hustler

iTrader: (6)

I've seen a car go through a wall before, without a neutral safety switch.

tronik

iTrader: (5)

Yet you start it all the time. If bridging the circuit works for you, fine. I'll take the free, and equally simple solution that provides a modicum of protection against a very expensive mistake. But I'm sure you have a lot of things to do in that extra 4:30 of time you saved. specifically:

Joe Perez

iTrader: (8)

Think for a moment about how the clutch works.

The pressure plate is attached to the flywheel, and the friction disc is sandwiched in between them. At rest (foot off the pedal) the spring section of the plate causes the plate to be pressed against the disc, which is them pressed against the flywheel. However since the plate is attached to the flywheel, the net lateral force transmitted to the crank is zero.

To disengage the clutch, the slave cylinder moves the clutch fork, which (through the throwout bearing) pressed forward on the spring section of the pressure plate. The force imparted upon the pressure plate is transmitted through the flywheel to the crank. IOW, when you step on the clutch, you are attempting to push the crankshaft out through the front of the engine. This load is taken up by the thrust bearing surface, which as miatamoxie shows, is set into one of the main bearing caps. Here's a page which discusses and pictures the Miata thrust bearing: 99 Miata thrust bearing failure

I can see both sides of the argument here. Yes, there is no doubt some residual oil left on the bearing from the previous day. OTOH, there's a difference between "some residual oil" and an actual flow of pressurized oil, insofar as maintaining the integrity of a lubricating film and preventing direct metal-to-metal contact.

To me, it seems silly not to bypass the clutch switch as a form of cheap insurance, especially when we are installing pressure plates whose spring force is considerably greater than that of the plate that Mazda designed for the engine originally.

elesjuan

iTrader: (11)

Theres a reason my front bumper is missing paint.

Remote start w/failed e-brake switch FTL.



Thank god my driveway is offset from the garage overhead door.

paul

iTrader: (21)

I guess morons should do it with the safety switch. I warned about that 5+yrs ago on my website when I first did the mod. To this day I have never started my car in gear, any of them, nor has my girlfriend. Guess we're a lil smarter this far north.

elesjuan

iTrader: (11)

I had the installer of my alarm/remote start install a kill switch on the E-Brake.. So if the brake was not set it wouldn't crank. This was a switch which I never tested, and should have. All it took was one cold winter when I was in a hurry and forgot to set the brake.

It chipped the paint on my car, thats the extent of the damage. **** happens.

Saml01

iTrader: (9)

I see what you are saying but I doubt that the sheering force, which is a side to side force by the pressure plate on the crank really makes any affect. Next I dont understand how oil pressure can produce some sort of difference in reducing that sheering force. I dont see how oil pressure is supposed to reduce the potential for the crank to move forward potentially damaging thrust bearings at startup. It just all sounds like snake oil.

Has there ever been a documented failure of thrust bearings due to heavier pressure plates?

olderguy

iTrader: (19)

Anecdote: I never did the clutch bypass. When I opened my motor at around 100K, I specifically looked at the thrust bearing. The bearing had no wear at all and still had the original liquid honed surface except for a small shiney spot that had contacted the crank.

Granted I was not running the heaviest pressure plate I could(OEM for 55K and 1.8 RPS Sport for 45K), but I left the clutch safety in place.

fmowry

iTrader: (8)

So you want to install a switch to override your clutch override. Makes sense. I guarantee you'll either leave the switch off, defeating the purpose, or leave it on, defeating the purpose of the override.

I'd tell you to leave it alone to save five minutes, but I'm not sure you can tell time.

Frank

Thucydides

There's a neutral switch in the transmission which can be wired to act as a bypass switch as well, enabling the motor to be started by either 1) pushing in the clutch, or 2) putting the transmission in neutral. The clutch switch is "closed" when the clutch pedal is depressed; the neutral switch is "closed" when the transmission is in neutral. Wired correctly either switch, or both switches, can be used to complete the starter circuit through the starter interlock switch location. This can solve the problem of starting the motor without using the clutch; and doing so safety.

I haven't figured out where to make the connection between the two circuits yet, but both circuit connectors (X-09 and X-12, per the shop manual) are close by to each other on the passenger side of the engine bay near the fuse block. A few minutes with a test light should show the correct circuits and how they might be wired in parallel to work together.

turbobluemiata

iTrader: (8)

or just bend a piece of aluminum 2 times like FM does and sell it for $15 dollars lol

Savington

iTrader: (31)

That would be ******* cool.

ZX-Tex

iTrader: (15)

Yes indeed it would. I had no idea there was a neutral switch. I'm going to look at the wiring diagrams asap.

So what is the neutral switch used for now? It is not an AND gate with the clutch switch since the starter can be engaged with the clutch in and the car in gear. So it must be for something else.

EDIT: OK it looks like the neutral switch just goes to terminal 1V in the ECU. It is not in the starter circuit. From what I can tell it is not used for the Cruise Control. So what is it for?

Joe Perez

iTrader: (8)

On NAs, the transmission neutral switch is wired in parallel to the upper clutch switch, which feeds the ECU and cruise control system. It is a brown/white wire. In NBs, the neutral switch is separate from the clutch switch, and is a violet wire. In either case, you'd want to install a relay off the line in question, as the load of the starter solenoid would easily fry the switch.

For the NA, the switch is a closure to ground, and has VB applied to it by the ECU. The neutral switch is closed to ground when in neutral, and open when in gear. The clutch switch is likewise closed when the pedal is depressed and open when at rest.

So, for the NA you can place a heavy duty relay such that +12 is applied to the (+) side of the coil, and the (-) side is connected to the neutral/clutch switch wire. In theory, it should not harm the ECU to see +12 on this input, as that's what it's applying as a pullup. In the diagram, I have illustrated a blocking diode, such as a 1N4001. It's probably not necessary, but I'm including it just to be safe.

Here is a marked-up illustration from the '92 FSM, which applies to '90-'95.



For '96-'97 (and probably late '95) the brown/white wire is at 1L on the ECU instead of 1V.


On the NB, I am slightly confused by the documentation, which lists the test conditions for the neutral switch with it removed from the transmission. By comparing the neutral test procedure to the clutch switch test procedure, I believe that the action of these switches is opposite the NA- the switch is closed to ground when the transmission is not in neutral. I can't be sure however, as the two circuits are separate and might therefore be opposite one another in action. For such a scenario, the wiring would be the same, except using the N.C. terminal of the relay, necessitating a double-throw relay, as most automotive relays are single-throw N.O. Can someone with an NB verify for be whether the neutral switch pin of the ECU (1V in '99-'00, 4H in '01-'05) is closed to ground when in neutral or when in gear?

Thucydides

Joe, why isn't the clutch switch fried by the starter solenoid; is it a heavier load capable switch or is there something else going on?

The other thing I'm confused about is that since the switches are already wired in parallel, why doesn't the starter already engage when the transmission is in neutral?

Also, you've "X-ed" out the starter interlock switch, which I believe is another term for the clutch switch. This switch wouldn't be removed, only supplemented by your relay circuit. Yes, no???

Vashthestampede

iTrader: (17)

I've had the FM clip in for years now with no issues. I just wanted to reduce wear and it was like $3 additional to an order I was already placing.

Vash-

Thucydides

No offense, Vash, but we've all heard the arguments against overriding the clutch switch. In summary, there are those arguments which basically champion laziness (I am very susceptible to these), those which say there isn't a problem (which aren't necessarily totally convincing, particularly with cars which are started infrequently and with very heavy clutch springs), and that of safety (which, as I get older and more forgetful, becomes increasingly important).

I've only made a suggestion to eliminate the safety argument and Joe's come up with what is almost certainly a workable solution. So if you're satisfied, you're done. But if you'd like your girlfriend/mother/grandmother/etc. (or you, after a night on the town) to be able to start your car without loading the unpressurized engine thrust bearing, and while significantly reducing the possibility of driving it through the garage door, have a closer look at Joe's wiring diagram.

Vashthestampede

iTrader: (17)

lol.....blah blah blah.

Vash-

Thucydides

Funny thing, Vash, is that's exactly what I thought when I read your response, having read similar posts about how brilliant those folks who can bend a paper clip are a hundred times before. The only difference is that being the nice guy I am I took the high road.

By the way, I see you're in Danbury. My brothers a police officer there and he, like a lot of other of that sort, think Miata's are ***** cars. It would be great if you could take him for a ride and scare the **** out of him for me. I'd owe you big time for that!

CryoSlash

on startup there is no oil being pushed around when cold and having a heavy pp will kill the thrust bearings. This is a good cheap mod that will insure live to your car.