My '86 GTI build

[Rabbit Farmer]

Do you need to know how fast you are going?

[walterclark]

I have found it very useful when comparing points of one run or technique against another (usually from data logs) and as a gauge under braking before downshifting when trying different corner entry speeds.

I think the biggest drawback to using a rear wheel speed sensor is going to be the fact that in left hand corners the left rear, where the pickup is located, is going to slow or stop while the wheel is in the air so for a time the info wont be useful. I can always add a sensor to the right rear as well and build a comparator that will always forward the highest value to the Megasquirt but I dont think that is going to be needed.

[Super1303]

Maybe put a generic hall effect sensor in the tranny case. Use the ring gear or any fixed gear on the counter shaft for a speed signal generator.
Just an idea for ya.

[Rabbit Farmer]

I agree with you that a speedometer has value. Was just curiosity for me if you needed the speedometer or just trying to bring your car up to the normal street spec (if you will).

[walterclark]

The 02A actually has one variation where the speedo gear-drive output is replaced with a Hall or VR sensor so I thought about doing that direction but the same "port" doesnt exist on the 02J and I want to avoid spending unnecessarily on the 02A where the expense doesnt work on a J as well. I considered just using a generic threaded sensor where I could drill/tap a hole in the diff case and mount one but decided the work involved was more than I wanted to get into for this.

I like having the analog speedo on the dash working as on a normal car but what I find most useful while in the seat is the digital speed readout on my smartphone from the Megasquirt. When I glance at the analog speedo what registers in my brain is an approximate speed such as >75 <80. When I glance at the display on my smartphone what registers is 78. Last winter I toyed with the idea of adding a permanent LED 2.5 digit display of speed on the analog gauge face where the odometer used to be. The Arduino that drives the speedo stepper motor can handle it. What stopped me was that I never found a suitable display...Large enough digits in a small enough package to fit in the available space and with an interface that worked directly with an Arduino serial output. I am still mulling over the idea of replacing the analog dash with a 10-11" notebook and now that the last generation premium Androids are selling for <200 used, I may get one after Christmas and start playing with it with this in mind. I know the app I run on my smartphone is powerful enough to create a great dashboard, and the couple things I display on its smallish screen are useful to me while driving.

[walterclark]

Just an update to close out the year.

Since the last update I have focused on the new pedal cluster.

The first problem getting a racing pedal set into the car is that the new sets assume a flat firewall and the GTI, especially in the area of the stock cluster is heavily stamped to create some rigidity for the OEM brake pedal assembly.

I took a bunch of comparative measurements to locate the OEM pedal arms' pivot points and where the pedals themselves are located in space relative to a few "hard spots" in the footwell. I did the same for the steering column, the far end of which is anchored to a bracket bolted to the OEM cluster. I compared those measurements against the new pedal cluster geometry with a goal of locating the new set in the same 3 dimensional space as the old and defining where the "new" firewall needs to be.

I cut most the firewall in front of the driver footwell out - amounting to a rectangle that is roughly 12" wide and 14" high. Then I made some cuts into the remaining firewall either side of that and used a hammer and dolly to flatten a few inches of the remaining metal to the vertical plane I felt was needed for the new pedals and then welded up those seams, leaving a nice flat rectangle into which can be welded a piece of flat sheet steel against which the new pedals will mount.



I temporarily mounted the pedals (Willwood set and the OEM throttle pedal) and steering column a number of times and learned that the column cannot sit exactly as it did stock and clear the pedal arms, clevis mechanisms and balance bar screw. It needs to be about 3/4" lower on the firewall end to let me mount the new pedals close to stock height above the floor. This means I needed to shim the upper end mount down a little to keep the column angle from getting too extreme, I needed to relocate the hole and boot thru which the column goes thru the firewall, and I needed to shorten the shaft between the U joint on the lower end of the column and the U joint on the top of the rack.

I created what I will call V1 of the mounting bracket for the brake clutch pedal cluster which also located the the lower end of the steering column using its original locating yoke that I welded to an arm on the column housing so as to clear the pedal cluster. This original bracket anchored the mounting tabs of the pedal cluster that are further away from the firewall up to the horizontal bottom of the plenum (where the old ECM was and present wiper motor is located). My plan was to mount the cluster to the firewall and then reinforce the firewall with L aluminum to keep it from flexing. So I made the bracket, punched the holes in the new firewall needed for the pedal cluster and mounted it all up. The throttle pedal is mounted in a sheetmetal U bracket attached to the new firewall that uses the original pivot pin.

Turns out I had a few problems. First, I seem to have miscalculated where the pedal cluster needed to mount in order to both clear the steering column and to locate the pedals at the right height. Second I realized the V1 bracket and bracing was not going to stand up for very long under the force of using the brake pedal because I managed to design it all so the loads would be trying to pull all the bolts thru sheetmetal. The cluster needed to move 1/4" outboard and about half an inch up and I really need a bracket design that is in compression under load. I seem to have gotten the throttle pedal location right...I did have a good reference that was not removed when the firewall was cut and modified. There is a pedal stop welded to the floorpan and I had used that as a reference point for the vertical and horizontal position of the pedal.



I punched a couple more holes in the firewall to relocate the brake/clutch pedal cluster to the proper location and have verified the steering column has good clearances to all the moving bits on the pedal cluster. I have designed a new set of brackets that attach to top and bottom corners of the firewall where it meets the floorpan and plenum reinforced points and is structured such that the bracket and pedal cluster attachments are primarily in compression under load. I will construct the brackets right after the new year.



I have also done some reconfiguration of the brake lines. The rear brake lines M10 bubble flare fittings now go into an Earl's T located about where the rear dual proportioning valve was located. The single line forward from the T connects using a standard SAE 3/8" 45 degree inverted flair. That line will pass thru a lever type proportioning valve, mounted inside the cockpit to the center tunnel and from there to a 2 pound residual pressure check valve on the front of the rear MC. The front will be similar with the T a few inches below its MC and check valve. I just need to buy a good quality flair tool for these. I have one for the metric bubble flairs, but all I have for IF is one of those crappy $10 Home Depot tools that sort of works but only on soft copper tube.

[sdwarf36]

Looks real good Walter.

[Rabbit Farmer]

Glad you added pictures... it was hard to visualize all your work. Looks great!

[walterclark]

Thanks. I just wish I had realized that I needed to move the pedals a bit before I welded in and seam sealed the new firewall sheet metal...it was punched with the bolt and MC holes where I thought they needed to be just before it went in. Now I need to either cut it all back out and make a new one or cut and punch a small panel just around the new pedal assembly mount location, then cut a somewhat smaller rectangle out of the firewall and stitch or screw the new small panel onto the hole. I am inclined toward the latter since the middle area of the firewall around the pedal assembly mount will not need to support any load and will be stabilized by being sandwiched between the pedal assembly and master cylinders. All it really needs to do is not leak. That will get done after I make up the new mounting brackets to solidly hold the pedal assembly where is is right now.

[walterclark]

Second verse of the pedal cluster.

I think I got this one right. Where the first iteration mounted the pedal bracket in the middle of a flat firewall and braced it to the middle of the plenum - both of which flexed and needed additional bracing, this one mounts to the top and bottom of the firewall where there are 2-3 layers of sheetmetal at the seams and the edge changes direction into the plenum and floor. This is a LOT more rigid.



The new brackets are 1/2" square tube - triangulated to the 1" L (formerly 1" square tube) that holds the Wilwood pedal cluster. I also moved the throttle pedal mount off the firewall and onto the right bracket...much more stable this way. The throttle pedal pivot can be seen in the above photo and with the pedal attached below. The V1 throttle pedal mount was attached to the firewall where you see a sort of beige rectangle behind it in the above photo.





It seems to be very strong and actually ends up weighing slightly less than the OEM cluster...>6 pounds less if you include removal of the vacuum booster.

Before painting it I still need to fabricate a mount for the lower steering column. I will again use the stock system which is a U shaped piece of sheetmetal on the top of the column (which I relocated up and back from the original position to clear the pedal cluster pivots) that slides over a round fixed point on the car. That fixed point will be a bar running between the new brackets and above the pedal pivots. I used a hollow metal bar on V1 with stop washers welded to it to control the side-side motion of the relocated stock bracket and that worked well. I need to mount up the K-frame and steering rack and reinstall the column to get the geometry of that right before making or modifying anything.

Finally I will need to cut the part of the firewall that has the wrong locations of the required holes for the cluster to master cylinders and make a new one. That should be a pretty straight forward small piece that will get stitch welded in once it is correctly located.