Transistor trick Trick?
 

I know I'm going to get alot of put downs for this but...

Could you fire the 2nd gen coil pack/ignitor using a GM HEI module? I know the 2nd gen ignitor won't work without some sort of adjustable dwell input and also it requires a different input than the J109 signal (hence the whole idea of the Transistor trick) but I keep coming back to a simpler/cheaper way to fire this puppy. The HEI IS a standalone module with it's own varible dwell output after all. Also maybe the HEI would put out too much current and this would need to be reduced/resistored to work properly.

O.K.; maybe it's just dumb and I CERTAINLY don't know enough about electronics to say for sure but...!

I've been watching the T-Trick thread with interest (all million pages of it!) and MUCH admiration and I REALLY don't want it to sound as if I'm dissing the great work going on here. It's just that this idea hit me and I'm curious to know if it has some chance of working.

Please keep up the good work!

Sanspistons for good, clean fun

Bump for info...

I haven't done any testing with the GM modules. In general, they serve the same purpose as the J-109s, so there may not be any difference. There could be a possibility that the dwell on the GM HEI modules differ from the J-109 with the loads that we are dealing with. The impact could be positive or negative depending on if the dwell is smaller or larger. The only way to know for sure is to experiment.

From what I can tell with the J-109 is that the dwell appears to be greater with less current. I believe this is the greatest reason for our overheating issues. I believe with the J-109 connected to the coil, the dwell is say 7 ms at idle. When connected to the TT, the dwell is more like 26 ms. If I had access to a portable o-scope, I could test it out and know for sure (could also test an HEI module to see how it behaves).

I don't thinkthat anyone knows for sure if the HEI would be better or not. Someone would need to try to find out.

hmm

Kent, I've notice the coil has some effect on the dwell as well. A diamond coil pulls less amps than a comparable Bosch for instance. The differences in inductance, number of windings etc. Sorry I don't remember the differences, nor can I check inductance.

Just because an HEI can safely switch more amps than a J-109, it won't send any more power through a Diamond or any other coil, unless certain parameters are met: RPM, engine load etc.

It seems the J-109 works best with a Diamond coil because neither will overheat the other.

In all, I'd recommend an HEI over a J-109 if attempting to run a 2nd gen leading coil; mainly because they're cheaper, easier to find, and can switch more power before going into current-limit mode. This could be advantageous with a 2nd gen coil where the J-109 would come up short.

Jeff,

I don't doubt there could be differences. Different inductance (related to impedance) means different current at a given RPM. Based on what I have seen with the TT, the J-109 (I suspect the HEI as well) alters the dwell based on current (or inductance/resistance in otherwords, impedance).

What Jeff is talking about is capacity of the ignitor. The HEI can handle larger loads than the J-109 and I suspect the 2nd gen ignitor could outperform both. The question is whether the HEI would have a differnt dwell than the J-109 when connected to the TT circuit. I suspect the difference to be small if the is any. One solution could be to place a large resistor in place of the coil with the TT connected. This could reduce the dwell and the coil heating problem. The main issue with this is that there is still a large load on the J-109, and the resistor would need to probably have a heatsink and be rated for fairly high powers (50W - 100W). An inductor may also be needed to get the same overall behavior as having the 1st gen coil still connected.

This could all be figured out with the right equipment. A portable o-scope and a meter for measuring inductance would do the job. Too bad I don't have either.

Sorry it took so long to read/reply to your responses: Sat. evening seems to be the only time I get to look at the 'net at all these days (those 50 hour work weeks get you...)

Reading back it seems I've confused the issue. My main question was could an HEI trigger the ENTIRE 2nd gen. ignitor/coil pack by itself WITHOUT having to use the Transistor Trick at all?!

Obviously no one has tried this yet, and I don't expect a yes/no answer. Just fishing for opinions at this point really...

If/when I get some spare time I'll try this combo and let you know if it works or just burns both modules to a glowing, smoking pile... Wish me luck!

Sanspistons for a wider, brighter smile!

I don't think so. The HEI is pretty much like the J-109. It pulls the coil - to ground to charge the coil. The 2nd gen pack is kind of the opposite. It requires an incoming positive 5v pulse to start the charging. The actual charging may actually occur just before the 2nd gen pack receives the 5v pulse. When the 5v signal drops to 0v, the 2nd gen coil fires.

So you need to atleast flip the signal over to get it to work. The basic circuit to do this is in the simplified TT write-up. The only question will be if the pulse from the HEI is too long and creates the coil heating probs. I can guide you though how to do it if you want to give it a shot.

Thanks, gsl-se addict for the quick reply! I figured that this would be a too simple hook-up from what I remember of the original T-T write-up. After over a year and Katrina later and with my poor old 56k I'm loath to try to tackle the main T-T listing! I'd be very interested in the simplified T-T write up.

Coil overheating: I remember something about this also, did anybody ever figure out how hot a 2nd gen pack was supposed to operate at normally? This would help in the overheating detection process.

Sanspistons: collapsed lower hose @ 115mph = busted rear rotor = new street-ported motor = busted bank account...

I can email the write-up to you if you would like. I can resize photos and stuff if that would help. I also have some circuit boads and parts if you don't want to build the circuit by hand.

The newer circuit tried to narrow the pulse to the 2nd gen pack to help the heat issue. The circuit works, but the timing gets all messed up because the coil fires off the trailing edge of the pulse (we cut the pulse short, it fires too early). I am trying to add a larger ballast resistor in the 2nd gen pack to help. This will limit the current instead of limiting the pulse. It is not as elegant, but I think could do the job. This way people could use the simple TT without issue. I have been trying to test, but with surgery, Christmas, and work, there has been no time. I hope to figure it out soon.

Anyway, you can pm me your email if you would like me to just send you the write-up.

Kent

Thanks for the info, Kent! It may be some time before I get to start on this project as I am pushed for spare time. Also I'm going to the 24hrs of Daytona at the end of the month and it might be a few weeks afterward before I start on this circuit.

Thanks again for the support!

Sanspistons for higher G's and lower E.T.'s!!!