Early 911/930 pedal box SCRS style with DBW and G50 clutch

[dannobee]

I've been slowly making progress on my 930 update. The ECM/PCM work is nearly all complete, and I wanted to show one way of adapting an early 911/930 pedal box to Drive-by-wire, so that your modern ECM/PCM can give you modern features like traction control, cruise control, launch control, etc. I'm using a Link FuryX, but most modern ECM/PCM's can use the input from the APP Sensor to run an E-Throttle by just clicking a few times in the setup software.

It took quite a bit of perusing and scheming to find an Accelerator Pedal Position sensor that could easily adapt to the stock pedal box. Since I worked at dealerships for quite awhile, I wanted something that could be easily adapted and be at least stock appearing. I figured that since I was upgrading the brakes on my 930 anyway, and would be installing the G50/50, I could incorporate all of the changes in one fell swoop.

I ended up using an APP from a Nissan 350z (circa 03-09). I cut off the extension and enlarged the hole for a rod to connect the factory gas pedal link to the sensor.





I also changed from a single master cylinder to the SCRS style dual master cylinders with a balance bar. Since early 911/930's didn't have power brakes, the pedal always felt "heavy," and I feared the girlfriend wouldn't have enough leg strength to utilize all of the power of the brakes on track days, I changed the pedal ratio from 5.4 to 6.5. We'll see how that works out. "Do the math" on the caliper piston and master cylinder sizes to take it back to near factory brake balance if you choose to copy this setup. The stock brake light switch was reused and the original bracket was trimmed and welded in place. A large flat washer on the master cylinder rod actuates the switch, just like the factory setup.

Since I'm also upgrading the transmission to a G50/50 and a hydraulic clutch setup, another master cylinder was needed, along with finding a place to hang it, along with constructing a new clutch pedal to clear the master cylinder rod. Stock G50 pedal boxes locate the master cylinder right where the SCRS master cyliinders would go, so that option was out. I came up with this setup.







The whole setup fits neatly under the stock floorboard and carpet, and retains the factory pedals. The front to rear brake balance can be adjusted by either adding the dash mounted brake balance cable and knob, or by pulling up the carpet and floor board and manually adjusting the balance.

I've been busy with work, so time has been limited, but I hope to be making quite a bit more progress on my project in the next few months.

[dannobee]

Here's a short of the setup in action.

https://www.youtube.com/shorts/Akc6_Vbv0qc


And of course, with the Link FuryX controlling the throttle body.

https://www.youtube.com/shorts/D9_dgNHkajY

[Cory M]

Nice!

[chrisbalich]

It looks like you have welded the vertical (MC mounting) plate to a stock pedal box then reinforced it, and have modified the brake pedal to accommodate the balance bar. Is that about the gist of it?

If so, what pedal box did you start with?
(I’m thinking a dual MC setup like this belongs in my SC.)

[dannobee]

This one started life as a 914 pedal assembly but the bases are all the same. The brake pedal is fabricated with only the serrated foot pedal used from the stock one. There simply isn't enough room on a stock brake pedal to fit the requisite tube to hold the balance bar (at least in my humble opinion).

For the clutch pedal I fabricated the lower part to clear the clutch master cylinder rod. The vertical part of the pedal is from a G50 car, but any 74-89 clutch pedal would work for the baseline. Just be careful that the motion of the pedal doesn't contact the master cylinder rod. The pivot for the clutch master cylinder was the old brake master cylinder pivot, with a pin welded to the clutch pedal.

The brake switch is stock. I even used the stock bracket. The actuator is a fender washer held onto one of the brake master cylinders with nuts. It operates like the factory setup.

It took some perusing of various catalogs to find an APP sensor that would work, and the side reinforcement doubles as the mounting plate for the APP sensor. The link bar is needed because the two arcs are different.

When it's all mounted in place, it looks like a bone stock factory one, until you pull up the floor board.

[Pork Chops]

Originally Posted by dannobee

Here's a short of the setup in action.

https://www.youtube.com/shorts/Akc6_Vbv0qc


And of course, with the Link FuryX controlling the throttle body.

https://www.youtube.com/shorts/D9_dgNHkajY

Excellent work. How does the return spring work?

[dannobee]

The return spring is integral to the APP sensor. If you want/need a stiffer spring, you can always add one to the factory pivot bracket. On the engine side, the throttle body is drive by wire, so there is no external throttle spring or linkage.

[3rd_gear_Ted]

Big kudos for that project.
Put that set up in in a Spec 911 race car and the Cup car guys will be.....