I have a 1980 Flyer transit bus that came from Seattle and that I have owned for 9 years. I drive it a few thousand miles a year and have had no problems in that time. It recently developed a fuel leak around the throttle shaft so while I had the pump taken off, I thought it would be a good time to get the governor turned up so I could get a little more speed out of the old beast.The head mechanic at the Seattle Metro bus yard told me that it was governed at 2050 rpm [no tach], so I figured that a few hundred rpms would equate with more speed. The pump man assured me that they could do that, but they would have to put it on the
bench to do calibration and that would cost me an extra $125. We agreed on that and when I picked up the bus, he looked me in the eye and said that is should run 2 or 3 hundred more rpms. When I took it out on the freeway, it ran the same speed as before, 43 mph in second, and 60 in high. It has an air throttle that is either on or off and now it seems that I have to take my foot almost all the way off before it drops down to idle speed where before it would drop to idle almost as soon as I lifted my foot a slight amount. I don't know if that would equate to more rpms, all I know is it still goes the same speed as before. I don't have a tach so I can't tell or prove to the pump man that it isn't running any more rpms than before. Is there anything in the transmission [V730] that regulates the top speed or shifting speed or in the pump itself? I would appreciate greatly if anyone could give me any ideas on this. I want to get my facts straight before I have a confrontation with the pump outfit. I hate to think that they would not have done the work that I paid for, but I did mention that I had to leave in a few days. I do have to leave soon so I need to get this situation resolved before I go. [they did fix the fuel leak, by the way].
This topic was moved from the Help board to this board to get more attention. The Help board is more designed for permenant information.
Richard
OK, The slow return to idle is a throttle leakage problem. The leakage is set at the throttle shaft. There are 2 lock screws with set screws on the throttle shaft. One in front of the shaft and one behind it. If my memory is right, the set screw closest to the compressor is the leakage. I think you want to increase it so loosen the jam nut and turn the screw in about 1/8 turn at a time until you are happy with it. Mark your start point so you can go back.
The 903 uses a different set of governor springs from the inline engines. My guess is the shop did not have the correct spring. You can use RPM shims alone to raise the RPM but it will also increase the horsepower and torque and most shops don't like to take responsibility for that. It will also produce a little more smoke. I think they should either fix your pump, or give you back your money. I live in Kent so if you are not satisfied, let me know and I can put some shims in it or help you set it up.(Free). It would be nice to have a pyro on it and set it to run about 1000 degrees on the cold side of the turbo. If you went to Cummins and bought a 2300 rpm, rpm spring for a 903, it may or may not work with your torque springs. We also used to just stretch the old spring, and have good results. It was nice of them to fix the fuel leak on the throttle shaft, but that was only a 3 cent O ring.
First- the rpm setting of the engine and the shift points in the transmission is totally separate. The 903 set at 2050 is extremely conservative. You could safely take that up to 2600rpm no load (remember the 903 has a shorter stroke [4.75"] compared to the N14/NTC engine [6.00"]), since 2600rpm would be the same piston speed as the N14 at 2100rpm.
Once you change the engine rpm, you have to change the shift governor in the V730. I believe that the highest shift is 2600rpm on the V730. If you're doing 60 at the prescribed 2050rpm, then at 2600rpm you'd be doing 76mph. Sounds good to me!. Cummins rated the marine version of the 903 at 2600rpm with the governor set at close to 2800rpm. Some truckers regularly cranked the 903 up to 3000rpm! Good Luck, TomC