That would work. There is no issues with the 1st gen ignitors. The load on them is much lower than with stock ignition. The issue is in the 2nd gen coil pack.

When the ignitor goes into current limting mode (after the coil saturates), I believe the current draw is something like 7.5amp. I also think the 2nd gen ballast is 0.5Ohm, but someone should check to be sure. Anyway, with these numbers, the resistor produces

P=I^2R= (7.5)^2*0.5 =28W

for the ignitor, we can look at the trace posted by renns early in this thread. It appears that when the the ignitor goes into current limiting mode, the voltage at the coil (-) terminal increases by about 6v (hard to tell exactly). So,

P = IV = 7.5*6 = 45W

So if these numbers are correct, the ignitor produces the majority of the heat during this stage. If someone can measure the resistance of the ballast resistor, that would help.

So, for the simple TT circuit, you have two options:

1. Add an additional power resistor inline to the power line. Even better would be to put this resistor bewteen the 2nd gen ignitor C terminal and the coil (-), so that the igntior will get full battery voltage. This additional resistor will reduce the current flow through the coil/ignitor to reduce the heat generated in both. The disadvantage of using this method is that the coil will charge slower. This is okay most of the time since we are driving the coil with a long charge time (will saturate anyway). The problem may be at high RPM where the coil charge times are shorter. Perhaps reduced performance will be expected. For the resistor, you want a fairly small value (perhaps 1 Ohm or so). The resistor will have to be large in terms of power handling. Depending on the resistance used, you want a resistor rated for 60W-100W. Very large typically with a heatsink.

2. Bypass the ballast resistor in the coil pack and replace it with an external resistor. It will need to large as the one above. What this would do is move the 28W or so that the resistor is producing away from the coil pack.

Once we get the bugs worked out on this circuit, it will really be the best solution as it fixes the cause instead of fixing the symptoms.

I am probably going to pickup an o-scope on ebay. I wish I was in the US now. On ebay.com, you get 2000+ matches for oscilloscope. On ebay.fr, you only get like 30 matches. Many on the ebay.fr have little or no feedback and many don't take paypal either. I see a fair number listed in the UK, but shipping would be expensive.

Kent

 

Is there a simple Cliff's notes version of how to do this? The formulas and all that **** is lost on me.

 

Well, right now we are woking on this heat issue. The 1st gen dizzy/ignitor produces a signal that is too long. This makes the 2nd gen pack get very hot and causes a short life. The circuit that I am working on now limits this pulse, so the coil won't get hot. The other option is to use the simple circuit (one that produces too much heat) and either:

- move the ballast resistor in the 2nd gen pack to so me other spot (moves a heat source away)
- add resistance to the coil power to cut down current (the parts in the coil pack will produce less heat)

Once this is figured out completely, I will make another thread that has only the final design information. That way you can build your own or I can supply you with a kit or assembled circuit.

Hope this makes sense.

Kent

 

Is the heat problem only if you use a transistor or ballast resistor? What if I go with the simple route of just using the coil?

 

Yeah, if you do the regular 2GCDFIS (fire 2nd gen coil with 1st gen ignitor), there is no problem. There is more perfomance and a better spark with the TT. This is because the 2nd gen ignitor can handle larger currents and fires better at high RPM. That is the basic goal of all this: to use the 2nd gen ignitor/coil without an ECU.

 

Now, is there a way to use the whole ignition off the FC, but without switching to the FI and ECU?

 

For that kind of setup, you should check over in the Megasquirt forums and the like. You can use the ignition system from the FC, but you still need some way of controlling it. They have some solutions, but their bottom line is that you have to have some sort of ECU to make it work.

Kent, the dead resistor I pulled out is rated 5W 0.35K. It's definitely dead, I checked it with the multimeter just now. The working one is in the car now, so I can't test until later.

As far as testing the 2nd gen ignitor, I think what I'll do is set up everything without the resistor and see what I get. That, sadly, is easier than the alternative.

 

I should amend that. The resistor actually said "5W 0.35OhmK"

 

That is what I was thinking (0.35 Ohm). I see that RadioShack carries a 0.47 Ohm, 5w resistor if you want to replace your ballast.

 

What about the 1 ohm 10W?

 

That may work. I am not sure of how the ignitor goes into current limiting mode. Maybe it adjusts voltage to control current. If this is the case, 10W may not be high enough with 1 Ohm. You could run two 10W, 1ohm resistors in parallel. This would behave like a 0.5 ohm resistor. However, the current would be cut in half to each resistor.

If voltage is controlled (expects the coil resistance + 0.35 Ohm), then you would probably be better with a single 1 Ohm or 0.47 Ohm resistor. Higher resistance means less heat generated in this case.

So, if current controlled, less resistance is better. If voltage controlled, more resistance is better. It would probably be best to keep near the stock resistance. If you have an electronics shop nearby, they probably have more selection than RS.

 

That's the big downside to working on this project--there are no other electronics shops in this city. I though I found one, but all they carry is testing equipment. I'll have to stick with RS for now.

 

Thought I had something, deleted it. Sorry.

 

Another thought guys, could we perhaps use an RFI Suppressor(Ferrite) that clamps around certain wires to remove noise?

http://www.osco.uk.com/ferrite.htm
http://www.ferrishield.com/

I'm not sure what frequency we would want, but perhaps this can help??

Paul.

 

Yeah. Those may help. We will have to do more testing to see what is really going on. I am having my dad ship up my 2nd gen coil, my old TT, power supply, and some other stuff. I plan on biding on an o-scope this weekend. Trying to figure which one I want. The selection is not nearly as good as in the US and many sellers don't even take paypal.

I may go ahead and get the caps and diodes to do the modes devitek tried. I can then order more parts once we know what we need. There is a place in France similar to RadioShack that I can get the parts from. Having the old TT, I can see if the same problem exists on the old circuit and compare it to the new circuit.

My goal is to get these done and shipped by the end of the month. In the beginning of May, I will be out of town for 2 weeks, so I want to make sure they get out before then. Thanks to the guys that have helped testing and thanks to everyone for waiting patiently.

Kent

 

Awesome that sounds great!

This Is MattG!!

I am just here at Gotham Racing watching Steve Kan work his magic with my buddies FC.

So that is why im on a different user. Let me just say that gotham is freaking sweet they got 20b's every where i think I jizzed my pants a little bit!

 

I spent most of yesterday rewiring coil packs and TT's, both the simple and the other. After determining, beyond a shadow of a doubt, that one of the ignitors is dead, I also confirmed what others have experienced. The simple trick heats that coil pack up fast, within a few minutes it was getting quite hot to the touch. The current TT model, however, stayed relatively cool in comparison. After a longer drive tomorrow, I'll see how much it really heats up.

 

Cool. I bought an o-scope. Hopefully I will get it this week some time. I need to order some probes as this scope doesn't have any with it. My dad will be shipping my coil pack and stuff either today or tomorrow. I will put in an order for some diodes and caps tonight as well. I will try to do some testing as soon as I get the scope. I won't be able to really test until I get the stuff from my dad, though. I will be nice to find out what is going on. I am pretty much out of ideas based on what info that we currently have. I am going to have to poke around on the circuit with the o-scope and see what is going on. Hopefully it will just be a simple fix. The nice thing about getting the test equipment here is that I will be able to test each circuit before it goes out. I will also do any mods required on the kit versions so you guys don't have to deal with it.

Kent

 

Update: I'm back to running just the coil, not the ignitor. When I did this, I tried one of the ballast resistors from RS, and the coil would not operate at all. Bypassing the resistor, and she runs quite well.

 

Hmm any other progress? I am still running the TT 2.1 without R2 - it's still going great however I just checked the coilpack then and its way way way to hot to touch after driving for about 25 minutes. So, don't know how long it will last, pretty short on time right now to put into this - looking forward to some more development soon

 

Well, I am still waiting on my stuff. The o-scope had to be paid by check, so that slowed things down some and Monday was a holiday here. Hopefully I should get most everything this week. There are a couple other things I will order this week, but I can start testing once the o-scope gets here. I had to wait until I found what my Dad was able to find to ship to me. My 2nd gen coil pack and stuff should be here this week too, I hope. It will be nice to finally find out what is happening in the circuit. Then we can find a solution to fix it.

 

Hey guys, today I had a chance to see how hot the coilpack got in a 2nd gen.. well not scientifically, but after 20 minutes of driving it was too hot to touch/hold finger on it for more than a second or 2.

I guess the outside temperature is only indicative of the actual component temprature inside so keeping it as low as possible would be ideal.

 

Well, my car started running rough on the way home yesterday. I checked it out and guess what? No leading spark at all. Looks like my coil pack might have finally bit the dust. Back to Ebay...

 

That's too bad. It did hold up for quite awhile. I will get you hooked up with the new board once we get these kinks worked out.

Kent

 

No problem Kent. Like you said, it held out for quite some time. When I get the replacement, I might try to get creative with a heatsink and external mounting for the ignitor. Maybe I'll even throw a fan on it, just for ***** and giggles...