Outer Limits 4x4 Board

G'day,
I have come across a GT40T Coil which looks to be in good condition and i got for free. I had it installed on my 94 1.3 sierra for the past week and then had some issues with my ignition system. One of the high tension leads had died so i put on a new set today but i also removed the coil and replaced it with the original Suzuki one. Is this coil going to be alright on my 1.3? I went and had a look in a Bosch catalogue and they don't list any coils for the Sierra. So my question is, will the GT40 destroy the distributer or any other parts of the ignition?

Also what type of gains should i get from a sports coil? I found it a little bit easier to start in the mornings when i had the GT40 but that could have been a coincidence or my imagination but there doesn't seem to be any other benefits...

Cheers,
Kit

Bosch don't recommend a replacement coil for the Sierra.

The ignition module on many small Jap engines of this period is pretty average - much better than points but definitely limited.

With this in mind a standard coil is a safe bet - random coil substitution could well lead to module failure. There's far more to module / coil selection than most people understand.

As for failed leads - leads in good condition wont be effected significantly by coil changes - the discharge energy will increase but the firing voltage will be around the same- its a function of plug gap and cylinder pressure.

A high energy ignition system may produce better starting / idle and perhaps a small power /economy gain but it requires a matched module and coil.

So there are small gains to be made, but they require a change of module and coil to reliably achieve this. Whilst the GT40 coil is better than many compatible standard coils it certainly isn't a state of the art unit by current standards.

Dont use it it will destroy your ignition system as such as you are experiencing, thats why its not recommended in the book. It will brake down your distributor and gie you more troubles than its worth.

My original coil (the one that came with the car when purchased)
finally died, small crack on the centre shaft for the plug.
Popped some electrical tape on it to get me arround.
that day a guy at work said he had 4 coils off gemeni's in his garage and I can have one for free..
Sweet. got there and they are all GT40's.
I figured why not,..
Replaced the plugs with an import twin point plug able to run a larger charge.
Bingo, better Starting, I wouldnt say better econemy. but slightly more pull.

anyway

The gt40 has been in the car for 2 yrs now,
Havent had to replace anything to do with the timing or spark plugs or leads.
The dizzy is still fine, slight carbon build up but nothing out of the ordinary.
If I clean the plugs every service and make sure the gap stays the same then they run fine.

only fluctuations is the crappy fuel you get from different servo's, or the amount of crappy water that gets in there tanks

my 2c

Thanks for the help fellas i'll just stick with the original coil. The new leads seems to have made a huge difference by themselves and got rid of any misfiring and made it easier to start anyways.
Just out of curiosity since a GT40 coil may damage the dissi etc would an msd multi spark type system do the same? Not that i have the money to buy one an try it out just curious if they'd beneifit a sierra and work?

Thanks again for the advice!

Anything that replaces the original module will solve the problem - an MSD fits into this category.

Good and all as MSD's are, some engines just don't seem to run well with them ( they are a type of CDI ) and they are @#$%^ expensive ! The multi spark bit is required to make up for the short duration spark created by CDI's ( MSD ) - normal inductor based coils generate a long spark by default.

Whilst they are well made they certainly aren't built to OE standards and IMO are a bit too bulky and complex for a hard working 4WD. Ignition systems have come a long long way.

You can improve the zooks ignition energy really cheaply if you have some electrical skills by substituting a different module and coil.

The BOSCH module and coil off the old Holden in line six are absolutely ideal and have around three times the ignition energy of the stock zook.
This combination still has around the highest output of "normal" ignition systems regardless of year.

The dissy has to come out , the standard module removed and a shielded lead from the zook VR pickup made up to run to the new module which is externally mounted on a small heatsink.

Takes about 4 hours and if you get the parts from a "self serve" wrecker - probably would cost $20 - buying new a fair bit more, but IMO theres just no point.

If its sounding too technical then I would advise leaving it stock - its not hard but you do need some electrical and engine expertiese.

I have run lots of them - and still do.

Wow thanks for the information MightyMouse!!! A mate of mine has an old early 80's dunnydore with a holden blue motor that I might be able to scavenge some parts off soon. Is that the kind of Holden I'm looking for?

The dissy has to come out , the standard module removed and a shielded lead from the zook VR pickup made up to run to the new module which is externally mounted on a small heatsink.

You wouldn't happen to have some pics of this lying around would you? My dad is a retired auto spark so I guess we could figure this out if we had a pic or 2 to work off
With the larger amount of power going to the sparkplugs is it safe to open up the gap a little bit on them? Or would that put to much stress on the components still?

Thanks again for the info!

I run a crane fireball ignition on my heavily modified V8 commodore. Now even though they come with a pretty good ignition system standard, the crane did see a noticeable improvement at high revs. Now bear in mind this is on a very worked motor with higher than stock compression and a very large revvy cam.

On a fairly stock zook (I would say any running stock compression ratio) I think the effort would far outwiegh the gains like mighty mouse has already implied. Stick with the stock unit and just run good leads, plugs and good nice cap and rotor and concentrate on other areas for better gains.

Oh and BTW with the beefed up ignition in my commy I gapped the plugs out another .3 mm's and it works fine.

The old dunnydoor might do the trick !

On the distributor base will be a flange with a sheet metal cover, under which will be a Bosch module - the last three digits should be 021. It will have four terminals. Try NOT to wipe the white heatsink grease off the module base - it helps with heat conduction to the heatsink.

You will also need the ignition coil. Unlike low energy ones, its got an extended male top. get the mounting bracket and HT lead just to be safe. Its an oil filled unit ( the cylinder type ) but if you want a more modern looking, transformer coil then you need a Bosch HEC715. Use either - they both perform the same but the HEC715 wont be on wrecks

Before you remove your distributor from the car - note the position of the rotor to make it easy to put back and very importantly mark the position of the distributor body relative to the engine. Scribe a line, texta mark - but this is important - you will need it later.

Now for the "difficult" stuff - there will be a fixed mounted pickup in the dissy body - that is on the same plane as the reluctor ( the star thingy ) - there will be two wires from this to the ignition module. There may be a plastic cover. You need to cut these two wires and extend them with shielded cable ( like audio cable - 2 cores and a woven metal screen around them ) to reach to wherever your going to mount the new module. The screen needs to be grounded at one end only.



Note the pics NOT a zook pickup, but your dissy will have the reluctor ( the star thingy ) and a pickup ( the coil in the top RHS with the metal tooth that almost touches the reluctor ) AND the ignition module. Its the wires from the pickup to the module that are cut and extended. The old module can be left in or discarded as required ( or reconnected if all else fails... )

The new shielded lead needs to run out of the distributor - a grommet is highly recommended. If you have removed the old module you might be able to reuse the hole.

IF you have removed the pickup coil make sure the gap between the reluctor and pickup tooth is as close as you can get WITHOUT touching. Make sure you rotate the reluctor - some have a wobble.

Thats the distributor mods done. Put the distributor back using the alignment marks.

Mount the coil and module - a small heatsink is required for the module - so make a 3mm thick aluminum bracket about 50x50mm for the module and that will do. Mounting the module with the coil usually is easiest and in the same position the stock coil was mounted as that gives you easy access to the loom.

The connections on the module are :

7 - Negative input from reluctor ( the bit in the dissy )
8 - Positive input from reluctor
15 - 12V for module
16 - coil negative.

So ignition power goes to the coil positive terminal and to module terminal 15, a ballast resistor is not required. You can pick up power from the old coil positive connection on the loom ( not the old coil - just its loom connection )

Coil negative goes to module terminal 16, connect the new coils negative to the old coils negative terminal on the loom so the ECU / tacho gets ignition pulses. Make certain the heatsink/module is earthed.

The shielded cable that you have just installed goes to terminals 7 & 8 - don't make them permanent just yet. Make sure the screen is grounded as described above.

That's it... cross fingers and start.

Get a timing light - if you have to move the dissy body lots to get the timing right then reverse the connections to terminals 7 & 8. This matters - reverse connection will run but the dwell control in the module will operate incorrectly.

If your going to do this - do it properly, nothings worse than poor wiring leading to breakdowns. If your mystified by all this then DON'T DO IT, its not that hard but some basic electrical and mechanical knowledge is required.


As for plug gaps - a better ignition system will fire larger plug gaps, which is generally a good thing as far as combustion is concerned. However it will also raise the firing voltage of the plug placing greater stress on the leads, cap etc. With components in good condition this generally isn't a problem but with old crap......

With your dad's help this should be straightforward - then you can post a "blow by blow" how to with pics ( I still can't find my #$%@ camera )!