Transistor trick for 2GCDFIS. - RX7Club.com - Mazda RX7 Forum

1st Generation Specific (1979-1985) 1979-1985 Discussion including performance modifications and technical support sections

Transistor trick for 2GCDFIS.

Reply

 
 
Old 04-04-05, 04:01 AM
  #1
Lapping = Fapping
Thread Starter
iTrader: (12)
 
Jeff20B's Avatar
 
Join Date: Aug 2001
Location: Near Seattle
Posts: 15,341
Thanked 7 Times in 7 Posts
Transistor trick for 2GCDFIS.

I presented the idea a few days ago that you could trigger a 2nd gen leading ignitor with a J-109. It generated some interest so I've decided to start a thread about it where we can discuss our successes and failures (and hopefully there will be more successes than failures ).

No one has actually done this before to my knowledge, but the theory seems doable. The basic idea is to keep the 2nd gen leading ignitor triggering the 2nd gen coil because it's more powerful and is capable of handling a lot more current than a J-109. For instance, it doesn't enter current limiting mode until later and keeps a long dwell period up to a much higher RPM than a J-109. We're talking about excellent sparks up past 9k RPM!

Testing a J-109 triggering a Diamond coil alongside a 2nd gen leading ignitor triggering its double ended coil showed major differences just sparking into the air. Granted there are some fundamental differences sparking at normal atmospheric pressure vs in a running engine, but the 2nd gen setup showed an observably stronger spark on both plugs at the same time next to the smaller, quieter spark output from the J-109 setup. We can assume the 2nd gen setup would outperform a J-109 sparking under similar conditions in an engine.

My MegaSquirt's dwell settings were a bit on the high side in order to trigger the J-109 and have it produce a dwell curve similar to when it is triggered by the variable reluctance sensor (pickup) and reluctor wheel in a stock 1st gen distributor. In other words, the J-109 was designed to trigger from a 0 to 100 (or more) volt alternating current and not necessarily a 5 volt square wave from an ECU. The resultant dwell curve was actually very similar to the curve I observed from each coil on the DLIDFIS setup in my REPU consisting of three J-109s and three Diamiond coils.

Now that I had a base to build from, I hooked the 2nd gen leading ignitor to the MegaSquirt without changing the dwell settings and was blown away by how much more powerful it was. I gotta say if I was going to MegaSquirt a 13B, I would have used the 2nd gen coil assembly on it right then and there (no need for EDIS). However since my MS is going onto a slightly different engine, and I hadn't even tried changing the dwell timings to some more conservative numbers, I figured I'd keep the 2nd gen assembly around for more tests. I tried other dwell settings and realised the 2nd gen leading ignitor had more or less the same end result no matter which numbers I entered; it continued to have a very long dwell period and very powerful sparks from below idle speeds to over 9k. It was actually still up to 50% at 9k! That's very nice for you bridgey and peripheral types. The 2nd gen ignitor looks much more capable of producing consistanly more powerful sparks well beyond the (observed) limited powerband of a J-109, and in my opinion, is worth figuring out how to hook it up in a 1st gen without an ECU.

Note: the J-109 peaked around 3-4k at 58% dwell duty cycle and dropped off above and below but the 2nd gen ignitor was way more broad staying above 50% duty cycle for a lot longer within the RPM range of a typical rotary (I tested up to 9k). Since changing the dwell settings didn't seem to affect the 2nd gen ignitor nearly as much as the J-109, I assume that as the dwell curve drops off above and below 3-4k, the same long healthy dwell period I observed on my dwell meter at high RPM will still be there. More testing is required.

The aluminum base of the 2nd gen coil assembly did get hot pretty quickly, even with lower dwell numbers, so since I'm not sure how much it normally heats up on a stock 2nd gen RX-7, I was unqualified to make any hard descisions at that time. I didn't run any lengthy tests for heat, but it still stayed cooler than the dizzy housing of a running 1st gen. Then again, Mazda mounted the 2nd gen coil assemblies on the firewall I assume for less direct heating from the engine, but how much heat is too much? Thoughts?

Ok, now on to the instructions. I first came across the idea about this time last year on the nopistons forum when 83turbo presented it in a DLIDFIS thread over there. I've learned quite a lot about ECUs and how they control ignitors since then, but as far as I know, no one has ever tried to trigger a 2nd gen leading ignitor with a J-109 yet. The theory is sound, but it just takes someone to do it. Is anyone interested in actually trying? I know there are a lot of 2GCDFIS users here. Wouldn't it be great to get more powerful sparks out of your setup with only a little extra work?

I know you're all getting anxious for me to spill it already, so here goes. These are the ultra-simple instructions lifted from the thread on nopistons as presented by 83turbo.

Get a PNP transistor (2N3906 or whatever). Emitter goes to +12.
Collector goes to red wire on the '86 ignitor. Base goes to a 1K
resistor. Other end of the resistor goes to both the J109 ignitor
output and to another 1K resistor. Other end of this resistor goes
to +12v. I haven't tried this but it looks like it should work.

Or, if you have an NPN PN2222A general purpose transistor like I do:

To use an NPN:
Emitter goes to ground.
Collector goes to '86 ignitor red wire and to a 1k resistor to +12v
Base goes to J109 ignitor output and to a 1k resistor to +12v

From what I've learned doing MegaSquirt stuff recently, those 1k resistors that connect 12V to the transistor and ignitor are pull-up or pull-down resistors. I actually added a few to my MegaSquirt for it to function the way I wanted it to for ignition input and output. The idea is simple enough.

Ok, so according to the instructions for an NPN transistor, I'd need to wire it up something like this.


Since the PN2222A can only handle up to 6 volts on its base, I added another 1k resistor to limit the current although I'm doubtful it'll be enough. What is a good resistor value to drop 12-14 volts down to 5-6 volts and not get too hot in the process? Of course it will be pulsed at no more than an observed 58% dwell duty cycle, but that was just on my setup. I'm sure others will vary to some degree. I'm thinking 60% is what the Mazda and Mitsubishi engineers aimed for. Either way, it will not heat nearly as much as if it were on continuously (if you're familiar with pulsed vs CW lasers, it's the same idea).

Well there you have it. I have no idea if the above circuit diagram will even work since I don't trust my ability to correctly wire up a transistor further than I could throw one. Any electrical or adventurous people out there care to try it? Standard disclaimers apply; use at your own risk.
Attached Thumbnails Transistor trick for 2GCDFIS.-2gcdfis.gif  

Last edited by Jeff20B; 04-04-05 at 04:10 AM.
Jeff20B is offline  
Reply With Quote
Old 04-04-05, 08:46 AM
  #2
Right near Malloy
iTrader: (27)
 
Pele's Avatar
 
Join Date: Dec 1999
Location: Behind a workbench, repairing FC Electronics.
Posts: 7,566
Thanked 8 Times in 5 Posts
I keep trying to do the math to calculate how many watt resistor you need, but all I have to go in a 6 volts... I think I need another number, probably the current handling capability of the transistor base to emitter.

I can't find it on any of the datasheets I look at... All I can find are maximum collector to emitter currents (1 amp, Absolute Maximum.)

Gah. My electronics math skills have gone down the *******. I've been a machinist for far too long. I need to get back into discrete electronics. None of this RF bullshit that I do at work.

Sorry I have nothing really useful to add to this thread. I was just curious what you use for drawing schematics.
Pele is offline  
Reply With Quote
Old 04-04-05, 02:08 PM
  #3
Super Moderator
10 Year Member
iTrader: (3)
 
gsl-se addict's Avatar
 
Join Date: Jan 2003
Location: Lynchburg, VA
Posts: 5,096
Thanks: 0
Thanked 1 Time in 1 Post
Jeff,

It looks like that it could work. I could try to model that circuit a little later today or tonight. I will try a 14 volt square wave and vary the waveform form (700rpm/60sec/min)*2sparks per rotation = 23 Hz and then increase to 10,000 rpm = 333 Hz. This will tells the voltages, current, and power of all points in the circuit. I am pretty sure I have the data sheet for that transitor. I will try to modify the circuit some if it doesn't meet the requirements.


Kent
gsl-se addict is offline  
Reply With Quote
Old 04-04-05, 03:56 PM
  #4
Lapping = Fapping
Thread Starter
iTrader: (12)
 
Jeff20B's Avatar
 
Join Date: Aug 2001
Location: Near Seattle
Posts: 15,341
Thanked 7 Times in 7 Posts
The pull-ups only need to be 1/4 watt I believe (it worked fine on my MS). The current limiting resistor should probably be a half watt at least.

I use Windows Paint program.

Here is a schematic of the transistor. http://www.fairchildsemi.com/ds/PN/PN2222A.pdf

Kent, go for it and let us know. If there's time today, I'll see if I can set it up too.
Jeff20B is offline  
Reply With Quote
Old 04-05-05, 02:46 AM
  #5
Super Moderator
10 Year Member
iTrader: (3)
 
gsl-se addict's Avatar
 
Join Date: Jan 2003
Location: Lynchburg, VA
Posts: 5,096
Thanks: 0
Thanked 1 Time in 1 Post
Jeff: I am having a bit of a problem with one of the pspice libraries. It only gives me problems when I have the transistor present. I will look at it more sometime tomorrow. We may what to add a zener diode at the output or maybe a 5V regulator to limit the voltage to 5V. I believe your circuit will pull the output up to 12V (don't we want a 5v wavefrom?). I will post up the results once I get it up and running. Do you any idea of the amount of current needed to trigger the 2nd gen igniter? I will see what I can come up with.

Kent
gsl-se addict is offline  
Reply With Quote
Old 04-05-05, 03:38 AM
  #6
Banned. I got OWNED!!!
 
TurboSE's Avatar
 
Join Date: Mar 2005
Location: SF CALI
Posts: 564
Thanks: 0
Thanked 0 Times in 0 Posts
What about MOSFET transistors?????
TurboSE is offline  
Reply With Quote
Old 04-05-05, 06:36 AM
  #7
Lapping = Fapping
Thread Starter
iTrader: (12)
 
Jeff20B's Avatar
 
Join Date: Aug 2001
Location: Near Seattle
Posts: 15,341
Thanked 7 Times in 7 Posts
Kent, I'd say 20mA or less... probably.

For testing purposes, 12V can be used, without harming the ignitor. I don't know if there will be any long-term problems using 12 volts though. Hmm, maybe a Radio Shack 7805 5 volt voltage regulator would be a good idea, like you suggested.

Wait a minute. Are you talking about turning the voltage reg on and off with the transistor? There might be some lag time. Would a PNP transistor be a better choice with a 5 volt reg?

Maybe we could add one more current limiting resistor in series between the transistor and the red wire of the 2nd gen ignitor. Thoughts?

Turbo SE, a MOSFET wouldn't be necessary since a very small amount of current needs to be switched here. You're welcome to try it though.
Jeff20B is offline  
Reply With Quote
Old 04-05-05, 10:08 AM
  #8
Rotary Enthusiast
10 Year Member
 
jayroc's Avatar
 
Join Date: Jun 2002
Location: Owensboro, KY
Posts: 1,056
Thanks: 0
Thanked 0 Times in 0 Posts
So, you're trying to make a circuit to mimic the 5v square wave controlling the coils that originally came from the 2g ECU, right? Do you really want to keep the j109 if you got an ignitor on the 2g coil? Can you just do something with the output of the dizzy itself?
I'm sure there are 5v timing circuits already in existence that will work excellent for this very purpose, too. What about a 555 timer IC?
Though, I only had 2 years of electronics way back in highschool, I want to help if I can. This seems very interesting.

Last edited by jayroc; 04-05-05 at 10:11 AM.
jayroc is offline  
Reply With Quote
Old 04-05-05, 10:16 AM
  #9
Burning Oil-Grinding 3rd
10 Year Member
 
Hades12's Avatar
 
Join Date: Apr 2002
Location: Union Mills NC
Posts: 4,094
Thanks: 0
Thanked 0 Times in 0 Posts
What about a Zeiner to cap the 12 down to 5.
Hades12 is offline  
Reply With Quote
Old 04-05-05, 10:28 AM
  #10
Rotary Enthusiast
10 Year Member
 
jayroc's Avatar
 
Join Date: Jun 2002
Location: Owensboro, KY
Posts: 1,056
Thanks: 0
Thanked 0 Times in 0 Posts
BTW, what is the waveform that comes out of the dizzy vs off the ignitor? I imagine it's something like a noisy sinewave off the dizzy..
jayroc is offline  
Reply With Quote
Old 04-05-05, 12:41 PM
  #11
Junior Member
5 Year Member
 
Join Date: Jan 2005
Location: so cal
Posts: 25
Thanks: 0
Thanked 0 Times in 0 Posts
What frequency (Hz) range are you expecting to operate the BJT? A mosfet *may* be a better choice for this type of switching circuit. Also, what bias are you running, or have measured? I might also advise you run the circuit in quiescent mode. Overall, good work
J9R8 is offline  
Reply With Quote
Old 04-05-05, 01:30 PM
  #12
Super Moderator
10 Year Member
iTrader: (3)
 
gsl-se addict's Avatar
 
Join Date: Jan 2003
Location: Lynchburg, VA
Posts: 5,096
Thanks: 0
Thanked 1 Time in 1 Post
Jeff: No, I mean use a regulator or a zener diode on the output in a way to limit the range from 0 to 5v (that is what is done with the MS: the pull-up resistor goes to 5V). A PNP may work better, but we will see. I will try a few different things later and let you know what I come up with.

TurboSE: A MOSFET would work here as well, but I don't think it will be needed. I don't think there will be the current need or speed to require MOSFETs.

jayroc: You may be able to do something with a 555, but I am not sure if it will have the current capability needed.

J9R8: See my post above for the frequency range. I suspect the frequency will never be more than about 300 Hz or so. So we don't need anything real fast.

This will be a fun project. I will try to post some reults tonight.

Kent
gsl-se addict is offline  
Reply With Quote
Old 04-05-05, 03:28 PM
  #13
Banned. I got OWNED!!!
iTrader: (2)
 
Join Date: Oct 2004
Location: London, Ontario
Posts: 6,122
Thanks: 0
Thanked 0 Times in 0 Posts
This might seem a dumb question ... but i'm not all that much into car electronics yet so try to fill me in a bit ... First is this something that would only work with fuel injected rotary ... or will it also work for a 12a carbbed setup?

Also where is the J109 located in our cars. And where would the one from the second gen be. I would like to go to the junk yard tomorrow and pull them out so that I would be able to do some testing. Also i could use the teachers here in college to help me out with all this stuff
dj55b is offline  
Reply With Quote
Old 04-05-05, 03:34 PM
  #14
Super Moderator
10 Year Member
iTrader: (3)
 
gsl-se addict's Avatar
 
Join Date: Jan 2003
Location: Lynchburg, VA
Posts: 5,096
Thanks: 0
Thanked 1 Time in 1 Post
It would work with either carbed or FI. The j-109s are on the distributor (two small black boxes (for '81-'85 models). They look like Jeff20B's avatar. The '80 uses j-105's mounted on the fender and the '79 uses a points system, so it doesn't use them.

The 2nd gens have the igniter attached to the coil. You will want to get the leading coil (one coil, with two output posts). The igniter should be on the back of it.
gsl-se addict is offline  
Reply With Quote
Old 04-05-05, 04:04 PM
  #15
Lapping = Fapping
Thread Starter
iTrader: (12)
 
Jeff20B's Avatar
 
Join Date: Aug 2001
Location: Near Seattle
Posts: 15,341
Thanked 7 Times in 7 Posts
Well-put. I'd just like to add that to remove the coil assembly from the inner fender of a 2nd gen RX-7, there are three or four 10mm nuts and a couple disconnectable wires holding it in.

jayroc, the output of the variable reluctance sensor is sort of a lopsided AC or in other words, a dirty sine wave as you suspected. It can't trigger the 2nd gen ignitor correctly so you must either build a circuit that would condition the sine wave and then feed it to the 2nd gen ignitor (with hopefully the right dwell time and everything) or just let a J-109 do it.

Like I said above, I don't trust my ability to hook up a transistor further than I could throw it, and pull-up or pull-down resistors also give me trouble. Keep the ideas coming.
Jeff20B is offline  
Reply With Quote
 
 
 

Related Topics
Thread
Thread Starter
Forum
Replies
Last Post
MazdaMike02
Canadian For Sale/ Wanted/ Classifieds
8
02-12-16 03:54 PM
MazdaMike02
2nd Generation RX-7 (1986-1992) Parts
5
11-29-15 11:38 AM
TrboMike
NE RX-7 Forum
4
09-28-15 10:40 PM


Thread Tools
Search this Thread
Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



All times are GMT -5. The time now is 02:17 AM.


All content Copyright 2007 by Internet Brands, Inc. We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.
 
  • Ask a Question
    Get answers from community experts
Question Title:
Description:
Your question will be posted in: