DML FAQ : Electronics : Will an MSD ignition system give me more power? I've heard some people get less power with one.
From Mark Kuzia:
It depends what you are doing. On the street, the MSD makes my truck run smoother and it does feel more responsive below 3000rpm, but not for all out horsepower and drag racing. I verified this with dyno runs (2 with, and 2 without). There has been much debate in the past about the MSD, I am just presenting to you guys what I found. Look at the graph on my site, click on the "TECHNICAL" button and see for yourself what the dyno found out for me (click on the graph to enlarge). I fully expected to make more power with the MSD, I was shocked that the MSD actually killed top-end power, and sucked away torque all across the band. I am just as disappointed as you are, I wasted $129 on a red box that makes my truck slower.
As a another matter, I felt the MSD did work on my '99 V-8 Dak with the OBD-II system. For some odd reason they do not work well with the OBD-I, this is not the first time it was brought up, others have said the same before, I just didn't believe them. It is up to you to make your own decisions, check your facts and decide on your own. My website shows an install for a 1999 Dakota, not for OBD-I systems.
From Sam South:
I had one on my 98 3.9 and it "felt" stronger, but when it was installed on my 95 5.2 it definitely felt like I lost a few ponies. I left it on anyway thinking maybe I was wrong about it, but after I saw with my own eyes the difference it made on Mark's Dak(I went with him that day to the dyno) it's coming off and not going back on.
I'm inclined to believe that the difference in MSD performance on '95s vs. '96+s is because of the OBD system (through '95 it was OBD-I; after that, the Dak uses OBD-II). My '98 had the MSD on from around 10K until I sold it at 45K and bought the '95, it was on both trucks with fresh Mopar cap/rotors and Mopar/MSD wires, and also on the '95 I've used Accel and Mopar cap and rotor. With all these changes the only real difference I felt was with the MSD box itself.
From Jon Steiger:
Bill Tierney has been saying this for years; few people wanted to believe him though. Although the truck may "feel" stronger, he has consistantly documented a .2 second loss (gain in ET) in the 1/4 mile when the MSD is activated. Regarding the OBD-I vs OBD-II theory, his truck is a '93, so there's another data point for an OBD-I truck that doesn't make its best power with the MSD.