| Author | Message | ||
| Mark R. Obtinario (Cowlitzcoach)
Registered Member Username: Cowlitzcoach Post Number: 129 Registered: 4-2001 Posted From: 204.245.250.139 Rating: N/A |
Hi, Just this week TriMet, the local transit agency in Portland, OR, announced the completion of a test of electric cooling fans on several of their transit buses. The test results so far have been very favorable. According to the press statements, the electric fan equipped buses had a 10% decrease in fuel use. With fuel prices here in the wet NW averaging over $3.00 per gallon, a 10% decrease in fuel use translates into a significant savings. Over the next few months the whole fleet is going to be converted to electric cooling fans, up to eight fans per bus. I think several caveats need to be considered before one makes a lot of changes on one's own bus. Portland, OR does not normally get that hot, ever. Once in a while the temps will go above 90 degrees and once in a blue moon the Hg will go above 100. None of the TriMet buses are equipped with A/C. All of the buses used in the tests were equipped with modern power packages, none of which were 2-cycle DD's. Portland, OR does have some pretty good and steep hills. But the longest and steepest is not more than three miles and the top of the hill is not much more than 1000 feet in elevation. I am thinking that if the engineering is well thought out I think electric fans can replace engine driven fans, particularly in transit use. In transit use the engine is either idling or coasting more than it is working hard. I am thinking the majority in fuel savings occurred while the bus engine was idling at stops, a time in which a lot of cooling is not required. With up to eight small cooling fans cooling the only amount of air flow that is required is used. With engine driven fans it is a sort of an all or nothing propisition, even with fan clutches. It will be interesting to see how well the experiment will work as the age of the buses increase. In any case, it does give one some food for thought. Mark O. | ||
| Tim Strommen (Tim_strommen)
Registered Member Username: Tim_strommen Post Number: 262 Registered: 11-2004 Posted From: 67.169.151.53 Rating: N/A |
I found it was more cost effective on my 2-stroke DD to replace the Thermostatic-Hydraulic-Speed-Control valve (stock) with a large volume bypass valve (at the pump) for idling at low temps, and an electronically controlled proportioning valve which is aware of its operating conditions ([digital] engine temp, ambient air temp, radiator water inlet temp, throttle position, and exhaust temp). I was fortunate enough to already have a two-stage hydraulic pump (one stage for the fan, one for the power-steering/wheelchair lift). When operating conditions are appropriate - the bypass valve gets popped open and unloads the fan circuit right at the pump (on the engine). Of course - since I'm still working on the suspension, floor, and exterior walls I have no idea about any fuel effieciancy gains - if any (it's parked...) I did experiment with a single electric replacement for the hydraulic fan - but found it inadequet and inefficient (both in space consumption and reliability). I'm not suprised that they are using 8 fans - I'd expect they'd need to be stacked or something to get the suction on side mounted radiators. Mark - do you have any pictures? Cheers! -Tim | ||
| Tim Strommen (Tim_strommen)
Registered Member Username: Tim_strommen Post Number: 263 Registered: 11-2004 Posted From: 67.169.151.53 Rating: N/A |
Hmmm... I found the press release from TriMet... ...and the company building the fans... ...and the datasheet for their fan products. Looks like the fans draw from 20-40 Amps (maximum static pressure of about 3.4 in H2O @ 1000cfm). With 8 fans - that's about 320 amps, which roughly works out to about 15HP. One would need a big battery bank and a big alternator to run the fans and all the other accesories in a bus (lights, ventilation fans, engine controls, etc.). -Tim | ||
| john w. roan (Chessie4905)
Registered Member Username: Chessie4905 Post Number: 373 Registered: 10-2003 Posted From: 71.58.126.56 Rating: |
Looks like a lot of complexity. GM's hydraulic fans were a lot simpler and were-are used for years. The later ones had an air valve port in the Vernatherm that, with air pressure applied, would make the fan run at full speed. Was used when air conditioning was running. Easy to setup for any GM road coaches with hydraulic fan.( Vernatherm is the name of the temperature actuated valve- mounted in cooling system. |
