Howe has been telling our team that we need to have the orbital be lower than the full hydro reservoir. They’re suggesting possibly putting the reservoir in the back of the chassis up by the rear mount radiator (or move the orbital much lower which has its own issues) to solve some of the pump killing issues we’re having. I feel like this is ridiculous as I’ve always only heard about having the reservoir be higher than the pump (which it definitely is). We only got about 20 hours on the Howe trophy truck pump and it is completely smoked and costing us over a grand to rebuild so we’re trying to figure out a solution to where we don’t have to rebuild pumps several times a year. This is on our 4400 TMR car by the way. What do you guys think?
Is this a billet aluminum TT pump or one of the older cast iron ones? Orbital height relative to the pump doesn't matter at all and all this talk of internal flow regulation versus non-regulated versus externally regulated does greatly impact cavitation, heat and pump life.
Trying hard not to write a novel right now... TT pumps are 20cc/rev displacement and none of the billet aluminum TT pumps out there from either Howe or PSS have any internal valving whatsoever. That means that the pump displacement multiplied by shaft RPM is the theoretical flow rate that the pump is trying to circulate THROUGH the system.
This works out to be roughly 5 GPM per 1000 RPM so if you are spinning a TT pump at 6K RPM, it is trying to move 30 GPM but can't physically pull that much in from the reservoir. Even though these billet pumps are not regulated, they will hit a max flow rate dependent on plumbing and system design. With a -16 feed hose and few PSI in the reservoir, I have found that limit tends to be around 15 GPM. This means that at 6K RPM, approximately 50% of the volume within the internal pump cavities consists of vapor bubbles from cavitation which both erodes away at the pump internals and generates massive amounts of heat for two reasons:
1) Pushing 15+ GPM through the hoses/orbital/etc. generates heat due to friction/pressure loss through valve orifices and;
2) Those cavitation bubbles in the pump collapse when they hit the high pressure side of the pump and just like how a diesel engine works by compression ignition, an imploding vapor bubble sees a huge increase in heat as the volume of the bubble is instantly compressed.
There are external flow control valves available (not to be confused with external pressure relief valves) that regulate the flow rate going to the orbital, however, they return the excess flow to the reservoir which does not help the pump cavitation issue because the pump is still ultimately limited by how much oil it can pull in from the reservoir.
The RDT pump that I introduced as my own alternative to the TT pump has the same displacement but is an all new design and does feature internal flow control. Some might argue that because I am dumping the excess flow straight back into the pump body, that it is generating heat. And to answer this honestly, it does, however we have to ultimately compare this to the alternative of a non-regulated pump of the same displacement at high RPM. When the pump has an internal flow control valve, it is limiting the max discharge flow rate to, in my case, approximately 10 GPM which the pump can easily pull enough in from the reservoir to replace. While cavitation will still be inevitable to an extent at high RPM, having the excess flow dump straight back into the pump results in a very significant net reduction in cavitation and hence, heat load.
This isn't just theory either. I have data from a race team earlier this summer that started testing out the RDT on two trucks where they had previously been using billet (non-regulated) TT pumps. Just by swapping to the internally flow controlled RDT pump, vortex reservoir, and my high flow filter/relief valve but keeping their original cooler (radiator style), they saw steering temps drop by 60 degrees F compared to the old setup while at the same time improving steering performance and feel, particularly at low rpm.
As for the ram, the only reason I would suspect a leaking seal is if you are able to turn the steering wheel without moving the tires or vice versa. Otherwise, it is very unlikely that the piston seal is failing.
Feel free to shoot me a message or call tomorrow and I'd be happy to go over your setup with you.
