Only The Rotary

I am looking for info on a technique to convert a 1990 RX7 coils to a more modern and less expensive set up. The cost of a "New" Mazda Leading and Trailing coil/igniter set is close to $1500. A Coil for newer cars are in the $40 range. Has anyone had success converting 2nd gen cars to use an alternative Coil set up?

lduley

iTrader: (1)

Not worth the hassle IMO, the stock mazda coils are good to almost 400 horse, and RARELY fail, and used ones can be had for cheap

Not sure how you could make different coils work with the CAS without an aftermarket ECU either

DC5Daniel

iTrader: (10)

You're going to spend $1000+ on an ECU and then $400 on coils. Just buy a second hand replacement.

misterstyx69

iTrader: (142)

Coils rarely give up..so NEW and Cheap do not enter the picture.
Used and Stock do...

Iduley hit the nail on the head.

Buying an ECU and coils on an N/A doesn't really do anything for you except drain your wallet and give you bling.
If you want a bit of hotter spark then look into an MSD or Jacobs unit.
Overspending on a N/A can get expensive real fast and unless you get the Total BUG to go "bigger,better,Faster" then the Parts you mention are just shiny objects to tell your friends about.
They however can help you (mainly ECU) if you decide to go to a Turbo engine.
Personally that would be about the first on my list IF I was starting ...again....(oh no..you got me thinkin..I am Outta here!)

Aaron Cake

iTrader: (1)

You certainly could. In fact it wouldn't really even be rocket science.

The leading coil is just a waste spark coil on an ignitor. Straight replacement with two coils is dead easy.

The trailing has a unique ignitor that uses a toggle signal. It's less straightforward to replace but if you keep the ignitor and just use at as a switch, then replacement is much like the leading.

No point though. Coils just don't fail on these cars (never seen a bad one) and used replacements are dirt cheap.

Only The Rotary

Thanks for all of the good advice I appreciate all the good tips. This engine was rebuilt by aprofessional and has only about 10K on it.It started running rough then sat for several months as I did not have time to work in it.
Aaron, I am following the Cosmo project so I think I would be over my head to retro fit this car with a Megasquirt. I did follow your tips for cleaning grounding points.
My testing shows me the following info. (Timing light and Voltmeter)

• Leading coil fires one rotor consistently and the other rotor inconsistently.
• Trailing coil does not fire at all.
• Voltage to Trailing coil is 12 volts and alternates from 5 to 0 to 5 as engine is rotated.
• Visual inspection of wiring looks normal.
• Visual inspection of the Crank angle sensor looks okay, but not sure what to look for.
  
  The following parts have been replaced but made no difference.

• Oil Metering Pump (because old one was giving error code)
• ECM 351 – had an extra and wanted to be sure it was not stuck in Limp Mode.
• Leading coils swapped for a set from a running car
• Trailing coils swapped for a set from a running car.
• New NGK wires
• New NGK spark plugs
  
  
  I am having trouble uploading a video that I took. I’ll try again tomorrow.

Only The Rotary

Here is a quick video of engine running poorly. Notice the timing light is intermittent while attached to L2 wire.

Aaron Cake

iTrader: (1)

There's no reason to replace the stock ECU with a standalone for this issue.

Don't use a timing light to check for spark. It is not reliable. Only way to check for spark is to disconnect the lead from the plug and use a spark tester or spare plug.

The car will run without trailing spark at all, and run just fine. Ignore the trailing coil issue for now. May not even exist if the timing light was the only spark confirmation.

The leading coil fires waste spark. Since you have swapped another leading coil on, that is likely not the issue.

CASs can fail. But I can't think of a failure mode that would allow the car to run yet not produce spark. The CAS just provides the position of the engine to the ECU, it is the ECU that fires spark based on the position.

Have you checked that both rotors are receiving fuel? Fuel injector issues are VERY common especially if the car has sat.

misterstyx69

iTrader: (142)

The leading coil fires BOTH leading plugs at the same time so if you think that one side is bad then switch the plug wires and see if that makes the other do what you say it is doing.
IF it acts up then your coil is bad.
If not then your coil is fine.(put plug wires back to L1 to L1 and L2 to L2)

Only The Rotary

After taking Aaron and MisterStyx's advice I bought an in-line spark tester. this tests show that I was wrong about coils not firing. The timing light test had me thinking that the coils were not firing, but they are.
So I still have a engine that runs rough and smokes. It seems like a very rich exhaust and not an oil burning smell. it surges up and down during Idle and stutters when throttle is opened. I cleaned the MAF sensor but it did not make any difference.
I also notice that the oil pressure gauge is showing very low pressure. close to 0. I hope that is a sensor problem because this is a fairly new engine.
I plan to do a smoke test for vacuum leaks soon. I did not find a vacuum leak using the Carb cleaner test.
I will hook up a separate Oil pressure gauge to rule out engine problem,
The Saga continues.....

lduley

iTrader: (1)

save yourself a lot of hassle and start with a compression test

just because it's a recent rebuild, doesn't mean it's indestructible

Aaron Cake

iTrader: (1)

Again, how long did it sit? After sitting, you almost certainly will have one or more bad fuel injectors.

Fuel system been all flushed out?

As above, vacuum leaks would explain the surging.

You can get a stethoscope and listen to each primary injector as the car is running. Should hear each one clicking strongly in a rhythm.

Only The Rotary

Update::
I took Aaron's advice and replaced all 4 injectors. the old ones were Original and looked pretty bad. Long story short... I finally acquired the correct UIM gasket and reassembled all of the intake components last night. upon start up... the engine started and revved up to about 6000 RPM's and stayed there. The Throttle and Cruise cables are not holding the throttle open. the exhaust seems to be very rich. I think that this problem is related to the idle control or something around the throttle body. I am digging through old threads to see what to check.
anymore advice is appreciated.

lduley

iTrader: (1)

TRIPLE CHECK that your throttle cable is on correctly, mine slipped out've its guide JUST BARELY and held the throttle plates open just enough to do what yours is, i didn't think that was my problem either, but it was

Aaron Cake

iTrader: (1)

And make sure the secondary throttle plates are not sticking open. Seen that a number of times lately.

Only The Rotary

This car has really frustrated my efforts to fix. Aaron, I checked the Secondary throttle plates and they are not sticking open.
I replaced both upper Intake Manifold gaskets and sealed with a bit of RTV, I put the whole intake system back together. I did notice that the port on the intake manifold that comes from the Catalytic converter is blocked off, but I don't think that would affect anything. I tested the Idle Air control valve and it is operational. the resistance is correct and it opens and closes when 12 volts are applied.
upon start up.... the RPMs jump to 6000 and then..... over the course of 15 seconds.... slowly come down to 2000 then the engine shuts off. the New Injectors seem to have caused it to run smoother.... but I cannot understand the run away Idle speed.
I did a quick smoke test by putting smoke into the brake booster line. The only leak seems to be a small leak around the Primary injectors. could that explain the idle problems? I have ordered new injector seals and O-rings just in case. I have torn down and reassembled this intake 4 times and it is disheartening to say the least.