SNG Barratt V12 Ignition system

[andrewh]

I have an XJ12 with the SNGB ignition system installed. Its not been trouble free to be honest, but when working it has been superb. The trouble is it has a tendency to overheat, just like they always did, and stop working until the bonnet is opened and temperature dissipates. I am trying to establish the facts behind the SNGB Ballast resistor and therefore the coil that should be used with it. I have had the amplifier changed a few times and it has recently been tested to be good. However, the Ballast resistor is showing 0.6 ohms of resistance vs a new one of 1.0 Ohms apparently ( I have not tested this myself but have been told these figures) Now call me stupid but I had been led to believe that the SNG Ballast resistor was in fact not a real BR but a dummy, and therefore presumably have no resistance built into it? If thats the case the coil should be non BR coil. Anyone know much about the SNG ignition system ?

[lowact]

Your issues and description of an Opus system, why do you think you have a SNGB modified system? Are you able to post photos of the inside of the distributor and of the inside of the amplifier?
viewtopic.php?f=6&t=15092&hilit=Lucas+CEI
viewtopic.php?f=6&t=19296&p=156699&hili ... EI#p156652

[MontanaDiver]

I have the SNG system since 2017. I had a failure in 2020 and they replaced the system, it was destroying the rotor. Meltdown and contaminated the cap. Certainly worth checking due to the heat issue. I am now running a Lucas rotor and had no issues so far. I always carry and extra cap and rotor.

I had the same issue with a heat soak no start and blamed it on the ignition ballast getting hot. I added coolers to the ballast and piped air from the wheel well to the ballast with a 150 cu ft per minute capacity. I blamed the ballast until I was at a show and waiting to get into the arena. I idled for at least 10 minutes and she died. Took me a couple minutes to restart and I started looking at a vapor lock. Hadn’t considered this issue in cars since the 70’s with carbureted big blocks in pick up trucks.

After increasing the fuel pressure to 7 pounds to simply increase the flow rate through the non-return valve on the drivers side, I decided I was on the correct approach. I bought a 1/2” pipe foam pice to cover the crossover fuel line from the right pair to the left pair of carbs. I now get in the car, turn the ignition to on to power up the fuel pump, then buckle my seat belt, store my cell phone and put my glasses on(wasting 10 seconds of fuel pump time) and then start the engine. Starts hot in less than four seconds in 90 degree heat.

The foam took a bit to install with the breather and balancer pipes in the same area. Remove the rain guards and have patience.

Dennis

[MarekH]

A similar strategy is adopted with fuel injected cars whereby the fuel pressure reference to manifold vacuum is passed through a temperature sensor on the fuel rail. Fresh fuel quickly drops the fuel rail temperature and the car then operates normally.

....I had the same issue with a heat soak no start and blamed it on the ignition ballast getting hot.

That was never entirely logical because the ballast is bypassed during cranking - there is a white/blue feed directly from the starter relay rather than the normal white wire during cranking. This approximately halves the ballast resistance during cranking because it shorts out one of the resistors.

I hope you drop the pressure back down after cranking. Running a high fuel pressure may cause problems elsewhere one day.

kind regards
Marek

[Nialls Shortbear]

When I installed the SNG Barratt system I modified the loom provided so I could mount the amplifier up front on the picture rail and its worked fine from the start but the car is still low mileage since the restart to be fair. It seemed ridiculous to me they would make the wire lengths so it had to be there in the Hot Vee in the name of making it look original when it isnt, and many folks swear by relocating the opus similarly. I had the impression it was a non ballasted system and they do give you a decent installation book, would it not be given away by the resistance of the coil that came with the kit?