Theoretical Q ... adjusting the rev limiter on my diesel ZTR

[TSO]

I mow with a 66" Hustler Super Z diesel (25 HP Shibaura). It's a great mower, efficient, comfortable, nice cut, etc etc etc.

Like anything else, there are times when I could use slightly more power. The RPM's are set by hand throttle position, but there is no tach to see what RPM's I'm actually running. From appearances, it looks like the hand throttle is linked with a metal cable. The mechanical rev limiter is the point where the lever cannot move forward any further. It would be easy to adjust the throttle lever to move forward further, but I haven't checked to see if the cable can actually move forward any further...

Ok so anyways ... what would be the noticeable problems with increasing the RPM's? If, for example, the stock "wide open" throttle position produced 2000 RPM's, and I adjusted it 10 %, so that I'm now running 2200 RPM's... What's gonna happen?

I'm assuming that there is a safety margin built in to promote engine longevity, but I'm wondering what happens (and especially how soon) if I bypass the safety constraints?

 

[The Fred]

I would leave the RPM alone and instead find the way to get more fuel to the injectors.

You could turn it up a little at a time. If it smokes on load turn it back it won't make any more power at that point without getting more air in.

The blade tip speed is set by the highest RPM. If I am understanding correctly it sounds like you want more go power not RPM.

Good luck and nice machine, Fred

 

[Poopdeck Pappy]

Design Technology, Inc., Home of the Tiny-Tach - Diesel Tiny-Tach Tachometer

I think you can buy them through Amazon.

You will want an accurate tach to make sure you're not over-revving the motor. I think, for example, that most gasoline mower engines are designed to be run at 3600rpm. (I think that's with the blades engaged but the mower not under load.) If you cranked one of them up 10%, that would be almost 4,000rpm, and bad things would probably happen to that engine.

I suspect that Hustler knows a little something about what RPM that diesel motor should be run at. Unless it was not set up right at the factory, it should be at that setting now. The tach would be helpful for determining if it is indeed running at that speed. If it is, I'd leave it alone. Plus, the torque curve of that engine might show that it's making max torque at less than max RPM, and increasing the RPM could be counterproductive.