zbigtim Posted June 13, 2010 Share Posted June 13, 2010 I've been looking for an inexpensive way to install modern, electronic Speedometer and Tachometer. Right now I have the stock gauges with the speedhut EL Glow Overlays, which looks awesome (in my opinion) but the speedo reads 10 mph low and the tach does not work sometimes under 1200 rpm, and is off by about 200 rpm according to megasquirt. So, browsing through the local pick 'n' pull I decided to give the '95 Maxima Gauges a try. $20 got me the entire gauge cluster. I had to trim the corners of the gauges to fit in the original "cups". A dremel tool made quick work of this. I'm not quite done with the assembly yet, but well on my way. After researching with the Maxima Factory Service Manual, I believe that the tachometer will work with no problem on the megasquirt Tach Out. But, the speedometer scaling is my next biggest hurdle. I have connected a speed sensor from a 5-speed 240SX (which fits the stock 4 and 5 speed transmissions) and tested the speedometer with a power supply and a drill. It works fine. Back to the scaling. Does anybody know if the frequency to speed ratio can be changed with the "adj" points on the speedometer circuit board? Please look at the next pic in the red circle. Or will I need some kind of signal condition circuit in between the speed sensor and speedometer (frequency to frequency conversion)? -Tim 1 Quote Link to comment Share on other sites More sharing options...
getoffmyinternet Posted June 13, 2010 Share Posted June 13, 2010 Does the manual say anything about what those adjustment numbers do, can you just experiment jumping different ones? I'm not familiar with those, is it like a small percentage multiplier for different size tires etc? Never heard of being able to adjust a stock speedo like that. If only you could figure out how the circuit actually converts the frequency into mechanical movement of the needle and set it off by a little bit with a resistor or something simple like that. I was trying to convert a speedo once and couldn't for the life of me find signal multipliers that weren't in whole numbers, and your gauge apparently isn't off by a factor of a whole number. I have seen speedo adapters that are supposed to be universal though and can be programmed to make any gauge work just like you would calibrate an autometer, but the price of those probably defeats the purpose of using the maxima gauges in the first place... If you're lucky you can find a cog for the speed sensor that gets it close enough but that's a long shot. Have you given up on the stock gauges? It sounds like your new speedo is in the same boat as your old one. If the tach doesn't read real low, it's probably not high enough input voltage. It couldn't just be off by a certain amount though, there has to be a ratio that it is off, which should tell you it's hooked up to the wrong signal source. Just thinking out loud. Quote Link to comment Share on other sites More sharing options...
Alonso* Posted June 13, 2010 Share Posted June 13, 2010 Yes it is adjustable. S14 240sx speedometer has the same thing. Freshalloy.com and zilvia.net come to mind, I know it has been posted there before. Search for speedometer calibration Quote Link to comment Share on other sites More sharing options...
zbigtim Posted June 13, 2010 Author Share Posted June 13, 2010 Have you given up on the stock gauges? It sounds like your new speedo is in the same boat as your old one. I have no idea what the maxima gauge is going to read. I have not had it in the car yet. I can only assume it will be off because of the mismatch of parts. The universal converter is about $80 from Dakota Digital, which yes, defeats the purpose of using the junkyard gauges. I am going to experiment with the "adj" solder pads. I assume it is a binary coded multiplier. Im going to set my fluke meter on the sensor and read the freq. and compare to the speed reading. Then change the adj setting and repeat, till I figure out the math. Thank you for the replys! -Tim Quote Link to comment Share on other sites More sharing options...
zbigtim Posted June 14, 2010 Author Share Posted June 14, 2010 Thanks Alonso. I think I found what you were talking about. (Thanks to Knate's post off of zilvia.net forum, here is the following value of each jumper on the binary divider) Quote: Originally Posted by knate Here's how it works. It uses the adjustment points as a binary divider. The more switches on, the lower the speedometer will go. 9 is the most significan bit, and each switch below that will have half the effect on your needle. Here's a list of how they affect the needle. All these numbers are based on my eye reading the needle and some calculations, so they are not 100% perfect. ADJ 9: -49.4% ADJ 8: -24.7% ADJ 7: -12.4% ADJ 6: -6.2% ADJ 5: -3.1% ADJ 4: -1.5% ADJ 3: -0.8% ADJ 2: -0.4% ADJ 1: -0.2% ADJ 0: -0.1% I have confirmed some of this. The maxima speedo had 4,5,&7 bits "on". I ran the speedo again with the drill, reading 49 mph. When I removed the solder on bit #7 the speed indication increased to 56mph, which is approx a 12.5% increase. According to the post from JBrant on 240SXFORUMS this adjustment only works on the speed indication and not the odometer. I will try some time trials hopefully tomorrow to confirm this. Hopefully this is not the case. http://www.240sxforums.com/forums/do-yourself-section/130489-240sx-speedometer-error-s14-s13-speed-sensor-reads-double.html -Tim Quote Link to comment Share on other sites More sharing options...
getoffmyinternet Posted June 14, 2010 Share Posted June 14, 2010 Yeah that doesn't make any sense. Why would they have the two circuits independent of one another such that the odometer can only read correctly in the factory position? I would think that there's one circuit that counts the frequency and sends it both to the odometer to count the miles and then to the needle to average it out. The needle is basically the odometer with a clock added on that it divides by, so they would only conflict with each other if it was the clock you're altering with those adjustments to fool it into thinking it's moving faster. Quote Link to comment Share on other sites More sharing options...
zbigtim Posted June 17, 2010 Author Share Posted June 17, 2010 (edited) Well, I did the time trial tonight and the results were not what I wanted. I chucked the speed sensor in the drill press so I would have a consistent speed, as opposed to the cordless. With bits 4 and 5 on (7 is still removed), I ran the drill, speed showing 116.5 MPH, for one minute. At this speed for one minute, the odometer should have registered 1.94 miles, but it only registered 1.7, which is a 12.4% error. So I believe that confirms what JBrant said, that the adjustments only affect the speedometer and not the odometer. At this point, if I still want to use the Maxima speedometer, I will need the dakota converter box or build my own. Now that I have my car back from the shop (state safety inspection), I think I will install the sensor and see how far off the speedometer really is. Edited June 17, 2010 by zbigtim Quote Link to comment Share on other sites More sharing options...
getoffmyinternet Posted June 18, 2010 Share Posted June 18, 2010 Wow that's really bizarre. Defeats the purpose of being able to adjust it imo. Perhaps instead of changing the signal it just tunes the the current going to the actual needle to decrease the deviation, ie for alternate faces with higher top speed markings. Quote Link to comment Share on other sites More sharing options...
Xnke Posted June 20, 2010 Share Posted June 20, 2010 That's because the speedo is not supposed to be calibrated to the car, but to the gauge face. You use the proper speedo cog in the transmission matched to the rear end ratio, in order to make the speedometer correct. solder the jumper back, put it in the gauge cup, and it's done. Just use the right speedo cog and you're finished. Quote Link to comment Share on other sites More sharing options...
getoffmyinternet Posted June 20, 2010 Share Posted June 20, 2010 Just use the right speedo cog and you're finished. Yeah I'm sure they have a cog for every possible combo, you need to come down from 19 teeth to what, 16.5? Quote Link to comment Share on other sites More sharing options...
zbigtim Posted June 21, 2010 Author Share Posted June 21, 2010 Well, I'm not sure what I'm going to need yet. I have not actually installed this setup in the car yet. I just got my car back from state inspection, and I have the 4-speed out, installing a freshly rebuilt 5-speed. I plan on doing some temporary wiring for the speedo to see what cog I will need. To do the conversion right, I'm going to remove the dash to install the wiring from the megasqirt for the tach. I also need to route the speedo sensor wiring from the tranny through the firewall, and up to the dash harness. This will all be much easier with the dash out. All that being said, it will probably be a few weeks before I get to that point. I will certainly keep posting my progress. Thanks for all your input guys... -Tim Quote Link to comment Share on other sites More sharing options...
Xnke Posted July 2, 2010 Share Posted July 2, 2010 Getoffmyinternet...the 95 maxima uses the same type of speedo cogs as the F4W71B and FS5W71B and C manual transmissions...they use the same R180/R200 rear ends...the rear end ratio for a '95 maxima can be determined and the appropriate speedo cog obtained. It's just like when you swap rear end ratios, and keep the cog matched to the rear end. zBigTim, what color speedo cog is on the sensor? how many teeth are on it? What rear end ratio are you running? Quote Link to comment Share on other sites More sharing options...
zbigtim Posted July 19, 2010 Author Share Posted July 19, 2010 Sorry, been out for a while! I just installed the rebuilt 5-Speed today. Still need to finish up all the loose ends. But, the 240SX sensor installed just fine, and it has a red, 20-tooth cog just like the mechanical one that came out of the 4-speed that I was using. On the surface this seems like good news, but thats only if the maxima has the same final ratio and tire height as my Z. My Z has the stock rear end for '76 as far as I know. And, correct me if I'm wrong, I think it is a R200 with a 3.545 ratio. Quote Link to comment Share on other sites More sharing options...
Xnke Posted August 14, 2010 Share Posted August 14, 2010 You will need to find a VSS sensor that has the correct color/toothcount cog on it if you want your speedometer to be correct. There's really not any other good way to do it unless you have a programmable speedometer. I THINK the 3.545 rear end uses a black speedo cog; but somewhere in these forums is a good list of what color/tooth cogs are for what rear ends. The red/20 tooth cog is for a 4.11 rear end. Quote Link to comment Share on other sites More sharing options...
zbigtim Posted August 16, 2010 Author Share Posted August 16, 2010 Thats interesting Xnke, I'm not sure I've ever seen a black one. I have a red and yellow one, and the electronic one I pulled from the 240sx was red also. I'm sorry, I haven't posted any results. Truth is, the car is now off the jacks w/ 5-speed installed but I havn't wired the speedo up yet. I hope to do that this week. Did have some fun today at the local Z-Car show put on by the Gateway Z Club. Thanks, -Tim Quote Link to comment Share on other sites More sharing options...
Xnke Posted August 19, 2010 Share Posted August 19, 2010 Ok, my mistake; the Black speedo cog is for the 3.545 rear, blue for 3.700, white for 3.900, and red for 4.110. I'm still looking for the correct cog for my 3.36 rear end; I have a black one in my transmission at the moment. Quote Link to comment Share on other sites More sharing options...
wagon jon Posted October 14, 2010 Share Posted October 14, 2010 Oooh, that looks good! Post more progress pics as time permits! Quote Link to comment Share on other sites More sharing options...
dzeyene Posted March 31, 2011 Share Posted March 31, 2011 any updates bigtim?? Quote Link to comment Share on other sites More sharing options...
zbigtim Posted April 2, 2011 Author Share Posted April 2, 2011 I have no news yet. But I am close. Recently I have pulled my injector rail, sold it, and am buildig a new one with 440cc injectors. Pulled the tranny because of a massive oil leak in the bell housing. I just received my new wheels (Rota RB-R, 16X8). So, hopefully in the next week or so, my car will be back together, able to test the speedo. I will absolutly post my findings. Quote Link to comment Share on other sites More sharing options...
rejracer Posted May 4, 2011 Share Posted May 4, 2011 (edited) Correct Cogs: teeth Color Ratio 16 yellow 3.364 17 black 3.545 18 Blue 3.70 19 White 3.90 20 Red 4.11 21 Purple 4.38 Sounds like you need the speedo cog to set the odometer and the dip switches to scale the speedo. On the old speedo cogs you could switch the cog itself out from the body. Is that possible on the speed sensors? I like the design with the dip switches. This will enable you to make a new face if you wanted a 200mph speedo without major work. I might end up doing this mod to get an electronic speedo. Hope that helps. Edited May 4, 2011 by rejracer Quote Link to comment Share on other sites More sharing options...
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