Discovery Water Pump Overdrive Pulley
Rock Crawling
Joined: Apr 2021
Posts: 346
Likes: 124
From: sfbay
I suspect the OEM style thermostats allow quite a bit of bypass which is probably taking away from the impact of the smaller pulley. Perhaps you'd see more difference in temp with an inline which doesn't allow any coolant to bypass the radiator.
See below for some engineering thoughts:
Running temperatures are generally not affected by waterpump speed, you can test/demonstrate this by shifting from D to 3 at any time, so no real surprise on this. The driving temperatures are affected more by engine load (BTU's in to the cooling system) and the D2 radiator size (BTU's out capacity).
Makes sense as at idle the fan would be running slightly faster.
Is the tensioner at the bottom of its travel? If so, you could use a shorter belt. If not, the issue could be the reduction in surface area and/or a friction factor difference (plastics generally have lower friction coefficients than steel), you may need to sand the surface a bit or built some small ridges in the cad model.
Agreed, the Disco idles at approximately 670 rpm stock, and at that speed the water pump does not pump enough fluid to keep the engine cool. From testing my shifting in to neutral and revving the engine we know we need the equivalent of approximately 1200-1500 rpm, which would require a pulley of approximately 1/2 the size which would be quite small.
Running temperatures are generally not affected by waterpump speed, you can test/demonstrate this by shifting from D to 3 at any time, so no real surprise on this. The driving temperatures are affected more by engine load (BTU's in to the cooling system) and the D2 radiator size (BTU's out capacity).
Makes sense as at idle the fan would be running slightly faster.
4. On very hot days (high 90s), there was a belt slip / squeal at low RPM (when parking) when the A/C compressor was on. I believe this was due to insufficient tension on the belt from the smaller pulley. My first instinct on the fix for this would be to change the tensioner pulley for a larger model.
5. The glass-filled nylon pulley held up well. The only deformation I could find was around the bolt holes where I slightly overtightened the bolts and compressed the nylon a bit.
Overall, I am somewhat underwhelmed with the results. I expected a bit more. Since the results are so similar to the factory pulley, I am wondering if the factory thermostat is having a bit of an influence still. I am considering testing the inline thermostat (which I used to run on one of my old Discos back in the day) with the pulley. Ultimately, however, I am starting to think that 10% may just not be enough of size difference.
Overall, I am somewhat underwhelmed with the results. I expected a bit more. Since the results are so similar to the factory pulley, I am wondering if the factory thermostat is having a bit of an influence still. I am considering testing the inline thermostat (which I used to run on one of my old Discos back in the day) with the pulley. Ultimately, however, I am starting to think that 10% may just not be enough of size difference.
Thread
Thread Starter
Forum
Replies
Last Post
