Perhaps I'm over-thinking it, but if the new, improved Twin Cam high flow pump flows 8% more oil, and scavenges 20% more efficiently, I would have to assume that the oil pressure readings should be higher on models with oil pressure gauges across the rpm range.

So for those that have upgraded their cam plate/oil pump, have you noticed any difference in where the needle sits?

Bench test numbers vs real life operating question. I'll have to replace my old style pump eventually and thought about this when I replace the next set of cams.

Thanks for the input...

 

Oil pressure is set by the relief spring not the pump flow....

I have A fueling plate and pump. Dont exactly know why, it came with the kit at the behest of my engine builder.. It has similar numbers to what you quote.

 

I understand that...But if the pressure isn't higher at the gauge, the motor isn't really getting any more oil.

Is my assumption valid?

 

The gauge reads pressure. Amount of oil would be flow rate. Depending on the configuration the pressure gauge may or may not have an equal change.

 

I believe I am thinking like Stiggy. If you push 8% more oil through the same spaces, wouldn't the pressure have to increase?

 

Makes sense you should be able to see it on the gauge.....so you gotta wonder if its all hype.

 

KING hit it on the head. the relief spring in the cam plate is what sets the pressure. The oil pump has the ability to pick up and produce more and that keeps a more constant lubricating system happy

 

Well the principals of physics say that if you put more volume through the same space that was already filled the pressure increases. If your pump is making enough pressure to open the by-pass (it is) then putting more volume through the same space should increase pressure, except for one thing. When the by-pass opens it increases the size of the space, you'll only see an increase in pressure when the increased volume can't get past the by-pass (like when the oil is cold). If you want more pressure replace your by-pass spring (a pretty simple operation) with a stronger spring from Baisley's or shim it with a shim from Zipper's. I took the Zipper's shim and sanded it until it was 1/2 as thick and I still have 40-45 psi when the oil is hot. As for the scavenging, shimming won't help that.

 

in order to make a direct compare, you would have to move the pressure relief valve from the old cam plate to the new one. you could have higher flow, but less pressure.....the pressure relief valve controls this. you can buy different pressure relief valves with different PSI's. Why would you want to do this......the higher the PSI rating of the pressure relief valve, the longer it takes for the oil to bleed down after shut down. No pressure relief valve would give the highest flow rate, but would bleed down almost immediately upon shut down. A point to consider is a lot of folks replace the oil pumps and cam plates simply becuase the crank operated the oil pump out of round and the pump cut into the stock cam plate.

 

Pressure relief valves don't have different PSI's; the pressure to open the relief valve is controlled by the spring. Hence the Baisley spring. The bypassing occurs when the pressure is too high. Like when the oil is cold and thick. The spring and bypass system prevents oil pressure from getting too high. A stiffer spring will create higher pressure on the high end but on the low end the bypass is closed and if the pump is only making 5 psi that's all you can get.......... even if you permanently plug the bypass shut.

The pressure relief valve does not control oil pressure; the pressure sending unit is downstream of the relief valve. As a general rule, the upgraded pump will produce higher pressures across the board. The oil pressure light will come on when pressure drops below 4psi. The early pumps, again as a general rule, would produce about 8psi at idle and less than 30psi at cruise. Of course this will vary from bike to bike because of manufacturing tolerances in the "tightness" of the oil pump; more volume through the same space will result in higher pressures. I have two early models and have converted one to the later model cam plate and pump. Idle oil pressure is definitely higher with the later pump, almost double. At cruise, not so much but there is about a 10%-15% increase in cruise oil pressure and the plate and pump are the only changes.

The TC oil pumps are positive displacement pumps which meanss that as long as the engine is running, some oil is being moved. However, if the oil pump discharge volume is low, there may not be enough pressure to lift the oil to the rockers (the highest point). The oil's then going to follow the path of least resistance to the cam and crank. So, just because oil is returning to the tank does not that mean everything is getting the amount of oil it should at idle. Allowing for the height difference in the crank and rocker arms, I'd guess it takes at least another 2 to 3 pounds to get the the rocker arms. One pound of pressure will lift water 27.7 inches for comparison. Allowing for frictional losses, 2 to 3 pounds over what it takes for the oil to lube the crank may not be too much.

Bottom line is that the TC oiling system is more about volume that pressure. I would be more concerned about higher than normal pressures than lowern than normal pressures.