Thread: manual ignition advance

I can't comment on your LPG settings, but there is a far better way to have two different timing solutions -

Try this kit:
http://www.siliconchip.com.au/cms/A_108521/article.html

There are various professional units around, but they are in the performance class of gear.

thanks fellas,
Langy, that's a LOT more civilised that a mower cable
That's ultimately what I would have prefered but just did not realise it was possible without resorting to a full aftermarket ECU and coil packs. Brilliant.
PLR, yes my understanding is that LPG likes a lot of intial but not too much total.

I found the below here http://www.centuryperformance.com/timing.asp
"It is our recommendation that when you are using vacuum advance distributors, that you connect the vacuum advance to "full manifold vacuum". There are two schools on where to connect the vacuum advance line. On older applications the connection point was to "ported" vacuum. Ported vacuum means the port is drawing vacuum "above" the throttle blades in the carburetor. This means that as RPM increases, vacuum increases and in turn, vacuum advance increases. This was fine on older applications with high lead fuel and other ancient engine designs. Using this set up today can cause detonation problems, overheating, and other grief.
With our suggestion of using the vacuum connection to full manifold vacuum, the port will be drawing vacuum below the throttle blades. A good running street engine will have a measured vacuum at idle between 14"-20" of manifold vacuum. Now, this will give you a ton of advance at idle, but as load increases (vacuum drops) you will take timing away. This is excellent for the faster burning fuels offered today as well as in the fact that when you put your foot into the throttle and get the RPM building, you DO NOT need or want additional timing. On a RV or tow vehicle, when you put your foot into the throttle and downshift to climb a grade, you DO NOT want added timing that will slow the vehicle and add heat. You want the added timing for subtle throttle response, and low load engine efficiency. So, when you are cruising at freeway speeds or in town traffic, you have the added timing to save fuel, add throttle response, and overall give you a better feel."
Now from my memory (the LR is not here at work to look) the vacuum advance is ported just to the outside of the butterfly. With this in mind I think I'll modify to full manifold vacuum which should achieve what I want for LPG. I'm thinking I could then just quickly remove and plug the vacuum line for extended petrol use if it is too brutal. Although with 98ron and being a low comp engine it seems to be pretty tolerant, whereas the use of low grade petrol would make it impossible to tune for both - this is probably where most people come unstuck, as the cheapskates who put their car on gas also put cheap fuel in them

Onboard switchable advance curves would be the ultimate though so I'll keep looking into that.

EDIT. If fiddling the vacuum advance works well I could jerry rig a solenoid in the vacuum line to a switch in the cab.

Ok so that's some good numbers to shoot for to start with. Seat of the pants always wins but a base line helps get started. thanks.
I just double checked my RAVE cd and it does say to set dynamic timing at 800rpm max with vacuum disconnected, however I have removed the vacuum hose before at idle and there was not so much as a cough (and the vac advance unit is working perfectly and I have various new vacuum hoses).
My hunch is that as far as petrol goes it'll end up losing top end power but if it's grunty enough I'm a happy short shifter 95% of the time anyway.
So I'll put some of this theory into practice & see how I go.

Originally Posted by oldzook

thanks fellas,
Langy, that's a LOT more civilised that a mower cable
That's ultimately what I would have prefered but just did not realise it was possible without resorting to a full aftermarket ECU and coil packs. Brilliant.
PLR, yes my understanding is that LPG likes a lot of intial but not too much total.

Hi guys,

Has anyone done a distributorless ignition system? I've got the bits of a Ford EDIS-8, coil packs and a trigger wheel... Not installed yet. You can get the controller from the "megasqirt" (or "megajolt") website, but I'm gonna DIY my own software and sensors for a bit of fun. One of my reasons for doing all this is having a Petrol/Gas setting.

the jaycar delay kit based on a 555 timer is a good bet but limited in what it can do for you...

Id be looking at rigging up a second vacume unit that holds the dizzy in place as opposed to the bolts that stop it from turning...

apply vacume to it and the advance is adjusted accordingly.

Well I tee'd off the vacuum hose from the stepper motor's manifold. It is definitely running a lighter throttle on the open road. There's a good big long test hill on the Ippy hwy that I use to compare adjustments. It sailed up tonight at approx 1/2 pedal in 5th, whereas it was almost if not completely flat to floor before. Here's hoping economy improves accordingly but the way I hustled it along tonight I'll have to wait till next tank to find out

Only a couple of glitches; resetting my idle (geezus I hate that feckin stepper) and I have a small flat spot if you could call it that at about say 1800RPM, not a hiccup or cough, just goes thru a trough where it's fallen off the vacuum advance and the mechanical isn't quite up there yet untill a bit over 2000rpm. It's not bad, it's just there, lighter springs would probably sort it. It doesn't pull like a 14yr old from idle to redline.. yet, but it's reasonably strong from off idle to about 4200, which is fine, and more than it had before, with over-rev left to spare. Seemed happy enough on petrol too.
Going to take a bit more than an hour's work of an evening but it's got promise.

update.
The boss drove it today and she reports that it keeps accidently creeping up to 110.

This is all well and good, but what do I do since I have electronic ignition and both LPG and Petrol? ( 1993 Disco' V8i )

I have adjusted the timing as far forward as I can for LPG but when I flick over to petrol, she pings like a MF! ( although if I run her with a light foot she goes OK).

I too want to be able to click from one timing to another to suit both and all these chips seem to be for older/carby style motors.

I did look at the Megasquirt option a while back but it didn't appear to be viable at the time.

I have been wondering about a dyno-tune to see whether there is other ways it can be tweaked.

Cheers, Pete'