My 1987 V20 Suburban with a GEP 6500 engine, 4L80E and a Banks Sidewinder turbo has been a multi year build and shake down effort. Daily driver wise the truck does great. Trailer towing the truck does great as well. However, I built the truck to overland with my wife in the mountains too. In almost 4 years of using the truck I haven’t had a chance to take it above 1000 feet elevation until last weekend.
The truck morphed from my military truck addiction and I mostly talked about it with that world. I know a pretty good number of people are here and there though. Here is a very, very long build thread over on Steel Soldiers.
https://www.steelsoldiers.com/threads/m1007-cucv-suburban-clone-build-thread.74514/
There were several reasons I haven’t let it stretch it’s legs to the mountains besides my son finishing high school and starting college from which he graduates in May. My wife having multiple health issues over the years. There was also an oil leak I couldn’t see leaking sitting still but would dump a quart out over 200 miles (mechanical lift pump) that took a while to figure out. But tires was my biggest fear. I bought a set of H2 wheels for $250 during the build which had decent tread BFG all terrains. But, the date code was 2007. They rode smooth, but I just couldn’t convince myself to set out on a long trip with them. I finally spent the money for a new set back in the summer.
COVID shut downs kept us from going anywhere since then. However, I am the leader of the local Trail Life USA troop and the kids got the idea of climbing the highest mountain in Texas. Perfect long trip test for the Cowdog. It happened last weekend.
The shortest distance from here to there is 535 miles. The 80 mph speed limit easiest drive was I-10 and 610 miles total to our camp ground. Groups can’t stay at Federal parks yet so we used a private RV park/ camp ground in White’s City, NM. I left the 3.73 axles in the Cowdog and with the 315/75R17 (34.2 inch actual) tires and 4L80E 70 mph is almost exactly 2,000 rpm. Which is just what I wanted for my driving. We all know a Square body is well, square and not the best for high speed efficient travel. I have found the happy speed is 67-68.
Since I was leading the convoy and we had a time crunch for arrival. I ran 77 in 75 zones and found myself going 82 at 2400 rpm for a 317 mile section of pure interstate. I had gotten 16.7 mpg the 200 miles of mixed traffic and mostly 75 mph but gaining 1300 feet in elevation run to Junction. Running 82 had me at 3-4 psi of boost and 600°-800° EGT depending on the immediate grade. Once we got up to 3000 feet elevation the boost was staying closer to 5 and the EGT’s keep creeping up. I actually had to break cruise a few times when the gauge passed 1100°. That was ok because it only happened when it had to downshift and throttle was at least 65%. I got 13.59 mpg for that long uphill stretch.
Once filled up in Van Horn, we tooled along for 50 miles with our goal the Guadalupe Mountains filling the windshield more and more. I did not realize until then that the road goes through something called Guadalupe Pass at 5700 feet. We were 2600 feet and around 5 miles from the park. Oh boy. I had my aviation app, ForeFlight, open on my phone so I knew we had some going up to do in a hurry. Which we did. EGT went to 1100° real quick. I found 3rd gear not locked, 50% throttle and a steady 900° EGT had us at about 40 mph with 5-7 psi boost. We topped the pass at 214° coolant temp.
This was the hardest I have ever worked that engine and transmission in 14,000 miles. All fluids were good once we got to camp. But, I was kind of in a funk since I thought the truck would do better. Having to drive by EGT at only 5700 feet elevation does not bode well for any trips into real mountains. We wanted to leave for the peak climb at 0100 the next morning. It was 42° outside at 3600 feet and the truck didn’t want to start. It just spun and spun and spun, sputter and then spin some more. I recycled the glow plugs and tried again. It finally fired up on the 3rd very extended cranking attempt. What the heck is wrong with my truck?
We reached the summit before sun rise after a very grueling hike in the cold and dark. 9 hours on the mountain had me back at the truck sitting in 72° air at 5700 feet elevation. It didn’t want to start again. I just held the starter on for the second attempt and it finally fired up. I was really starting to worry I had hurt it climbing the pass the previous day. Everything checked out again at camp. It fired right up after I let it sit for an hour even.
We left the next morning at 0600. Another long start but voltage was being drawn by the glow plugs so I didn’t think that was it. 535 miles, loosing 3100 feet in elevation and running 75-80 all day got me two tanks of 15.6 and 15.8 mpg. The truck was performing as usual and EGT’s never got over 900° no matter how steep the grade. But I was running through my mind a host of what is wrong things.
Since we were camping in the mountain time zone and my watch was still on central time. I accidentally got up an hour early for the drive home. Once packed, I spent the time researching high EGT symptoms. I don’t have an intercooler. Which probably would have helped so much I wouldn’t have even noticed. Intercoolers can be fitted to a Square body. However, I already have a huge oil cooler ip there, a huge transmission cooler and an a/c condenser. I don’t want to loose any of them which makes an intercooler big enough to help either just about impossible or extremely expensive.
Then I came across water/meth injection. Up to 300° reduction in EGT with a significant power increase at the same time. I called and talked to the people at Snow Performance. They as salesmen of course said one of their kits would do what I want.
So, all of that was written so I could ask these questions:
Do I even have a problem or is this just normal performance for an indirect injection diesel at altitude when pushed?
Does elevation make cold starting a diesel that much more of an effort?
I had #2 diesel in the tank. Could fuel be part of the long cranking issues at 3600 feet?
The only reference to water/meth injection on this site I could find was a kit for sale a few years ago. Is there anyone here that has used it on a diesel and what results did you get?
Thanks, Tim
The truck morphed from my military truck addiction and I mostly talked about it with that world. I know a pretty good number of people are here and there though. Here is a very, very long build thread over on Steel Soldiers.
https://www.steelsoldiers.com/threads/m1007-cucv-suburban-clone-build-thread.74514/
There were several reasons I haven’t let it stretch it’s legs to the mountains besides my son finishing high school and starting college from which he graduates in May. My wife having multiple health issues over the years. There was also an oil leak I couldn’t see leaking sitting still but would dump a quart out over 200 miles (mechanical lift pump) that took a while to figure out. But tires was my biggest fear. I bought a set of H2 wheels for $250 during the build which had decent tread BFG all terrains. But, the date code was 2007. They rode smooth, but I just couldn’t convince myself to set out on a long trip with them. I finally spent the money for a new set back in the summer.
COVID shut downs kept us from going anywhere since then. However, I am the leader of the local Trail Life USA troop and the kids got the idea of climbing the highest mountain in Texas. Perfect long trip test for the Cowdog. It happened last weekend.
The shortest distance from here to there is 535 miles. The 80 mph speed limit easiest drive was I-10 and 610 miles total to our camp ground. Groups can’t stay at Federal parks yet so we used a private RV park/ camp ground in White’s City, NM. I left the 3.73 axles in the Cowdog and with the 315/75R17 (34.2 inch actual) tires and 4L80E 70 mph is almost exactly 2,000 rpm. Which is just what I wanted for my driving. We all know a Square body is well, square and not the best for high speed efficient travel. I have found the happy speed is 67-68.
Since I was leading the convoy and we had a time crunch for arrival. I ran 77 in 75 zones and found myself going 82 at 2400 rpm for a 317 mile section of pure interstate. I had gotten 16.7 mpg the 200 miles of mixed traffic and mostly 75 mph but gaining 1300 feet in elevation run to Junction. Running 82 had me at 3-4 psi of boost and 600°-800° EGT depending on the immediate grade. Once we got up to 3000 feet elevation the boost was staying closer to 5 and the EGT’s keep creeping up. I actually had to break cruise a few times when the gauge passed 1100°. That was ok because it only happened when it had to downshift and throttle was at least 65%. I got 13.59 mpg for that long uphill stretch.
Once filled up in Van Horn, we tooled along for 50 miles with our goal the Guadalupe Mountains filling the windshield more and more. I did not realize until then that the road goes through something called Guadalupe Pass at 5700 feet. We were 2600 feet and around 5 miles from the park. Oh boy. I had my aviation app, ForeFlight, open on my phone so I knew we had some going up to do in a hurry. Which we did. EGT went to 1100° real quick. I found 3rd gear not locked, 50% throttle and a steady 900° EGT had us at about 40 mph with 5-7 psi boost. We topped the pass at 214° coolant temp.
This was the hardest I have ever worked that engine and transmission in 14,000 miles. All fluids were good once we got to camp. But, I was kind of in a funk since I thought the truck would do better. Having to drive by EGT at only 5700 feet elevation does not bode well for any trips into real mountains. We wanted to leave for the peak climb at 0100 the next morning. It was 42° outside at 3600 feet and the truck didn’t want to start. It just spun and spun and spun, sputter and then spin some more. I recycled the glow plugs and tried again. It finally fired up on the 3rd very extended cranking attempt. What the heck is wrong with my truck?
We reached the summit before sun rise after a very grueling hike in the cold and dark. 9 hours on the mountain had me back at the truck sitting in 72° air at 5700 feet elevation. It didn’t want to start again. I just held the starter on for the second attempt and it finally fired up. I was really starting to worry I had hurt it climbing the pass the previous day. Everything checked out again at camp. It fired right up after I let it sit for an hour even.
We left the next morning at 0600. Another long start but voltage was being drawn by the glow plugs so I didn’t think that was it. 535 miles, loosing 3100 feet in elevation and running 75-80 all day got me two tanks of 15.6 and 15.8 mpg. The truck was performing as usual and EGT’s never got over 900° no matter how steep the grade. But I was running through my mind a host of what is wrong things.
Since we were camping in the mountain time zone and my watch was still on central time. I accidentally got up an hour early for the drive home. Once packed, I spent the time researching high EGT symptoms. I don’t have an intercooler. Which probably would have helped so much I wouldn’t have even noticed. Intercoolers can be fitted to a Square body. However, I already have a huge oil cooler ip there, a huge transmission cooler and an a/c condenser. I don’t want to loose any of them which makes an intercooler big enough to help either just about impossible or extremely expensive.
Then I came across water/meth injection. Up to 300° reduction in EGT with a significant power increase at the same time. I called and talked to the people at Snow Performance. They as salesmen of course said one of their kits would do what I want.
So, all of that was written so I could ask these questions:
Do I even have a problem or is this just normal performance for an indirect injection diesel at altitude when pushed?
Does elevation make cold starting a diesel that much more of an effort?
I had #2 diesel in the tank. Could fuel be part of the long cranking issues at 3600 feet?
The only reference to water/meth injection on this site I could find was a kit for sale a few years ago. Is there anyone here that has used it on a diesel and what results did you get?
Thanks, Tim
