OBD2 throttle body, which throttle cable?

[SHunter]

So I've been driving my swap for close to a year and its been great but there are a couple of little things that bug me. One of them is that the throttle cable isn't quite long enough. I'm using the OBD2 throttle body which I know most people on here aren't using but it's necessary when using the M50manifold.com kit. I'm using an e34 TB cable and the cable is just long enough to fit on the cruise control part of the TB and only after I bent the cable housing stop in a touch. Unfortunately this makes the throttle feel very touchy when driving and it's hard to drive smoothly. I've gotten used to it but its difficult for other people to drive my car, especially with a light flywheel and stiff clutch, and really noticeable after driving my girlfriend's stock e30 around.

Is there another cable that works better with the OBD2 TB? I haven't seen this mentioned in the 1,000,000 threads I've read about the swaps.

[drken]

I found the same thing. The e34 cable was a litttle too short, and trimming the grommet just let it pull through (no good). So, I used an e36 M3 cable instead, but I had to cut the end off (at the throttle body side), and use one of those cable stop screws. You know, looks like a little barrel with a set screw in one end. That has worked fine, but I still feel the throttle is a little "touchy"

Ken

[SHunter]

Yeah, my grommet is now starting to crack up. Thanks for the tip. I'll get a hold of an e36 throttle cable. Why'd you cut the end off? was it still too short? Its designed to work with that TB, so it should be the right length right?

SH

[drken]

Actually, no, it was too long. IIRC, I might have been able to make it work, but I didn't want to back the adjusting screw all the way out, as it would start hitting on my brake booster. At least, that's what I seem to remember. Although it was the correct cable for the throttle body, I guess the "pedal grommet to firewall clip" distance may be different in the e30s ( shorter) vs. e36s, accounting for the excess length. Just a theory- I haven't measured it.

Ken

[craiggroves91]

Correct me if I'm wrong, but I don't really think the throttle being touchy has anything to do with the throttle cable. All the throttle cable does is open the butterfly valve on the TB. How would changing the length of the cable change how it opens?

Throttle response is more related to other factors

[drken]

Changing the length of the cable would make no difference at all. I think the difference I feel may be due to a different motion ratio built into the accelerator pedal assemblies between the e36 and e30. In other words, maybe one pedal gives more throttle cable travel per inch of pedal travel than the other does. That would explain a more sensitive pedal with slightly less "resolution". Again, I haven't measured any of this-just theories at this point.

Ken

[SHunter]

You're right. It seems like the length of the cable shouldn't affect how the throttle feels but there are two things going on.

First thing is the cable is so short that when the throttle is closed the cable is taught. There is no slack at all. This makes it very touchy off idle and I think occasionally it will even hang just barely open.

The second thing is the OBD2 TB has two different sized "pulleys" that the cable can wrap around on its way to opening the butterfly. One is for the cruise control and one for the cable attached to the pedal. Right now I'm using the cruise control pulley because its the only one that fits. I can't explain the math part of it but it changes the pull ratio and I think might make the throttle operate different than expected.

I guess there's a third thing. My cable is pretty old and has some friction in it, which makes it hard to be smooth with of course. If I buy a brand new cable, I want one that will actually fit as factory intended.

I'll give the E36 one a shot and let you guys know what I think.

SH

[craiggroves91]

You're right. It seems like the length of the cable shouldn't affect how the throttle feels but there are two things going on.

First thing is the cable is so short that when the throttle is closed the cable is taught. There is no slack at all. This makes it very touchy off idle and I think occasionally it will even hang just barely open.

The second thing is the OBD2 TB has two different sized "pulleys" that the cable can wrap around on its way to opening the butterfly. One is for the cruise control and one for the cable attached to the pedal. Right now I'm using the cruise control pulley because its the only one that fits. I can't explain the math part of it but it changes the pull ratio and I think might make the throttle operate different than expected.

I guess there's a third thing. My cable is pretty old and has some friction in it, which makes it hard to be smooth with of course. If I buy a brand new cable, I want one that will actually fit as factory intended.

I'll give the E36 one a shot and let you guys know what I think.

SH

You want your throttle cable tight with no slack.
I have an s52 w/obd2 TB and the e34 cable fit on both the cruise control and normal pulley

[328ijunkie]

twitchy throttle indicates vac leak typically.

[SHunter]

cjdontthink: The throttle cable doesn't need to have any more than the slightest perceptible slack at idle but it definitely shouldn't be tight. If it's tight it won't close all the way. If you check the manual, it says just that. Mine would probably be fine but, like I mentioned earlier, my cable isn't the smoothest because of age and I think it hangs up from time to time.

As far as using the E34 cable on that TB, I don't know how you did it. There just isn't a lot of adjustment and mine isn't even close to being able to fit on the larger pulley. Maybe there are different versions of the TB?

328ijunkie: There could be a small vac leak I guess but I don't have any other reason to think so. The car drives great otherwise, idles well, and only has stored codes for the rear O2 sensors. Those couldn't be removed from my ECU when I did the swap. Usually even a small leak will store a long term fuel trim code.

All: This is a small problem mostly related to my throttle cable being old and having some friction in it. The grommet is starting to crack as well which is probably creating a little extra friction when the cable isn't aligned properly in the stop. I figure if I'm gonna replace the cable I should get one that fits the TB that I have and the E34 cable that I have doesn't fit correctly, even adjusted in as far as it goes. OBD2 E36 cable is in the mail. I'll let you know how it goes.

SH

[SHunter]

Well, I've had the E36 cable in for about a week and it feels much better. Honestly, I think a lot of what I was feeling was stickiness in my old cable. On the bench it felt fine but when my E34 cable was installed there was a lot of friction. Rev matching and especially taking off from a stop is much smoother now.

The new E36 cable is much easier to roll into from idle because it isn't tight at the idle stop and it's able to fit over the larger TB pulley like a factory setup. I believe this smooths the feel since you're using slightly more pedal travel to open the throttle all the way.

I needed to adjust my pedal height at WOT just a bit to achieve WOT with the new cable. I also had to adjust the E36 cable all the way out at the throttle body to keep from having too much cable slack at idle. If it stretches I'll have to use a set-screw cable stop like drken used.

Conclusion: If you have an old E34 cable lying around that still feels smooth it will work fine but you might have to bend the hanger or cut down the rubber grommet a little to get the throttle to close all the way. Otherwise a new E36 cable will more closely match the factory feel and adjustment.

SH

[orangechicken]

@SHunter: Finally some mention of the E34 not just bolting on. I went to replace the one in my S52 swap and ended up having to modify both the grommet and the end of the adjuster (the cable was too short / left the TB open slightly with the unmodified grommet, and the adjuster was too long and wouldn't let the pulley open once I modified the grommet).

I had bought the aluminum bushings (from http://www.meurosport.com/Aluminum_Bushings.php) but no way would they work with the E34 cable. Maybe the would with the M3 cable though… hmm... maybe I'll have to try that actually.

Why is there not more information about this out there? I can't see a way an unmodified E34 cable could work with an unmodified ODBII throttle body. How did you do it @craiggroves91 (I believe you… I must be missing something). Are you running the ODBII throttle body? Did you use the top or the bottom pulley?

[orangechicken]

Well, I've had the E36 cable in for about a week and it feels much better.

Do you have a part number? Is it 35411163228?

[Daeldalus]

anyone know if the e34 CC cable still works for this?
i definitely still want CC but after seeing this thread not sure if it will work.

if not which cable to get?

[328ijunkie]

E36 one.