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PostPosted: August 25, 2015, 2:55 pm 
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So i am converting my linkage shift to a cable shift on my B16 transmission using an MR2 shift assembly like the attached.

Attachment:
image (1).jpg


My questions is that when it comes to cables, how does travel affect the shift? I understand that too short would be an issue but what about too much travel? I cant really see a downside.


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PostPosted: August 25, 2015, 5:10 pm 
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The downsides to having a short cable movement for a given shifter throw are that it would amplify any slop in the linkage, and also a small amount of cable stretch would be amplified a the shifter. The result would be that the shifter feels vague and sloppy rather than crisp (kind of like some 80's american cars where you were never quite sure if it went into gear - the lever just kind of mushed into place). On the other hand, if your cable throw is too long you would start to feel the friction of the cable in the shifter as you were moving it quickly, and I think this would detract from the feel. This depends on the cable of course, and a good quality cable should have little friction so it may not be an issue. One other thing to consider is that you want to leave a little bit of room in the cable throw for engine movement, so you don't want to necessarily use the entirety of the available cable movement for the shift.


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PostPosted: August 25, 2015, 5:16 pm 
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^ also, if the cable travel is excessively long, the unsheathed ends of the cable will be very long and you could get slop from buckling or deflection in the ends of the cable. I'll measure the cable travel on my H22 trans when I get home to give you a reference.


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PostPosted: August 25, 2015, 8:15 pm 
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I don't know that there is a downside so much as there are practical limitations.

For longer cable travel the rocker arms either need to be larger or rotate further. Making them larger isn't really a problem, but you'll run into packaging restrictions eventually, and having them rotate further is limited by the rated swivel angle of the cable.

IMO, if you've got room for it, go with the longer travel.


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PostPosted: August 25, 2015, 8:28 pm 
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Looks like the transmission shaft only has .75" of travel and the cable needs to be about 40" long.

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PostPosted: August 25, 2015, 8:39 pm 
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So my H22 cables are roughly 56" long. The select cable has a max travel of 2.2", but the max the shifter can produce is 2.0, and the trans only requires 0.9". The shift cable has a max travel of 3.0", the shifter can only produce 2.4" of movement, and the trans only needs 1.6".


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PostPosted: August 25, 2015, 9:20 pm 
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Found this but i am not sure how much travel it has
http://www.jegs.com/i/B%26amp%3BM/130/80831/10002/-1

Or this one
http://www.summitracing.com/parts/lok-68180/overview/

This... i really dont know
http://www.summitracing.com/parts/csi-6003

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PostPosted: August 25, 2015, 10:22 pm 
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B&M has more detailed specs on their own site:

http://www.bmracing.com/products/80831-3-ft-shifter-cable-race-super-duty/

No such luck with the others.


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PostPosted: August 26, 2015, 8:27 am 
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Zac88GT wrote:
So my H22 cables are roughly 56" long. The select cable has a max travel of 2.2", but the max the shifter can produce is 2.0, and the trans only requires 0.9". The shift cable has a max travel of 3.0", the shifter can only produce 2.4" of movement, and the trans only needs 1.6".


Those are factory cables correct?

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PostPosted: August 26, 2015, 10:11 am 
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Yup, those are the original cables from a 95 Prelude SR-V


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PostPosted: August 26, 2015, 10:27 am 
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Its probably not what you want to hear but i would be exploring every avenue possible to get the rod shift working before I threw in the towel and went cable shift. I always think a cable shift is like stirring thick mud with a stick , they lack feel , precision and that " snick" feel (new word :) ) . If you have to its different but if you can avoid it you should, trust me I am old :)

Bob

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PostPosted: August 26, 2015, 10:33 am 
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Yeah i feel that i have looked at everything (along with a few other peeps). The problem is that the shift rod hits either the oi pan or lower tube when rotating. there just isn't enough room. With the cable shift I can easily route the them in a tight spot and dodge a bunch of other things running down the center tunnel. When it works it still sucks so i am confident that cables are the better solution.

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PostPosted: August 26, 2015, 10:45 am 
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On the gt40 the rod change goes through the drivers side sill and changes direction through uj`s three times and loses no feel. its made of 1" moly tube and is supported in the bearings below which retain the shift rod but allow a frictionless side to side and for and aft movement .

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Bob


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PostPosted: August 26, 2015, 10:56 am 
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yeah i have seen that but I would need quite a system to make that work. Mainly i would need to make a shifter, housing and the rear linkages. Still a bit easier with a cable.

any i bought an mr2 shift assembly.

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PostPosted: August 26, 2015, 12:09 pm 
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I thought about doing a combination of these two.

Attachment:
914-6-GT-36-SPEC-shifter-in-chassis.gif


Attachment:
7mCWZBpH.jpg


Attachment:
914-6-GT-36-SPEC-shifter.gif


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