Heel and toeing

[NorthernThrux]

Now that my gated shifter is dialled in and I'm getting used to the quirks of the 915 transmission, I've another question for the experts. I've been trying to improve my heel and toe technique on the downshifts, with limited success. I really need to dip into the throttle to get the rev matching blip that I want. Looking at the easy part of the throttle chain first, I see this situation at the transmission bell crank.



I need to move the ball cup forward by about 1/2" to 5/8" in order to get the bell crank pin to start to pull on the loop of the long engine throttle rod that goes up to the MFI. That's a lot of slack I feel. All bushings are new and everything moves perfectly. No slop in the line from the pedal to the ball cup at the transmission and no slop from the solid long throttle rod to the mfi. Just a very modest pull on the latter and you can hear the decel switch for the MFI click as the cross-rod comes off its stop. The only slack is in that bell crank pin having to travel so far to engage the end of the loop.

The pedal has the nylon stop on the pedal board screwed all the way down to the pedal board. When the accelerator pedal is pushed all the way down to this stop, it does appear that the throttle plates are fully open as best as I can tell by eye. Without the nylon stop, it's clear that they over rotate a touch.

Where should I be looking to adjust this so that throttle pedal actuation is more direct? There is only about 1/8" of adjustability remaining on the ball cup connection if I unsnug the lock nut and rotate it in some more to shorten it. Not nearly enough in my mind.

I think I read somewhere that the bell crank arm that connects to the long throttle rod should be at 90 degrees to the ground, and mine is clearly not. Does that mean I need to shorten some links on the pedal side as opposed to the engine side?

Ravi

[edmayo]

Possibly the return stop on the pedal box is bent back, should be at 90 deg. to the car centerline.

[gled49]

FTC. Full throttle check. The injection pump has has the throttle stop built in. Looks like you need to take up slack by tightening all ball cups, three that come to mind.

[raspritz]

Also consider the possibility that your brake pedal is too high. There are many possible causes of that. Heel-toeing an early 911 should be super-easy.

[NorthernThrux]

Thanks for the quick replies all. Good point on the pump stop Gordon. I forgot about that and pulled the air cleaner to check things. Thankful for all the experts here.

I got the Pneumovax 23 vaccine two days ago and although the low grade fever disappeared in a day, my left arm is so sore I won't be doing anything this weekend! But it looks like I need to concentrate on the pedal side of the bell crank.

Ravi

[frederik]

I spent quite a few hours working on this and still don't have it perfect (decided to use the summer for driving and the winter for further improvements). If you have full throttle, you're already good and you can take out a little slack. Having the bell crank on the transmission slightly upwards is good since this will give you more pull on the diagonal rod (otherwise you might lose full throttle). So I would leave this alone, and try to make the diagonal rod a little shorter. Note that it has two adjustments, one on the bottom and one on the top. You can also shorten the horizontal rod on top of the engine (this is the easiest one). You must check this with the engine hot; I noticed that it will tighten up a little bit when warm.

A completely different approach is to shorten the rod at the pedal a bit; this will make the bell crank more like 90 degrees but if you still get full throttle that's OK. In my experience, getting full throttle is the hard part (I'm 95% there). Taking out a little bit of extra slack should be easier.

In both cases you'll need to slightly unscrew the nylon stop at the bottom of the pedal.

Note: all of the above applies only if the stop at the pedal is not bent like Ed mentioned.

Whether all this will make it easier to heel and toe is debatable.

[frederik]

Just thought about it some more and I think you should really start at the pedal end and check whether the pedal is touching the small stop, that the stop is perpendicular and that it has the little rubber band. That's your baseline and then you take out the slack from there.

[Chris Pomares]

I’ve never learned to heel/toe. But the brake pedal bugged me. As I have 2 brake pedals I figured cutting one down was worth a try. So I had it shortened 1 1/4 inches. It works well for me.
I also personalized one of my shifters. The bend in the tube was increased so the shifter sits one more inch further towards the rear of the car.

[Haasman]

Just thought about it some more and I think you should really start at the pedal end and check whether the pedal is touching the small stop, that the stop is perpendicular and that it has the little rubber band. That's your baseline and then you take out the slack from there.

Logical way to start eliminating the too much play in the throttle linkage ..... question: Is there supposed to be any amount of play?

[edmayo]

I adjust for no slop,,,of course there will be some, but when you press pedal there is instant response.