I noticed when taking a look in another 3rd Gen's engine bay (John's) that the connector shown below (in my engine bay) plugs into, well, a plug...The said plug does not seem to exist in my engine bay...Anyone know what purpose it serves???

This is where it mounts, but I don't have anything to plug it into:

 

looks like the drop resistor - not 100% sure

 

Zat iz zee drop rezzizztor pluuuggg..

 

yes it is the
SHIFT_Tranny mod

 

And what's it do?

 

I noticed that you have a 5 speed, so it won't matter to you, but if you wish to learn more, may i refer you to the thread below:

http://forums.maxima.org/showthread.php?t=539603

BTW, its the drop resistor connector, which is mostly "useful" for automatics.

 

modulates the line pressure for the transmission so you use a lower pressure when shifting at lower throttle/rpms. Otherwise, you are basically doing a clutch-drop on every shift, which eventually (over the course of a few days) destroys your transmission. Manuals, of course, do not have these. Your left foot is your drop resistor.

 

Ahh...I must have gotten rid of it when I did the swap...duh

 

The actual drop resistor is under the air box though, thats just the connector for it, right...?

 

yup. i can see mine because i have a popcharger but normally it would be hidden by the stock airbox.

 

That connector is the reason for you having a 5 speed swapped into your car

 

Hmm,perhaps...what's your excuse for not having one?

 

I havent unplugged the connector yet and well as you can see by my other thread, I got other **** to take care of first then I can proceed with modding I still want a UDP since my current belts are reaching the end of their lifespan..they got 41k miles on em

 

for me, money. as soon as i'm more well off, i'll unplug that thing, let the tranny grenade and then nobody will hassle me for needing a new tranny. they will if i 'want' a different one, but not if i 'need' a new one.

toss in a 5speed, learn the clutch, and be on my merry way.

 

I'd laugh if they just said "meh, you can take public transportation for now"

 

I don't doubt it, actually. that or they'd just tell me to get a marshmallow. I mean, a camry. Seeing as how my brother's 93LE 2.2L leaks oil like a mother, and has cost him the entire book value of the car when he bought it just to repair it, so he's bought it twice just to keep it on the road. And then there's my mom's 99LE 2.2L which has piston slap out the ***, and also, oil management issues just like my brother's.

At that point, they'll just have to let me be. My car, my responsibility to fix it, however I see fit. They're to old to appreciate a third pedal.

 

I dont care for them but they're very reliable cars. My mom just sold her 91 2.0 with 276,000 for 500 bucks, STOLEN, flipped over, but the damn thing still ran. Like **** but it still ran and AC worked.

 

i got a spare 5-speed tranny

 

keep me in the back of your mind.. i may call you up someday

 

will do

 

oh, VG or VE tranny? OH and i'll be able to remove teh drop resistor after the swap for (dun dun DUN) weight reduction

 

VG. its pretty rare to find a VE 5-speed tranny down here. i only came across 1 and that was about 3 years ago. didn't want to get it cuz the guy wanted $300 for it when i paid $100 for my VG 5-speed.

 

np. less work with hubs/axles. erm... anything else i guess we oughta PM so it's not a chatterbox in here.

but i am curious
how the heck does a drop resistor work anyways? with just 2 wires.. how does that work? I would think that a one-in one-out resistor would be a fixed resistor but a drop resistor varies line pressure gradually doesn't it? just kinda been on my mind since this thread popped up

 

I'm surprised the tranny doesn't go into fail safe mode when you disconnect the drop resistor.

 

Item in question btw:

 

If you look in the FSM on page AT-41 you well see what the Line pressure system look like with the Dropping resistor

 

The drop resistor is indeed a simple animal - it has basically 2 states wrt the TCU - either the TCU outputs a fixed voltage signal (from terminal 2) to one of the resistor's legs and a resulting constant current flowing out of the resistor's other leg goes to the line pressure solenoid or

there is no voltage signal from the TCU and no current flows through the resistor.

The line pressure valve is closed (max pressure due to spring action closing the valve) when no voltage is applied to its solenoid. The solenoid acts on that valve by applying an opening force to the closing spring proportional to the amount of current flowing through the solenoid coils ..................... more current implies bigger opening.

The Nissan guys have determined from their engineering specs that a certain opening on that valve results in a desirable line pressure giving a comfortable shift characteristic under certain conditions while limiting the wear/stress on box components as far as possible .................... now that "opening" of the line pressure regulating valve is ensured by running just enough current through the solenoid coils (and thus the resistor) ...................... if you start farting around with the resistor you are looking for trouble no doubt because we do not have exact detail design knowledge of the operating conditions of the valve body and forces/timing required to control things internally via the valve body.

Note that the resistor is also bypassed to open the line pressure regulating valve completely under certain operating conditions from a separate output on the TCU (pin 1) directly connected to the valve' solenoid.

 

well if a drop resistor just adds resistance into the circuit then why can't the TCU just put out the correct voltage to begin with, without running it through a resistor?

 

Theoretically it can if it was designed to do that, but in practice you will find that there are lots more electronic theory and issues involved. Most important of which would be the design and demonstrable reliable operation (for years) of a "current source" (ISO a simple switching of a fixed voltage through a resistor) .................... and the cost of it.

You will just have to accept the way its designed on the Max as there is nothing one can realistically do about it.

 

basically as John Lennon said "let it be"

 

What they're trying to achieve is a reduced voltage to the solenoid. The simplest method is using the resistor as it will create the necessary voltage drop from 12-14V at the solenoid's current draw.

If they were to do it directly from the TCU, that would mean one of two methods:

1) Install the resistor internally (not wise as the resistor will be the same size and will produce the same amount of heat - in the engine bay it gets to cool off a little at least and keeps that heat away from any sensitive semiconductors in the TCU)

2) Facilitate separate linear or PWM (Pulse Width Modulation) regulation to control the voltage and in the case of PWM, have it in a closed loop system so that the voltage is closely monitored and adjusted to ensure the correct output voltage. This should be done separate from the microcontroller given that the line pressure solenoid only needs to be managed during the shift and I would estimate that is at a period of less than 200ms. Managing it directly from the microcontroller as it is required could prove to be technically unfeasible as the closed loop monitoring required would not guarantee rapid and reliable regulation of that voltage in such a short space of time. Longer running devices such as electric pumps (oil, fuel and water) are better suited to such control whereas a solenoid with such a short operating time would not work this way. However, having the voltage regulated to a separate rail (either by way of a linear regulator or a PWM regulator) would work. Linear may once again not be feasible depending on the current the solenoid would draw, which I'd imagine would be a reasonable amount given the force it would need to exert at those pressures. PWM would be the better way to go as it allows for higher power to flow without straining the components as much as linear would. This separate rail could then be switched by the TCU accordingly.

However, I would suspect that the developers of the TCU took the easy way out and just implemented a resistor for the task as it reduces the parts count, may possibly increase the reliability factor because of its simplicity and overall saves on manufacturing cost - the latter being the more important factor. These days, with the ever growing complexity of engine management systems (and guys like MoTeC raising the bar in the aftermarket world, as usual!), it wouldn't surprise me if the engineers have succumbed to the more complex methods in an effort to "clean up" the engine bay but to also take advantage of any spare inputs and outputs on their microcontrollers of choice for their automotive management systems. After all, if they're there, why not use them?

So just deal with the fact that at the time, the 3rd gen's solution was the best one as a compromise between cost and reliability - after all, it hasn't failed anyone (other than the typical mechanical issues of the auto transmission).