Forum Discussion
231 Replies
4x4ord wrote:
ShinerBock wrote:
The cam in the pump is not like the cam in an engine. The cam in the CP3 is more like the crankshaft in the engine. Increase the crank stroke on an engine and what does it do to its compression ratio and cylinder pressure?
Consider this: When the engine is running at 2500 rpm the CP4 pump is capable of pumping a certain volume of fuel. I don't know what that volume is but say it is 2 litres per minute. The CP 3 might be capable of pumping 2.5 litres per minute. Under part engine loads these pumps need to be throttled back. The injectors might only be injecting .5 litres per minute. There is a mechanism in place for controlling the pressure to what the ECM is calling for and limiting the volume of fuel being pumped. I believe the pump is throttled back by only allowing the required fuel to flow into the pump. Push the accelerator down and the fuel control actuator allows more fuel into the pump to match the fuel being injected into the engine. This is controlled electronically but exactly how I don't know. The thing is, if more pressure is being asked for by the ECM the pump needs to respond by pushing more volume into the rail. I think the change in the cam is likely more to do with providing higher volume for aftermarket HP increases... but I really don't know much about this stuff.
That is not exactly how it works....
If you go to the link you posted, they even state.Industrial Injection wrote:
10mm Stroker Shaft
To help increase rail pressure when fueling to higher rpms we have designed these pumps with our industry leading 10mm stroker shaft.
This also increases flow along with more pressure.ShinerBock wrote:
The cam in the pump is not like the cam in an engine. The cam in the CP3 is more like the crankshaft in the engine. Increase the crank stroke on an engine and what does it do to its compression ratio and cylinder pressure?
Consider this: When the engine is running at 2500 rpm the CP4 pump is capable of pumping a certain volume of fuel. I don't know what that volume is but say it is 2 litres per minute. The CP 3 might be capable of pumping 2.5 litres per minute. Under part engine loads these pumps need to be throttled back. The injectors might only be injecting .5 litres per minute. There is a mechanism in place for controlling the pressure to what the ECM is calling for and limiting the volume of fuel being pumped. I believe the pump is throttled back by only allowing the required fuel to flow into the pump. Push the accelerator down and the fuel control actuator allows more fuel into the pump to match the fuel being injected into the engine. This is controlled electronically but exactly how I don't know. The thing is, if more pressure is being asked for by the ECM the pump needs to respond by pushing more volume into the rail. I think the change in the cam is likely more to do with providing higher volume for aftermarket HP increases... but I really don't know much about this stuff.- The cam in the pump is not like the cam in an engine. The cam in the CP3 is more like the crankshaft in the engine. Increase the crank stroke on an engine and what does it do to its compression ratio and cylinder pressure?
- I'm not understanding why an increase in the stroke of the camshaft is needed to increase pressure if the CP3 is already pumping more fuel than the CP4 is per revolution. Obviously I realize that volume and pressure are two different things. I also realize that the higher pressure is needed for emissions where as power is mostly concerned with the volume of fuel. However, pressure and volume can be related. For instance pumping more fuel through an orifice will increase the pressure. There has to be something regulating the fuel pressure. My understanding is that the fuel pressure is controlled by the volume of fuel fed into the top of the pump. Basically the injection pump acts like a variable displacement pump because a controlled amount of fuel is fed into the pump rather than by mechanically varying the pump's displacement. Really what is important here is that the CP3 has a much better more reliable bottom end that is much less prone to failure and even if it does fail it doesn't pump debris into the high pressure side of the system destroying the entire fuel system. The CP4 is a poorly designed cheap pump.
4x4ord wrote:
ShinerBock wrote:
4x4ord wrote:
Conversion kit for Cummins
I can’t imagine the labour being much on a Cummins. Apparently it doesn’t require tuning which makes me think this CP3 is modified to put out more pressure than the CP3 previously used on the Cummins.
It doesn't require tuning because it is not a stock CP3. It has a 10mm "strocker" camshaft which increases pressure over a stock CP3.
Something must be different. I don't know much about these fuel systems so I might be totally out to lunch but I thought even in stock form the CP3 puts out more volume than the CP4? Regardless, I thought it was the fuel control actuator (FCA) that let more fuel into the pump when the ECM called for more pressure. My understanding is that the CP3 did not have a pressure sensor capable of measuring 29000 psi. When ECM calls for higher rail pressure the FCA lets more fuel into the top of the pump, increasing the fuel delivery and pressure. The problem would occur when the sensor reaches it measuring limit. At that point the pressure continues to rise but because it's not measured the ECM keeps calling for more. It doesn't really matter how it works .... I hope Bosch is supplying Cummins with a CP3.... it would be even better if the Duramax and Powerstroke could get something as reliable. A CP3 conversion is available for the Duramax but not the Powerstroke ... too bad for us Ford guys.:(
Volume and pressure are two different things. Just as with our previous discussion on turbos, volume is the max 82 lbs per minute that my turbo can flow while the max 40 psi is the pressure. A smaller turbo can match the same pressure, but it will not have the same flow at that PSI.
The smaller stroke camshaft on the stock CP3 did not allow for more than 26k psi. However, the "stoker" camshaft on the one in the link is able to increase pressure past that. The reason why the CP3 has more volume is due to have a greater displacement with 3 pistons rather than 2 on the CP4.
Basically how it works on a diesel is that you have a HPFP feeding a common rail that is shared by all or half(one rail for each side) on V configurations. That pump sucks in fuel and pressurizes it in the rail. The injectors then open and close accordingly and the more pressure you have the more fuel can be injected within this window(or multiple windows with todays multi-fire injectors). This is where having more pressure is beneficial to power and efficiency while meeting emissions.
However, there will be point or horsepower level where the pump cannot flow or pump more fuel and it begins to starve the rail or rails. This is where volume comes into play. A 3 piston CP3 may be able easily flow enough fuel for 700 hp while the 2 piston(technically not a piston) CP4 may only flow enough fuel for 550 hp.
You can make a lot of power with lower pressure mechanical pumps, but you will be dumping a lot of fuel all at once which will increase NOx and roll a lot of coal until you add enough air to burn it completely. Hence the reason why more pressure is needed to meet emissions and increase power. Things would be a lot different if we did not have to meet such stringent NOx requirements. With todays multi-fire injector and higher pressures you can add a lot more power before the engine starts to roll coal even without a DPF.
Imagine dumping a bunch of fuel at one shot a 3k psi versus dumping multiple finer mists of fuel at higher pressures around 26k psi. There will be a power limit to where the engine will start to roll coal on both engines because it will not have enough air to completely burn the fuel, however, that power limit will be much higher on the higher pressure multi-fire injected engine.ShinerBock wrote:
4x4ord wrote:
Conversion kit for Cummins
I can’t imagine the labour being much on a Cummins. Apparently it doesn’t require tuning which makes me think this CP3 is modified to put out more pressure than the CP3 previously used on the Cummins.
It doesn't require tuning because it is not a stock CP3. It has a 10mm "strocker" camshaft which increases pressure over a stock CP3.
Something must be different. I don't know much about these fuel systems so I might be totally out to lunch but I thought even in stock form the CP3 puts out more volume than the CP4? Regardless, I thought it was the fuel control actuator (FCA) that let more fuel into the pump when the ECM called for more pressure. My understanding is that the CP3 did not have a pressure sensor capable of measuring 29000 psi. When ECM calls for higher rail pressure the FCA lets more fuel into the top of the pump, increasing the fuel delivery and pressure. The problem would occur when the sensor reaches it measuring limit. At that point the pressure continues to rise but because it's not measured the ECM keeps calling for more. It doesn't really matter how it works .... I hope Bosch is supplying Cummins with a high pressure CP3.... it would be even better if the Duramax and Powerstroke could get something as reliable. A CP3 conversion is available for the Duramax but not the Powerstroke ... too bad for us Ford guys.:(- Makes me wonder if FCA will back date the 2019 to 2020 Cummins to use the CP3 if you have a CP4 fail under warranty now that they seem to have gone to the CP3 for 2021. I sure hope so because if my CP4 grenades I sure don't want another CP4 in my truck to grenade once the warranty is done.
4x4ord wrote:
Conversion kit for Cummins
I can’t imagine the labour being much on a Cummins. Apparently it doesn’t require tuning which makes me think this CP3 is modified to put out more pressure than the CP3 previously used on the Cummins.
It doesn't require tuning because it is not a stock CP3. It has a 10mm "strocker" camshaft which increases pressure over a stock CP3.- Conversion kit for Cummins
I can’t imagine the labour being much on a Cummins. Apparently it doesn’t require tuning which makes me think this CP3 is modified to put out more pressure than the CP3 previously used on the Cummins. - So how much does a new CP3 cost? Just ballpark w labor?
