Vacuum advance on crossflow (1700 Supersprint)

[orangepeel61]

Just been reading "loss of power on 1700 crossflow" post but didn't want to high Jack it.

 

It says the guys at the rolling road fitted a vacuum advance, but I thought this wouldn't work on 40 dcoes? 

 

I'm struggling to find more info. I already have hoses connected to the vacuum take offs on the carbs which I use for balancing, is there anything to be gained by joining them all up and connecting to the distributor? Sounds a bit too easy!

 

 

[Roger King]

It's not generally common to fit a vac advance to DCOEs because you get such a strong pulsing from each inlet tract that it can send the dizzy into a spasm. However, you can in theory connect all four inlet tracts together so the dizzy then sees a smoothed out signal. In practice I haven't found it to work too well but some playing about, maybe fitting a restrictor in the system to damp things down further might be worth trying. Bear in mind that this would be your experiment and your responsibility!

The principle, however, is very sound. 3D mapped systems which generally work off throttle position rather than inlet manifold depression aim to have the same result and are most definitely worthwhile.

[orangepeel61]

Thanks for your comments Roger, the vacuum gauges I use have in line "taps" to dampen the pulsing, when open the gauges go mad! But closed down give a smooth reading I could use these in the pipes.

For the cost of a couple of "T" pieces I think it's worth experimenting, I'll monitor the advance to insure it doesn't go too far and I take your point that it's my responsibility. 

Thanks, Neil. 

[Terry Field]

Is it worth talking to Aldon Distributors direct? It has been some years since I used them, but they were always very helpful.

[orangepeel61]

I was reading a recent post which brought up the old topic of vacuum advance and it prompted me to give an update here which may be useful and on reflection I should have done at the time.

I bought some “T” pieces and some more rubber pipe, connected all the carbs together and to the distributor and I have to say the improvement was amazing, the slow running/light throttle performance was so much better, manoeuvring around Sainsbury’s car park is no longer a problem and popping and banging is a distant memory.

When setting it up my vacuum gauges clearly showed that the pulsing from a single tract was far too erratic but when they were all connected together it was reduced considerably and more so when the distributor was added.

I should point out that the vacuum take offs I’m using are the ones on the carbs, not off the inlet manifold, I don’t think all DCOE’s have them. Mine are 40DCOE 151’s.

Distributor is Bosch.

Although this set up has been running for over 2 years now without problem and so worth looking into, please note Roger King’s comments and warning above, his knowledge and experience is far greater than mine. Maybe there’s something different about my car that makes it work or I’ve just been lucky?

Neil.

[Iamscotticus]

Thanks for the info Neil.  

Ive been looking into vacuum as well.  I really don't care to be needing a laptop, WiFi or Bluetooth to tune my ignition.

Have you gone with the points or a combo vac & electronic hall effect trigger system?

Aldon offers a Xflow vac with Ignitor and Ignitor V.2.  Which I find confusing.  I thought the point of the Ignitor was to be a unit that did the advance and retard without a vacuum line???  

[oilyhands]

When I last used an Ignitor (admittedly some considerable time ago)  it was just a trigger to replace the points/condensor rather than a programmable unit that controlled advance. It was a maintenance free unit which didn't suffer from all the inherent flaws of a points based system.

Oily

[orangepeel61]

Oily is correct, the Ignitor is just a trigger to replace the points with an amplifier to give a bigger pulse, I used one for a while until it starter misfiring, Burton Power were really good and refunded me. 

So I wouldn't be caught out by failing ignition again I replaced it with a Sparkrite SX4000 which is an amplifier that uses the points as a trigger, only a switching current goes through the points so they don't burn out, also the points gap is not an issue, as long as there is a small gap it will switch. The other feature I like is it has a switch on it that takes out the electronics and it reverts to purely points.

Neil.

[Iamscotticus]

Thanks Neil.  goid info.

Now Powerspark Ignition Ltd.

Edited November 30, 2023 by Iamscotticus

[Neil220]

I had an Aldon Ignitor on my Mini Cooper S for over 20 years with zero issues.

There are 2 advantages over points.

No point bounce at high revs, non S minis suffered more from this as the S had stronger points to help eliminate the problem. 

The ignitor produces a near perfect square wave pulse to the coil meaning one could increase the gap in the plugs and get a stronger spark

[Iamscotticus]

Does anyone have info on a Jennings dizzy with MSD internals?

[oilyhands]

On 30/11/2023 at 18:30, Neil220 said:

I had an Aldon Ignitor on my Mini Cooper S for over 20 years with zero issues.

There are 2 advantages over points.

No point bounce at high revs, non S minis suffered more from this as the S had stronger points to help eliminate the problem. 

The ignitor produces a near perfect square wave pulse to the coil meaning one could increase the gap in the plugs and get a stronger spark

And.. as points erode, the timing retards, this does not happen with a no contact system..

Oily

[orangepeel61]

A quick update, the Sparkrite SX4000 has now packed up! Car started coughing and spluttering and lost power.

The saving grace was I was able to flick the switch and revert to points, instant cure without drama or recovery truck.

Will be sticking with points from now on!

Neil.

[Golf Juliet Tango]

I have an Aldon ignitnor on my Crossflow, have done for a long time.

[orangepeel61]

The Aldon Ignitor that I had lasted 2 months, guess I'm just unlucky with electronics. Ironic really after spending 39 years as an electronics engineer! 🤣

[Miker7]

I've been slowly working on an electronic ignition that replaces a couple of parts in the fomoco dizzy (and can be restored back to behind a dizzy) to give you a reasonable resolution trigger wheel which will drive a custom speeduino board. This would mean you could "upgrade" to injection at a later date.

 

I'm a long away off - waiting on results of testing the tiny ECU board before we start making an enclosure & looking for a test mule. If you're interested let me know.

[Iamscotticus]

That's the thing about mechavs electronic timing.  Electronic timing often does last longer than points, but when it goes foul, it goes quick.  Points will eventually need replacing but they rarely fail suddenly.  Electronic timing has the convenience of set and forget, while the points dizzy will need gaping and maintenance to maintain top form.

I doubt the majority of electronic dizzy users will have the acumen to convert to points on the roadside.  It's something worth learning how, a personal goal of mine as my only experience wirh dizzys, besides the few cars I've owned, is the Lucas Aldon on the Cat.

[Colin_T]

Slightly off topic but hear me out…. when I would fit ignition only ECUs to vehicles with twin carburettors, Weber DCOE, dellorto dhla etc, and required a map sensor input it would be required to connect pipes from each inlet tract to dampen the pulsing effect going to the map sensor. 
 

best way for this was a single vac hose from each inlet tract, going to a common manifold block / balance tube. Then a single pipe to the map sensor > same should apply here, except of course go to your distributor.

Something like this ^^^^^^ 

[Gridgway]

21 hours ago, Miker7 said:

I've been slowly working on an electronic ignition that replaces a couple of parts in the fomoco dizzy (and can be restored back to behind a dizzy) to give you a reasonable resolution trigger wheel which will drive a custom speeduino board. This would mean you could "upgrade" to injection at a later date.

 

I'm a long away off - waiting on results of testing the tiny ECU board before we start making an enclosure & looking for a test mule. If you're interested let me know.

I'm definitely interested in such things as I'm looking to move past my Lucas AB14 in the next phase of my resto.

[Miker7]

Finally got in front of a laptop to reply properly.

My idea is hopefully simple & relatively easy to revert back to points - although at the roadside it would require you to carry a few bits so maybe not too practical. I've worked on the ford distributor because i have a few to play with. If someone could take photos of a lucas distributor i could see how practical that would be. Send me a direct message and I'll explain what I'd need.

For the ford distributor I've made a replacement base plate. This contains an optical sensor that outputs a 5v signal like a hall effect sensor or a VR sensor thats been through a VR conditioner every time it sees a trigger (if you don't understand that, it generates a pulse an ECU like Emerald can read). Before you fit my new plate you cable tie the bob weights in the distributor or remove them all together to get rid of mechanical advance and remove the vacuum advance. You then push on a trigger wheel in place of the rotor arm. This generates a unique pattern over 720 degrees so the ECU knows where in the engine cycle the engine is. It can then use this to trigger ignition (or injection or both).

As i want to maintain the period look, i'm currently experimenting with making the trigger wheel and rotor arm co-exist, this means you could use the existing coil and spark leads from the distributor. To trigger the existing coil you wire in a trigger module which isn't very big so can be hidden easily.

Then 'all' you need is the ECU. 

I've done a bit of development with Speeduino so thats what I've picked to play with. A very kind person in New Zealand has reviewed and repackaged the speeduino into a smaller footprint and is currently testing the board. I should be getting a test board to build an enclosure for soon - we're anticipating something around 11cm x 6cm - height i'm less sure off but 3 or 4 cm.

Now some bright sparks are going to point out we've only got trigger angle from the distributor and a coil output. Yep correct. That is the minimum we need to play. The speeduino system will use default values if it doesn't have anything else eg default air temperature is 24 degrees, default water temperature is 80. We can wire in a sensor for vacuum, air temperature, engine temperature etc .... as much as you want to add & the system can then take that into account improving cold start etc. It will also do things like a shift light. However for those just wanting a replacement to mechanical & vaccum advance - we can program in the ford standard and leave it at that.

All of this has taken a back seat due to being a hobby which has got waylaid due to a combination of family issues and buying a K series Caterham.

Note, If anyone want to replace MEMs with Speeduino, i've done the coding to support 5 different Rover flywheel trigger patterns - although i've stalled on the wiring side due to the MEMs ECU connector, i did find a source but it wasn't the £5 i was anticipating and as above life has prevented further investigation.

[Gridgway]

Does sound very interesting.  Is the Speeduino up to the rigours of a car environment?  Well they must be of course!

Just curious about the 720 degree pattern.  Why do you need 720 degrees, unless that is on the crank rather than the dizzy?

[Miker7]

To do sequential you need a signal over 720 degrees. Two ways if doing this, trigger off the cam shaft which runs at half engine speed (so 720 engine degrees per revolution) or have a primary trigger of the Crank (360 degrees) and a secondary trigger which indicates if that is the first or second revolution of the Crank to give you 720 degrees resolution.

 

If you only have a crank trigger you can never know if piston 1 is at tdc or bdc hence you have to use batch injection and wasted spark.

 

In this instance, as the distributor is driven off the cam shaft we have 720 degrees which isn't essential but nice to have for future potential upgrades.

 

Speeduino is on thousands of cars around the world. (Well thousands of units have been produced, I assume at least half make it into a car). It's as robust as the designer of the implementation makes. It's open source so you can take the hardware and implement as your see fit, then run the software on that. The man I'm working with had been building his own ecus since the 80s. He was blown away when he found speeduino as it allowed him to make a step change if what he did by leveraging the work done in the open source community.

[Gridgway]

Sorry, I am going to disagree here.  You don't need 720 degrees from the distributor as that's 4 revolutions of the crank - two complete cycles of all 4 cylinders.

The problem with the crank trigger that you describe isn't that #1 is at tdc or bdc.  It's that it is at tdc twice in the cycle.  So you can have #1 at tdc, but #3 is firing.

There's some basics to be got right here I think!  Sorry. 

[Miker7]

Terminology - one revolution of the distributor is 720 degrees of the engine - two revolutions of the Crank.

Everything is referenced to engine degrees and a full engine cycle is 720 degrees.

Spark 1 fires at some point before tdc. Tdc on cylinder 1 is 0 to degrees, so assuming spark 1 is on cylinder 1 & you're firing at 20 degrees before tdc, its therefore firing at 700 degrees. Spark 2 (in the firing sequence, not necessarily the second cylinder in the engine - you have to wire the second cylinder to fire to the correct spark plug - if your firing sequence is 1342 then you'd wire spark 2 to cylinder 3) would fire at some degrees prior to 180 degrees when that is cylinder is tdc. Spark 3 (cylinder 4) is prior to 360 degrees tdc, spark 4 (cylinder 2) is prior to 540 degrees. Etc.

You are correct I made a mistake explaining the TDC / BDC point. I am tired and was trying to say if you only know the engine reference over 360 degrees, wasted spark fires two cylinders at the same time - eg spark 1 and 3 as you don't know which one of those is TDC and full of fuel, whilst spark 2 and 4 aren't fired as they're both BDC.

Edited March 18 by Miker7