We got home last night, a day earlier than intended but that let us beat the winter weather that showed up today (perfect weather to go pick up a motorcycle). I haven't crawled under the RV, we just unpacked it and stuffed it back in the shop before the weather dropped to below freezing and ice. With that said, I made a lot of observations of the results of work over the 2500+ miles driven, and am really pleased overall.
The oil leak I was having from the oil filter housing is now fixe, as is the leak from the oil pan. No oil dripping there at all, at least not that I noticed from the side. And that's a good thing.
The remote oil cooler definitely is helping. The hottest oil temp I saw on the trip was about 215. However, the single cooler is a bit more of a restriction than I'd like it to be, and I think that in the summer when temps are hotter it won't cool as well as I'd like. So I'm going to do like I did for the transmission and run a second cooler in parallel. That will reduce the restriction and increase summer cooling. The oil didn't "overcool", even with OATs in the range of 13F so the system seems to work well.
Before this trip I'd installed a new fan-forced heater in the bedroom with a solenoid to shut of coolant flow when it's not turned on. It was cold enough that we were running that heater for more than 50% of the trip, and also running the heater up front. I'd insulated the hoses going from the engine up front so as to help that coolant stay hotter. Even in at night in sub-freezing temperatures, we were plenty comfortable in the RV - something that was just not the case before. We'd need to be running the generator and electric heaters.
Now, the big one - the electric fan cooling. I definitely learned a lot about the bus's cooling system on this trip. The short version is that the electric fan cooling absolutely works, and I have little doubt that it will work in the summer. OATs ranged from 13F up to about 65F. On our first leg leaving Kansas, it was in the low 20s/high teens and the fans didn't run at all. Natural airflow kept the coolant temps at 195 or so. As an added benefit, this helped the engine heater work better since the coolant was warmer than the <190 it would run with the giant fan running.
However the next morning heading towards Denver, the fans were working, and I would notice some odd behavior. The fans would seem to be doing just fine, and then all of a sudden the engine temp would climb and I would have a hard time getting it to cool back off. Pull over, temps would go back down to 195F or so very quickly (normally at idle the fans don't run at all I've found). Repeat process. After the second or third time this happened, I managed to catch what was occurring after I pulled over. The fan controllers were overheating and then shutting the fans off. Then they would ramp them up and back down again. When pulled over, it didn't take long for things to cool off and then it would go back to normal. I experimented a bit and found that if I limited the PWM to a max of 70% (so max 70% fan capacity) this wouldn't happen. I managed to figure this out before heading west from Denver, and it worked for the rest of the trip.
When I climbed up from Denver to the Eisenhower Tunnel it was 60-65 or so in Denver, and about 45 at the tunnel. That's far from worst case, but it wasn't frigid winter temps (like we then had in Grand Junction the next morning when we woke up). The fans didn't have trouble keeping the engine cool. The same was the case for any of the other numerous climbs I did on this trip. This was a mountainous, high altitude trip. In normal cruise, the engine mostly ran at around 200-205F (which is where Cat says it's most efficient), and extended higher throttle runs would get it to 210F (which is where the thermostats are fully open) and it would come back down after that. Since I did this all with 70% maximum fan PWM (which should theoretically be around 70% of max airflow), that gives me some extra margin.
One thing I was concerned about was reduced engine braking efficiency since the fan is no longer there to absorb all that horsepower. And the engine braking is worse. However, not as much worse as I had expected it to be. I'm still able to keep things plenty controlled. The Teton Pass is the only time I've felt that engine braking was marginal, and so I might be more worried there. But for everything else, it's fine.
Is it faster? Yes, absolutely. It's a 30,000 lbish bus with the Rover in tow, and makes 330 HP rated. It will not be fast. But the engine is definitely more responsive, and there is a lot more reserve horsepower. Acceleration is better. Before, above 2,000 RPM it felt like it would hit a wall. 75 MPH cruise was very strained. Now on level ground without a headwind, 75 isn't a strain on the engine. Heading home I had the cruise set at 80 for a while, and the engine felt unstressed and EGTs were even below 1000F (which is quite low for cruise on this engine).
Mileage? Way better. With the cruise set at 70-80 on level ground I was seeing 9+ MPG, something I'd never seen before. The worst I saw was still 7 or better, which is a far cry from the 5.5 I had previously gotten as my worst fuel economy.
The intercooler is one area where I may need to think about this some more. The engine basically doesn't need the fans at all at idle. Sit there and there's enough natural convection and airflow in most cases that it seems that it will keep it at 195 or so on its own. Maybe it'll run at the lowest setting for 30 seconds and shut the fans back off. What that ends up meaning is that if you floor it getting on the highway, the intercooler has no cooling and the induction air post-turbo gets really hot. I found out that the highest the ECU can read is 230F. Previously, the highest I'd ever seen was 175F, and now normal with lower fan airflow seems to be in the range of 160-170F. The higher temps in normal cruise aren't an issue as far as I'm concerned, but at full throttle if nothing else that means I'm giving up a good amount of horsepower (even though it's still faster). So, I have to decide what to do there. I'd be really curious to try water/methanol injection. I've never messed with it before and it seems well suited for the use case of cooling for shorter duration high boost runs. However probably the more logical option is to add a boost sensor to the Arduino and set in a loop to put the fans to full when boost gets above a certain amount.
So, there are some tweaks I need to do. Addressing induction air temps (at least for full throttle highway acceleration) is one. Another is fixing the overheating fan controllers. I have a few tests I want to do before moving them and redoing wiring, but I think this overall isn't insurmountable. If the controllers themselves can't handle the current, I may need to try to make something work with different (higher power) controllers. Now that I know how to make the general idea work, that wouldn't be too difficult.
When I add in the second oil cooler, I am also thinking about adding in a logic to ground (turn on) the oil cooler fans if the engine temp is above a certain value, since that will help cool the engine. However I think that the oil cooler fan likely naturally turns on anyway at that point.
I also want to seal up some of the air gaps around the radiator. There clearly is a level of natural airflow, and I think that will help force a bit more air through the radiator. I had figured I'd do that after I proved out the basic system.
All in all, for engineering multiple new systems, getting all this back together, doing one 20 minute test drive, and then driving it 2,500 miles, I'd say it went pretty damn well.
