Short Shift Bad For Rebuilt 915? - Page 2

DARISC · 12-06-2007, 08:45 PM

I've always been advised to stay away from short shifters and to go with the factory kit if I must have one (for the above stated reasons regarding synchro abuse).

I ended up putting the WEVO shifter on my 915 and I like the kinda "rifle bolt" feel of it. I didn't really dislike my VW bus-like stock shifter at all, just had the chance to buy a used WEVO and, having read all the great press about it, decided to try it.

It's definitely a shorter shift than stock but I don't notice a great deal more effort to shift it. I still respectfully let the synchros do their job without rushing them (I don't shift it any faster than I did with the original shifter).

I don't feel it's any "improvement" as far as getting the job done (doesn't do anything to the trans to "allow" it to shift quicker or more precisely - but I can see how it might invite abusive synchro forcing in some hands). But, liking the feel of it, I wouldn't go back to the old shifter.

When I put the shifter in I also went with WEVO trans/engine mounts and coupler, all of which add up to a package that feels quite a bit more all of a piece.

island911 · 12-06-2007, 10:14 PM

Just how quickly one shifts, a clean, rev-matched, low-force shift, is dependent on how quickly the rev's fall. --generally slower when putting around town, and faster when dropping off redline.

Also, the shorter the throw, then the less feel for the syncro matching you have. The wevo is VERY short. Not much in the way of "precision" IMO ... it just blows thru the syncro engagement. I suppose that makes it feel more binary - no 'in between.' a lot of people like that.

DARISC · 12-06-2007, 10:50 PM

Quote:

Originally Posted by island911

Just how quickly one shifts, a clean, rev-matched, low-force shift, is dependent on how quickly the rev's fall. --generally slower when putting around town, and faster when dropping off redline.

Exactly. First thing I did when I bought my car was disable the maddening decel thingy. And yes, absolute min. force. While I'm fully aware that one shouldn't, the 915, like other manual trans, CAN be shifted w/o clutching, and if done well gears can be engaged with ZERO force (having shifted every other trans I've ever driven without clutching, I just had to see if I could shift the 915 that way - both up and down the gears - all five of them).

Also, the shorter the throw, then the less feel for the syncro matching you have.

I don't have that perception; yes the throw is shorter and the spring load into the horizontal plane gives a more distinct mechanical feel than the stock shifter, but aside from that the feel for the synchros feels no different to me.

The wevo is VERY short. Not much in the way of "precision" IMO ...

I agree; NO increase in precision at all - the gears are still to be found at the exact same locations in three-space as they are with the stock shifter installed and the WEVO provides absolutely no guidance or precicision locating those positions.

it just blows thru the syncro engagement.

Not the way I use it, which is as gently as I used the stock shifter.

I suppose that makes it feel more binary - no 'in between.' a lot of people like that.

I always am of a base 5 mindset, so I don't know about that

..

JBO · 12-07-2007, 05:57 AM

It sounds silly, but the the thing I did a few months ago after reading a post on here that really improved the feel of the shifter and ease in finding gears was to add a large spring I got at Autozone to the shift lever. Now when I take it out of second the spring pulls the lever over and I move it straight up and right into 3rd and straight down to 4th. I have the stock shifter and was considering one of the other options, but now I'm not. I have to admit I was really surprised how much this $3 change helped.

dtw · 12-07-2007, 06:51 AM

Best advice I ever got when buying my first 911 was, "never apply more force to the shifter than you would to a raw egg". Fingertips only. People who shift with their whole fist don't drive my cars...they're welcome to the Mustang 'vert though.

gerrygug · gerrygug's Garage

Previous threads on this subject seemed to contain lots of positive comments on the Wevo product. It retails for $595.00 but most everyone who has one seems to comment favorably. Anyone have a Wevo?

DARISC · 12-07-2007, 09:34 AM

Quote:

Originally Posted by gerrygug

Previous threads on this subject seemed to contain lots of positive comments on the Wevo product. It retails for $595.00 but most everyone who has one seems to comment favorably. Anyone have a Wevo?

You might want to look at my posts on this thread - doh!

Thrasher · Thrasher's Garage

Quote:

Exactly. First thing I did when I bought my car was disable the maddening decel thingy.

What decel thingy?

DARISC · 12-07-2007, 11:21 AM

Quote:

Originally Posted by Thrasher

What decel thingy?

Below is from earlier thread - hope it helps (mine is disconnected and it neither smokes nor pops - just drops revs MUCH faster. Has to be connected for a smog cert. though):

"If you have your decel valve (vacuum limiter) connected, pull the vacuum line off of the decel valve nipple and plug with a golf tee. If that solves the problem then you need to fix/replace your decel valve or leave it unplugged. You can fix by pulling it out and squeezing it slightly in a vice (search on "decel valve vice").

The decel valve is located towards the right rear of the engine (rear = toward firewall). A bad decel valve will cause your idle to "float" - you come to a stop and the idle slowly begins to increase. When working correctly, the decel valve prevents rapid rpm drops in between shifts - it also prevents popping, smoking, on rapid deceleration.

BTW ... I have an 82 SC and it DOES have a decel valve."
__________________

Thrasher · Thrasher's Garage

Does this apply only to CIS cars, or will my 84 Carrera/Motronic have one of these? I've always wondered why the idle falls so quickly between shifts... just thought it was light flywheel.

john walker's workshop · 12-07-2007, 04:12 PM

the 3.2 has a decel valve in effect. it's the idle control valve. different than the CIS style entirely. all computer controlled. it opens just as the idle drops and grabs and controls the idle speed in one fell swoop. idle comes down and whoomp, stable.

DARISC · 12-07-2007, 04:37 PM

Quote:

Originally Posted by Thrasher

I've always wondered why the idle falls so quickly between shifts...

Like, that's a GOOD thing, yes?

Thrasher · Thrasher's Garage

Ok, thanks JWW... I've cleaned my ICV with alcohol and my idle is pretty stable, but my heel-toe blipping seems fruitless since the revs drop off so fast.

The 915 downshift from 3-2 is so slow for me that if I heel-toe/blip, by the time I'm getting into 2nd, the revs are down at idle.

Do I need to blip higher or longer? Or is double-declutching my best bet?

Sorry for the highjack, but this is without the short shift kit and my 84 has the longest shift of any Carrera, since they dropped it in '85.

911pcars · 12-07-2007, 06:16 PM

"...Do I need to blip higher or longer? Or is double-declutching my best bet?
..."

The speed difference between gears is greatest when the vehicle is at speed and the gearbox input shaft is idle (clutch disengaged), thus the most wear will be on the synchros at this point.

Rev-matching (blipping the gas in neutral) only matches the rotational speed of the flywheel (engine) and clutch disc (gearbox input shaft); it has nothing at all to do with the synchros. You must double-clutch (downshift) to relieve the synchros of speed matching duties and subsequent wear.

Sherwood

DARISC · 12-07-2007, 08:11 PM

[quote=911pcars;3632594You must double-clutch (downshift) to relieve the synchros of speed matching duties and subsequent wear.[/quote]

And if spot on (which is rare, no matter how good you get at it) NO force at all is necessary - the lever just goes there as fast as you care to chance that you've sufficently matched revs. Nice feeling, akin to finding the sweet spot hitting a tennis or golf ball - but much more expensive if you miss!

911pcars · 12-07-2007, 10:24 PM

"The 915 downshift from 3-2 is so slow for me that if I heel-toe/blip, by the time I'm getting into 2nd, the revs are down at idle.

Do I need to blip higher or longer? Or is double-declutching my best bet?"

I forgot to answer the first part of your question earlier.

If the downshift is completed (in a gear) but the engine speed drops, disengage the clutch and blip the throttle to match the engine speed to the same rotational speed the input shaft would be in that gear, then engage the clutch. That would be equivalent to an extended double-clutch. Speed match gearbox internals; speed match flywheel and clutch = smooth downshift with no drama.

Blipping the throttle is often needed to complete the second part of a double-clutch downshift, when the gear change isn't fast enough to complete during the rev in neutral and clutch engaged.

Probably better demo'd than explained (at least my explanation attempt):
Here's an explanation, but average visual display:
http://youtube.com/watch?v=jAvOOLYPmMM&feature=related

another at speed (RHD)
http://youtube.com/watch?v=WD5zq0Jkpoo

and a little faster (LHD):
http://youtube.com/watch?v=0j-3xIZK-Bk&feature=related

Sherwood