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I also run a fan but it's mounted on the cooler, and my capacity is the same as yours. It's nice to see your numbers under 180 degrees.

I remember pulling a broken diff during a 24 hour race at 2am (14 hours into the race - broken teeth on the R+P). At 6am it was still hot to the touch!
We cleared the garage with the burnt gear oil smell!! it was horrible...
 

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Discussion Starter · #1,262 ·
After a strong outing at the Barber Champcar race I learned that Grumpy has qualified for the Champcar National Championship race to be held at Road America in April. The rules are a little fuzzy but we may need to participate in 5 "races" to qualify and we only had 3 so I registered for Road Atlanta.

Repairs and updates included a new clutch, a short shifter, the fuel pressure gauge, alternator belt tensioner, a new light bar set-up, and other small items. I had the car ready a couple of weeks before the race and finally built a tire rack and fuel jug carrier for my trailer. I also added a 48" locking tool box and brackets on my fuel drum. Now I can carry everything to the track on my own.



After a 3.5 hour wait in the Tech line Friday we were ready for some testing. I took the car out for a shakedown and all was well except that 4th gear did not like downshifts. It was fine under power on upshifts but the 5-4 shift was not happening. We just drove around the problem all weekend. We put a new driver in next and he learned the car and track quickly. Mike and Nabil put in about 10 Laps each and we scrubbed in a set of brand new spares (and gave them a heat cycle, which seems to be important for RE71s). We did some final prep and headed away for Mexican, some video review for Tom (the new guy) and a good night's sleep.

Saturday morning Nabil took the car down to pit lane 15 minutes before the start of the race and I noticed that the dash was flashing... and the voltage was 11.5. After checking that the alternator belt was still on and had tension we guessed it was a dead alternator and Mike zoomed to Advance out for a replacement and new battery (just in case). We replaced the alternator and fortunately there was a Black Flag "come-to Jesus" meeting due to some very poor driving and decision making in the first 30 minutes. Nabil went back out with 14+ volts and drove us into the Top 15. A new driver to the team took the next stint and turned solid laps for an entire stint with no issues except a slow oil leak. He came in a little early due to a loss of power which turned out to be a disconnected VTC clip. He also mention hearing a noise like he ran over something on track. It turns out that idler on the belt tensioner I built was not quite the same width as the belt and a narrow section that wasn't supported finally separated and was tossed around striking the VTC connector (and probably smacking the hood which caused the noise that Tom heard). I reconnected the VTC and added some duct tape to secure it and we sent Mike out with a full tank.

Mike started turning stellar lap times as he negotiated traffic. He broke the PR of the car at RA within 5 laps and continued to get faster, eventually turning the FTD for the entire race (1:40.7). After an hour he radioed that the car had lost power and came into the pit. It turns out that the sliver of belt that let go also damaged the crank trigger wires. None were broken but all were bare wires. I taped them up and sent Mike back out, where he continued his run of stellar lap times.

The slow oil leak had us adding 1/2 quart at each stop but the pressure stayed high while driving. I was next up and got myself buckled in while the team checked the oil.. and looked down to see the tensioner idler wheel missing! Since the belt drives the ALT and water pump we were lucky that Mike came in when he did, it wouldn't have taken long to overheat in a major way. The only way to tension the belt now was spacing the alternator away from the pump with washers which is a pain in the ass with the engine out of the car, and worse with a hot, installed engine. I finally had to leave the driver seat to help with the repair and we lost 20 minutes in the process.

I jumped into the driver seat and had one of the most enjoyable stints ever in the Supra. I came out of the pit behind the lead Porsche 944 and we proceeded to have a 30 minute respectful battle through traffic. The car was handling great and I went 1.2 seconds faster than ever at RA (1:41.7). I was a little disappointed when the low-fuel light came on after 1:40 of green flag running. I dove into the pit and we put Nabil back into the car with rain on the way. We also replaced the left front tire to give him the best chance for decent rain laps.

The rain started about 5 laps later and got worse as the stint progressed. He drove straight off in T10 and had the presence of mind to avoid the sand and drive up the grass along the wall. Then later he had a small off in the esses with minimal damage.

We decided to put me back in the seat next and I entered the track at dusk in the rain. Within 10 laps it was dark, and then the snow started. Cars were leaving the track in exciting places almost every lap and the tow trucks never got a rest. Around 6:30 the conditions were terrible and after 6 laps of full course yellow they finally brought the field into pit lane. During the last few laps the track conditions got worse and it was interesting to see cars struggle to find traction between T10b and the bridge, and finally a car hit the bridge under FCY. The race was called at 7pm and I would not have gone back out even if they decided to race more - it was dangerous.

We ended the race in P18, 3rd in class, and Mike Taylor ended with FTD.

It is now time for GB2!

Sample video with the race FTD

 

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I just caught up, that was an awesome race and write up anove there!

Well here comes Grmpy 2.0. Its looking nice! Those strut tower supports will help a lot, I did that to one of my cars, plus bars on the front down to the frame rails too.
 

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Discussion Starter · #1,269 ·
An update on Grumpy 2.0:

All suspension has been swapped to the new chassis. The Fuel Cell is installed but not fully plumbed yet. The new containment seat is in for test fitting. A new battery holder is welded in and the fire system in installed.





 

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Do you have a photo of the frame rail bars?
Yup.
Do you have a photo of the frame rail bars?


From this build update, which covers fixing a rusty lower battery mount and the fallout from leaking acid into the frame rail. The last part of the update covers strengthening up the front end so it may be of interest to you (also shows how I reinforced and cleaned the attachment points)...
 

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Discussion Starter · #1,271 ·
OMG!!! That project is incredible, I would never have the patience or skill to attempt the depth of repairs that you did.
 

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Discussion Starter · #1,272 ·
The Fuel cell adopted the space where the diff cooler and pump lived in GB1, so I had to do some repackaging. There will be a bulkhead that separates the cell and diff cooler from the driver compartment.

I was able to cut the pump/cooler mount out of GB1 and make it fit in GB2. Only one hose will need to be lengthened.








Then I tackled the motor mounts. The original mounts were 1/4" steel and had to be modified when I moved the engine forward for the new oil pan (added material because I'm Lazy and didn't want to make new mounts). I was able to cut 2 lbs of steel off the exhaust side mount, but the intake side needed a new one. After reading too much I decided that 3/16" steel should be plenty strong for this application. I was also able to use 3 of the big bosses on the block to bolt it to, but all three were in different planes. That's why you'll see two spacers welded to the back.

New and Old



 

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Discussion Starter · #1,274 ·
I have a target test day June 11th. I hope to have the oil pan issue solved this week, then I can install the engine and drivetrain. After that I'm having a friend rewire the car (he does car wiring for a living). I plan to fabricate a new switch panel and accessory electrical panel away from the floor.
 

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Discussion Starter · #1,275 ·
The oil pan came back with some reinforcement and it took a couple of days to resolve some interference issues with the pickup tube. Then it was time to modify a K24Z3 water pump housing as a solution for tensioning the alternator belt. A good write-up of the process was done by a friend of mine with a KMiata swap: KMiata – Belt Tensioner

Today the engine went into GB2 with an SC300 W58 transmission. The shifter housing on this trans sits about 4" rearward from the Mk2 shifter location and puts the shift lever in a perfect place.



 

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is it the tripod shifter?
also I just noticed you used clear tubing for the fuel cell, I believe Lemons requires the reinforced tubing if it is not in it's own containment (ie trunk) if you plan on running it in Lemons at all. Are you going with a dry break?
 

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Discussion Starter · #1,277 ·
No tripod on the shifter, but the swan-neck lever of the SC300 puts it in a perfect position.
Champcar will require me to build a bulkhead between the driver and hatch area, so the clear pipe shouldn't be an issue.
 

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Diff cooler question here. At what temps does the diff fluid break down and fail to lubricate properly? # or 4 hundred degrees or is it more? Depends on additives and weight of oil also.
Too hot to touch with bare fingers is around 150*. Agreed? Diff oil cooler looks like a great idea but how do you know that it was needed? Bearing or gear failures ? Excess oil frothing?
Adding aluminum cooling fins to the diff looks good on paper. Couldn't hurt.
Thanks in advance. :sneaky:
 

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Discussion Starter · #1,280 ·
Dave, I have no science to back up my decision to install an oil cooler. I was using good quality 75W-90 gear oil with friction modifier added, and changing it after every race. My first diff failure happened at a 24-hour event - 18 hours into the race on a hot summer day/night. My 2nd diff failure occurred during another long race. It's possible that the oil temp had nothing to do with the failures, but with only 1 quart in the entire system I can tell you that it gets extremely hot. The diff we removed at 2am (18 hours of racing) was still hot to the touch 3 hours later on the ground. Both failures resulted in teeth broken off both pinion and ring gears.

From what I have read, temps above 140 start decreasing the life of gear oil. Every 20 degrees above that cuts the service life in half. The failure temp depends on the quality of base stock and additives.

I can't imagine a street-driven Supra requiring a cooler unless it's driven on the track with high HP. A good quality oil changed at regular intervals will survive a pretty good beating on track days. Endurance racing is a whole different beast. I added the cooler to double the volume of oil circulating in the system and it seems to be working (I still don't monitor temps).
 
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