Tengu

What year did they stop using the Mechanical pump? I am wondering if they continued to use the cam with the lobe for the mechanical fuel pump till they ran out of their stock. Is there a way to tell if your cam has this lobe?

joefarmer

I don't believe any 24v engines have that cam lobe. I have stock cams from a '98 24v and a '99 24v. Neither have the lobe.

brandon.

Fishin2Deep4U

The 12V and 24V cams are completely different. So, no old stock was used. Also, the 12V is still biuilt today for other applications. So, there are still new parts available.

I have a stock 24V cam that I am going to add a lift pump lobe to for my dad. He has eaten up 4 lift pumps and 1 VP. He does not want to add any performance to the truck, so this is a good option for him to get the reliability. But, it's an awful lot of work for just that lobe. I am trying to talk him into the RASP.

Dave

Don M

Yeah, when Cummins changed the engine to a VP, they changed the valve timing events and even used a different core camshaft. All 24 V camshafts are cast with no lobe on the cam. You cant use the 12 V cam in the 24 V engine either. It would not work very well at all. Valve events are too different. Lift is too low, etc.

Cummins mechanical fuel pumps are essentially bulletproof. Too bad they did not keep the system in the VP engines.

apwatson50

Don,

The pump you supply with your kit, is it a stock style piston lift pump from the 12 valve with just a different pressure spring? Or is it a completely different pump.

yarddog

Don, this was a very interesting read and I'm sold. It will be awhile before I have $1000 to do this but it's just a matter of time.

Have you given any thought into providing a stock grind replacement cam with a the pump lobe and offer it with a pump kit? I know many people would be interested in a kit that is comparable in price to the full FASS system. It might not be feasable but thought I'd ask.

Don M

The pump is not a Dodge/Cummins pump. It is a Cummins pump, just not the same one used on the Dodge application.

There are several reasons why the Dodge/Cummins pump is not optimal for the VP fuel system.

In addition, the fuel pump lobe is ground differently on our 24 Valve cam than the stock Dodge/Cummins pump lobe is ground. This is to help reduce pressure and the pulsing that comes with a direct bolt on of the 12 V Dodge/Cummins pump to the VP engine.

We also have another aftermarket pump that is not a Cummins part at all, but are still working out some dimensions to optimize it for the VP. The first few pumps we have tried are all delivering the high engine speed pressure we like, but the idle pressure is too low for most tastes. Around 6 PSI on some of the original test units. The master plan is to have an aftermarket pump at a reduced price compared to the Cummins parts we are using as a stop gap currently. It just takes some time to get everything tweaked and tested.

So, the Cummins pump is the best choice now. Good pressure ( 30 PSI ) and extra long service life. 100's of thousands of miles. It took some serious pump tests to get the pressure and cam profile correct on the Cummins pump. Now on to the aftermarket pump in earnest with the correct sizing to make it a pump we can market as well. Perhaps some additional cam lobe profiles changes too. Whatever it takes, right? LOL

Don~

Fishin2Deep4U

yarddog,

I won't reply for Don. But, I would think that Don could do that, but the price would be the same.

Don does use a much better grade of material in all his cams when compared to stock. Also, the factory makes a heck of a lot more of these things than the entire aftermarket combined. So, after you factor everything, you'll just end up at the same cost. At least that's my opinion.


Dave

Jetpilot

Why wouldn't you want to upgrade the cam to a Helix 1? If you are going to replace the cam why not improve on the setup, cost would probably be close if not identical.

Doug

yarddog

I know it would be ideal to upgrade the cam while you were in there but if you could buy a bullet proof lift pump fix for $500 wouldn't you? I would. I'm not interested in a RASP either. I want something that's configured as close to stock as possible.

I realize Don or any other cam grinder would probably have to start with a blank either way, but it could be made from "adequate" material not high cost alloy.

I do want a Helix 1 but an affordable stock cam with a pump lobe isn't a bad idea.

Just thinking out loud.

ramtd02

At 72 psi, you figure there was cavitation?? How? Would these pressures cause diesel too flash into vapor? Cavitation is a regular occurance on a centrifugal pump, but only when at low suction pressure, low flowrate times. A sliding vane pump does not cavitate. The vanes wear faster and more unevenly when the flow rates and pressures are low, this being because the vanes use the pumping medium as lubrication.

Don M

The idea was to show that high pressure over 72 did hurt performance during our dyno testing and just about everything under that was fine.

The pump we used to do the pressure testing was an Aeromotive A1000 electric. Even with the suction side of the pump under positive pressure it will cavitate slightly with higher regulator pressure settings. You can actually see it with a clear hose. The A1000 is a very efficient design but it does not like higher pressure settings.

Now, it is possible that the 12 V mechanical pressure pumps or a staged system might not cavitate from the higher pressure settings and make more HP, but we got no real gains with any settings over 40 PSI. 40 and up to 72 did not add anything measureable in performance.

I am fairly certain the problem was cavitation related because the clear hose revealed the bubbles. Though not 100% certain. I was pretty much beating a dead horse after 55 PSI anyway. The power was not increasing.

Don~

Mike D

How much timing was taken away? I assume the timing was for emissions? Is there that much difference between the lift and duration?

trailrydr9

I have been trying to decide weather to do the RASP, or this. Where would one look to find out how difficult this project would be? I really feel that even with the new cheeper price on the RASP systems, by the time that you get bigger fueling lines, you are still within a couple hundred bucks, and you get the added bennifit of a bigger cam. Does the service manual that Geno's has on his site show how to replace cam's? Is ther someplace here that I could look to see any pics of others that have done this?

Mike D

I don't think it very technical, it just take a while. If you do the work yourself, you're probably right with regards to cost.