View Full Version : FPSS vs. A/F shut down switch

02-22-2007, 11:55 PM
Getting ready to install my new HSW dry kit and I'm gathering up all the necessary safety equipment.

The dynotune A/F shut down switch seems cool b/c it would kill the system in a rich or lean condition, instead of just a lean one like a fpss. Is my thinking correct?

Anyone have experience with the A/F kill switch?

02-23-2007, 02:19 AM
I know that most folks don't see too much of a danger in a rich condition, nor does it typically foul the plugs from what I have read. I haven't read anything lately about a danger in getting too rich, but maybe some other folks have feedback on that. The kill switch is still a cool idea in the event of a failure causing a lean condition. Seems like it would be most beneficial with a wideband A/F probe. I've got a Harris Dry kit as well, but I think I'll just stick with a FPSS and a tune on a dyno. Getting the A/F cutoff and monitoring A/F with a wideband like it should be would end up costing me alot more. But if cost was no issue I would do it.

02-23-2007, 02:55 PM
good point... already have a fpss too.

what shot are you running and how much timing did you pull? is the timing out at all times or only when the spray is armed?

02-23-2007, 11:06 PM
I haven't installed my kit quite yet, it will have to wait until I get back from Iraq. But I plan on running a 100 shot. I had it dyno tuned a few years ago for the H/C setup, but don't remember what the timing was. I'll have to get it re-tuned before I hit the spray just to be safe. I'm adding 39lb injectors, and a FAST intake as well so I needed to have it tuned again regardless of nitrous. The timing will not correspond to the nitrous directly unless you have your own tuning software to switch between an NA and nitrous tune. But from what I read it's not a big problem, and you just run slightly richer NA until the the nitrous hits. With a good tune everything should run real smooth.