How To Convert Throttle Linkage on 3.6 Transplants? - Page 3

William Miller · 03-14-2007, 11:58 AM

Might work but I think it would have to have pretty thin walls and somewhat stiff. Or maybe put the tube on the rod while it is out and put a short piece of shrink tubing on the front end. Shrink it tight and try inserting it rod and all. Cut off the shrink tube and withdraw the rod.

I have no Idea if it will work, but if it does it might save an hour or more taking stuff apart and cussing.
My cable had a teflon or some other covering just on the part that was exposed.

jevvy · 03-19-2007, 10:43 AM

Right, have the cable installed and working quite well, I will writeup my process and load some snaps once its all nailed but thought I would just as a quick question.

Did any of you have any problems getting WOT - even with all the slack taken out the cable I dont seem to have enough pedal travel to get WOT at the throttle - any ideas?

Quick test of the pedal shows a huge improvement over the previous setup, pedal is light but feels very connected(excuse the pun), cant wait to try it out on the road.

William Miller · 03-19-2007, 11:16 AM

I haven't had mine on the road yet and actually I haven't checked for that. When I rebuilt my pedal cluster I noticed the the Throttle pedal arm hits the end of a screw that is driven thru the tub neat the front pedal cluster studs. It seems like it should have some kind of wider stop on the end of the bolt, but mine didn't.
It looks like I could screw (Back out) the stop a bit to get more throttle travel. The rod going from the arm to the pedal itself could be lengthened a bit to make up some of the difference.

The stop looks really odd, but I guess it does the trick.
Take a look and maybe you can back it out some and get that extra travel.

jevvy · 03-19-2007, 11:35 AM

ok, good call - I will look at that.

My "slide the tube up the tunnel" trick worked a treat & allows me to fit and remove the cable in a matter of minutes now which is a right result for tweaks.

Thanks for your help

DW SD · 03-19-2007, 04:40 PM

Jevvy,
Another option is to change the leverage ratios on the lever arms which pull the cables. If you want the throttle to open quicker, either lengthen the arm on the pedal side or shorten the arm on the throttle plate.

Doug

jevvy · 03-20-2007, 12:26 AM

thanks Doug, I'm thinking I might have to move the throttle cable ball up a bit on the throttle pedal lever to get a bit more full - I will look again tonight with a fresh pair of eyes.

Cheers, Jev

ischmitz · ischmitz's Garage

Quote:

Originally posted by DW SD
Jevvy,
Another option is to change the leverage ratios on the lever arms which pull the cables. If you want the throttle to open quicker, either lengthen the arm on the pedal side or shorten the arm on the throttle plate.

Doug

Aren't you having this backwards? For more throw you want to increase the radius on the throttle side (move the ball outwards by lengthening the arm) and/or decrease the radius of the ball on the pedal side (move the ball invards by shortening the arm)

jevvy · 03-20-2007, 01:56 AM

Ingo

Now im confused(doesnt take much)In my head to increase cable pull I have it as:

Increase length of lever at pedal or decrease lever length at throttle.

Does anyone know how close to the throttle stop 100% is read from the throttle position sensor? also is there a way to check this?

Thanks again guys

ischmitz · ischmitz's Garage

You can always cut off the stop at the pedal (later plastic model) or remove the white plastic stop screw under the throttle pedal (earlier model) to get WOT. That's what I did using the modified 964 cable. Works like a charm if you don't have thick carpet under the pedal. In the literal sense this is "pedal to the metal"....

jevvy · 03-20-2007, 02:29 AM

Hey ingo I was looking at the stop last night - fugly screw through the bulkhead and the placcy bit on the back of the pedal and was wondering if trimming that might release enough extra throw and seems an easier win that adjusting lever lengths.

I will re-fit the pedal board and look at how much I can trim before attacking the lever lengths.

Really appreciate the ideas etc and love the pedal to the metal idea!

CBRacerX · CBRacerX's Garage

I am using the PM version with a Varioram intake and generally happy since this is basically a Porsche part. However, I really like the solution adding a ball to the throttle crank and using the factory early car setup - I think I would look very carefully at that if doing it again.

Mahler9th · 03-20-2007, 07:23 AM

Just for the sake of posterity in this thread, I thought I'd add some comments.

First, on geomtery and WOT and throttle response. I expect that most thread viewers doing these conversions will be using factory computers, perhaps with custom chips. In this case, I suppose that if you stick with the factory TB, you oughtta try to emulate the factory geometry. That allows you to just copy what PAG did.

However, it may be possible to use a larger, aftermarket throttle body and still use the factory cpu with custom chips or what not. In this case, I would think you may want to optimize your geometry. Of course you want to ensure that you can get WOT. You paid for it, you oughtta get it. But you may also want to adjust things so that you can have a good amount of pedal travel, so that the throttle is not "on/off."

In my case, with a Haltech CPU and an 80 mm TB, and some aggressive cams (beyond RSR), my first attempt at geometry last winter was poor. It worked okay on the track, but was a little tough in the paddock, and for my occassional street drives.

So this winter, I changed the geometry a bit to increase the range of pedal travel and make the response just off of idle a little more gentle. To do this, I made a simple drawing and experimented with various linkage lengths, and the formula for the arc length of a circle-- s = r X theta.

Hopefully what I came up with will have benefits in the paddock, on the street, and comin' out of slow corners at the track. Haven't tried it yet.

Second, and quite important, it to carefully consider any changes to your throttle stop. I would think you want to make sure you have something robust and positive, as opposed to just using the throttle body. In my case, the plastic screw in the factory floor board was just too tall, so I replaced it with a metric bolt with the proper threads and height. Without a throttle stop, especially on the track or in AX, you could have some bad problems. I think you need to have a positive, robust stop.

SmartRacing Products sell one, in case you don't have, or don't want to use your factory unit. And it is pretty inexpensive.

- Mike

DW SD · 03-20-2007, 07:29 AM

Quote:

Originally posted by ischmitz
Aren't you having this backwards? For more throw you want to increase the radius on the throttle side (move the ball outwards by lengthening the arm) and/or decrease the radius of the ball on the pedal side (move the ball invards by shortening the arm)

No, not thinking about it backwards. If you want more effective throw, lengthen the pedal arm OR shorten the arm on the throttle plate.

The longer the distance between the pivot and the ball on the pedal equates to more cable pull from for a given angular rotation of the pedal.

AND the shorter the distance between the pivot and the ball on the throttle, necessitates less cable movement for a given angular change in the throttle plate.

I'd caution you on removing the throttle stop. Early on, I removed mine and ended up bending the arm to which the gas pedal is attached, because I would hit WOT on the engine side and continue pushing. Without the stop, something gives.

If you can't adjust for WOT, change the ratios and then adjust the stop accordingly.

Doug

ischmitz · ischmitz's Garage

Doug,
I was thinking about the pivot thing with the two arms on the 915 transmission. The way you describe it you are correct.

William Miller · 03-23-2007, 04:36 AM

From what I saw on my 81, the throttle stop under the pedal is just a bolt and it could be backed out a bit (Maybe instead of cutting it off) and still preform it's function to stop the pedal before stressing the linkage.

How much more do you need to go to get WOT?

On the engine side, my cable terminates with a cylinderical piece like on a bike brake cable. It snaps into a black plastic piece that snaps into the trottle arm itself. It seems like the plastic piece could easily be modified or replaced with something that would move the cable termination twards the pivot point reducing the throw a bit. It may only take a few mm at that end to get you WOT.

jevvy · 03-24-2007, 01:51 AM

Hey guys

Thanks for all the help. I have now got it all fitted and had a few test dives - very impressed. The throw is definitely longer but that great as one of my gripes with the old setup was that the levers involved were wrong and you got lots of cable pull low down making it hard to drive round town without looking like an idiot. I dont know if thats how Porsche designed it(easier modulation at high throttle positions) or whether it was the extra inch I added to one of the levers on the pivot to get WOT when the 3.6 went in that caused it but I didnt like the result. The new setup has resolved this without compromising higher throttle modulation, havent thought of any longer pedal throw disadvantages yet - anyone?

Heres some pics of the installation:

This was the copper reducer I bought - it was the closest match to what I thought I needed - some strange looks from the assistant

I the slotted the top and folded some tabs down onto a washer to form the stop for the throttle cable outer.

This is the stopper I made slid onto the cable and almost meeting the adjustable cable end that came with the 964 throttle cable I bought. No pics of the cable outer shortening process, I was too scared I would cock it up. Basically its really easy if you take your time and follow the advice in the thread above but make sure you measure again and again, you can take more off but you cant add it on so aim short if needs be.

This is the cable and stopper fitted to the chassis. I had to turn the copper piece down a bit to get a good tap-in fit. I will keep an eye on this but im pretty sure its going to do the trick.

This is the inside view where you can see the stopper just poking through. The biggest result I had was I managed to slide a piece of white tube into the exact route of the old rod. this meant I could slide the cable in and out easily while getting things sorted, I cant imagine doing this if you had to pass the cable up the tunnel NOT in a tube, it must be hell.

Overall a pleasant project with good initial results. I now have no links or pivots to consider/have slop - just 1 straight cable from pedal to throttle body. Action is very smooth - I was worried it would be too light before I drove it but I got used to it within an hour or so.

one last chuckle I had was I wanted to remove the old throttle pivot from the gearbox - I was over the moon when I discovered it was threaded and backed out easily - not so happy when the expensive mobil 1 gearbox oil started leaking :-( I should have known! How do I find out the thread type so I can find a replacement bolt to switch out?

William Miller · 03-24-2007, 09:02 AM

Looks great. Many ways to skin the cat!

jakermc · 09-22-2008, 11:49 AM

Quote:

Originally Posted by ischmitz

OK, I'll try to give some more details of the throttle cable setup I use.

The 964 cable is a bare steel cable that has the ball-pan connecting it to the pedal pivot point in the tunnel close to the pedal. The other end connects to the throttle body on the engine. The outer mantle running from the tunnel exit to the engine is made from rigid steel wires wrapped in black plastic sheeting.

I used a 1/4 inch teflon tube in the tunnel to route the steel cable. It makes sure the cable does not interfer with the shift linkage. The outer mantle of the 964 cable runs from the tunnel to the metal flange on the engine. It is a bit longer due to the shorter tunnel in 964/993 cars. I shortened it by cutting the plastic part with a sharp knife and using a triangular metal file to cut the steel wires. Once you have the right length you need to fabricate a stand-off at the tunnel exit. You can use a large washer welded onto the exit or a piece of steel tube. Since I had no access to a welder at the time I used a PVC reduction piece from an irigation system jammed into the tunnel exit.

The benefits of the 964 setup are that it does not use any linkage parts in the tunnel. There is not binding or dead play at all and you have a perfect pedal feel with no parasitic forces.

I have seen the early Timmens setups and they reminded me of cheap bicylce break parts from the early 70's. The Patric cable is nothing else but a modified 964 cable. I just didn't feel like droping a lot of cash so I did it myself from a used cable. Once I get back from Asia (business travel) I'll snap some pictures. The engine is currently out for some R&R so it's a good time.

Cheers,
Ingo (in Tokyo)

Reviving an old thread ...

I had the Timmons set-up and it did fail on me at the track after about 3 years and 5K track miles. After a track side repair with wire from a bicycle cable shifter I had my shop make a long term fix following what is described above.

WOW! As stated already, no parasitic forces and perfect pedal feel. The engine spools up faster for any given input of the throttle and its easier and faster to modulate the gas. If I mess up a corner and need to modulate, the penalty is not as great as I can quickly adjust and get back on full throttle a little bit faster. Also feel like I can come off corners faster as I reach full throttle just a little bit quicker. In reality it might not be a big gain in any particular corner, but over the course of a lap it adds up. I set a personal best on my first timed laps with the new set-up.