George,
You have done the mod and still have the 4th gear prob? Is this what you are saying?
Very strange you have had the same prob in 4th!
I also have my dyno chart with my car in 4th and it's perfect. This is starting to sound too wierd. I wonder if anyone else has experinced this "effect" in 4th?
Please state back on the mod.
Thanks.

 

I am still curious about this supposed mod. I ran a MSD switch before I made my own and had no probs with it on my 97. I checked the tach line coming out of the computer with my oscilliscope and checked out the signal one day doing some shakedown test. I had a flashback to the 5V signal claim. Well,....I found a sweet sweet 13.5 V square wave tach signal coming of the line. Couldn't have drawn it better with Autocad 2000. Now, I haven't got to look at any other LS1 years in C5's or Fbody's, but I would be more then happy to look at anyone car in the Chicago area to prove if all years have the 13.5V signal like mine or not. Any takers?????

 

What was your coolent and oil temps on the dyno? Where you running around 198* like in town conditions or did they run you off a cold motor to show bigger HP #'s. If your up to op temps and you run through the gears up to fourth wont you get a little hot? Or where you in 6th and then did a drop to 3rd and then into 4rth? The speed of the car shouldn't affect the quality of the tach line signal. More info please.

 

Yes, I had MSD rewire my window switch and I also had to cut the 2 wires to put it in 4 cyl. mode. I did this before I ever installed it because that's what MSD said to do. I never tried it without the mod. Probably would have still worked. I'm beginning to think I got ripped $35.

 

Allgonoshow - From a dead stop and going 1st, 2nd and 3rd it hits really hard with a 150 shot and once shifted into 4th it feels like a 10-20 shot. If going 80mph in 4th and just punching it, it will hit hard in 4th. Probably feels like a 100 shot with the 150 jets though.

 

I was at temp on the dyno runs (around 190). When I tried the 4th gear hit, iwas around 4000 RPM, and simply turned on the system, hit the gas and felt it hit. Then about 1-2 seconds later, I felt it drop off. I lifted my foot, thought about what just happened and slowed down to about 3500 RPM. Again I checked everything, bottle pressure at 1050PSI and fuel at 58PSI. I hit the gas to the floor, felt it hit and then drop out again. I then turned off the system and waited for my exit. After I left the hoghway, there was some open road so I tried it again in 2nd and the car went like it was on fire, shifted to 3rd and still screamed. Finally into 4th, felt it pulling hard then I got off it (stupid speed had been obtained). Everything was fine. Later I "ran" an Camaro SS and put 4 lengths on him in a instance when I shifted to 3rd gear and turn on the system. All seemed good. I have not had a chance to do a 4th gear hit again, but do plan on it after I wire the light up, and will have the Autotap on too.
I am just as confused as anyone I have mentioned this to.

Again, I am wondering if anyone has had a problem that the MSD "mod" has fixed and what that problem was. No one has given me a good answer yet. Is MSD just ripping people off for an extra $35.00. I would think if the LS1/LS6 needed this mod, then MSD would put a disclaimer on the package! It really sucks to see a company go "Oh, you have to give us $35.00 more because WE did not tell you it would not work". I wish I had a product like that!!!!!!

 

Hooking up a light to the relay to see if your MSD is messing up would work, BUT you guys said it still feels like it is on, just a real small shot. That makes me want to believe that your PCM is pulling some timing for KR. Don't know cause I wasn't in the car with you guys. An autotap would be very helpful here. Maybe some others can add or subtract anything from my guess.