Normally a throttle position sensor is used for load sensing, I've used Emerald ECUs but appreciate they are an overkill for ignition only setup. Mega jolt is a DIY/open source solution which is not expensive to implement, most systems can be triggered from a distributor or a crank sensor, if you are triggering from a distributor then you would need to lock the centrifugal advance.

There is an article on my website that outlines what may be required it's linked from www.dvandrews.co.uk, follow the link to  'Engine management systems...'

Oily

[alan c]

I had a similar experience when I went to a mapped ignition on a VX16V engine running twin 45's. Little if any change in power but more drivable and mpg improved

The ECU I had was overkill for what was required but I always had in mind to go to full injection which I then did some years later.

[Gridgway]

Thanks all for the info, interesting on the megajolt there Oily.  It may be that my BDR ends up on ITBs through the refurb project.  Depends a bit on what I do with the engine.  Not sure what's in it and whether it needs a refresh.  If it does, I'll probably spend on it for more revs and go ITBs.  What I should do is just get what I have working without upgraditis!