Jump to content
HybridZ
zbigtim

'95 Maxima Gauge Retrofit

Recommended Posts

You could use epoxy to put the gear on, just rough up the gear hole and shaft surfaces, assuming you can get it on concentric.

 

If your circuit works, I would not fiddle with the gears, that's a fairly slick setup. FYI.. GM ECU's take the VSS signal, and have programed into them the gear ratio and tire size to calculate the VSS output which goes to the Speedo, Cruise control, and body control modules. You are achieving the same thing.

 

I'll get pics of the VSS from the 87 300zx. The VSS has a gear for 3.70's, and I will test fit it for my spare 280zx 5spd.

Share this post


Link to post
Share on other sites

I got the chance to pull the 300zx VSS.

 

DSCN3369.JPG

 

The lineup from left to right.

1. 240z w/manual 3.364

2. 240z w/auto 3.54

3. Early 5spd 3.54

4. I am assuming 280zx 2+2 or GL model. 3.70

5. 87 300zx NA 3.70

DSCN3370.JPG

 

I disassembled the 300zx VSS and I was able to reassemble it with the 240z gear, based on that, I assume any of the gears will work with it. The VSS will also screw onto any of the the Cog bodies. If one were to have the right adapter, it would be possible to run this sensor behind the dash. Regardless, this sensor is nice, as it can be used with any L series transmission.

 

I think it's exactly what you need, it's certainly the part I am going to use when I do my gauges. One question: does the Maxima speedo have blinker indicators on the speedo face? I did not see them in the pics.

 

Thanks for the writeup, hope this sensor solves the problem you are facing.

 

PS... I need a red and a white cog(more interested in the white), you up for a trade? I have 1 black and 1 blue to trade. No big deal, I can source one from the jy here if you don't.

Edited by rejracer

Share this post


Link to post
Share on other sites

That would be great if we could work out a trade! That 300ZX sensor is exactly what I need. That would solve all the problems with getting a SX VSS to fit. Unfortunately, I do not have a white sensor. I have a red and yellow. I would be willing to pay cash (paypal). My local pick-n-pull does not have any 300ZXs, mostly 90's Maximas, Altimas, and a few 240SX.

 

As far as the blinkers are concerned, I plan on installing green LEDs behind the "0" and "8" on the tach, and blue and red LEDs for the High Beam and Brake indicators somewhere in the speedo. I wasn't too worried about this until, I figured out how to properly scale the speedo.

 

Good work as always rejracer.

Edited by zbigtim

Share this post


Link to post
Share on other sites

Been talking with Rejracer about the mounting of the gauges in the old "cups", so I thought I would share some pictures and some of my findings. I would also love to hear some input and/or ideas of a few things.

 

First off, there was some concern that the electronics of the speedometer will not fit inside the old cup. If you compare the cups side by side, the original speedometer cup is shallower than the tachometer. On the Maxima gauges the speedometer guts require a deeper housing, so I swapped the cups, mounting the Maxima Tach in the original speedometer cup and vise versa. The mounting tabs and holes are exactly the same between the cups, so I will still be able to mount the gauges in there original position (Speedometer on the left, and Tach on the right). I did have to cut a slot in the top of the speedometer cup to allow the circuit board to protrude past the housing (see pics). I don't think this will interfere with the dash, and plan on using some duct tape to keep dust and ambient light out of the housing.

 

The issue I'm working with now is how to secure the instruments in the cups with the proper depth to keep the gauge faces flush with the bezels. I want to keep the faces flush with the bezel because the faces are backlit, while the originals had a gap between the bezel and face to allow the instrument light "around" the face.

 

I plan on using an additional circuit in between the VSS and Speedometer to do some scaling because I don't want to have to try to find a VSS cog with the right amount of teeth. Also this will allow some adjustment for example if I decide to change tire sizes, or rear end ratios. But, I think it would absolutely be possible to wire the VSS directly to the speedometer and find the correct cog.

 

PICTURES:

 

Tachomter. Mock up mounting. As you can see from the front picture, I need to move the face forward towards the edge of the cup (where the bezel meets).

 

TachRear.jpgTachSide.jpg

 

 

Speedometer. As you can see on the top of the cup, where I had to cut a slot for the circuit board.

 

SpeedoSide.jpg

SpeedoRear1.jpg

SpeedoCupTop1.jpg

 

Speedometer. Also, need some mounting ideas here. I'm thinking of cutting a piece of plexi-glass and securing it inside the cup somehow.

 

SpeedoRear1.jpg

SpeedoRear.jpg

 

 

As mentioned above, I could use some ideas on securing the gauges to the cups.

 

 

 

-Tim

Edited by zbigtim

Share this post


Link to post
Share on other sites

As mentioned in the PM, Nylon standoffs would do the trick. If you are concerned about the strength of the standoffs, maybe try making a rear plate out of Plexiglass that centers the rear of the gauge to the housing. If you wanted to be really fancy, Secure the electrical connections with brass standoffs, then on the brass standoffs mount the plexiglass centering ring, then behind the plexiglass plate use Nylon standoffs connected to the brass standoffs, or use brass standoffs connected to the plexiglass plate using different fasteners (not connected to the other brass standoffs.

In Ascii art it would look like the following:

 

 

1 2 3

|----------

| |

|--|--|

| | |

|--|--|

| | |

|--|--|

| |

|----------

 

1 is the rear housing

2 is the plexiglass plate

3 is the back side of the gauge.

 

Would this solve the problem at hand?

 

I think the trick becomes finding standoffs with the right threads for compatibility with the gauges

 

Edit: The ascii art looks well in the editor window, but not using the web browser. copy and paste into a an editor that uses a monospace font.

Edited by rejracer

Share this post


Link to post
Share on other sites

Yes, I've been thinking about using a plexiglass plate to mount the gauge to, using the original screws. Then mount the plate to the back of the cup with spacer blocks. The blocks could either be epoxied to the cup or screwed. The plexigalss would give me the ability to mount and wire the gauge back lights in the proper locations to illuminate the clear plastic face backing.

Share this post


Link to post
Share on other sites

So how did this turn out? I want to use the same speedometer behind another gauge face but I need a way to calibrate the sensor. Did you ever get the other circuit made? If so I'd LOVE to see the circuit.

 

And why is the second circuit (LM2907) needed? Cannot the VSS be read as a dc signal as well as a pulse. I recall that Ford tests the VSS with a DC meter. But I could be wrong. More recent reading indicates it is AC.

 

Check out this link... http://v8nissans.com/forums/content.php?113-S14-speedometer-correction-with-z32-tranny-the-free-way It implies that a variable resistor across the indicated resister pads (resistor removed) could be used to tune the speedo to any drivetrain. Once the resistance is determined a trim resistor or fixed resistor could be soldered in-place.

 

Inquiring minds want know ...

Nick

Edited by DMCNick

Share this post


Link to post
Share on other sites

Well, I'm digging this thread back from the dead. I decided I was going to try and finish this up. I have finished the mounting of the speedo in the old gauge cup, wired the old harness to the speedo (plus a new wire from the VSS), and installed the speedo in the dash. I installed the black cog and 300ZX VSS that I bought from rejracer. On the road test, judging from the seat of my pants, the speed indication is about double what it should be. Although it was really cool to watch the speed jump 45 mph from gear to gear and eventually pegging the speedo at about 150mph, I need to adjust the speed signal. If I have time tomorrow, I will go for another drive with the garmin to see what the error really is. I'm not sure what the largest cog is for the speed sensor is, but I doubt that I can double the size of the black one.

 

Side.jpg

 

Side view showing the mounting plate made out of a 4" blank round cover for electrical boxes. The stand-offs are make of plastic wire nuts, cut to the proper heights. I then glued the new mounting plate to the old gauge cup with 5-minute epoxy.

 

 

 

inside.jpg

 

This is the new mounting plate glued in place.

 

 

 

Day.jpg

 

Day time view.

 

 

 

Night.jpg

 

Night time view.

 

 

I am determined to get this project finished. I promise I won't let this drag out for another 2-years!

 

-Tim

Share this post


Link to post
Share on other sites

Looking nice...

 

Now, I'm curious about this same type of setup, though I'll be installing the 08 350Z Speedo in my car. It gets it s timing off a different location. I was just going to print up the mounting cup for the speedo on my RepRap.

 

But reason I was writing was that if you're approximately double the pulses from the 300zx VSS, then it sounds like your VSS isn't connected right, or that it's not made the way you expected. A couple ways to address it, one is to measure the outputs on your maxima VSS, and see that the pulses per revolution is. If it's the same then it's a wiring deal, if not then perhaps you can make a frequency divider circuit to cut the pulses in half.

Share this post


Link to post
Share on other sites

Thanks Pharaohabq. That would be nice to have access to a rep rap. That would be so much better than trying to cob together a combination of old, new and extraneous parts. I am working on a new timing circuit to "re-scale" the VSS signal from the sensor; should be completed by the end of the week. I do believe the sensor is wired correctly, the wiring is very simple (+12, Ground, and VSS Signal). The VSS signal is referenced to ground and is an ac sine. The difference I guess is the RPMs required to move the mechanical speedometer, and the frequency range required by the electronic ones.

Share this post


Link to post
Share on other sites

Tim and I traded speedo cogs for a cluster, clusters were half the cost of what they were out here, and our yards had quite a few manual transmission cars to pull COG's from. I got the black faced gauges. Tim and I did very similar things on the mounting, but I opted to use the backing plate from the maxima cluster, I cut it out with a dremel tool and screwed it to the 240z tachometer cup.

 

I may end up pulling a 300zx cluster to see if I can do this without a divider circuit.

Share this post


Link to post
Share on other sites

After a lot of discussion, mainly through this thread, I have come to the conclusion that the only way to get the maxima speedometer to work properly is by constructing an add-on frequency converter. In theory, this is very similar to the SGI-5 model made by dakota digital.

 

-The speedometer cannot be adjusted internally. The adjustment solder pads will adjust the pointer but not the odometer. I believe this is so different faces can be used on the same electronics. (K/H vs. M/H, or different max speed).

 

-The 300zx VSS worked very nice mechanically, because is will mount on the existing mechanical speed sensor. I knew there was not a snow balls chance in hell that the speed signal would match the speedometer, but I was hoping it would be close enough that I could change to one of the six different sensors available and make it work that way. It turns out that the speed signal was off by by a factor of .435. So when I was driving at 50mph according to my gps, the speedometer was displaying 115mph! This is way too much to overcome by changing sensors.

 

How the circuit works: The VSS from the 300zx (or any Nissan that I have seen so far) outputs an A.C. sine wave with the frequency proportional to the speed of the vehicle. The LM2907 is specifically designed for this type of sensor. The LM2907 outputs a voltage (DC) proportional to the frequency being produced by the VSS. I have coupled this output to the AD654 via the 10K pot. The pot. works as a voltage divider, so that I can change the full scale voltage going to the AD654. The AD654 does just the opposite of the LM2907, it take the voltage in and converts this to a DC square wave who's frequency is proportional to the voltage on its input. Since the Nissan speedometer will not sense the DC square wave (the input must be A.C.), I used the capacitor/resistor network to AC couple the output to the speedometer. This scheme does not produce a true sine wave but it really does not matter. What matters is that the voltage crosses zero.

 

During my speed trials in the car using my gps unit and fluke multimeter, I determined that the Maxima speedometer deflects full scale (140 MPH) at 309Hz. I also found that the 300ZX VSS would output 709Hz at 140MPH (Mathmatical projection of course). So using a sine wave generator I inputed a frequency of 709Hz and adjusted the 10K pot until I measured 309Hz out. I also checked the linearity by adjusting the input in 100Hz steps and measuring the output. It seems to be right on. Of course once I install the circuit in the Z, I will fine tune the calibration to the gps.

Share this post


Link to post
Share on other sites

Well, I finally got all the stuff together to make a circuit board. I decided to chemical etch the board instead of photo-etch. The photo-etch process seemed to be more complicated, but I understand is better suited if I wanted to mass produce the board. The board is small enough, I'm thinking of mounting it to the back of the speedometer.

 

MaskedCopper.jpg

I was able to mask the copper layer by transferring a laser printed pattern on glossy photo paper with a hot clothes iron. This picture shows the board after the transfer.

 

EtchedCopper.jpg

After an acid bath, the copper that was left exposed is etched away.

 

BottomComplete.jpg

After cleaning the mask and soldering the components on the board. I had a little bit of trouble on the soldering because the tip of my soldering iron was too blunt, and the solder could have been thinner. Any extra solder or mis-placement of the iron allowed the ground plane to soak up excess solder. But the solder still did not bridge any of the traces. Whew!

 

TopComplete-1.jpg

This is the top view after the board was completed and tested. Ready for installing in the car and final calibration done with a road test and my GPS.

Share this post


Link to post
Share on other sites

Most people are scared of building electronics like this, so this will probably not be done very much.

 

Building my own etched circuit boards is something I need to get familiar with. Usually I just use the point to point generic boards.

 

 

I would agree. I've tinkered with electronics, seems like my whole life, and have always used the proto boards. This was my first attempt at etching my own board, and found it relatively easy. There is tons of info on the web on this topic.

 

I'm pressing on with the mod. I think all the difficult parts have been solved. The next step will be the tach, and I think that is going to be much more straight forward.

 

I think may get more enjoyment out of the problem solving than the actual finished product.

 

-Tim

Share this post


Link to post
Share on other sites

Doing a little research on this, it seems that the Maxima and the 240SX BOTH have a year split at 1994. It is fairly common to have an S13 SR20 swap go into an S14 USDM chassis.

 

When the speed sensor is adapted over but the speedometer is not...the speedo reads twice as fast. Just like the S13 speed sensor and the 95+ maxima speedometer...I'd wager that the speed sensor for an S14 would work just fine with the 95+ maxima speedo. I have an S13 speedo sensor, but I'll see if I can aquire an S14 sensor and test it out. If it works, then this could be a very easy way to get both a stronger transmission, plus an accurate speedometer!

Share this post


Link to post
Share on other sites

Bringing this back from the dead. I have gone through this thread a large number of times, and am working through figuring out the schematic and the PCB layout, which do not match each other. (Close, but there are parts on the board that are not in any of the schematics, and parts in the schematics that are not on the board)

 

I do have the speedo working on the bench, though. The tach is quite straightforward, the Megasquirt Tacho Output circuit works like a charm.

 

The speedometer doesn't care if it's a sine wave, or a square wave, as long as it's a bipolar signal. It only need about a 3V output to work, but that 3 volts MUST cross zero volts, so it's more like a minimum of +/- 1.5V. I solved this by referencing ground in an odd manner and that solved the issues with the speedo acting funny at low speeds.

 

EDIT:

 

I've figured out the "floats at low speeds problem, too...The differentiator capacitor was too small, and so the speedo would cut out at high speeds and would float at low speeds/nearly stopped/stopped. Upping it from 0.1uf to 0.22uf fixed both problems nicely.

Edited by Xnke

Share this post


Link to post
Share on other sites

Here's some shots of how I did the gauge cups for this conversion. After making those few tweaks to the speedo drive circuit, this was the next challenge.

Getting started. Heat up some 4.5" PVC pipe and shove a quart paint can inside it. Dunk in water, and beat the paint can back out of it.

IMAG0504_zps2c693b0f.jpg

Turn it down to fit in the bezel:

IMAG0505_zps83c2a26c.jpg

Fits!

IMAG0506_zps9511d0df.jpg

I hole-sawed the back of the Maxima cluster out around the speedo and tach mounting points, leaving me with a circle-ish chunk with the mounting points intact. This leaves me with a nice backing plate to use. The backing plate was then mounted to the gauge, and the whole assembly fitted into the bezel. Then the backing plate was then taped up with aluminum foil tape, used for ductwork, because it's stiff enough to hold it in place during handling, like so:

IMAG0507_zpseef6c28e.jpg

Now, the gauge is removed from the backing plate, and we have a nice little channel to fill full of JB weld to permanently secure the backing plate.

IMAG0508_zps9dfd67c1.jpg

Like this:

IMAG0509_zpse163265c.jpg

After letting it harden up for a few hours, this is the result:

IMAG0501_zps134be3c7.jpg

The bezel fits perfectly over the gauge, but the bezel needs to be sanded and painted, since the little lip inside had to be filed out to allow the shine-through type backlit face to fit correctly...the original gauges are opaque and the light wraps around a gap around the edge of the face.

Still working on getting the gauges lit correctly.

Share this post


Link to post
Share on other sites

Nice work Xnke!  Wish I had access to a lathe and the skills to use it.

 

Hey, You say you had no trouble getting the tach to work with the MS Tach Out.  Iv'e got my tach mocked up on the bench, but cannot get the tach to span higher than about 3750rpm without the pointer getting erratic.  I'm just using a square wave generator right now, found the scale to be about 1000 rpm for every 50Hz, using a 50% duty cycle.  I wonder if I just have a bad tach.

 

Using the circuit in the MS Extra Hardware Manual

 

http://www.msextra.com/doc/ms1extra/MS_Extra_Hardware_Manual.htm#tachoout

 

-Tim

Edited by zbigtim

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

×