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The rotarys all have weak ignitions from the first RXs to the RX8. Upgrading the ignition gets you
better MPG and better performance and smoother running. Its a win/win in my book.
Lets put it this way, I can start my car even if its completely flooded. It may take a few cranks but
it starts. Couldn't do that with the stock ignition ever. Had to pull plugs and so on.
It doesn't hurt that the parts are readily available either. The stock ignitors are good to about 3 - 4 amps
while the HEIs start at around 6 stock and go up from there if you get performance
brands. This means more power to make the spark.
Thanks for the plug of my thread, always appreciated.
They are weak in different ways but they are all weak in some way. The 1st gens didn't have
enough power, the FCs blew out the leading coils on a regular basis, same for the FDs. The
RX8s have weak coils AND they blew them out as you stated after about 30K.
Why mazda can't spend the small amount of money to use higher quality ignition parts is beyond
me.
No idea if it is a performance benefit but I am pretty happy with my LS coil setup, $12 each for the coils and replacements are available at any auto parts store in the country.
Upgrading the ignition gets you
better MPG and better performance and smoother running.
What's your opinion of the best vehicles to harvest from? I read that you got inspiration from the Jeep forums, are they generally good donors for the HEI's and coils? Or would you just buy new parts?
Originally Posted by mhr650
No idea if it is a performance benefit but I am pretty happy with my LS coil setup, $12 each for the coils and replacements are available at any auto parts store in the country.
Nice location on your setup...short plug wires. I don't see the HEI's separate (or other signal wiring etc.), they must be incorporated into the coils or some other box? I assume you use the distributor reluctor signals just like other setups? And you did Leading and Trailing. Ever try it just with the Leading?
What's your opinion of the best vehicles to harvest from? I read that you got inspiration from the Jeep forums, are they generally good donors for the HEI's and coils? Or would you just buy new parts?
Nice location on your setup...short plug wires. I don't see the HEI's separate (or other signal wiring etc.), they must be incorporated into the coils or some other box? I assume you use the distributor reluctor signals just like other setups? And you did Leading and Trailing. Ever try it just with the Leading?
Fun stuff, thanks for all of the info.
The parts are so cheap, I would recommend getting new, at least on the HEIs. I grabbed the TFI coils off of F150s at pullapart. Take a DVM with you to make sure
you get good ones. The jeeps didn't come with these originallly. The HEI are from late 80s/early 90s GM products and the TFI are from mostly the same
vintage.
You can easily just do the leading and not put leads on the trailing. I ran that way
for a few years before I decided to add the trailing. Works great and its hard to
notice the difference really.
and 3 of theses guys (edit: apologies for the GIANT ebay graphic here, forum renders the link this way) http://www.ebay.com/itm/GM-Ignition-Module-High-Temp-Heavy-Duty-4-Prong-D1906HT-LX301-CBE4/380822674666?_trksid=p2047675.c100005.m1851&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D2%26asc%3D37470%26meid%3D270d2ab41d0746e3ba8a42d8ddee296e%26pid%3D100005%26rk%3D1%26rkt%3D6%26sd%3D320635444061
Wow. $9 for the HEI seems pretty cheap. Maybe too cheap?
No idea if it is a performance benefit but I am pretty happy with my LS coil setup, $12 each for the coils and replacements are available at any auto parts store in the country.
I like how this set up looks, what kind of ignitors did you use,can't tell from the picture
Recently I went from only leading ignition using 4 prong HEI modules and 2 Ford TFI F150 coils
to a single FC leading coil and the trailing coil a TFI one going through the dizzy. Still the same
HEI modules and dizzy wiring except one HEI is for trailing and the other is now for leading.
Previously I did notice some ignition breakup on the leading TFI setup at around 7K but it
was minor and mostly just bounced the tach a bit. I had assumed this was maybe some
noise or a tach wiring issue.
Now its smooth as silk and I don't think it changed the power output but no before after
measurements to document that. After reading that thread it appears the FC coil is a
good choice for NA setups at least.
J9 you are right, we should have section just for ignitions and have it split into generations
or NA/boosted/EFI or something along those lines. Theres a lot of good info floating around
but its king of hard to find it easily.
Recently I went from only leading ignition using 4 prong HEI modules and 2 Ford TFI F150 coils
to a single FC leading coil and the trailing coil a TFI one going through the dizzy. Still the same
HEI modules and dizzy wiring except one HEI is for trailing and the other is now for leading.
Previously I did notice some ignition breakup on the leading TFI setup at around 7K but it
was minor and mostly just bounced the tach a bit. I had assumed this was maybe some
noise or a tach wiring issue.
Now its smooth as silk and I don't think it changed the power output but no before after
measurements to document that. After reading that thread it appears the FC coil is a
good choice for NA setups at least.
t_g,
So, is this silky setup essentially "in place upgrades" for the stock FB distributor, i.e. you are going through the cap and rotor but with with 4 pin HEI modules wired in and better leading (FC )better trailing (TFI) coils?
If so, it sounds like a simple upgrade to wire in HEI modules in place of the stock ignitors, keep the FB coils (initially) and see what you get. Or are the stock FB coils the really weak point once you swap in HEI's? Will they support HEI modules or crap out in 6 weeks?
This is all theoretical to me until I actually work on my setup and see. But I'm tempted to listen to your experience and emulate your latest setup but with the Ford type coils (TFI right?) and 4 pin HEI modules that I have ordered.
Stepping back a bit, it amazes me that all the rotating cap/rotor stuff (a high voltage spinning mess of arcing and carbon trails ) can result in smoother ignition than the dedicated electrical paths to the spark plug gap in a DFI setup. Maybe the harmonics in the rotor to cap arcing introduce some beneficial timing to the spark at the plug?
So, is this silky setup essentially "in place upgrades" for the stock FB distributor, i.e. you are going through the cap and rotor but with with 4 pin HEI modules wired in and better leading (FC )better trailing (TFI) coils?
If so, it sounds like a simple upgrade to wire in HEI modules in place of the stock ignitors, keep the FB coils (initially) and see what you get. Or are the stock FB coils the really weak point once you swap in HEI's? Will they support HEI modules or crap out in 6 weeks?
This is all theoretical to me until I actually work on my setup and see. But I'm tempted to listen to your experience and emulate your latest setup but with the Ford type coils (TFI right?) and 4 pin HEI modules that I have ordered.
Stepping back a bit, it amazes me that all the rotating cap/rotor stuff (a high voltage spinning mess of arcing and carbon trails ) can result in smoother ignition than the dedicated electrical paths to the spark plug gap in a DFI setup. Maybe the harmonics in the rotor to cap arcing introduce some beneficial timing to the spark at the plug?
Tom
The leading is run directly off of the FC coils and is a wasted spark direct fire
setup, doesn't go thru the cap at all. Its driven by one of the HEI modules. The
trailing goes thru the cap using the leading positions to get the best path thru
the dizzy cap into the trailing. The single TFI coil is driven by the other HEI module
and feeds into the dizzy for the trailing. I wanted a solution that still only used
2 HEI modules and allowed me to still mount my coils in my modified stock
coil holders. It all almost looks stock but its not.
Makes folks that are familar with rotaries stare at it for awhile. LOL
The leading is run directly off of the FC coils and is a wasted spark direct fire
setup, doesn't go thru the cap at all. Its driven by one of the HEI modules. The
trailing goes thru the cap using the leading positions to get the best path thru
the dizzy cap into the trailing. The single TFI coil is driven by the other HEI module
and feeds into the dizzy for the trailing. I wanted a solution that still only used
2 HEI modules and allowed me to still mount my coils in my modified stock
coil holders. It all almost looks stock but its not.
Makes folks that are familar with rotaries stare at it for awhile. LOL
Can you please post up a picture of your set up t.g.
So, is this silky setup essentially "in place upgrades" for the stock FB distributor, i.e. you are going through the cap and rotor but...
just to take a step back, there are a few considerations for an ignition system on any engine.
the first is that as power (combustion pressure) goes up, the energy required to fire the spark plug goes up.
two, the system, being electric, basically follows Ohms law, except that time is involved, as the coil needs to fire once every 180 degrees. so to increase ignition power, we can increase voltage, use a larger coil, and sometimes charge the coil longer, or some combination of the three.
now, for the 1st gen, we must use the cap for trailing. if you fire the trailings in waste spark, one is ok, the other is in the intake stroke, so we must have the cap. also the distributor controls dwell time, so that is fixed, and since it fires twice per revolution, dwell time gets short. there is 10ms of dwell at 6000rpm (60 seconds/1000) and its /2 for the distributor/waste spark, you can see the LS coil looses a ton of power going from 6ms to 3ms.
what we CAN do is several little things. first we can use spark plugs that take less power to fire, like the Rx8 plugs, or the racing plugs. these also have a benefit of being a better design, they misfire less. bypassing the cap for the leadings helps too
we can increase voltage to the coils, they charge faster at 14v vs 12v....
we can run larger coils, to a point. in general larger coils take longer to charge, so this is a case where too big is too big.
The leading is run directly off of the FC coils and is a wasted spark direct fire
...snip...
Makes folks that are familar with rotaries stare at it for awhile. LOL
Originally Posted by j9fd3s
just to take a step back, there are a few considerations for an ignition system on any engine.
we can run larger coils, to a point. in general larger coils take longer to charge, so this is a case where too big is too big.
...snip...
or you can go CDI...
Thanks for all of the information. Lots of acronyms in these ignition systems! I'm going to try the extremely well documented TFIDLS and see what I get. I'm mostly interested in solid starting and smooth running.
So guys, I finally got off my butt after 2 months now and worked on my TFIDFS for my 83 FB. My approach was to integrate the parts in a completely reversible way, easy to bring back to stock if ever needed. So I used existing mounting bosses and customized the brackets to fit those. Still need to clean up the wiring, I got impatient .
I bought some new LS1 coils and HEI's off of eBay. I only did the leading and left the trailing totally stock.
I read t_g's thread about 17 times (every few days) and eventually the fundamentals penetrated into my cortex. So many awesome contributors. This forum is just great. So much information, careful consideration of questions, collegial discussion.
=================> THANK YOU <================
First run was really rough until I fixed a stupid connection error (reversed W + G on just one of the HEI's). 2nd run was way better and it idles very smooth and feels good all the way to red line.
Tom
Here are some photos.
1. This is the connection to the Hall effect sensor. I grounded the shield using the old igniter's attachment point. The white plastic is the plug that is normally covered by the OEM igniter. I put dedicated spade connectors into that. I'll swath it in dielectric grease to seal it up. Any better ideas...how did you guys do your connections?
The wire is high quality audio signal cable with ample foil and woven copper shields. It struck me that the signal coming from the Hall effect/reluctor must be a pretty low voltage.
2. Overhead view of the coils and igniters on a heat-sinking aluminum strip. I placed the assembly of the coils and HEIs (they are on a riser) into the space above the AC compressor. I diverted the battery power lead from the OEM leading coil. The ground for the HEIs goes straight to the negative battery terminal. I'm planning to wire in the suggested relay and go to 12V at the positive battery terminal. But I got impatient.
3. Some details of the coil assembly. The HEIs sit above, just out of the shot. I joined the 2 coils with an aluminum plate and machine screws through the flux guides. There were some perfect holes for 10-32 screws, it is super rigid.
4. Left side view showing the mounting point. It's a channeled aluminum extrusion scribed to the curve of the shock tower and sandwiched with the old coil wire bracket mounting points. The LS1 coil's steel flux guide sits perfectly in the channel.
5. Details of the HEIs sitting on their elevated heat sink/mounting plate. It is attached by the 2 screws shown to a riser, and then into the joining plate between the 2 LS1 coils. On the right you can see the other support bracket that is clamped onto the shock tower bolt and holds the coil assembly via another piece of extruded channel.
Looks really nice. You can get replacement connectors for the TFI coils or reuse old ones instead
of the spades in there. Glad to hear it performans well.
08-04-16, 09:54 AM
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