I have looked at a lot of data with the gray CPS in my truck and in others, and I hate that thing. The idle sucks, the PERDELs are high on 3 and 8, and Stinky just doesn't "sound right" on any tuning I've ever had (including stock), with a stock truck or a modified truck. I was able to get my hands on a black Ford CPS, and that made a big difference in Stinky in every scenario - I experimented back and for the with gray and black many times. I have seen a lot of information on the Riffraff Diesel OEM CPS, and I bought one as a backup... but I have not installed it in Stinky to verify what I'm reading on it.

I now have new intel: A fellow member swapped from the gray to Clay's OEM CPS and his all-around performance shot up, including fuel economy. His RPMs dropped (per MPH) as well. While I'm still sorting out the "why" of all this, it's almost irrelevant: What matters is the improvement with such an inexpensive and easy change of hardware on an aging truck.

I AM NOT SAYING BREAK OUT YOUR CARD AND BUY THIS NOW! I will also not suggest that a new CPS will miraculously take your economy from 14 MPG to 17.5 MPG - there are too many variables on owners and conditions of the different trucks. I am saying all my experience and research says the gray CPS is not ideal, and Ford seems to agree - since they no longer sell the one that was in my truck (installed in 2010 by Ford before I bought it). There is a newer gray one at the dealership with a purple O-ring, but I can't keep up with the variations on these things. I just know Clay has done his homework, and he is providing the best available product he can get on his shelf. One member put that in, and it was a radical improvement over one of the variations of gray CPSs - just like the black one did for Stinky.

If you don't have a backup CPS, I'd order one of these. If you can afford to experiment - this is an inexpensive and easy throw at the dart board.

Numbers: I have 3.73 gearing with stock-sized tires, and I get 2000 RPM at 72 MPH. The member in question went from 2000 RPM at 68 MPH to 2000 RPM at 73 MPH... just by changing from a gray to a "Clay". I suggest you look at your speedo and your tach, but you need to compare it with others of like gearing and tire size. If your RPMs read high for the speed, then you are a candidate for this experiment - or a new torque converter... but that would be a different thread.

This has been a public service announcement of the Stink-N-Rich research and development team.

 

Thanks for keeping us informed. I purchased two extra black CPSs from Clay before the supply disappeared in about 2011. My truck had a black CPS, along with a black spare CPS in the glove box, at the time I purchased it. Ford wanted to change mine out under recall when I had them install the recall wire harness that was involved with cruise control - to reduce a fire risk. I asked them if I got to keep the black one or if they kept it. They told me they kept it. I told them no thanks. They looked at me sorta strange, but I'd never read anything positive about the Gray one they were going to install at the time. And I wasn't about to trade my black for their gray.

 

So it changed either the tires or the gearing. That's the ONLY way the RPM/MPH ratio can change. A CPS CANNOT do this!

 

I was wondering the same thing Mark.

 

Stop trying to make so much sense.

 

Isn't the cam sensor the source of the signal for the tachometer. Which reports RPMs?

I understand that if there is no slippage whatsoever in the drive train between the engine crankshaft and the output drive shaft, that the RPM and speedometer ratio cannot change or drift - such as when in overdrive.

But can the CPS be a source of errant RPM information?

 

I have no clue on this one. I know the #8 "door" for the CPS is the skinniest one, and the #3 comes in second on the anorexic metal pageant. I can only speculate that the CPS wasn't reading 8 correctly, making the CPS miscount... but that's a long throw down the field.

 

Just for reference, I have 3:73's and 35 inch tires. I am running 2000rpm at 72mph with the speedometer re-calibrated using AE.

 

I have 4:10 gears and running 235 85 16 tires and im at 2200 rpm at 70 so im eating fuel on the freeway so i just put a set of 265 75 16 tires on to bring down the rpm's a bit, gotta try a run and see how it goes but i havent seen a difference in changing cps's im running a new black ,purple o-ring international cps and it runs good

 

You likely won't see any change in RPM by switching tires. 235/85/16 and 265/75/16's are almost identical in overall height. Your downfall is the 4:10 gears.
For the record, I run about 68 mph @ 2000 rpm with 235/85/16 and 285/75/16 tires.

 

this is the only one I can find, is it the good one?Motorcraft Cam Position Sensor CPS 94.5-03 - Riffraff Diesel Performance

 

That is the one.

I have talked to rich about this and agree 100% with him thoughts. I swapped mine out with the one listed above and have 285 tires fixed with AE. I also experienced the change from 68 to 73 mph at 2,000 rpms. I don't understand it either.

 

This is one of those things I can't bring myself to believe without seeing it firsthand. Like Mark said, the CPS can't change the drive ratio; it's physically impossible. If the CPS was doing any miscounting of cylinders, it should cause a code to be thrown, or at least a stumble/stall condition.

 

Without looking at my CPS in the DuHa, I think these two are the same... and the one at Riffraff is the one I was referring to.

Remember - I'm not stating this is a miracle cure for anything. I'm saying if you have the $25 and ten minutes, it's worth a shot - IF YOU ARE HAVING ISSUES WITH YOUR TRUCK.

 

While it might be possible that it's changing what the gauge is telling you rpm's are, it can't actually be changing rpm's at any given speed, that is impossible.

Since our tach is not mechanical that would lead me to believe our stock tachometer is yet another idiot gauge that is telling you something that may not be completely accurate with either CPS.