My '86 GTI build

[Rabbit Farmer]

What did you think of Wavetrac LSD?

Found this while looking for information on this LSD.

[walterclark]

For the most part it felt like the Quaife and Peloquin.

Until I compared this years Ascutney videos with last years, I wasnt sure the unique feature of the Wavetrac that keeps power to the ground even when one wheel is unloaded was doing much. Based on this pair of clips from this year (first clip) and last year it would seem I now have less inside tire wheelspin coming out of a tight turn.



Seems I am a creature of habit. Despite having slightly different gear ratios and different brake master cylinder/pedal setup, I apexed this turn at exactly the same speed in both cases.

This is Wavetrac's video showing basically how it works:

[walterclark]

I signed up for a track day at Thompson in June. The purpose is to give me a place and the time to dial in the rear brake bias. Only problem is they want things like rear view mirrors and working brake lights since I will not be the only person on the road.

Found the mirror that came off the drivers door, well 2 actually...A red one that came off the actual door that is on the drivers side right now, and a black one that was on the door I crunched at Mt Washington. Bolted up the black one.

The inside mirror was a wide angle Longacre until I switched to a backup cam and a little monitor, then it and one of the tabs on the roll cage that mounted it (drivers side) came out (the tab then looked like a "helmet splitter" with no mirror attached). Found one of the OEM inside mirrors (I probably have 3-4) and mounted it to the Longacre mirror tab on the passenger side. Should be good enough for a day.

For the brake light, I had kept the stock pedal switch and part of its bracket but decided a while ago it was too much work to fab up a solid bracket for it to work with the Wilwood pedal set. I then got a kit from Jegs that adds a pressure switch to the brake lines for the lights, but I never installed it...The only one who ever follows me is Don and he stays well back on the bring down so doesnt even notice I dont have them. I just need to install that...On one of the front lines since they get the majority of the brake pressure. Spent an hour driving around looking for a couple 3/8"-24 3/16" IF tube nuts. Here is a tip: Advance Auto Parts "In Stock" on their web page is meaningless. Took till the 3rd store before I found them...And I do me I. The parts people looked at me like I was from outer space when I said I needed "a couple 3/8"-24 3/16" brake tube inverted flare tube nuts". In each case they ended up walking me "in back" so I could get what I needed (or in 2 of the places confirm they didnt actually have them).

I think I will use the Hoosier A6's that I ran in 2013 and up until CTTC 2014 as they have decent tread left but have hardened up enough that I dont want to use them at a hillclimb. I know the last "Autocross" tire I ran at a road course (Hancook's at Lime Rock) were roasted pretty badly by the end of 2-15 minute sessions, but they were almost new at the time. Maybe these will hold up if I pay attention and pit when they start to feel greasy.

[walterclark]

The spring I ordered to add to the shifter arrived.



Added it in parallel with the original as shown. Really firms up that 3-4 gate "neutral" position so it should not be the least bit difficult to find 3rd.

Couple things I also found.

I had to partially dismantle the stuff you see in the pic to add the spring and when I reinstalled it I adjusted things again. This time I read a few posts regarding adjusting the shifter and realized that last time I may have left it set so it was sort of predisposed to find 1st more easily than it should while looking for 3rd. I think I corrected it this time.

Another thing that I guess I just didnt really notice before is that when you take your hand off the shifter, whether it is in 1st, 3rd, or 5th (or 2nd or 4th) the left-right position of the shift lever returns to something very close to the 3-4 position. Kind of odd, but not a problem so long as I remember it does that.

[walterclark]

I tried something relative to the Wavetrac today...

I put the right front control arm on a floor jack so the tire was not in contact with the ground, set the rest of the car on its tires and tried to move it in 1st and Reverse. In each case it would start to move then stop before actually getting anywhere and then the RF wheel would spin.

So, the "lock-up" it is offering me currently doesnt permit any useful torque to be applied to the tire on the ground as far as I can see.

Wavetrac literature suggests the stock setup is suitable for "most" applications but there are optional parts available if it isnt enough. Unless it behaves differently somehow after "break-in" or currently while in use than it just did for me in this little test, I think I am going to need some of those optional parts. I sent email...

I also installed that brake pressure switch today. I hate "NPT" fittings. The sensor uses a steel 1/8 NPT male fitting that goes into the brass NPT/IF/IF Tee in its kit. Couldnt get it tight enough to stop it from weeping from the NPT port until I added Teflon pipe tape and was able to crank it down a bit further (it was even sucking air in on the MC backstroke before the tape and extra tightening the "lube" of the tape permitted).

[walterclark]

Todays project was to dig a bit further into and fix the speedo problem...essentially it was shutting down above 50MPH. I guessed it was an input overload to my converter module as VR sensors normally increase output as the pule rate increases. When I opened the converter module a few days ago I found a broken wire on the sensor input and assumed that might be the issue. But after fixing the broken wire it continued to shut down above 50.

I re-measured the VR output, this time by spinning the hub up to and above 50, and learned that this VW sensors output plateaus around 3V and 20mph. The circuit on the module input I built assumed a continuous increase in voltage with frequency (>10V at higher speeds is quite normal for a VR sensor) and so it has what amounts to a high frequency filter that reduces the signal getting to the electronics. In theory this circuit equalizes the voltage so it is always about the same level regardless of frequency. Since the input signal flattened out on its own already the input filter of the module was essentially reducing the signal as frequency increased, so by around 50MPH, the input level dropped below the detection levels of the circuit downstream of the filter. I disabled the filter and retested. I got solid speeds up to 70MPH which is the fastest I can spin the hub with my cordless drill.

That is the risk with OEM type sensors. Since they are an automotive replacement part, no one publishes the specs on them so they might not behave the way a "standard" sensor (in this case a generic "off the shelf" VR) normally behaves.

[Rabbit Farmer]

Good information on the LSD. I am wondering if it is beefy enough for my application.... specifically, will it take the abuse of full throttle and the constant bumps (light wheel, spin, full weight back on tire, repeat until the top of the hill). Plus, will it give me my two wheel drive or the one wheel drive that you have shown in your test. I will have to look into the optional parts.

[KevinGale]

...
Wavetrac literature suggests the stock setup is suitable for "most" applications but there are optional parts available if it isnt enough. Unless it behaves differently somehow after "break-in" or currently while in use than it just did for me in this little test, I think I am going to need some of those optional parts. I sent email...

On their end: "Hey Joe, some guy just emailed and said the placebo effect isn't enough for him and he needs parts that actually do something."

[sdwarf36]

Oh- I see you've dealt with phantom grip before.

[walterclark]

Steve and I have exchanged email with Wavetrac (me a couple times).

They insist my "test" is not a valid one for their diff as it was never designed to move a car from a stop with an axle broken or one wheel off the ground, but that it DOES work when the car is moving and a drive wheel lifts off the pavement.

The turn at Okemo check 3 always causes me problems with the inside front lifting after the apex and I have numerous videos showing the RPM jumping up and the car just coasting for about 2 seconds while I wait for the turn to straighten enough to get some grip on the inside tire. It also happens at other places but for a much shorter time and since the diff runs in a normal TBD (open) mode until enough left and right output shaft speed differential cranks the Wavetrac mechanism together (not sure how much of a rotation or rotations this is), it may not be obviously different than a TBD in some of these places.

This is a clip from check 3 Okemo 2 2014, my last and fastest run on Sunday, so by then I had learned how to manage the throttle better. If you look carefully enough you can see my speed decrease for a moment after I pass the apex where I should be able to go WOT, but cant. This clip is from a composite video/datalog I made then, and I added the TPS.



I pieced these clips together from this year and last years Acsutney 1. The first is with the Wavetrac in the 02A, the second is with the Peloquin in the 020. I have datalogs but didnt initially include them in any post production videos so they are not here either.



The tires are not the same ones, but they are the same model and have the same relative age and use in each (almost full season from previous year).

Things other than the difference between the Wavetrac and Peloquin that could contribute to the difference seen include speed at the apex, how aggressive I was with the throttle, and the small difference in gear ratios between the trannies. The car speed when I applied the throttle in each clip appears to be exactly the same and the throttle went to 100% similarly in both cases but in the older video I backed it out to 70% and got back onto it when it hooked up again so it may have well spun longer otherwise. The RPM in the older vid was around 4200 and in the newer one 3900, so there would be about 3 ft-lb more torque available in the older one.