Question for the electrical theory guru's
#2
Waffles - hmmm good
![](https://www.rx7club.com/images/misc/15_year_icon.png)
iTrader: (1)
The tach signal can come from either coil. In fact for the SA it comes from the leading because
the trailing is turned on and off in stock operation to help with emissions.
The ignitor firing triggers the coil, not the reverse. Its that trigger signal thats used basically for
the tach.
the trailing is turned on and off in stock operation to help with emissions.
The ignitor firing triggers the coil, not the reverse. Its that trigger signal thats used basically for
the tach.
#3
Unfortunately the tach signal wire is buried down in the harness somewhere so you'll have to do some digging if you want to separate and hook it to the leading coil.
Are you trying to eliminate trailing for some reason? Or just curious about these interesting cars?
Are you trying to eliminate trailing for some reason? Or just curious about these interesting cars?
#4
Old [Sch|F]ool
![](/images/misc/20_year_icon.png)
![Smilie](https://www.rx7club.com/images/smilies/smile.gif)
I think putting the tach on trailing is a good thing. It lets you know that your trailing is dead. When the leading dies, it's pretty obvious, but you can drive perfectly well with no trailing.
#5
If you pay attention, you can hear when trailing is firing. It's subtle but noticeable with experience. SA guys can hear it kick in and out as it's switched.
Smog guys, on the other hand, insist on clamping the timing lead to the top(trailing) plug wire, then can't understand why it cuts out under early acceleration.
Smog guys, on the other hand, insist on clamping the timing lead to the top(trailing) plug wire, then can't understand why it cuts out under early acceleration.
Trending Topics
#8
Moderator
![](/images/misc/20_year_icon.png)
iTrader: (3)
Join Date: Mar 2001
Location: https://www2.mazda.com/en/100th/
Posts: 30,989
Received 2,688 Likes
on
1,903 Posts
If you pay attention, you can hear when trailing is firing. It's subtle but noticeable with experience. SA guys can hear it kick in and out as it's switched.
Smog guys, on the other hand, insist on clamping the timing lead to the top(trailing) plug wire, then can't understand why it cuts out under early acceleration.
Smog guys, on the other hand, insist on clamping the timing lead to the top(trailing) plug wire, then can't understand why it cuts out under early acceleration.
there are two hoses there, a big one and a small one, and i guess every other car has the big one being the tank vent, the FC uses the small one (FB does too).
so when the smog guy goes to put the pliers on the wrong hose, they are surprised when i yell at em....
#9
Moderator
![](/images/misc/20_year_icon.png)
iTrader: (3)
Join Date: Mar 2001
Location: https://www2.mazda.com/en/100th/
Posts: 30,989
Received 2,688 Likes
on
1,903 Posts
if you're using the pickup in the distributor i think you can.
however ALL the OEM's use a fuel cut, so you should think about just doing that.
#10
the FC has the same problem, they test if the gas tank holds vacuum, and they do this by putting a vacuum fitting in place of the gas cap, and then putting a clamp on the tank vent hose right next to the charcoal canister.
there are two hoses there, a big one and a small one, and i guess every other car has the big one being the tank vent, the FC uses the small one (FB does too).
so when the smog guy goes to put the pliers on the wrong hose, they are surprised when i yell at em....
there are two hoses there, a big one and a small one, and i guess every other car has the big one being the tank vent, the FC uses the small one (FB does too).
so when the smog guy goes to put the pliers on the wrong hose, they are surprised when i yell at em....
I've had to lead several by the hand.
I even colored my tank vent line on the firewall red so it's easy to find.
#12
I attached how I currently have things hooked up. The "tach signal" is where I am running the tach and getting a signal to the haltech.
The msd is running off a gutted ignitor. The leading is direct fire and the trailing is one 2nd gen trailing coil firing through the dizzy.
The msd is running off a gutted ignitor. The leading is direct fire and the trailing is one 2nd gen trailing coil firing through the dizzy.
#13
Waffles - hmmm good
![](https://www.rx7club.com/images/misc/15_year_icon.png)
iTrader: (1)
I attached how I currently have things hooked up. The "tach signal" is where I am running the tach and getting a signal to the haltech.
The msd is running off a gutted ignitor. The leading is direct fire and the trailing is one 2nd gen trailing coil firing through the dizzy.
The msd is running off a gutted ignitor. The leading is direct fire and the trailing is one 2nd gen trailing coil firing through the dizzy.
#15
Moderator
![](/images/misc/20_year_icon.png)
iTrader: (3)
Join Date: Mar 2001
Location: https://www2.mazda.com/en/100th/
Posts: 30,989
Received 2,688 Likes
on
1,903 Posts
I attached how I currently have things hooked up. The "tach signal" is where I am running the tach and getting a signal to the haltech.
The msd is running off a gutted ignitor. The leading is direct fire and the trailing is one 2nd gen trailing coil firing through the dizzy.
The msd is running off a gutted ignitor. The leading is direct fire and the trailing is one 2nd gen trailing coil firing through the dizzy.
#16
Old [Sch|F]ool
![](/images/misc/20_year_icon.png)
What I have on my car is a Megasquirt and an MSD. The MSD reads from the leading pickup and the MSD's tach signal gives the Megasquirt its tach signal. MSD drives both ignition systems, I run with no split. (It's actually an FC trailing coil assembly, with one of the trailing coils replaced with a leading coil. Leading is direct fire, trailing goes through the distributor)
The trailing pickup and ignitor go to a little thingy I made where the original trailing coil leads attach to it and a small resistor (1k ohm?) connects the two. This gives the wire going to the tach the alternating power and ground that it needs.
You can sort of see what is going on here:
Thread
Thread Starter
Forum
Replies
Last Post
Nosferatu
2nd Generation Specific (1986-1992)
7
09-05-15 02:13 PM