rx7lives

2nd Gen distributor and coils in a 1st gen SE?

Has anyone done this? I've found the schematic but the crank sensor goes to the ECU and so do the coils. The coils have their own ignitors so I'm assuming if I can get the correct connectors, I can test it off of the car. The problem is I have the parts except for the wiring harness and I'd prefer to use the stock connectors.
Thank you for any answers.

Twilightoptics

iTrader: (1)

You wont have any timing increase if you can get it to work. The CAS is just a trigger to the ECM to let it know where the crank is. The ECM then dictates when to fire the coils.

rx7lives

OK, I'm a moron, I didn't think of the two vacuum advance parts on the distributor.

Is it possible to hook up the leading coil using the stock ignitors? I can't see how to hook up the trailing ones without a crank angle sensor since they fire at different times unless I hook the output of the trailing coil to the normal coil input on the distributor.

Does anyone know if the 2nd gen coils are better or is it worth it to invest in an MSD?

Thank you all for your help.

Siraniko

iTrader: (13)

Dlidfis is cheaper and work as good as msd boxes. On the other hand, msd with coils is much better than using msd with fc coil

rx7lives

OK, it looks like the leading coil is easy and since they fire 180 degrees apart, it's no big deal.

The trailing ignition is a nightmare.
Here are the connections:

Black/yellow strip=+12 for both, they are on the same connector.
Black/Red stripe= goes to the ECU but I don't know what it's for, it could be for advance.
Yellow/Green=TAC.
Black/Yellow= tells the coils(s) to fire.
Brown= selects which of the two coils to fire.
The mounting bracket is the ground.

The problem is to get the correct coil to fire. I'm trying to design a circuit that will select the correct coil to fire; there's only two sensors in the dist so it would be easy to use the leading coil to determine which trailing coils fires, only problem, how do I select the correct coil?

I think about this for a while, I've got a spare SE dist with a bunch of spare ignitors. I need a reference point so it knows to fire the correct coil.

j9fd3s

iTrader: (3)

its a waste of time, the distributor cap does this for you....

on the FC the ECU looks at the CAS and then decides when to fire the coils, so timing is 100% handled in the ECU.

also the FC uses a "toggle" function which is weird. the coil gets a "trigger" or "tach" the FSM says IGT-T trailing trigger, and this fires the coil. the select switches between the two coils, mazda calls it IGT-s for select.

so to fire T1, just the trigger gets a signal. to fire T2, the IGT-s is on, and then it gets a trigger.

so the toggle makes things hard, because its fairly unique. the 3 rotors use it as well, except they add another toggle, as there are three outputs.

the other wire that goes to the ECU is a confirmation signal, the ecu knows the coil fires.

dbragg

iTrader: (7)

Going to an FC is a well known obvious improvement, but you're saying once you add an MSD to the mix that it's better to use factory style coils? Why do you say this? Experience or technical data? Not doubting you, old wise rotary-jedi, I just like knowledge

Siraniko

iTrader: (13)

I have experimented with both set-up and IMHO, the MSD with coil set-up, as supposed to FC coil. I dont own any sophisticated electronic devices but using a timing gun, I've noticed that the flash on coil set-up is more consistent than a FC. In fact, my cars ran better with it so I ditch the FC coil pack.

Siraniko

iTrader: (13)

I forget to mention that my plugs are cleaner too or it has a nicer burn

t_g_farrell

iTrader: (1)

Using separate coils per leading plug is always better than using the FC coil. My
setup for instance uses two Ford TFI coils, one per plug and it is a much better spark
than using the FC coil I had before. I think its because the two coils operate
independently as opposed to the FC coil, which shares the coil across firing events
to both plugs. I'm not using an MSD either, so its not an issue.

Back to OP post. The CAS allows an ECU to monitor the eshaft rotation and then
compute on the fly when to fire and what plug to fire. It also controls the advance
or retarding of the timing as well. A dizzy supplies an analog electrical signal to a
device that triggers the coils to fire (the ingnitor). The dizzy controls advance/retard
of the timing by both mechanical and vacuum advance mechanism contained in the
dizzy itself.

One can not be used in place of the other, all other things staying the same. If you want to
use the 2G CAS then you need a standalone or a 2G ECU and the attendent wiring
and supporting electronics.

Maybe you confused using the 2G coils with using the 2G CAS. You can use the 2G coil
easily and it is a step up from using the stock coils.

j9fd3s

iTrader: (3)

i don't have anything to gauge it with, but i also agree that the FC setup isn't an improvement over the stock FB stuff.

i actually like my MSD into the dizzy setup, seems like i have a lot of spark, its simple, clean, and i can switch to stock in 5 minutes if i needed too

Siraniko

iTrader: (13)

Since ignition is the topic, I will throw in the direct fire using FC leading coil (and also using the FC trailing coil set-up) as a replacement for stock coil; this is the one without a MSD box or DLIDFIS. Its a waste of time IMHO. yes, there is a direct fire but the spark is weak. Just my $0.02.

t_g_farrell

iTrader: (1)

+1

85TIIDEVIL

iTrader: (2)

I have a 87TurboII chassis all still stock that I just dropped a used 87T motor in. I set-up a Dellorto carb on it and kept the CAS. My plan at the moment was just to get the thing moving. Nothing on the engine harness is hooked up at all (except a ground ring and coolant temp). The car started right up first shot. Can this work safey if I decide to drive the car around like this for a little while. I've asked for some help in the 2nd gen section but nobody has answered..???

Sorry to thread jack but it's right on the same topic. ANY input / help at all woud be great.

j9fd3s

iTrader: (3)

you will have to manually check to see what the timing does with only those two sensors hooked up.

85TIIDEVIL

iTrader: (2)

Ehhhh. Well now the I'm having trouble with the fuel. The stock pump is not putting out the proper voltage I believe. Maybe once the car starts again the voltage will kick back up...? I don't really know I'm not familar w/how it works in it's stock manner. I wiped out a fuel pressure gauge b/c I pegged it way past the 15psi mark. The Holley regulator seems to be having trouble keeping the fuel at 4psi for the Dellorto on a EFI pump even w/a big fat return into a gascan... and with tooo much pressure lots of fuel was cleary dripping into the carb throats. Now I think the needle and seat is out of wack b/c I can't get fuel to fill the bowls any longer even with a 4-5ish voltage / trickel from the pump. Bah, the cheap kid shortcut way of using what I have laying around doesn't seem to be working. It looks like I'm going to need to spend some $. So checking timing right now has been put slightly back on the to do list.

rx7lives

Thank you for all your replies and inputs. I've concluded that:

1) Can't use the 2nd gen crank sensor in an SE unless I cut up a 2nd gen ECU just to fire the plugs-too much work with zero return.

2) If you ignore the module that is mounted in the 2nd gen leading coils and just use the two terminals on the coil, you can use the stock ignitor or at least it's working on my work bench mock up. Someone has mentioned that you end up firing two plugs with one coil which is what the 2nd gen does. Yet, when I check the resistance between the high tension end of the coils it actually looks like they're two coils connected in parallel with separate high tension outputs so it is two separate outputs but I wonder how the stock ignitor handles the load, even with the ballast resistor? I'm wondering if I can use the stock ignitor to fire the 2nd gen ignitor-coil combo so I'll try that on the bench.
The problem is I don't have any room for the larger 2nd gen coil unless I get a shorter A/C drive belt and move the compressor closer to the engine. There's also the option of removing the coil from the bracket that contains the mount and internal ignitor which should give me some room but I don't want to use duck tape to mount it and it eliminates the 2nd gen ignitor and heat sink provided the two can be made to work anyways.
I'm still going to try to use the stock ignitor to fire the 2nd gen ignitor just to see if it can be done.

3) This thread has makes a lot of sense. https://www.rx7club.com/showthread.p...hreadid=216618.

I consider this to be the best option which is to use three stock RX7 ignitors using the one on the dist as a sensor and using two other ones mounted on an aluminum heat sink as the ones that fire the two coils. I've got a bunch of ignitors and I'm sure one is dead so I won't mind using it to convert the tiny inside of the coil sensor connectors to normal sized push on connectors even though I've got the correct male ones; it seems that using the correct connectors won't make that great of a mechanical connection although you still need them (female for the ignitor side) for the two real ignitors but since they'll end up going thru a heatsink, I can make a good mechanical connection by using decent wire management.

4) Is there a difference between the leading and trailing coils and if so, which one should I double up on for the two leading coils?

I read someone say that after this I should move my trailing wires on the dist to the leading position. What is the gain and isn't there a timing difference between where the dist rotor is and where trailing ignitor thinks it is?

I'd like to thank everyone for their input. I'm still kicking myself over missing the the fact that the crank sensor doesn't have vacuum or mechanical advance.