My Throttle Cable Conversion

[Captain Obvious]

I recently completed a throttle cable conversion on my 77 280Z. Combined with my new throttle body, it's smooth as can be. Without going into all the gory details, here's some pics.

Here's an overview pic. Cable come through the bulkhead and swerves a soft S-bend towards the master cylinders. This allows some slack in the cable to account for engine movement while running. It also allows clearance for the EGR valve if you are running one. My PO removed mine, but I may reinstall at some point so I wanted the cable to clear. Top level overview:

Here's the bulkhead passthrough. I made a threaded adapter and sealing nut on the lathe. The flats allow me to get wrenches on the passthrough from the engine compartment so I don't have to use tools up under the dash. This is the second passthrough I made... First one had the tightening nut on the other side under the dash. It worked fine, but was a real PITA to tighten with wrenches up under there. So I spun it around and made another one with the installation direction reversed:. Don't mind the loose A/C grommet:

Here's another pic of the firewall passthrough. In this pic, you can see how the cable is held into the passthrough. The metal ring is crimped into a hex and that clamps down on the cable sheath holding it in place. Since the sheath is pretty much always in compression, it doesn't have to be a hard lock, but it's nice that the sheath is a decent friction fit into the passthrough. Yes, that's a cable RG-6 crimp tool used for cable TV and Ethernet. I got lucky and it works great for what I was doing:

Under the dash, I converted over to a different connection design on the pedal. I purchased an already messed up pedal from someone with a failed cable conversion. He had already removed the original ball stud, so I drilled the hole out to the correct size to tap with threads and ran a tap through. I also made an "L" bracket adapter to attach to a Honda Civic throttle cable. I ground a little off the end of the pedal to get the angles right, and... Here's the parts separate:

Another pic showing my original pedal next to my modified version. Here's the parts put together. A little blue threadlock on the bolt and it looks like this:

So out in the engine compartment for the termination end at the throttle body, I made a bracket that mounts where my AAR used to attach. I have switched over to a different throttle body and the AAR is no longer needed so those holes were re-purposed for my cable bracket:

And here's another pic of the bracket up by the throttle body. Note that doing it this way also allows me to adjust the throttle cable play extremely easy using the original Civic adjustment nuts:

I'll talk about the cable itself in a little bit.

[wal280z]

You did make TWO sets of these, yes?

You KNOW I need this, yes?

???

[wheee!]

Here’s a start..!

[Patcon]

@Captain Obvious

If you're feeling OCD, you could send me that bracket and bolts during the salt season and I can make it pretty for you!

[Captain Obvious]

Wait... Isn't it clear that I'm pretty much always feeling a little OCD?  

Thanks for the offer. Might take you up on that during salt season.

[Captain Obvious]

So about the cable itself... I started with a Honda Civic cable. 96-2000 will work. I think there might be some slight differences in length, but they are all longer than necessary, so it doesn't matter. Here's what I started with:

I cut the original pedal termination off so I could pull the cable out of the sheath. I tried a couple different methods and I found a dremel cutting disk worked best for this Just go slow and let the disk cut. If you try to force it through, you'll blue the cable and fray the strands. After I cut the termination off, I pulled the cable out of the sheath and used the same Dremel cutting disk to shorten the sheath. Here's the tool I used:

Now, since I cut off the original termination, I needed a way to replace it once I had shortened the cable. Inspiration hit while I was messing with the Dremel... I made an adjustable cable end stop based on the Dremel collet system. This allowed me to set the cable length by tightening up the collet where the length was within the adjustablility range of the lock-nuts out in the engine compartment. After going through the effort to make this collet system, I wouldn't do it again. I would just use a block with a hole through it and a locking screw to squish the cable. Once you have the cable length set, you should never need to adjust this again ever. When I first did this, I had no idea how many times I would need to adjust the cable length to get it right. In the end, I didn't have to adjust the termination more than once and it turns out that I put way more effort into this part than I really needed to. It's pretty though:

So here's the whole under-dash setup. Note that this pic has my first design feedthrough for the fireawll with the threads and ring on the other (inconvenient) side. I made as second one with the threads on the other side so to minimize the under-dash wrenching. The collet lock works great, but is really overkill:

[Captain Obvious]

Just a couple additional thoughts and pics. In a few application specific locations, the Civic cable includes some outer layer protective covering (over the cable sheathing). They use these short covering stubs in areas where there is a cable clamp or where there is a high risk of abrasion. It's another outer layer of protection for the cable inside.

These areas are held in place (to keep them from sliding up and down the cable) by crimped metal rings. I found the hex crimped rings are usually jussssst loose enough that you can slide the protective covering up and down the cable a little if you really try. Here's one of the protected areas where you can see the metal rings on the ends. I was able to move this outer cover around to get it into a spot where I wanted it:

And here's where I wanted it... I nabbed a throttle cable clamp off (something) and attached it to one of the unused holes in my intake manifold. Slid the outer protective cover so it was centered where the clamp would be in the middle. This keeps the cable from flopping around:

And earlier, I admitted overkill on my underdash pedal termination lock. If I were doing it again, something like this would be just fine. Put on a washer with a tiny hole in it, and then put one of these on. This one is Dorman P/N 03337. Not as glamorous, but would work just fine. Less than five bucks off the shelf:

[wal280z]

21 hours ago, Captain Obvious said:

Wait... Isn't it clear that I'm pretty much always feeling a little OCD?  

Say it isn't so....

21 hours ago, Captain Obvious said:

So about the cable itself... I started with a Honda Civic cable. 96-2000 will work. I think there might be some slight differences in length, but they are all longer than necessary, so it doesn't matter.

I see what is on my 'to do list' for tomorrow. @Captain Obvious - trade you some HVAC parts for some brackets. No plating necessary. ?

Oh, the good news, she wasn't the 'bucking bronco' on the drive back.... Smooth as silk. But, I did hear a troublesome 'clunk' on a right hand ramp. Will bring it to the DIY garage on Sunday to investigate.

[Captain Obvious]

Haha!! Glad to hear your drive home from Zcon was less whiplashy than the trip there. 

For those of you who weren't at Zcon and haven't heard any of the stories... Once you got @wal280z's car up to cruising RPM, it had two throttle positions:

1) Accelerating, and
2) Face through the windshield

There was no in-between. Digital.

So there is clearly a couple issues going on that made it very uncomfortable to drive. (As a side note, I'm thinking it's something like high intake vacuum from a freshly rebuilt strong engine and a BCDD that is not working at all.) But it wasn't the time or place to fix the real root problem(s), but as a bush fix, we disconnected the TPS connector. That way the ECU would not know that the pedal was in the idle position and would not trigger the fuel cut. It was a successful Band-Aid that made the car a lot easier to drive. Didn't fix the problem, but at least masked it enough to make the car a lot easier to drive.

So, Wayne... I'd be happy to help you with a cable conversion, but you've got other things you need to work out as well! Of course, I'm touting my throttle body conversion in conjunction with the cable. With the two of them, my car is the smoothest ever. I wish I had it with me in Atlanta so you could have given it a try!

[Patcon]

1 hour ago, Captain Obvious said:

I wish I had it with me in Atlanta so you could have given it a try!

Branson!!!

[czeromedia]

So @Captain Obvious, im trying to do this conversion myself. Did i miss the part about the actual throttle body conversion? are you using a 240sx TB with a civic cable?  

[Captain Obvious]

I did a couple different iterations up at the throttle body. The first version was to make a new piece of linkage that fit onto the original throttle that allowed for the use of the cable. And things spiraled out of control from there.    

The current (and hopefully last) revision is to convert over to a Nissan Sentra throttle body that originally used a cable pull.

Let me look back through my pics and see what I have.