Attention: TDR Forum Junkies After reading posts about surging and big turbos for towing I figured that I would post my observations...
I just came back from a 700 mile towing trip to Reno-Carson City and back to Elko to test out my new-used car trailer. The route involved 550 miles of 70-75 mph I80 (2 "big pulls" w/ Emigrant and Golconda Summits) with 50 miles city and the remaining on US#395 (55 to 0 to 70 to 0 mph etc. ) to visit RankRam.
I figured I was at ~15,000 lbs total, with the windcatcher windshield up on my jeep, spare jeep/truck parts, etc. . My trailer is surprisingly heavy for a car trailer in that the trailer empty combined with the switch to winter diesel cost me about 1. 5 mpg (Yes, I drove with my empty trailer for 1/2 tank just to see!). I towed with the 100 HP injectors, TST 1x0 for timing only, 25% on the MP-8, which should put me at about 400-425 RWHP based on my previous dynos. These are my results with the SPS66 turbo:
->Flat cruise at 75 mph: 8 psi boost, 850* EGT
->Rolling hill at 75 mph: 10-12 psi boost, 900*-925* EGT
->Easy part of above summits 75 mph: 20 psi boost, 1000* EGT
->Steep part of above summits 75 mph: 25-30 psi boost, 1050* EGT
->overall mileage = 12. 8 mpg (I hate winter fuel!)
I finally noticed turbo surge 3 times during this trip and now that I know what it is I know for sure that I also experienced it once empty 2 weeks ago. These were the surge conditions:
1) 1X empty and 2X towing: interstate on-ramp when someone in front of me slowed down, but I was too lazy too downshift at about 1300 rpm and I had to feather the throttle. If I more than feathered the throttle then no surge.
2) 1X steady cruise on US#395 and some dude cut in front of me and slowed down to where I got in between 5th and 6th gear normally, but decided to stay in 6th - again having to feather the throttle.
I think in terms of the surging, the performance cam probably brings the surge rpm lower since the engine is allowed to breathe easier and consume the air the turbo is generating. In my case the rpm is in the lugging range anyway for all intents-and-purposes. That is, I should have downshifted to have the power to get out of these situations anyway in terms of good defensive driving. Also, the surging did not produce any fluttering in the boost gauge as others have reported. This is interesting as the only surge sympton I had was a real faint chaw-chaw-chaw sound like the sled pullers make at the end of a pull, but a heck of a lot quieter. I did have to turn the stereo down to hear this sound; otherwise it was so quiet and could be mistaken for road noise.
Some other things I noticed:
->With 100 HP injectors the truck does throw continuous slight black smoke until fully up to operating temp. I think if I would have turned the fuel pressure (MP8) down this would have helped.
->I tried a couple of times turning the TST up to level 2, but it just fuels too hard when towing with my mods. Basically goes like this: clear-black-clear black-clear-black through every shift
->Almost every stop I started in 1st gear, which ticked a lot of the Christmas shoppers off, but they sure get surprised when they think they can wing around me by the time I am in 3rd - especially with how fast this turbo spools when it hits 10 psi.
->driving on US#395 with the sudden speed changes wasn't too bad even if I kept it in 6th. As long as I rolled into the throttle rather than feathering it, the turbo did fine.
->in the 20-30 psi boost range the EGT basically just sat at ~1000*. Extrapolating out that would be ~1200*EGT at ~40 psi ~400-425 RWHP.
->I don't know if I would want to tow at any higher power levels than what I did. It was more than enough to pass anyone on the hills with power to spare to get me into trouble if I dared. Further, in the previous point the EGT were still in check at the power level I ran at.
What's the verdict?
1) So far the turbo hasn't disappointed me. I need to tow a heavier load to fully see how it does. Anyone have a trailer they will let me borrow? :-laf
2) However, the surge thing intrigues me. The cam probably dropped the surge rpm into lugging territory anyway so I think the lack of a cam upgrade would definitely make me want to switch back to a smaller turbo. I'll see how it goes over the next 6 months or so. I know that if I did go back to a 62 mm, I would hate it empty on the back roads because I couldn't stay in the throttle as much. There is no icing on this cake!
Here's my rig from this morning:
I just came back from a 700 mile towing trip to Reno-Carson City and back to Elko to test out my new-used car trailer. The route involved 550 miles of 70-75 mph I80 (2 "big pulls" w/ Emigrant and Golconda Summits) with 50 miles city and the remaining on US#395 (55 to 0 to 70 to 0 mph etc. ) to visit RankRam.
I figured I was at ~15,000 lbs total, with the windcatcher windshield up on my jeep, spare jeep/truck parts, etc. . My trailer is surprisingly heavy for a car trailer in that the trailer empty combined with the switch to winter diesel cost me about 1. 5 mpg (Yes, I drove with my empty trailer for 1/2 tank just to see!). I towed with the 100 HP injectors, TST 1x0 for timing only, 25% on the MP-8, which should put me at about 400-425 RWHP based on my previous dynos. These are my results with the SPS66 turbo:
->Flat cruise at 75 mph: 8 psi boost, 850* EGT
->Rolling hill at 75 mph: 10-12 psi boost, 900*-925* EGT
->Easy part of above summits 75 mph: 20 psi boost, 1000* EGT
->Steep part of above summits 75 mph: 25-30 psi boost, 1050* EGT
->overall mileage = 12. 8 mpg (I hate winter fuel!)
I finally noticed turbo surge 3 times during this trip and now that I know what it is I know for sure that I also experienced it once empty 2 weeks ago. These were the surge conditions:
1) 1X empty and 2X towing: interstate on-ramp when someone in front of me slowed down, but I was too lazy too downshift at about 1300 rpm and I had to feather the throttle. If I more than feathered the throttle then no surge.
2) 1X steady cruise on US#395 and some dude cut in front of me and slowed down to where I got in between 5th and 6th gear normally, but decided to stay in 6th - again having to feather the throttle.
I think in terms of the surging, the performance cam probably brings the surge rpm lower since the engine is allowed to breathe easier and consume the air the turbo is generating. In my case the rpm is in the lugging range anyway for all intents-and-purposes. That is, I should have downshifted to have the power to get out of these situations anyway in terms of good defensive driving. Also, the surging did not produce any fluttering in the boost gauge as others have reported. This is interesting as the only surge sympton I had was a real faint chaw-chaw-chaw sound like the sled pullers make at the end of a pull, but a heck of a lot quieter. I did have to turn the stereo down to hear this sound; otherwise it was so quiet and could be mistaken for road noise.
Some other things I noticed:
->With 100 HP injectors the truck does throw continuous slight black smoke until fully up to operating temp. I think if I would have turned the fuel pressure (MP8) down this would have helped.
->I tried a couple of times turning the TST up to level 2, but it just fuels too hard when towing with my mods. Basically goes like this: clear-black-clear black-clear-black through every shift
->Almost every stop I started in 1st gear, which ticked a lot of the Christmas shoppers off, but they sure get surprised when they think they can wing around me by the time I am in 3rd - especially with how fast this turbo spools when it hits 10 psi.
->driving on US#395 with the sudden speed changes wasn't too bad even if I kept it in 6th. As long as I rolled into the throttle rather than feathering it, the turbo did fine.
->in the 20-30 psi boost range the EGT basically just sat at ~1000*. Extrapolating out that would be ~1200*EGT at ~40 psi ~400-425 RWHP.
->I don't know if I would want to tow at any higher power levels than what I did. It was more than enough to pass anyone on the hills with power to spare to get me into trouble if I dared. Further, in the previous point the EGT were still in check at the power level I ran at.
What's the verdict?
1) So far the turbo hasn't disappointed me. I need to tow a heavier load to fully see how it does. Anyone have a trailer they will let me borrow? :-laf
2) However, the surge thing intrigues me. The cam probably dropped the surge rpm into lugging territory anyway so I think the lack of a cam upgrade would definitely make me want to switch back to a smaller turbo. I'll see how it goes over the next 6 months or so. I know that if I did go back to a 62 mm, I would hate it empty on the back roads because I couldn't stay in the throttle as much. There is no icing on this cake!
Here's my rig from this morning:
. 
