Triumph tr7 ignition

[Nige T]

I am planning on fitting and Aldon / Petronix electronic ignition to my TR7. I have read about other owners by-passing the ballast resistor and taking a switched live feed direct to the coil, either from the white wire coming from the ignition switch, or from a switched feed on the fuse box.

My question is will the existing wiring support the additional load placed on it by supplying the coil as well? And what if I wanted to use a high output / sports type coil?

Any advice would be appreciated.

Nigel

[Beans]

I have fitted various electronic ignitions to my TR7's
On both cars I kept the ballast wire and 6V coil.

Just connect the live feed for the unit from a 12V source.

[Clive]

on a dolly 1850 I have just fitted electronic ignition (a cheaper "stealth" one) but teh distributer is identical. And teh dolly uses a 6v coil/ballast.

I fed the electronic ignition live direct from the ignition live terminals of the fusebox, all no issue at all. I assume the EI unit only draws a small current and switches teh coil negative to earth. Whatever, this EI ran in another identical setup no problem for thousands of miles.

[RobPearce]

As Beans and Clive both said, an EI will drive a ballasted coil fine, it's only the EI's own (low current) supply that needs to be direct from the ignition live circuit. I've done so with several makes over the years.

[Howard]

With the original TR7 ignition, when you turn the ignition key to start the car, an auxiliary contact on the starter relay applies 12v direct to the coil. When the engine starts and you release the key, the 12v is disconnected and the coil is fed via the ballast wire which reduces the coil voltage to about 6v.

My very old electronic ignition is wired this way and works well:-

12v supply from white wire to electronic ignition whenever the car is running

12v supply to coil when starting - white yellow wire from starter relay fed from 12v brown wire through aux contact.

Approx 6v via ballast wire when engine is running. Also white yellow wire joined to white yellow wire (to coil) at starter relay.

Howard

 

[Nige T]

On 11/12/2022 at 22:18, Howard said:

With the original TR7 ignition, when you turn the ignition key to start the car, an auxiliary contact on the starter relay applies 12v direct to the coil. When the engine starts and you release the key, the 12v is disconnected and the coil is fed via the ballast wire which reduces the coil voltage to about 6v.

My very old electronic ignition is wired this way and works well:-

12v supply from white wire to electronic ignition whenever the car is running

12v supply to coil when starting - white yellow wire from starter relay fed from 12v brown wire through aux contact.

Approx 6v via ballast wire when engine is running. Also white yellow wire joined to white yellow wire (to coil) at starter relay.

Howard

 

 

[Nige T]

Many thanks for your responses. Once I have purchased the electronic ignition, I have a feeling I will be back here asking more questions (car electrics are not my strong point)!!

Would anyone have any recommendations regarding EI modules, the fit in distributor type?

Nigel

[Clive]

55 minutes ago, Nige T said:

Many thanks for your responses. Once I have purchased the electronic ignition, I have a feeling I will be back here asking more questions (car electrics are not my strong point)!!

Would anyone have any recommendations regarding EI modules, the fit in distributor type?

Nigel

https://www.ebay.co.uk/itm/182178882551

That is what I have been using without any issues for several years and lots of miles.

[Nige T]

Thought I would update on my electronic ignition, which I finally got around to fitting. I decided to go with the Petronix unit in the end as I had it fitted in a previous classic with no issues. Also, the Petronix unit for the TR7 uses the existing cam lobes, rather than having to fit a magnetic sleeve which would have meant dismantling the distributor.

As I had read, the distributor bolts are a pig to get at, so I bent a ring spanner in the vice as attached photo which did the job and saved my knuckles. To get the bolts back in, I held them firm in the ring of the spanner with a very small piece of rag and then held the washer to the underside with a smear of heavy duty grease. A slow process, but got there in the end.

As I was getting low voltage readings from the original ballast supply, I decided to bypass the ballast resistor and connect to the switched live white wire from the ignition as suggested, also fitting a new non ballast coil. So far, so good 😊. Nigel

[Nige T]

After fitting the Petronix ignition, the TR7 seems to be running reasonably well. It is fitted with the AC Delco distributor and I checked the static timing after fitting the EI. The Haynes manual states that static timing is okay for most practical purposes, whereas the Lucas distributor needs to be dynamically timed. Any thoughts or comments would be appreciated