I've got a TNT kit on my car and running a msd 6al with a window switch and a full throttle switch. if I run the spray my tach will bounce around all over the place and the n2o feels like its turning on and off. the tach will shoot past seven and it will cut the n2o off then it will fall back down and bounce around all over the place. it only does it on spray daily driving it reads right all the time. Thinking about getting rid of all the msd stuff and getting the mallory 685. Any thoughts on what the problem could be I checked all the wires and they seem to be installed correctly.

 

na, you just have it wired wrong. Did you try bypassing the msd and see what happens? Where did you pick up the tach signal? If you can post your schematic, it might be easier for us to diagnose.

 

The tach signal I'm using is the one coming out of the side of the 6al box. I basicaly used the wiring schematics from this section. I said f it today and went and bought the Mallory 685 box so I can make adjustments from in the side car and not have to worry about pills.