Speedo and Tach Cutting Out

[mr2nv]

I have a '93 with a beams swap...used the full harness. Using an MSD tach adapter with 5sfe gauge cluster for tach. The first time this happened I was cruising on the highway at around 100-110 mph and I believe the speedo cut out. After turning the car off and back on, speedo worked fine. Then this past week I was at the track and at least twice the tach cut out with it working fine after turning the car off and back on. Can't remember when it happened at the track but probably in high rpms if that makes a difference. Anyone have any ideas why this is happening?

[Servin]

When you were crusing at 110 you probably hit speed cut. Also maybe loose wiring on the tach adpater?

[mr2nv]

Well, what is speed cut? 110 seems a bit low. And what is supposed to happen when it hits speed cut? Would loose wiring account for the fact that if I shut off the car and re-start it, the tach works fine? I've hit many bumps and driven many miles but the tach never cut off until this track day.

[94MR2]

In japan they put speed limiters on the cars to keep them from being able to go a certain speed. The ecu cuts the engine off of either fuel or spark I cant remember.

[Servin]

Originally Posted by mr2nv

Well, what is speed cut? 110 seems a bit low. And what is supposed to happen when it hits speed cut? Would loose wiring account for the fact that if I shut off the car and re-start it, the tach works fine? I've hit many bumps and driven many miles but the tach never cut off until this track day.

I cant say for the BEAMS as my isnt in yet but I know it can be a terrible feeling were the car jerks and the speed drops. In other cases it simply hits a wall were the car will not rev higher and the speeds will gradually lower.

Doesnt sound like it. If it were loose it woul start to become a intermittent problem i.e everytime you hit a bump it would stop working. Are you using the electrical tach or still using the mechanical tach?

[mr2nv]

I highly doubt it was speed cut in the sense that the car did not slow down or go into any kind of limp mode.

I'm using the electrical gauges that came with my 93 MR2.

I'll probably have to bring it in to my mechanic...He installed the tach adapter and has an MR2 so maybe he'll have a clue.

[puretone]

faulty speedsensor?
freaky/bad/loosening connection on the BEAMS---->5SFE gauges cluster wiring?
is your tach adapter tied down properly?

my old 5SFE tach died over a period of time, showing less and less RPMS over time, to the point where it said it was doing 1200 RPM @ rev limiter....so I figured it was time to replace it. Turned out it was burned out resistor on the tach.

for your speedo & tach to do similar sort of thing could mean that a ground wire to the gauges could be bunked...or getting extra volts from another lose wire some place.

the Gentlemen's agreement suggests 180Km/h to be the speed cut, which is about 111.85 mph so give or take a little for the 'correction' of the speedsensor and you would have been hitting the speed cut off programming on the ECU.
get a FCD, go past prissy 180

[mr2nv]

Thanks for the advice...now that you mention it, last week at the track, on the straight the car didn't seem to want to accelerate past about 110 in 4th gear. Would the speed cut just make the car hit the wall at 110 and stay there cause that's how it felt. You don't mean FCD fuel cut defender do you? Can you recommend what device to get for speed cut defender?

[puretone]

Originally Posted by mr2nv

Thanks for the advice...now that you mention it, last week at the track, on the straight the car didn't seem to want to accelerate past about 110 in 4th gear. Would the speed cut just make the car hit the wall at 110 and stay there cause that's how it felt. You don't mean FCD fuel cut defender do you? Can you recommend what device to get for speed cut defender?

I noticed my Celica goes passed the 180Km/h mark on the BEAMS gauges cluster I wired in myself. I will attribute that to the 'correction' it does. I do run out of enough straight/safe road to see if it does anything after that speed.
I assume it will do the standard Toyota brick-wall/slow bog down all other Toyota's seem to do at similar speeds.

FCD = FCD yes, DIY.

it's fun to do as well!

Diy Fcd - Club Aristo - The Toyota Aristo Owners Club
Soarer Central: Soarer Fuel cut
DIY FCD Project

& all the geeky talk you can have at a radioshack!

[94MR2]

Umm isnt the fcd for turbo engines that fuel cut when they hit a preset boost limit? I think you guys are confusing the fuel cut defencer with the speed cut defencer

[mr2nv]

I know that the FCD is for fuel cut for turbos but it might use the same type of DIY wiring but the FCD targets voltages I think and the speed cut targets the frequency. I'm looking to maybe get an apex-i rsm.

[94MR2]

or the hks sld