3 replies to this topic

[mvahora]

Currently in the process of getting my fast road mini back on the road after many years!

 

I've used a 43d dizzy + Lumenition Magnetronic Electronic Ignition in the past along with the GT40T transformer sports coil. I note the GT40T is not to be used with electronic ignitions but a lot of people have said there is no issue doing it. In fact the engine builder who built my engine was the one who put it on and its been running flawlessly for years. 

 

Specs are:

1310cc

285 Piper cam

twin hs4s

maniflow lcb + exhaust

ported polished head to suit cam

3.44:1 final drive

 

I've now upgraded to more performance parts so will be getting a new dizzy such as the Aldon mapped to suit.

 

In regards to the coil should I stick with the GT40T coil or change it to something else? Also how do I check the resistance values are okay between the gt40t and the new electronic dizzy i get from Aldon? 

 

pic below of the GT40T 

Attached Files

•  bosch gt40t.png   477.14K   3 downloads
•  bosch gt40t1.png   138.42K   2 downloads

Edited by mvahora, 01 November 2021 - 09:22 AM.

[Ethel]

You can just measure the resistance between the LT terminals. It really depends on the current handling capability of whatever is doing the switching. Contact breaker points need around 3 Ohms of resistance all in.

[mvahora]

You can just measure the resistance between the LT terminals. It really depends on the current handling capability of whatever is doing the switching. Contact breaker points need around 3 Ohms of resistance all in.

 

Thanks, I found the below written on another forum which now makes me wonder whether I should continue using my GT40T coil with an electronic ignition or not. Any help would be appreciated.  

 

The GT40 coil delivers more energy than most OE coils.
The GT40 col is a 12v direct connect and, being a 3 ohm coil, is intended for point (or those hall effect replacements).
The GT40T coil is also 3 ohms - The "T" stands for Transformer.
GT40 and GT40T are basically the same in application.
The GT40R and GT40TR is a 1.5 ohm coil inded for points systems and used in conjunction with a 1.5 ohm "ballast" resistor.
The GT40R/GT40TR is essentially a 6v coil.

If your distributor has points, or a hall effect device as a points replacement, then the GT40 (without resistor) or GT40R (with resistor) can be used.
The GT40T/GT40TR type has been discontinued. These have a slightly higher energy output but they also overheat much faster if the ignition is left on (engine not running).
Too many coils went up in smoke so Bosch discontinued them.
The 3 ohm/1.5 ohm coils are for basic Low Energy Ignition systems run at around 2 amps.

If your dizzy has a reluctor pickup it will need an ignition control module.
If your dizzy (even is a hall effect pickup) has an ignition module then it is, most likely, a High energy ignition (HEI) system.
These run around 6 amps through the coil.
The HEI coils are usually in the 0.5 ohm range (primary coil resistance).
MEC717/718 and HEC715/716 are typical HEI coils.

You can use a GT40 coil driven by an ignition module... you will simply get a poor spark.
If you use a HEI coil on a points system you will burn out the points very quickly (and destroy hall effect type points immediately).

So, have a look at the target dizzy, work out if it is a points type (or a hall pickup serving as points) or if intended to work with a module.
If a points type then you can use the original coil or a GT40.
If your car has a ballast then work out what coil voltage is being applied - it may be 6v, 8v or 9v.
If the coil matching the dizzy is a 12 volt then you will need to bypass your ballast.
If your coil is 6v that you could use a GT40R.
If you can find a GT40T or GT40TR( application dependent) grab that as they are a better coil (just don't leave the ignition on too long).

The optimum is if you can find a dizzy/ignition module combo.
The HEI outputs 2 to 3 times the energy that a standard points type ignition.
The module controls dwell so you get maximum spark energy at all revs.
It will also cut current to the coil when the engine is not running.
Some generate multiple sparks when starting.
Just make sure you obtain the matching coil with the dizzy

Edited by mvahora, 02 November 2021 - 09:52 AM.

[Ethel]

I've always thought there's an element of snake oil poured on performance ignition. Being ideal territory for generic products "one coil fits all" made for easy pickings. There was some validity for 8, or more, cylinder race engines turning high rpm with barely any time between plugs firing. A road going A Series is a leisurely stroll in comparison, as well as been one of the best burners going. Then electronic triggering is a huge leap in capability for any ignition.

 

That said as you already own it the only reason not to use it would be if it negatively affects other bits. Transistor tech has improved hugely so it's perfectly possible to make it work over a wide range of conditions.