View Full Version : Knock knock
02-05-2009, 02:41 PM
I'm getting further on my carb-to-EFI swap on my 1978 FJ-40/GM 350 engine. I am wondering if I should use a knock sensor or not.
My tranny is an SM-465 (manual). I read somewhere that a knock sensor may pick up tranny noises with a manual transmission. Of course, being that my Cruiser is 30+ years old, I have a lot of other noises as well. ;)
Does anyone have any experience with or opinion about this kind of setup? Should I run a knock sensor or not?
02-05-2009, 02:47 PM
Dunno if the GM EFI is any smarter, but the knock sensor on my 22R-E is just plugging a hole in the block and as near as I can tell doesn't do much to affect the EFI system in a meaningful way. But a 22R is not a quiet motor and add in a header and what-not and I think it is easily confused. I can often hear a bit of detonation that the EFI doesn't stop nor does it throw the CEL. Might be mine is dead, I dunno.
02-05-2009, 03:38 PM
Broadly speaking, if you have a hyperactive knock sensor, you will sense a loss of engine performance. You'd have to compare seat-of-the-pants performance before and after sensor installation to tell if this is a problem (or somehow dynamically monitor the timing).
If you have no sensor, you may see more spark knock than you like, which you should be able to hear. If you put it all together and don't hear or sense spark knock and performance is good, I guess I'd try to skip it.
I've heard of some folks that try to slightly isolate the knock sensor (so that's it's not so sensitive) but that would be a trial and error effort.
02-06-2009, 10:44 AM
I can often hear a bit of detonation that the EFI doesn't stop nor does it throw the CEL. Might be mine is dead, I dunno.
If it was, you'd have a CEL. Frankly they are worthless except as a means of illuminating the ol'
02-09-2009, 09:34 PM
Thanks for the feedback. Won't I have to reprogram the ECU if I skip the knock sensor, though?
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