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2GCDFIS w/ TT (Transistor Trick) Write-Up (Simplified Design)

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2GCDFIS w/ TT (Transistor Trick) Write-Up (Simplified Design)

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Old 11-16-10, 02:19 PM
  #51  
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Yeah I hear thats a great setup
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Old 11-16-10, 04:13 PM
  #52  
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Unfortunately, I haven't had time to improve on this this. Work and home renovations have killed my spare time.

hoang: You can follow the 1st post in the thread to build one, if you are handy. If not, I do still have some spares/parts and might be able to help you out. Just shoot me a pm.

Ken: You box with the switch on it was a combination of number 2. and 3. on the list (depending on the switch position). I only made a few of those when we were 1st testing things. You seemed to like it on the 'fixed' mode. Others that were using it at the time liked it in the other mode. The difference may have been in how timing was set (idle vs. at 4k RPM).

The auto setup is ideal and would prevent the overheating issue. Circuitwise, the design is fine. However, I made the mistake of forgetting that the coil fires off the trailing edge of the pulse. This means that if you simply cut the pulse short, the coil fires at the wrong time. D'oh! I was putting the design together in Europe without a car, so I wasn't able to test the timing. A couple buddies did some testing and found the timing to retard. The timing was actually advanced, but so much that the e-shaft was making nearly a full revolution in that time period, so it effectively looked and behaved as retarded. I actually spent a lot of time trying to figure out what was going on. Looking into electrical noise, false trips, grounding isssues, etc. The circuit worked on the bench and also in code simulations. I then was explaining to someone how it all worked and then I realized I had forgot about the trailing edge thing.

I was able to leave out a capacitor and basically cut out this function. It basically takes it back to the original design (much nicer circuit board, though), but has the overheating issue. Essentially, to make this design work well, I need the circuit to figure out when the spark needs to occur and start charging the coil some amount of time before that happens. It is real easy to make a circuit do something after something happens, but can be tricky to do it beforehand.

I'll get back to it someday. In fact, I have a 2nd gen CAS and leading/trailing coils sitting in a box in hopes taking this to the next stage.
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Old 07-23-12, 10:21 PM
  #53  
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So, i'm thinking it's time for me to jump on this band wagon with my thoughts and improvements. i have a few questions, specifically for GSl-SE addict.
1. do you know what the dwell time is for the transistor trick?(or is static or linear slope?)
2. can you adjust said dwell?
3. (not a question) i bet dwell is high at low rpm and low at high...<-ding ding
My plan is to use these new AEM smart coils that 3rd gen guys are using for there 500-600 hp setups.
The testbed= 85 GSL-se w/ 91 n/a swap, running auxports/vdi, and the stock(85!) ecu/afm, with 680cc+460cc turned on at ~5k.(i'll do a build thread when it lays down 200rwhp(probably after rebuild and port..)
Option 1.
AEM High Output Inductive Dumb Ignition Coil 30-2852 | eBay
AEM dump coil(no ignitor) with an GM/tfi HEI ignitor.
The 4, 7, and 8 pin HEI modules will all work with a weak analog waveform as
generated by the mag pickup in the distributor.
no worring about dwell.
Option 2.
AEM High Output IGBT Inductive Smart Ignition Coil 30-2853 | eBay
Aem smart coil, expect a 5v square signal like the FC coils, so will be building a TT board, but could you use a a Varible resisitor to adjust dwell,or change a resistor, ideally i want to run 4.5 Ms. i understand that dwell is usually controlled through the later generation ecus.


EDIT! I found my MF'ING answer:
v0.9 This is fixed pulse only [ PLAUSIBLE OPTION ]
Trying to fix the heating issue of the ignitor, I made it so the pulse was just a fixed amount (2.2 ms). The J-109 just told when to fire. The J-109 had no control of the width. This was found to have better top end than v0.8, but was weaker down low. Kentetsu loves this circuit and may be running a lot of mechanical advance to help compensate. Kent thought this circuit felt weak but his timing was set to stock.
The heating issue is from too much dwell at low rpm, but power loss from too little at higher rpm. the AEM smart coil like 4.5ms static, or up to 6.0ms dynamic(6.0 for brief moments when needed)
Can i have this schematic, but with the pulse(dwell) adjusted to ~4.5.
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Old 08-24-12, 09:28 PM
  #54  
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tagging this for later read.

have an RX4 full bridged early 13B block with a holley 650DP mechanical/RB intake/duals into 3" exhaust and the previous ignitions just sucked too much *** to handle it.. running a J109 distributor with 2GCDFIS seemed to give the best results so far with a hard lock on the distributor(springless and dashpots locked in place internally running about 35 degrees of advance). working on running the FC ignitor since the J109 solely seems to be being overworked(ignition is breaking up from 6500-8000). running BUR9EQ plugs in leadings, no trailings firing at the moment to optimize leading timing then the trailings will be done later on.

i know the FC ignition is good for much more than this setup can put out. bounced around trying to setup the DLIDFIS but preliminary attempts didn't give much better results. probably be much easier to just have him get a CDI but i consider them bandaids for weak ignitions.

if i try this i will let you guys know the results.

Last edited by RotaryEvolution; 08-24-12 at 09:45 PM.
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Old 08-25-12, 10:07 AM
  #55  
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Originally Posted by RotaryEvolution View Post
tagging this for later read.

have an RX4 full bridged early 13B block with a holley 650DP mechanical/RB intake/duals into 3" exhaust and the previous ignitions just sucked too much *** to handle it.. running a J109 distributor with 2GCDFIS seemed to give the best results so far with a hard lock on the distributor(springless and dashpots locked in place internally running about 35 degrees of advance). working on running the FC ignitor since the J109 solely seems to be being overworked(ignition is breaking up from 6500-8000). running BUR9EQ plugs in leadings, no trailings firing at the moment to optimize leading timing then the trailings will be done later on.

i know the FC ignition is good for much more than this setup can put out. bounced around trying to setup the DLIDFIS but preliminary attempts didn't give much better results. probably be much easier to just have him get a CDI but i consider them bandaids for weak ignitions.

if i try this i will let you guys know the results.
Try some better ignitors, the j109s are weak. GM HEIs work well but not above 8K.
Also use a coil per leading, the 2G coil is sharing a coil across the leading plugs
and isn't as string as a coil per leading would be. You need a lot of spark energy
to cleanly burn that bigger charge from a bridge. If your running above 8K you
pretty much have to go CDI I think.
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Old 08-25-12, 12:12 PM
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well i already put together the TT box, will try it today and see if it works better than the J109 firing the 2G coil. if it still can't cut it then will be either going to CDI or to DLIDFIS with new coils or both.
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Old 08-25-12, 08:03 PM
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built the box and tested it today, it definitely feels better than the DLIDFIS and simplified 2GCDFIS as the breakup was much less pronounced.

problem encountered though is the TT box and 2G ignitor(2nd gen coil base) get super hot after a short period of time and the TT box cuts out(LED turns off) until we let it cool off for a bit and then it works for a short period again. so, unfortunately still seems insufficient to even match the stock 2G FC setup with this TT emulator. will be picking up a MSD 6A with MSD coils to do a CDI DLIDFIS setup and be done with it.

it would probably do ok for cars pushing sub 200whp and only hitting high revs periodically, ambient temp here was near 100F when we tested it and it will need to see at minimum those temperatures during summer. if i had the time i would try the GM ignitors but at this point i'm tired of dicking with the ignition.

had hoped this would bring out the potential of the 2G coils but still not quite there. the single J109 and it's flat curve beyond 4k is still apparent when triggering dual coils(but much less). the 2G coil was mounted behind the battery so it wasn't really getting any airflow which was problem #2 but this RX4 still has A/C so space is limited, probably wouldn't have been such an issue if it was mounted to the strut tower to get air from the fan.

Last edited by RotaryEvolution; 08-25-12 at 08:20 PM.
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Old 08-27-12, 04:03 PM
  #58  
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MSD 6A + blaster 2 coils pretty much eliminated the problem, now it's just down to fine tuning the holley 650.

J109's can burn in hell, seems like there's just no way to really amp them up. maybe sometime in the future i can give my impressions on the GM ignitors with a similar setup.
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Old 09-01-12, 04:46 PM
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Made mine up today, using a different PCB design for a cleaner finish -



Had to break the end off so that the long lines were separated from each other



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