Speed & Position Sensors in Manual Trans KA

[tloof]

I've done a search concerning the 4th & 5th position sensors and the speed sensor on the 240SX manual transmission, and there seems to be no definite concensus as to whether they can be eliminated or not & the ECU still function correctly and still disable the speed limit function. Several members said all you have to do is disconnect the position switches and the speed limit is disabled, but others said that it wouldn't work unless the speed input signal to the ECU was also disconnected.

My question is whether the position switches are actually for the purpose of limiting how fast you can go in those gears, or if it is really used to modify the fuel curve in cruise conditions when in those gears? Since it appears that the speed limit function within the ECU is NOT disabled when the position switches are disconnected, I suspect that they are really used by the ECU to modify the fuel curve in cruise conditions when in those gears to increase fuel efficiency, but I am not positive about that? Does any one on this website know for sure?

In my case I originally swapped a KA24E in my Nissan 720 pickup in which I used the original 720's FS5W71B transmission that didn't have the position switches, but that I did add into my transmission by drilling & tapping the provided bosses already on the case for those sensors (4th & 5th position). I am now upgrading to the KA24DE with a newer generation & much stronger FS5W71C transmission from out of an '87 V6 200SX (it has the exact same guts as the KADE 240SX's have but with the shorter tailshaft housing that matches the same length as the original 720 transmission had...but you do have to swap all the guts & tailshaft housing onto the original truck version main case). I am now trying to decide if I really need to drill & tap the case & tailshaft housing to install those position switches, or if that is a complete waste of time. Also, while the speed limit function is really not an issue for me (basically a 720 truck shouldn't really ever be driven above 110 mph due to stability problems), is the speed signal into the ECU even necessary, or is it used to adjust things like shutting off fuel flow when deaccelerating with the TB in a closed position in order to increase the fuel efficiency of the engine? Anyone have the answers concerning this issue?

[Bigvinnie]

My understanding from what Devious showed me a while back was that if those sensors were disconnected that it does infact increase fuel richness.Beyond working as the governors for rev in 4th and 5th, they also work to conserve fuel.The only altenative that I believe could be done is retuning the ecu, or getting a bikirom and doing it yourself (but this would mean that you would need to get a DE ecu from 91-93 OBD1) . I don't believe there is any way to just switch off the sensors, I don't find bypassing the lines to be very effective.