Technical Classis 500 Wasted Spark

[Alex9721]

Hi All
I have heard that getting a wasted spark conversion improves reliability, so was trying to look on the forum to understand what is how easy a conversion is and the benefits. Has anyone done a conversion on a classic fiat 500? If so can you details on how this went and pointers on the parts and steps needed to undertake the conversion.
Thanks Alex

 

[bugsymike]

Cars like Citroen 2CVs used that system for cheapness I think, but modern cars use it for cleaner emissions.
Not sure how it would increase reliability unless the entire ignition system including spark plugs was duplicated, I know WW2 military aircraft had something like that along with twin magnetos, spark plugs, etc. I suppose it is harder to walk home when an aircraft engine dies.
Still it would be interesting to hear other thoughts re the benefits of wasted spark set up.

 

[the hobbler]

Cars like Citroen 2CVs used that system for cheapness I think, but modern cars use it for cleaner emissions.
Not sure how it would increase reliability unless the entire ignition system including spark plugs was duplicated, I know WW2 military aircraft had something like that along with twin magnetos, spark plugs, etc. I suppose it is harder to walk home when an aircraft engine dies.
Still it would be interesting to hear other thoughts re the benefits of wasted spark set up.

I am in the process of fitting "wasted-spark" ignition onto a 500 engine (enlarged to 595). The original coil was fitted to the left hand side of the engine bay, which has made it easier to install. I have replaced the original coil with a "twin outlet" coil (the last of the air-cooled '126' models used a round 'twin-outlet'coil) which has enabled me to run 2 short ignition-leads to the spark-plugs. The wire from the coil to the distributor just runs round the front of the engine bay. I have left the distributor on 'points', and fitted a'flat-cap' as no rotor-arm or plug-leads are being used on the coil. The 'flat-caps' are only designed for the '126', but by filing a new 'location-slot' on the 'flat-cap', it will fit a 500 distributor.The reason for no distributor-cap or rotor-arm is that BOTH the spark-plugs fire at the same time---inlet AND exhaust, which makes the exhaust firing "wasted" and the spark does not have to be "directed" by a rotor-arm.

 

[thefiatfactory]

Hi All
I have heard that getting a wasted spark conversion improves reliability, so was trying to look on the forum to understand what is how easy a conversion is and the benefits. Has anyone done a conversion on a classic fiat 500? If so can you details on how this went and pointers on the parts and steps needed to undertake the conversion.
Thanks Alex

The simplest way would simply be to replace the coil with a dual outlet item or just trigger two identical coils simultaneously. You could then lose the distributor cap and replace it with a simple dust cover.

The coil (or coils) is still triggered by the original points, but instead of the coil H/T discharge travelling down the coil lead to the distributor cap/across the rotor/thru the cap and along the plug lead to the plug... the coil has two HT leads (or there are two identical coils discharging in unison) that goes straight to each spark plug and they both fire together.

One plug is going to trigger ignition as the cylinder is compressing after the intake stroke, the other will be a "wasted spark" triggering in the cylinder that's on its exhaust stroke.

The stock 126P from around 1986 on has the dual outlet coil and the distributor cover instead of a cap, so it's how the factory does it, cheap.

A modern dual outlet coil is something like a Marelli BAE800 like this,


and the FSM cover to replace the distributor cap looks like this

and clips onto the original distributor to keep the road trash out.

SteveC

 

[Alex9721]

Thanks all. I really appreciate all the comments which is helping build my understanding. I have a few more questions. When removing the distributor cap and rotor arm, what other adjustments do I need to make to set the distributor to be set to “on points” and how is the twin outlet coil triggered by the original distributor as it looks like the twin outlet coil has just two outlets for connecting to the spark plugs?

I have also been looking at twin outlet coils online such as the MobileIron CE-13 which does not have a ballast resistor which is shown on the BAE800. If I get a twin outlet coil without a ballast restrictor and buy a separate ballast restrictor, where should this be wired in and should the condenser remain the same? Thanks

 

[thefiatfactory]

Thanks all. I really appreciate all the comments which is helping build my understanding. I have a few more questions. When removing the distributor cap and rotor arm, what other adjustments do I need to make to set the distributor to be set to “on points” and how is the twin outlet coil triggered by the original distributor as it looks like the twin outlet coil has just two outlets for connecting to the spark plugs?

I have also been looking at twin outlet coils online such as the MobileIron CE-13 which does not have a ballast resistor which is shown on the BAE800. If I get a twin outlet coil without a ballast restrictor and buy a separate ballast restrictor, where should this be wired in and should the condenser remain the same? Thanks

meh, Tiawanese coils don't really inspire me.

BAE800 doesn't have a ballast resistor, it suits electronic ignitions on many Fiat models.

BZ600a is the stock marelli item for a 126

the coil is triggered by the low tension lead from the distributor, the other post on the coil will be power on with the key.

SteveC

 

[Alex9721]

Cheers Steve. I'll order some bits and try and get it done over the Easter break.

 

[Toshi 975]

I like the twin spark set up due to its simplicity but on one car I ran I burnt out two new twin spark coils then bought a replacement that had this little leaflet in the box. Sorted out with a £10 ballast resistor.

 

[the hobbler]

View attachment 483793
I like the twin spark set up due to its simplicity but on one car I ran I burnt out two new twin spark coils then bought a replacement that had this little leaflet in the box. Sorted out with a £10 ballast resistor.

I always try to use the "Magneti Marelli" coil:---170290120607. This coil does NOT need a ballast resister, but if you are using it with ;points', it will still need a condenser. I use the "Swiftune Competition" condenser as it can be fitted remote from the distributor. When you fit a "twin-outlet coil" and retain the 'points', you set the points, and the static-timing (10 deg BTDC) as normal. Being that both plugs will fire at the same time, you do not need a rotor-arm or a distributor-cap to "aim" the spark. A "flat-cap" can then be fitted, which is neat and tidy; but if you are fitting a 126 "flat-cap" to a 500, you will need to file a small slot in the top, side-wall of the distributor in order that the "flat-cap" will sit, and clip-down' correctly.

 

[Alex9721]

This has been great advise. Many Thanks..... I might come back with a few more queries when i start the work.

 

[Pete O]

Cars like Citroen 2CVs used that system for cheapness I think, but modern cars use it for cleaner emissions.
Not sure how it would increase reliability unless the entire ignition system including spark plugs was duplicated, I know WW2 military aircraft had something like that along with twin magnetos, spark plugs, etc. I suppose it is harder to walk home when an aircraft engine dies.
Still it would be interesting to hear other thoughts re the benefits of wasted spark set up.

Confusing the 'wasted spark' concept with twin-spark ignition systems. Piston-engine aircraft have two complete ignition systems and two spark plugs in each combustion chamber, for redundancy as well as more complete burn esp at low RPM. Mazda rotarys have this too, leading and trailing spark plugs and two distributors (or a ridiculously complicated one), necessary because of the shape of the combustion chamber.
Wasted spark means the spark plug fires every 360degrees of crankshaft rotation, ie top of exhaust stroke as well as top of compression stroke. I recall working on one of those horrible Honda microcars of the early 70s that had this system from factory. Makes a lot of sense with a 2-cylinder engine.

 

[Pete O]

I wonder how grafting two HT leads together into a Y would go? Couldn't do it on a high-energy ignition, but if a junction could be effectively insulated and isolated from the metalwork, no other modification would be necessary.

 

[the hobbler]

I wonder how grafting two HT leads together into a Y would go? Couldn't do it on a high-energy ignition, but if a junction could be effectively insulated and isolated from the metalwork, no other modification would be necessary.

A possibility---but would a 'normal' coil have enough 'grunt' to fire 2 spark-plugs at the same time---not a job that they were designed to do, whereas the "twin-outlet" coil IS designed for such a task.

 

[Pete O]

A possibility---but would a 'normal' coil have enough 'grunt' to fire 2 spark-plugs at the same time---not a job that they were designed to do, whereas the "twin-outlet" coil IS designed for such a task.

It would be interesting to try it. I would think it would supply sufficient current considering the dwell time of a 2-cylinder motor is 4 times that of a V8 which will run off the same coil, i.e. magnetic field has somewhere around 4 times the build time. Ask me in about 40 years when I get my Cinq running.

 

[thefiatfactory]

It would be interesting to try it. I would think it would supply sufficient current considering the dwell time of a 2-cylinder motor is 4 times that of a V8 which will run off the same coil, i.e. magnetic field has somewhere around 4 times the build time. Ask me in about 40 years when I get my Cinq running.

nope, wouldn't work.

all it would take is one plug gap to be slightly smaller than the other, and it would only ever fire that plug, it's only going to find a path to ground once, it can't make two sparks... it will always find the easiest path.

even the tiniest thing, like one lead a little longer, anything that offered more resistance on one of your "branches", a little corrosion on the plug terminal even, and the spark will always go the other way.

just stop and think about it for a bit and you'll go ... ahhhh

SteveC

 

[thefiatfactory]

What the "go to" in the day was, well how I did it a few times and pretty sure others did too ... I fitted a second set of points and a second coil, not wasted spark, but definitely a performance upgrade.

500 distributor is easy, it has a screwed in base that mounts the points, so I just got another, cut it appropriately, and positioned another set of points 180 degrees around from the original, two condensors, two points, two coils... that's how you increase the dwell time, oh and you have to grind one of the distributor cam lobes away so there was only one... doubled the dwell and coil saturation time,

I'm sure these days with a 3D printer you could print out a base with two point mounts very easily with CAD software, I did it the cave man way of cut/weld/grind, got it pretty close the few times I did it, but was never exactly 180, was always 179.5 or 180.5 degrees around, but it worked well, required a dwell meter to set the points as they really need to be close to the same gap to get the same dwell

that was the old fashioned way to do it... formula one cars in the 60's still had distributors with points, but they had lots of them, before the days of electronic or even CDI ignitions...

I grew up around an engine that was a V8, had 16 valves and 16 spark plugs. 4 camshafts, two distributors (one driven off each bank of the V) each distributor had four points (so dual points per coil) and two coils. To ensure a spark every cycle at high revs, the engine ran two distributors, four coils, 8 sets of points and 16 spark plugs.

It took quite a while to set the ignition up "just right" ... that had mechanical fuel injection too, so the injection needed timing to get the engine to really be "on song"... and my Dad was the guy that had the "ear" to set these up, sounded glorious at 9000 rpm.

bonus points if you can guess


SteveC

 

[the hobbler]

I

What the "go to" in the day was, well how I did it a few times and pretty sure others did too ... I fitted a second set of points and a second coil, not wasted spark, but definitely a performance upgrade.

500 distributor is easy, it has a screwed in base that mounts the points, so I just got another, cut it appropriately, and positioned another set of points 180 degrees around from the original, two condensors, two points, two coils... that's how you increase the dwell time, oh and you have to grind one of the distributor cam lobes away so there was only one... doubled the dwell and coil saturation time,

I'm sure these days with a 3D printer you could print out a base with two point mounts very easily with CAD software, I did it the cave man way of cut/weld/grind, got it pretty close the few times I did it, but was never exactly 180, was always 179.5 or 180.5 degrees around, but it worked well, required a dwell meter to set the points as they really need to be close to the same gap to get the same dwell

that was the old fashioned way to do it... formula one cars in the 60's still had distributors with points, but they had lots of them, before the days of electronic or even CDI ignitions...

I grew up around an engine that was a V8, had 16 valves and 16 spark plugs. 4 camshafts, two distributors (one driven off each bank of the V) each distributor had four points (so dual points per coil) and two coils. To ensure a spark every cycle at high revs, the engine ran two distributors, four coils, 8 sets of points and 16 spark plugs.

It took quite a while to set the ignition up "just right" ... that had mechanical fuel injection too, so the injection needed timing to get the engine to really be "on song"... and my Dad was the guy that had the "ear" to set these up, sounded glorious at 9000 rpm.

bonus points if you can guess
View attachment 483987

SteveC

Is it a "Repco"?----The original Repco V8 was based on the Buic-Oldsmoblie crankcase (basically the "Rover V8) and was a SOHC (per bank) re-design---the Mk2 version of that engine went to DOHC (per bank), but sadly, was not as successfull as the earlier SOHC engines.

 

[thefiatfactory]

I

Is it a "Repco"?----The original Repco V8 was based on the Buic-Oldsmoblie crankcase (basically the "Rover V8) and was a SOHC (per bank) re-design---the Mk2 version of that engine went to DOHC (per bank), but sadly, was not as successfull as the earlier SOHC engines.

Nope, you're talking Repco-Brabham V8 as used by the late Sir Jack, which as you rightly say had its origins in a buick production engine.

This one I'm talking about was exactly the opposite .

It began life as a formula one engine, when the formula was 3 litres. This engine was also made as a 2500cc V8 and also a 2000cc V8 and also used in sports cars. Later, in the early 1970's the engine (in a detuned version with just one plug per cylinder) found its way into a production car, a quad cam V8 of 2500cc that had a planned run of 10,000 units, but they only ended up making about 4500 of them

SteveC

 

[bugsymike]

Confusing the 'wasted spark' concept with twin-spark ignition systems. Piston-engine aircraft have two complete ignition systems and two spark plugs in each combustion chamber, for redundancy as well as more complete burn esp at low RPM. Mazda rotarys have this too, leading and trailing spark plugs and two distributors (or a ridiculously complicated one), necessary because of the shape of the combustion chamber.
Wasted spark means the spark plug fires every 360degrees of crankshaft rotation, ie top of exhaust stroke as well as top of compression stroke. I recall working on one of those horrible Honda microcars of the early 70s that had this system from factory. Makes a lot of sense with a 2-cylinder engine.

Thank you, I was aware of that, as I said at #2, also the mention of Mazda rotary engines with leading and trailing distributors using contact points etc. I worked as a foreman of a Mazda Dealership in the 1970s and rebuilt a few RX3s and RX4s.

 

[the hobbler]

Nope, you're talking Repco-Brabham V8 as used by the late Sir Jack, which as you rightly say had its origins in a buick production engine.

This one I'm talking about was exactly the opposite .

It began life as a formula one engine, when the formula was 3 litres. This engine was also made as a 2500cc V8 and also a 2000cc V8 and also used in sports cars. Later, in the early 1970's the engine (in a detuned version with just one plug per cylinder) found its way into a production car, a quad cam V8 of 2500cc that had a planned run of 10,000 units, but they only ended up making about 4500 of them

SteveC

You have piqued my interest Steve----who made the engine initially---was it Lancia? Please put me out of my misery.