PicoScope 7 Automotive
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New Holland CR 8.9 Combine
New Holland CR 8.9 Combine
Customer concern about during road operation the max mph would surge as would engine load, observed symptoms were loping road speed (25 down to 18)mph on flat and slight declines less than ~5%, and engine load on machine display would vary from 0% to 85%.
In checking with our tech specialist for the product it was found that the hydro motor manufacturer Bosch struggles at matching their motor adjustment specs to the New Holland control software.
In my understanding the motor control software has a given range it is programmed to operate in, the motor adjustment from Bosch does not match in that same range.
In the example I have attached the before current control spec is from no load no speed spec of ~400ma to a full load max road speed of just over ~1000ma.
After adjustment the no load no speed spec is still ~400ma and the max load top road speed is set to ~1200ma.
This adjustment made at the control valve of the hydro motor resolved the surge and smoothed out the engine load variation. Adjustment was roughly equal to two flats on the locking nut.
Thanks for reading.
In checking with our tech specialist for the product it was found that the hydro motor manufacturer Bosch struggles at matching their motor adjustment specs to the New Holland control software.
In my understanding the motor control software has a given range it is programmed to operate in, the motor adjustment from Bosch does not match in that same range.
In the example I have attached the before current control spec is from no load no speed spec of ~400ma to a full load max road speed of just over ~1000ma.
After adjustment the no load no speed spec is still ~400ma and the max load top road speed is set to ~1200ma.
This adjustment made at the control valve of the hydro motor resolved the surge and smoothed out the engine load variation. Adjustment was roughly equal to two flats on the locking nut.
Thanks for reading.
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ben.martins
- Pico Staff Member
- Posts: 543
- Joined: Tue May 16, 2017 1:02 pm
Re: New Holland CR 8.9 Combine
Thanks for sharing muttnjeff,
Amazing how a slight adjustment can ensure a smoother operation. I had a similar experience with a JCB JS220. The hydraulic pump had been replaced due to noise and leakages but after refitting the pump, the engine would stall when operating a service causing.
When looking at the data we could see that the pumps weren't even getting close to the pressure we were expecting yet the engine was being dragged down. It was only when we spent some time investigating the operation of the pump, K3V pumps as seen here - topic22508.html, along with a PQ test did we notice the pumps weren't automatically being de-stroked when the pressure had reached a certain value and so loading the engine to the point it would stall.
With the K3V pumps there are a number of adjustments you can make to move the point the swash plate is moved based on the pressure. A couple of turns to lower the point the pressure would start to reduce the flow saw the engine no longer stalling and the machine back in operation. A small lesson learnt with these types of pumps but also that when fitting a new pump to an old engine is that the pump would have been adjusted to the original specification when the machine was new. It doesn't take into account that the engine output which would have reduced over the years.
Thanks again.
Kind regards
Ben
Amazing how a slight adjustment can ensure a smoother operation. I had a similar experience with a JCB JS220. The hydraulic pump had been replaced due to noise and leakages but after refitting the pump, the engine would stall when operating a service causing.
When looking at the data we could see that the pumps weren't even getting close to the pressure we were expecting yet the engine was being dragged down. It was only when we spent some time investigating the operation of the pump, K3V pumps as seen here - topic22508.html, along with a PQ test did we notice the pumps weren't automatically being de-stroked when the pressure had reached a certain value and so loading the engine to the point it would stall.
With the K3V pumps there are a number of adjustments you can make to move the point the swash plate is moved based on the pressure. A couple of turns to lower the point the pressure would start to reduce the flow saw the engine no longer stalling and the machine back in operation. A small lesson learnt with these types of pumps but also that when fitting a new pump to an old engine is that the pump would have been adjusted to the original specification when the machine was new. It doesn't take into account that the engine output which would have reduced over the years.
Thanks again.
Kind regards
Ben