RB25DET -> Z31T.. Update.

[Dramier]

Engine is in, tranny is in, all the "hard" stuff is in. Engine bay is being detailed and painted, engine polished and cleaned up.

 

We're waiting on the Greddy intake to replace the stock one, mushroom filter, and FMIC so we can do the final bolt-on and find out if we've wasted our time and money. We decided not to fire it up with the stock components since it was 10x easier to install the FMIC and intake with the engine out and car still partially torn down than after it's running.

 

Not sure when it will be ready to fire for the first time, but hopefully before the end of the month. I had meant to get some pictures this weekend, but forgot I'm attending a big car meet in Atlanta Saturday & Sunday. I'm going to try and get up there Monday and take some pictures of the engine/tranny sitting in the car to share, even if they won't show it actually bolted since we're waiting on the FMIC and such. Slowly, but surely, it's all coming togethor.

 

Wanted to run a topic by you guys, since you probably have more knowledge than I'll ever learn on Hybrid's. My Z31T has the digital guages stock, and I've been studying the wiring diagrams and thinking about attempting to retain it with the Skyline powerplant in the car.

 

The tachometer part is simple, since it is a straight wire from the ECU. Technically I should be able to just plug it in, so to speak. The speedometer is a different animal. Since I'm not sure how familiar all of you are with the schematic parts of the digital dash, I'll cover a little background information. The stock VSS cable is an analog cable that runs into the back of the digital dash, just like an analog dash. It connects to a connector/receptical (sic) that converts it to a digital signal. From there it goes into a microcomputer that processes the signal into a digital readout. Now, in theory, I should be able to connect the cable, either directly if I'm lucky, or hybrid part of it from a Skyline cluster and such, then put a potentiometer (variable resistor) in-line between the digital converter and the microcomputer. Then, put it on the dyno, and dial in the correct resistance to modify the Skyline number into the correct read-out on the digital dash.

 

If anybody sees any flaws in that logic, or knows of a smarter way to do it and keep the digital dash, please feel free to lend forth your wisdom. I would really like to keep the digital dash in the effort to keep as much stock Nissan as possible, but if I have to I will goto an aftermarket guage cluster. I also wouldn't mind recommendations on a good aftermarket guage cluster if those of you have ideas, since some of you have done RB engine swaps.

 

Thanks in advance, and I hope to be posting the next update with pictures and video.

[Doug71zt]

The digital speedo works on frequency, not current flow or voltage. The variable resistor idea won't work. Is you RB tranny an electrical speedo output? If it is cable, just screw the Z31 cable onto the tranny and presto. You may have to change the speedo pinion in the tranny to get the right speedo reading - it depends on your rear end ratio and tire size. No problem. If the RB tranny has an electrical output from a VSS, first try to screw the VSS off of the speedo drive pinion - the later Z31 have this set-up. It is just a VSS that screwed onto a standard speedo drive pinion. Then you can hook up the stock cable. If it is an integral VSS with a reluctor ring on the tranny output shaft and a sensor in the tranny case - just hook it up to the digital dash VSS output wires - you will probably have to take the dash display apart to do this. Chances are - it will drive the speedo with no problems - it may be off a bit, but Nissan is pretty consistant across their vehicle line - there is a fair bit of parts-bin sharing going on - so it may have the same # of pulses per revolution. I'm sorry I cant be more specific, but I haven't seen an RB 25 tranny up close yet.

 

Good luck - let us know what you find.

 

Doug

[Dramier]

Wow.. I was not expecting that much great information in a reply! Doug71zt I really appreciate the write-up of information, and I will definitly try it out and see. I also haven't looked at the tranny and VSS cable yet, so I'm not sure what the setup is.

 

Understandably, it's still something to do later on, and I'm just doing my homework now so I can be prepared to tackle it.

 

I had no idea it was such a different setup with how it measures the speed. I just took a look at the wiring diagram.. heh...

 

I'll post pictures of the tranny and cable, and the rest of it if I get it to work. If not, well, I've already contacted Dakota Digital guages about a custom application.

 

Thanks again Doug!!!