MSD worth the weight and cost?
 

Any advice on running MSD boxes? I have done some research but looking for more opinions. They are about 5 lbs each, so that's 5 or 15lbs depending on if I do only leading or leading and trailing.

Race car built to SCCA EP specs, will spend all it's time at high RPM. S5/S6 NA streetport motor, Microtech, stock coils.

Was thinking of doing MSD 6(a, al, t, nt, etc) on the leading and (2) on the trailing or a DIS-2 on the trailing. Will be buying used MSD. Is it worth the weight and cost? I need to save all the weight and money I can.

I think the MSD is worth it's weight in gold. Running just one on the leading will make a noticeable difference. I have always run them in my cars and they make a huge improvement. Consider a Mallory VIA. That's what I'm ruinning now. They're almost Identical to the MSD 6A, but they're digital and more powerfull and have a smaller amp draw. MSD is 1 amp per 1000 RPM and the Mallory is only .6. Plus it's more powerfull, and about $50 cheaper then the MSD now! Since you're NA you really won't notice running it on the Trailing. The only reason to run it on the trailing is incase the leading spark blows out you have the insurance that because of the the extra voltage MSD gives to the trailing. The trailing might still spark, making the car less likely to misfire at high RPM's. Usually high RPM misfires are only a problem for really rich high boost applications. Just throw on on the Leading and I gautrentee you'll love the crisper throttle response it gives and peace of mind.
You can follow these instructions for the Mallory as well. Mallory was kind enough to color their wires identical to MSD.
http://fc3spro.com/TECH/HOWTO/CDI/cdi.html

Good post, thank you. Hadn't thought about the Mallory but am now.

I'm going to do something on the leading. Have not decided about trailing, other opinions agree or disagree with Hyper?

I use a msd box on my first gen EP rx7. On the dyno it didn't make anymore HP but did give it a little more torque. The throttle response is way quicker. I wired it to direct fire the leading plugs and ran the trailing thru the distributor. I think it's worth it.

FWIW Tom Thrash does not run one. Stock ignition. That was enough for me to pull mine out. His 13b power is way up there.

I might mess with it again one of these days. The biggest problem with my race car is the driver, when I get that fixed than I'll worry about a couple HP.

Is there a link to the Mallory box? I googled mallory via and checked summitracing.com for it.

Also, Summit racing has a box that's stronger than the MSD 6A. It's only $140 versus MSD's 6a at $180 or so.
But! The summit unit says it provides mutiple sparks up to 3,000 RPM's. I don't really know when the MSD stops multiple sparking, or even if it stops at all. I've read that the MSD's spark for 20 degree's after the initial spark. That doesn't quite make sense to me considering I'm firing it with a coil outlet and not a crank angle sensor. How does it know how long 20 degree's is?

The multispark feature switches off at 3000rpms on the MSD as well.

An MSD will only produce a better spark, especially with the high RPM, this has to help. The only thing it can hurt is 1) bank account 2) add weight (5lbs each approx for the 6 boxes) 3) uses lots of amps

I would imagine reasons 2 and 3 may be why Thrash does not run one. I do believe he runs a total loss system as I saw 2 batteries in his car which led me to believe no alternator.

A 6 box uses 1amp per 1000RPM, so figure 9-10 amps per box. That's a big drain. Use 3 boxes and you are at 25-30amps.

I have purchased a 6TN box for the leading now. I am debating on the trailing of either (2) 6TN boxes or (1) DIS-2. The (2) 6 boxes would use 18-20amps while the DIS-2 Plus is 3.5amps up to 10,000 RPM.

This has got me thinking a DIS-2 is the way to go on the trailing with the 6TN on the leading. Total amps used would be around 13 vs 25-30.

I suck at electrical but common sense tells me the less amps I use, the less the alternator has to work, which means the less it robs the motor of HP. I am running an alternator with an Optima red top mounted in the car.

Any thoughts on this latest setup idea? I'd still prefer (3) 6TN boxes over the DIS-2 but think the amp draw is getting up there. I have decided though I want to address leading and trailing spark.

20 amps x 14 volts = 280 watts

By definition, 1 horsepower = 746 watts (assuming 100% efficiency)

An alternator is probably around 85% efficient, so to make 280 watts, you would need about 0.47 horsepower (that's good :)

The horsepower draw of 20 amps off of an alternator is not as bad as the inertia loss of spinning it up and down (that's bad :(

I run an alternator on my race car; I make strong horsepower, and my crew does not want to have to screw around with having to worry about charging the battery all the time (they told me so)

Good info. Like I said, I suck at electrical :)

So maybe (3) boxes won't be such a drain.

2 years of Ignition research all in 1 thread. Turned out that My MSD didn't die, but it was just a carb issue. And it's not via. its 6A, but Mallory uses roman numerals. Use the Mallory it has more power and much less amp draw.
https://www.rx7club.com/showthread.p...hlight=digital

I used to run 2 x DIS-4 on my 20B. They performed quite well once I finally figured out they needed to be set to waste spark mode :)

Unfortunately we could never solve a problem where the ignition would simply 'shut off' after long repeated use, like a long dyno tuning session. After several hours of running the car just wouldn't start again and had no spark when tested. After loading back onto the trailer 30 minutes later, it started fine.

For Weekend Drags at the track & daily driving. You guys think a MSD DIGITAL 6 PLUS IGNITION would be find? I was thinking this route because it has the Rev limiter & The 2 Step built in. The step up is 13B N/A 6port with 48DCOE Webbers Headers full exhaust on Stock 2nd gen ignition step up not 1st gen style. & a hell of a deal on the MSD Digital 6 let me know what you guys think.



Trini

I was going to go with (3) 6TN boxes, in fact I have already purchased (2) of them that I'll now be putting on that auction site.

I came across a deal on a MSD Digitial 6 Plus and decided to change plans. I picked up a Digital 6 Plus for the leading and have a DIS-2 Plus picked out for the trailing. The ignition will be all digital, weigh less, 2 vs. 3 components and draw less amps. Seems to me this was the optimum setup, just not the cheapest but I found some deals.

FWIW, I have a Jacob's Rotary Pro Pak on my car. I added it back when the car was street/autocross and ran the stock ECU. Fuel mileage got a lot better with just the addition of the Jacobs box... got even better when I added the Microtech ECU to the mix...