rpm on mmm

[Danner]

"At any rate, the cut quality for me running @ 2650 is so nice that IMO, there's no need to tax the engine/driveline/implement and me anymore than I need to."

The flaw in your reasoning is that running the engine at a lower RPM is better for it.

This is an incorrect assumption. It is higher torque, not higher speed, that is harder on the engine. Since power (what it takes to get the job done) is speed times torque, when you run the engine slower, you increase the torque.

It is much netter to run the engine at the higher speed and keep the torque as low as possible.

Yes, I am an engineer.

 

[roamerr]

Wide Open. I want the blades turning as fast as they can. Even somewhat dull blades give a good cut at full throttle.

 

[kcender]

If travel speed and blade speed are matched throughout the RPM spectrum, then (in theory) the blades should be engaging the grass for the same ammount of time at any RPM.

I cannot visually tell the difference between cut quality with pedal to the floor @ 2650 or pedal to the floor WOT. If I rev the engine up and slow the travel down, I can tell the difference, but it is not worth traveling slower to get it.

At any rate, the cut quality for me running @ 2650 is so nice that IMO, there's no need to tax the engine/driveline/implement and me anymore than I need to. Also, according to the fuel consumption chart, it's running most efficient in the band between about 2000 and 2800 RPM.

@ 2650, the ride is better, reaction times are better and you really don't lose anytime (negligible at best)

Just my $.02

I agree.That is why I run around 2600 to 2650 RPM when mowing.:thumbsup:

 

[dodge man]

Wide open for me. If you have a drier lawn and not very think grass, you might be able to run less. I think people tend to back down the RPM's with the thought they are saving the engine, but these things are meant to be run wide open when mowing.

 

[MoreCowbell]

I have a BX2350 with a 60" regular cut MMM. Together, the manuals do tell you what to run the engine at, but they make you work for it :confused2:.

Here is how I calculated it: The MMM manual (for my deck) specifies a blade spindle speed of 2647 RPM. Since the spindle is driven by a gearbox with a 17:18 gear ratio, the driveshaft speed needs to be 2500 RPM to achieve the specified blade spindle speed.

"Coincidentally", the BX2350 manual specifically references the 2500 RPM mid-PTO speed and says 3043 RPM on the engine will produce that PTO speed.

So, I try to shoot for something around 3043 on the tach when mowing.

My MMM manual coveres several different models and gives different spindle speeds for each one (probably due to blade length differences), but I would bet that each is geared so that 2500 RPM on the mid-PTO speed generates the specified spindle speed.

 

[KeithInSpace]

I don't have a tach. Even if I did, I don't suspect I'd be shooting for "3043" anythings. That's like not being satisfied with 59 or 60 on your speedometer...I shoot for 59.76 MPH to maximize my speed while staying under 60...

I run at WOT, but for a different reason. I run the OEM bagger unit that is rear PTO driven. I've tried running off-WOT, but the sucking efficiency of the fan head in the bagger seems to drop off precipitously. This results in more frequent clogs in the feeder tube from the mower deck to the bagger's fan head.

I run WOT to maximize the sucking and have less clogging.

 

[MoreCowbell]

I don't have a tach. Even if I did, I don't suspect I'd be shooting for "3043" anythings. That's like not being satisfied with 59 or 60 on your speedometer...I shoot for 59.76 MPH to maximize my speed while staying under 60...

Of course it is unrealistic to set an exact engine speed. That's why I said "around" 3043 RPM. That engine speed is from the manual which is why I referred to it.

Running at WOT is fine. I was just descibing what I think the manufacturer is specifying in its roundabout way.

 

[KeithInSpace]

I was having a bit of fun there. Sorry.

 

[SPYDERLK]

I try to keep mine under 5000rpm.

 

[bellweather]

(BX22) owners manual recommends full throttle for mowing. High RPM is especially needed now that I installed a grass catcher (Kubota grass catcher manual also recommends full throttle).