Another week of some long nights and some progress. We got the MAF sensor issue sorted out on CHUGSzilla and Thundercat is once again sitting on tracks, now with all new belting! What is just baffling the bejesus out of us is this:
Thundercat is a long track machine, and it has 31 grousers per track. The original order sheet shows a grouser pitch (spacing between grousers) of 6 1/16”. But when we removed the tracks late last March we discovered the grouser spacing was 5 7/8”. That was a factory available spacing, so perhaps a previous owner mistakenly replaced the belts with new ones punched at 5 7/8”, even though it was “wrong” for this machine?
The tracks were really tight and we punched all new rubber belts with grouser spacing 3/16” longer at the correct 6 1/16” distance. It would seem they shouldn’t be so tight, right? Mathematically, 31 x 5.875 = 182.125 and 31 x 6.0625 = 187.9375. That’s 5.8125 (5 13/16”) longer, so they should be somewhat looser. Yeah, they should be, but pulling them together with a track jack they seem awfully tight. Why?
After getting the track installation finished, we did fire it up Thursday night and the engine barked to life immediately saying “Where have you two knuckleheads been? I’m ready. Let me at that snow!”
Thundercat pre-track installation. Shamefully, it’s been this way for almost a year.
The closest SnoTel site to Cedar Hollow is called Beaver Divide. It’s a bit north, and it’s lower in elevation at 8,280’, but it’s showing 132% of normal snow-water equivalent on this date, and 117% of median peak snow-water equivalent. The median peak date for that site is on March 30th. The point being, early in the year being above or below normal has less meaning because at that point not as much snow has normally fallen. But being significantly above normal late in the season portends good things for lake, reservoir, and drought considerations.
Anyway, on Sunday morning we loaded up both machines and set out for Cedar Hollow, after stopping for fuel, of course.
Another great day of snowcatting! We did get a little snow last week, but as April approaches, the temperatures are warming, and snow is melting. It was very interesting to have both machines to compare side by side in the same conditions. There is a lot of similarity, and some differences between the two machines. Honestly, I was somewhat surprised at the difference in how they performed in identical conditions. I think Scott was as well.
A quote attributed to Carole Shelby horsepower sells cars, but
A quote attributed to Carroll Shelby: “Horsepower sells cars, but torque wins races”.
The 8.1 Vortec engine in Thundercat produces a lot of torque, and the horsepower number isn’t all that impressive. Somewhat surprisingly, the 8.1 engine's horsepower and torque specs varied throughout the production years. The engine in Thundercat is a 2002, and fortunately 2002 was about the high water mark with 340 HP and 455 foot pounds of torque.
The L94 6.2 liter engine in CHUGSzilla is no slouch in the torque department with a peak of 417 foot pounds at 4,200 RPM. It’s horsepower is rated at 403 at 5,700 RPM, but due to hydraulic pump limitations, the rev limiter has been set to 4,750 RPM.
But when you look closely at the respective torque curves, the 8.1 produces at least 400 foot pounds of torque from about 1,000 RPM all the way to about 4,300 RPM. Conversely, the L94 doesn’t make 400 foot pounds until about 3,500 RPM, and then it drops below that threshold at about 5,200 RPM, though in CHUGSzilla the range only extends to 4,750 RPM. (We think in a race CHUGszilla is probably faster, as it makes its power at higher RPMs.)
But, how this plays out in the field is Thundercat could hold a higher gear in the snow conditions today at the elevations we were operating. Different snow conditions and different elevations might tell a different story. Going up the trail last week in the 1544 the sweet spot was about 3,000 RPM and third gear. CHUGSzilla was pretty happy at that same RPM and gear (all three machines have identical transmissions and ring and pinion ratios). Today, I started out leading in Thundercat, and it was perfectly content at 3,000 RPM... in fourth gear, but CHUGSzilla couldn’t hold it.
When we arrived at the "tester hill”, I just pointed Thundercat up the hill, stepped on the loud pedal, and let it climb… all the way to the top. No question… it made it look easy. Last week with CHUGSzilla on the hill, Scott had said when he was ready to start down the hill he thought “Wow, that’s a long way down”. I had the same feeling, and stopped to take a pic.
After that we continued up the trail and then turned to the east to find our play area - that for some reason snowmobiles don’t seem to go to. Good deal for us! Great snow and two snowcats performing well. We could go pretty much anywhere there weren’t trees. It was truly fun, and I’ll bet Scott also had an ear-to-ear grin, too. Experiences like that make long hours of work worth it. It was serious fun!
After stopping for lunch, we swapped machines and it was interesting to see the differences. On the inside, Thundercat is noticeably quieter. And having just driven Thundercat, its transmission just performs better. The first time we really ran Thundercat was at SV 2022 and the transmission shifted really hard. "Really hard" means uncomfortably so. After we returned from SV 2022, I spoke with the AT545 expert at the local Allison dealer and he recommended an Allison “soft shift” modulator. I bought one, we installed it, and it made a big difference. I told The Infamous WBJ1 about this, and he asked us to install the same modulator in CHUGSzilla’s transmission. So… we did. But for some reason CHUGSzilla’s transmission shifts much harder than Thundercat's. (I’ll call the AT545 expert at the Allison dealer and get his thoughts.) But playing in the snow, on the trails and climbing hills, Thundercat seemed to consistently be able to run in third climbing a hill while CHUGSzilla usually had to downshift to second.
Also when we stopped for lunch I noticed the right backup light on CHUGSzilla had departed. Great… that will be fun to try and find. (See why I call it "CHUGSzilla the PITA”?) We continued on to what I’ll call the "mine site”. Thats where this pic was taken back in 2016. (Yes, that would be Scott driving.)
Scott decided to try again in Thundercat, and here’s the result.
I tried taking some videos of Scott driving Thundercat, but the tracks would kick up snow and the windshield would get water droplets. The iPhone would focus on those, so the videos were disappointing. (One hand on the steering wheel, and one hand on the iPhone left no hands to turn on the wipers.) We backtracked along our route looking for the missing backup light. At one point Scott turned off the trail and tried climbing a bit of a berm and the tracks started spinning. He backed up, tried again and no problem. Seeing this, I thought “Hmmm, let me try CHUGSzilla's E-lockers.” So I switched on both E-lockers and climbed the berm uneventfully. Would CHUGSzilla have made it without them? I don’t know, but with them engaged it was a non issue.
On the way up I had led until climbing the tester hill, and then Scott led after that. When we returned to the tester hill on the way back we had not found the backup light. I wanted a video of Thundercat climbing the hill, and I asked Scott to drive it so I could video him. The video is a bit long because I wanted to capture the climb and the descent. Notice as Scott starts downhill Thundercat starts to slide on the snow. That gives you an idea how steep that section was!
After that, we switched machines again and I was in Thundercat and Scott was leading in CHUGSzilla. A minute or two later he stopped and climbed out of CHUGSzilla. He triumphantly held up the missing backup light! The rest of the trip back to the trailhead was uneventful.
While we certainly had fun, testing usually reveals issues requiring attention, and Sunday was no exception. Thundercat has had a noise coming from the left front track that has perplexed us, and we finally figured out where that's coming from. CHUGszilla continues to throw OBD codes. We resolved the problems with the Mass Air Flow Sensor, but the Check Engine Light came on again, and we’ll need to see what the issue is this time.
Yup, the snowcat Gods continue to punish us!
Thundercat is a long track machine, and it has 31 grousers per track. The original order sheet shows a grouser pitch (spacing between grousers) of 6 1/16”. But when we removed the tracks late last March we discovered the grouser spacing was 5 7/8”. That was a factory available spacing, so perhaps a previous owner mistakenly replaced the belts with new ones punched at 5 7/8”, even though it was “wrong” for this machine?
The tracks were really tight and we punched all new rubber belts with grouser spacing 3/16” longer at the correct 6 1/16” distance. It would seem they shouldn’t be so tight, right? Mathematically, 31 x 5.875 = 182.125 and 31 x 6.0625 = 187.9375. That’s 5.8125 (5 13/16”) longer, so they should be somewhat looser. Yeah, they should be, but pulling them together with a track jack they seem awfully tight. Why?
After getting the track installation finished, we did fire it up Thursday night and the engine barked to life immediately saying “Where have you two knuckleheads been? I’m ready. Let me at that snow!”
Thundercat pre-track installation. Shamefully, it’s been this way for almost a year.
The closest SnoTel site to Cedar Hollow is called Beaver Divide. It’s a bit north, and it’s lower in elevation at 8,280’, but it’s showing 132% of normal snow-water equivalent on this date, and 117% of median peak snow-water equivalent. The median peak date for that site is on March 30th. The point being, early in the year being above or below normal has less meaning because at that point not as much snow has normally fallen. But being significantly above normal late in the season portends good things for lake, reservoir, and drought considerations.
Anyway, on Sunday morning we loaded up both machines and set out for Cedar Hollow, after stopping for fuel, of course.
Another great day of snowcatting! We did get a little snow last week, but as April approaches, the temperatures are warming, and snow is melting. It was very interesting to have both machines to compare side by side in the same conditions. There is a lot of similarity, and some differences between the two machines. Honestly, I was somewhat surprised at the difference in how they performed in identical conditions. I think Scott was as well.
A quote attributed to Carole Shelby horsepower sells cars, but
A quote attributed to Carroll Shelby: “Horsepower sells cars, but torque wins races”.
The 8.1 Vortec engine in Thundercat produces a lot of torque, and the horsepower number isn’t all that impressive. Somewhat surprisingly, the 8.1 engine's horsepower and torque specs varied throughout the production years. The engine in Thundercat is a 2002, and fortunately 2002 was about the high water mark with 340 HP and 455 foot pounds of torque.
The L94 6.2 liter engine in CHUGSzilla is no slouch in the torque department with a peak of 417 foot pounds at 4,200 RPM. It’s horsepower is rated at 403 at 5,700 RPM, but due to hydraulic pump limitations, the rev limiter has been set to 4,750 RPM.
But when you look closely at the respective torque curves, the 8.1 produces at least 400 foot pounds of torque from about 1,000 RPM all the way to about 4,300 RPM. Conversely, the L94 doesn’t make 400 foot pounds until about 3,500 RPM, and then it drops below that threshold at about 5,200 RPM, though in CHUGSzilla the range only extends to 4,750 RPM. (We think in a race CHUGszilla is probably faster, as it makes its power at higher RPMs.)
But, how this plays out in the field is Thundercat could hold a higher gear in the snow conditions today at the elevations we were operating. Different snow conditions and different elevations might tell a different story. Going up the trail last week in the 1544 the sweet spot was about 3,000 RPM and third gear. CHUGSzilla was pretty happy at that same RPM and gear (all three machines have identical transmissions and ring and pinion ratios). Today, I started out leading in Thundercat, and it was perfectly content at 3,000 RPM... in fourth gear, but CHUGSzilla couldn’t hold it.
When we arrived at the "tester hill”, I just pointed Thundercat up the hill, stepped on the loud pedal, and let it climb… all the way to the top. No question… it made it look easy. Last week with CHUGSzilla on the hill, Scott had said when he was ready to start down the hill he thought “Wow, that’s a long way down”. I had the same feeling, and stopped to take a pic.
After that we continued up the trail and then turned to the east to find our play area - that for some reason snowmobiles don’t seem to go to. Good deal for us! Great snow and two snowcats performing well. We could go pretty much anywhere there weren’t trees. It was truly fun, and I’ll bet Scott also had an ear-to-ear grin, too. Experiences like that make long hours of work worth it. It was serious fun!
After stopping for lunch, we swapped machines and it was interesting to see the differences. On the inside, Thundercat is noticeably quieter. And having just driven Thundercat, its transmission just performs better. The first time we really ran Thundercat was at SV 2022 and the transmission shifted really hard. "Really hard" means uncomfortably so. After we returned from SV 2022, I spoke with the AT545 expert at the local Allison dealer and he recommended an Allison “soft shift” modulator. I bought one, we installed it, and it made a big difference. I told The Infamous WBJ1 about this, and he asked us to install the same modulator in CHUGSzilla’s transmission. So… we did. But for some reason CHUGSzilla’s transmission shifts much harder than Thundercat's. (I’ll call the AT545 expert at the Allison dealer and get his thoughts.) But playing in the snow, on the trails and climbing hills, Thundercat seemed to consistently be able to run in third climbing a hill while CHUGSzilla usually had to downshift to second.
Also when we stopped for lunch I noticed the right backup light on CHUGSzilla had departed. Great… that will be fun to try and find. (See why I call it "CHUGSzilla the PITA”?) We continued on to what I’ll call the "mine site”. Thats where this pic was taken back in 2016. (Yes, that would be Scott driving.)
Scott decided to try again in Thundercat, and here’s the result.
I tried taking some videos of Scott driving Thundercat, but the tracks would kick up snow and the windshield would get water droplets. The iPhone would focus on those, so the videos were disappointing. (One hand on the steering wheel, and one hand on the iPhone left no hands to turn on the wipers.) We backtracked along our route looking for the missing backup light. At one point Scott turned off the trail and tried climbing a bit of a berm and the tracks started spinning. He backed up, tried again and no problem. Seeing this, I thought “Hmmm, let me try CHUGSzilla's E-lockers.” So I switched on both E-lockers and climbed the berm uneventfully. Would CHUGSzilla have made it without them? I don’t know, but with them engaged it was a non issue.
On the way up I had led until climbing the tester hill, and then Scott led after that. When we returned to the tester hill on the way back we had not found the backup light. I wanted a video of Thundercat climbing the hill, and I asked Scott to drive it so I could video him. The video is a bit long because I wanted to capture the climb and the descent. Notice as Scott starts downhill Thundercat starts to slide on the snow. That gives you an idea how steep that section was!
After that, we switched machines again and I was in Thundercat and Scott was leading in CHUGSzilla. A minute or two later he stopped and climbed out of CHUGSzilla. He triumphantly held up the missing backup light! The rest of the trip back to the trailhead was uneventful.
While we certainly had fun, testing usually reveals issues requiring attention, and Sunday was no exception. Thundercat has had a noise coming from the left front track that has perplexed us, and we finally figured out where that's coming from. CHUGszilla continues to throw OBD codes. We resolved the problems with the Mass Air Flow Sensor, but the Check Engine Light came on again, and we’ll need to see what the issue is this time.
Yup, the snowcat Gods continue to punish us!
