Well, I decided to replace my coils. With 235,000 miles and 20 years, they probably weren't the best.

Since the cheapies are like 23 bucks and the OE's were 35 (Mitsubishi) I opted for 2 MSD Blaster Coils. I looked at the Accel's, but they were more expensive and didn't really say what was better about them. Since I am going to try the MSD Direct fire 6 setup eventually, I went with the 35.00 MSD's. I noticed the Mitsubishi's I pulled out were 12volt coils. I read a couple people saying they were 9v's, so maybe an older year.

So I put them in and can't really tell any difference. I thought I noticed a slightly smoother idle (with lights and brake on) but can't tell. I think it idled a little better on cold start because the coils probably came into operating range alot quicker than the old ones. I can't say for sure. I checked my fuel/air ratio led and I was still cruising about 570 to 600 mv's with lights on, same as before.

I am still running Autolite plug wires. I tried to compare them but the boxes really have crap for comparison. Even the MSD's for 85 bucks(V8) had a lousy description as to why you should buy them. I was told you need to match the MSD's up with a low resistance supression wire. The guy at the auto place said he tried them all and it was a bunch of crap. Maybe when I install the DI system it will be necessary, but not now.

Anyone looking to improve performance on their car by just adding the coils, sorry to dissapoint you, save your 73 bucks.

 

The fact that you didn't notice any difference just shows you that your old coils were still doing what they were supposed to, although they were old. Probably a good idea to change them anyway, considering their age. The only way you'd have gotten any performance improvement out of new hotter coils was if your old coils were shot. Other than that, upgrading to new hotter coils won't make your car go any faster than upgrading to a new "hotter battery" will.

Generally speaking, upgrading to hotter coils is something you do to keep your ignition up to speed with other mods done to fuel, intake, and ignition system.

I plan to change coils, rotor, cap, and wires soon because mine are really old also. Not so my car goes faster, but so it "continues to go"

I think your $73 was money well spent.

 

I agree, I wasn't expecting any real increase. I was hoping to further restore smoothness back into my car as well as decrease my warm up time. All though, it's tough to keep an FA running smooth. I was reading the TSB's for 84 and 85 and they appear to have had problems out the door. The 85 being worse since it was sadled with some last minute add'l smog crap. However, my red 84 never had that problem. Never had any problems as a matter of fact for 191k miles until a tree fell on it. Grrr. I'll see if I can dig up a photo.

Anyways. I am sure if I took a good look at the upper RPM's these coils would supply a better stronger signal. I always had problems up past 7k, maybe I'll try to beep it tomorrow and see.

 

Ok, I did some checking. I measured the resistance of my Mazda OE plug wires from long ago. They had a whopping 6,000 Ohms per foot! I measured my autolites and they were about 1,000 Ohms per foot. I know MSD says there's are 50 Ohms per foot. If anyone else has a different brand, like Bosch, let me know what resistance yours is.

I find it strange that the autolites and Mazda OE's are so high, according to MSD. It might just be because they are functioning as a resistor, dropping the amount of work the ignitor is doing. If that's true though, then using the lower resistant wires would allow more current to flow, which may be good for the MSD 6 device; if installed, but bad if using an ignitor and no MSD 6 unit.

I did a similar thing to drop the power across the air/fuel led I made. I used a 50 ohm resistor to limit the 200ma across the device so some of the heat would dissapate across the resistor, resisting the regulator's work. I.e, I had a 14.4 volt source (alt running), and the regulator was a 5v out (wanted it limited to 6 volts in). So 8.4 volts/.2amps is 42 ohms.

So, anyways, if someone could post some wire resistances, preferrable the MSD's also, if available it would be great to compare.

I also read that the hotter coils are more beneficial if you gap up the plug. They increase the spark length and the higher voltage bridges the distance just fine. However, the reports were from piston engine users.

 

i had the same disappointment when i switched to MSD coils many years ago ... thinking, more spark = more power! holy cow - was i wrong.

my best guess it that you'll probably pick up some upper RPM spark intensity/strength and a couple miles per gallon, but that's about it. no power, and no perceptible change in smoothness. of course ... i was young and not-so-sage then, so i didn't think to measure the mileage before and after ... so i have no data to back this up.

well, just think of it this way ... you've got NEW coils, it;s one less thing to worry about.

 

Well, I keep a running total on my mileage so I will know exactly what it does. I am trying to get above my 17.3 mpg (half highway and half city). It's not that bad though. My friend has a 89 BMW 6 cyl, It is just a little faster than my car and gets only 22 mpg with EFI.

I think the big problem is now I drive 70mph not 60 (speed limit went to 65 here in CA). So I am doing almost 4k. I think our cars were geared for that 60mph cruise.

I still can't decide which DFI system to do. I looked at Mallory but it says it won't do odd fire and can't find anyone that uses one. I looked at Crane Cam, and there are people using them in rotaries, but they say not to on Crane Cam's site. The Crane Cam has quite a few more features than MSD and appears to be more reliable. I am looking at Accel, but I can't find any descent info on it.

I have read about a lot of unit failures on the MSD's. I read that it is analog and consumes more power, the Crane Cam and Mallory are both digital and consume less power. Further, the Crane Cam puts out more plug gap power. So I am totally confused. You'd think large manufacturers would actualyl have descent web sites considering so much of their products are sold mail order.

 

What about DLIDFIS? Ever thought about that?

 

Not yet, I am still trying to figure out what it is. Here is a dyno chart off a V-8 I found from a magazine at

http://www.cranecams.com/ignition/4wheeldyno.htm

Haha, things are so confusing. Notice where they all fall compared to baseline.

 

Here's a good place to start.

https://www.rx7club.com/forum/showth...threadid=85362

I plan to try it soon.

 

Ok I figured out what it is and I actually have all the parts necessary, if so inclined. I may try it but am unsure. I live in a CA, so I am wary of anything that would bring me aggravation smog wise. Although this mod looks easy to undo.

I am really confused though. I found a couple of people sharing dyno info and I don't get it. They have 13b's and are showing like 105 BHP & 103 ft-lbs stock. What's up with that?

My 12a is supposed to be like 107 BHP stock. With 101 ft-lbs of torque. Is there some magical translation that's going on that I don't know about? Is it because they're running large wheels, changing their moment arms?

 

The 12A has 107hp at the engine. Are you sure these 13B guys aren't talking rwhp?

 

Ya, these guys are talking at the wheels. What is a 12a then at the wheels? So I can compare.