Best practice for 1st gen ingnition system?

[lateapex911]

I have been getting erratic readings from my AIM system as it reads the RPMs. I'm using a stock ignition system, and I have been meaning to upgrade for years. I'm a little concerned that my spark isn't what it should be.

What is the best practice for a 1st gen racing ignition system?
(And, for you EEs who might be kind enough to answer, terms like "wasted spark" confuse me, LOL, although I do understand the MSD concept.

Many use MSD..it that appropriate?

What do you all use?

[tom_sprecher]

Sometimes I feel my spark isn't what it should be but I'm 46 now and only getting older every day...

My car came with an MSD it which is now better than 8 years old and seems to work just fine.

[Daryl]

Are you using an inductive pickup? Are you getting the signal from the Leading coil or the trailing coil? Does the RPM trace on the aim erratic or seem "wrong"? Does it get all weird at high rpm or everywhere?

[joeracerx95]

I use the stock ignition system. It seems to work just fine.

[Festus E. Simkins]

I use two MSDs. It was recommended to me years ago when I first built the car. No problems ever.

[Z3_GoCar]

I have been getting erratic readings from my AIM system as it reads the RPMs. I'm using a stock ignition system, and I have been meaning to upgrade for years. I'm a little concerned that my spark isn't what it should be.

What is the best practice for a 1st gen racing ignition system?
(And, for you EEs who might be kind enough to answer, terms like "wasted spark" confuse me, LOL, although I do understand the MSD concept.

Many use MSD..it that appropriate?

What do you all use?

So Jake,

Wasted spark* is wasted on you??

How about twisted shielded pair (TSP)? In general, instrumentation is always dealing with cross talk, currents induced in a pair of wires that carry tiny currents from sensors. The induced currents can mask the real signal causing either a false trigger or no trigger. TSP is used in the wire from the crank trigger. Cross talk there would mean that the spark fires at the wrong time. Look on-line at the Digi-key catalog, they have TSP wire for instrumentation and security cameras.

James

* Wasted spark is when a motor of n-cylinders, note n is some even number of cylinders, has n/2 coils. Each coil is conneted to two cylinders that arrive at top-dead center at the same time. Note that while one is compressing the fuel/air mixture the other is scavanging exhaust. The reason for the name wasted spark is because the spark in the exhaust scavanging cylinder may be considered wasted.

[dyoungre]

Jake,
Does your tach jump around at the same time that the signal on your data jump? Is there misfire? If not, then what Jim said is probably root cause - simply noise on your tach signal. If the tach is erratic as well, or you can feel misses that go along with the noise, then I'd check the slop in your distributor. They do wear, and can cause erratic pickup signals.

[lateapex911]

OK, guys, thanks for the responses.

here's the skinny. Tach wire was run neatly along with other wires. As the cars seems as powerful as any other NE RX-7, I couldn't immediately assume actual ignition issues.

So, I undid the neat harness, and left it flopping about. Problem instantly solved! Viola! Seems being messy has it's advantages?

(I'll make it neat, but a respectful distance AWAY from the mean wires, or I'll go shielded.) Thanks for the suggestions, and James gets a free beer when he comes to CT, as he hit it first.

And if you ever come to the track Dave, I'll give you one too!

[dyoungre]

Plan now is to try to make it to the Pocono double in July, since it is only an hour and a half from home. It's amazing how busy the twins keep us.

[kbailey]

So to ask the original question one level deeper...I have heard from several people MSD boxes are worth some power. Anyone know how much power? (I have two used 6A's in the garage and I am trying to decide whether or not to put them in the IT7).

Thanks for any info-

Kevin Bailey
WDCR IT7

[tom_sprecher]

I don't have any before and after dyno runs but if I had two MSD's in my garage one of them would be in the car and the other would be a spare.

$.02

[jvarble]

So to ask the original question one level deeper...I have heard from several people MSD boxes are worth some power. Anyone know how much power? (I have two used 6A's in the garage and I am trying to decide whether or not to put them in the IT7).

Thanks for any info-

Kevin Bailey
WDCR IT7

Kevin
in years past i did a lot of dyno testing at mandeville auto tech on 12a's and what we found was
if you are using the mazda ing. there was no real gain in horse power using the msd's.
they were a big help with crank fire ing. which we can't use in IT, however using a real good grade of plug wires "racing beat red" made more power than stock mazda wires or the blue NGK wires at above 5000 RPM.
i guess what i'm saying is the stock mazda coils are a LOT better than people give them credit for.
hope this helps

[kbailey]

Tom, J- thanks for the advice an info.

I am a firm believer in the less parts there are, the less parts that can fail- That and the fact that I am already 108 lbs over weight (we did a pretty good job targetting 2380 lbs when we built it) every few pounds counts so I think I'll be ebaying those boxes-

Kevin