My '86 GTI build

Re: My '86 GTI build

Postby sciroccohp » Sat Nov 14, 2015 7:13 pm

no, very similar setup to yours but with stock brakes all around. I need to investigate which master cylinders I have since I always have too much rear brake under light pedal. Its good timing as a reminder, I just mounted the pedal cluster in the new car. so it is still easy to get out.
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Re: My '86 GTI build

Postby sdwarf36 » Sat Nov 14, 2015 8:09 pm

Was or is the car a rear drum car? I just found out something by accident last week on my street car. While having to replace a rotted brake line, I ended up eliminating the weight sensing proportioning valve on the real axle. Afterwards I couldn't get the pedal from being to long. If you hit it a couple of times, it would be up top. Let it it sit 10 seconds it would go towards the floor. Turns out one of my self adjusters in the rear wasn't adjusting. Once I tapped thing around a bit, I got the shoes closer to the drum. Turns out the proportioning valve also has a residual valve in it. (Although the Bentley says nothing about it. :? ) My shoes were moving back too much-and without residual pressure holding them, my pedal was long. Now eliminating the proportioning valve, you can feel the back brakes hit sooner + harder.
Translating road racing to hillclimbing:
Proper tire selection== nothing hooks up on moss or wet leaves.
Staying on the racing line==anything paved is considered good.
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Re: My '86 GTI build

Postby sciroccohp » Sat Nov 14, 2015 8:19 pm

I have manual adjusters on the drums that I tighten every run. If definitely got better when the balance bar was set to all front, I just think I have the wrong masters and the cylinders are so much smaller in the back.
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Re: My '86 GTI build

Postby walterclark » Sat Nov 14, 2015 10:15 pm

Your rear drums may need a different bias than my rear discs but when I added the Wilwood lever proportioning valve (260-8420), set to about the middle, I was able to dial my preferred bias in nicely with the balance bar without running it to an extreme end. With the lever I can quickly adjust the rear to add more or less braking if I desire. I have a good deal of trouble remembering how much and which way I moved the balance bar if I mess with it while driving so I try to leave it alone.

I have the larger 54mm calipers (versus the stock 48mm) from a B3 Passat (and some Golf/Jetta III models using the 10.1 rotors). They came along with the steering knuckles from the 1990 Passat donor that also supplied my engine and transmission.

I also use the 2PSI residual pressure check valves to keep the calipers from retracting too much, to eliminate the need to "pump" the brakes once. Wilwood also sells a 10PSI version for drums. Wilwood says the 2PSI for discs are only needed when the MC's are mounted below the level of the calipers but the 10PSI is needed to compensate for drum shoe return spring pressure.
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Re: My '86 GTI build

Postby sdwarf36 » Sun Nov 15, 2015 9:47 am

I know that some road race cars run a 2psi residual valve to prevent pad knock-back from bouncing over curbs + rumble strips. Which is probably equal to bouncing up Ascutney.
I'm betting that the stock load leveling proporting valve doesn't go from 0% to 100%-it must do some restriction at all times. Mine had the linkage disconnected for years-but by bypassing it, it definately has more rear brake than before.
Translating road racing to hillclimbing:
Proper tire selection== nothing hooks up on moss or wet leaves.
Staying on the racing line==anything paved is considered good.
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Re: My '86 GTI build

Postby walterclark » Sun Nov 15, 2015 1:20 pm

sdwarf36 wrote:I know that some road race cars run a 2psi residual valve to prevent pad knock-back from bouncing over curbs + rumble strips. Which is probably equal to bouncing up Ascutney.
I'm betting that the stock load leveling proporting valve doesn't go from 0% to 100%-it must do some restriction at all times. Mine had the linkage disconnected for years-but by bypassing it, it definately has more rear brake than before.


i used that dual valve on the GTI before I replaced the brake lines and went F/R rather than diagonal. I controlled it with a threaded rod and knob from inside the car. It had some range but as you say probably nowhere near 0-100%. Since there was no other restricter in the rear lines and the rear brakes each shared half of the dual MC with a larger front, they must have had some residual restriction.
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Re: My '86 GTI build

Postby walterclark » Mon Nov 23, 2015 5:35 pm

The spacers I needed to correctly set the output shaft bearing preload in the 02A arrived Saturday so I reassembled the transmission over the weekend and this morning. I didnt like the look of the bearings on the output shaft from the 02J whenh I pulled that R:P, so replaced them. The manual said to expect to need to change the spacer when either the shaft or bearings are replaced and it seemed of the spacers I have on hand the one closest to being right left things just a little too tight. Then I decided I didnt want to reuse the 1 season used Amsoil gear lube but I only have on hand half what I needed to replace it, so that is on order. The lube I removed seems to have finished up the job of cleaning the transmission internals during the season (as good synthetic oils are supposed to do) and while probably just fine to reuse, is kind of dirty looking so off to the recycle center with that. The transmission stays on the bench a quart low and with a note until the Amsoil order arrives...I am getting old and forget things if I am not deliberate about stuff like this.

Dave Estey shared a web link with me that has a most helpful brake calculator tool. http://www.tceperformanceproducts.com/dual-bias-calc/ I learned a lot from this when I modeled what I have now. The first thing is that with the right compound I dont need to change out any brake hardware to get the stopping power I want with the manual brakes. I just need the right Mu pads on both ends of the car. What I have now is not right and the result is that I have too little front bite until (if) I get those up above 500F.

On another note, I bid on and won a 10" Samsung Nexus tablet. I have been trying to get one of these at what I would call a good price for about a year to use as a virtual dashboard. Finally. There were two auctions listed by different sellers that ended only 2 minutes apart, where the early one was a one owner primo condition example with lots of accessories and the second was a bare tablet being sold without anything by one of those used computer sellers. The second one is what I submitted to eSnipe and I got it for my price with only a couple competing bids. I think part of the reason for success is that most automated biding services wont let you bid on similar items (meaning I only want to win one of them) that end within about 5 minutes of one another, so some of my usual competition must have gone after the first one (which sold for about 50% more than my ceiling). Anyway I received the tablet Saturday and been messing with it since. I think it is going to work for me. Providing charge power to it is going to be tricky because of how it behaves (long story) but after doing some experiments I think I figured out how to handle powering it. The real HD display is stunning and I think if I shield it from direct sunlight, it will be plenty bright enough. Unlike the cheap knockoff Android tablet I bought a while back, this one is plenty fast enough to provide a smooth and up to date real time display. I still plan to have at least a few dedicated warning LEDs on the instrument panel since I can make them much brighter and they wont suddenly freeze up and fail to indicate which is always a possibility with a computer-tablet-turned-dashboard.

Couple pics posted on Facebook:

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Re: My '86 GTI build

Postby Rabbit Farmer » Mon Nov 23, 2015 10:50 pm

The transmission stays on the bench a quart low and with a note until the Amsoil order arrives...I am getting old and forget things if I am not deliberate about stuff like this.


I recall the "wrench on the camshaft" incident.

Nice looking dash. 1600 EGT! Melty melty....
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Re: My '86 GTI build

Postby walterclark » Tue Nov 24, 2015 8:06 am

That would be why its backlit in red.

The megasquirt isnt in the car right now (and for these pics), but on my bench being driven by the JimStim Megasquirt Stimulator. The Lambda to the Megasquirt comes via a CAN bus when in the car and I dont have a simulator for that...which is why its reading 0.5.
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Re: My '86 GTI build

Postby drummingpariah » Tue Nov 24, 2015 10:50 am

I'm eager to see how you mount the tablet in the dash. I don't love the typical sprung-arm tablet holders that are commonly available. I can't help but imagine my expensive electronics flying across the car and/or out the window during hard cornering.
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