Opinion needed on raising fuel rail pressure

[Parshal]

Re: Injection Pump

Originally posted by 4xquadrod

Also, is the pressure raised all the time or just when you are on it?

The link that catcracker provided about common rail said that the pressure is always there.

 

[Bob4x4]

No need to wonder what pressures you are getting with or w/out the box the system has a transducer. You can drive it with a scanner and see exactly what pressures are doing.



Bob

 

[Parshal]

I had a long conversation with Aaron at Edge yesterday about raising rail pressure and the results. He told me that they have not seen any problems raising the rail pressure on the Cummins. When asked about long-term problems he replied that when the Duramax common rail first came out they tried to raise rail pressure and immediately had problems. He said the Cummins is handling the higher pressure whereas the Duramax could not.



He mentioned that while the module only raises rail pressure the engine's ECM adjusts timing as a result of the higher pressure. He also mentioned that the EZ just raises the power curve and that a new box will actually adjust timing (as well as increasing rail pressure) and change the power curve. It will add another 40 or so horsepower than the EZ.



With regard to mgonske's problem of a faulty pressure relief valve (the only "problem" reported to Edge so far), Aaron said that this is a common problem on a common rail system and that it may or may not be related to the EZ. He certainly did not seem concerned about it being a possible by-product of pressures being too high.



After my conversations with both Aaron and Bryce I feel much more comfortable with raising the rail pressure. Of course, I'm new to the diesel world and may be listening too much to salesmen but everything I've heard is both plausible and believable.

 

[Marco]

It appears as though your Bosch guys overseas and ours here in North America are at odd with one another. There's a surprise Is it possible you guys have a different injection pump in use, or that there has recently been a changeup?



With all the respect I have for you guys in the States, I think I know about changes/new diesel injection systems a long time before you.

There's already a next generation CR system out and used in a few cars here. The Cummins CR system is already obsolete...



Just to clear things up a little, the max pressure in the CR is not always applied. It's a regulated system. At idle the pressure is about at the same level ( only slightly higher ) like what would've been found in the VP.



Reasons are mainly two. The injectors are not fast enough to meter the fuel correctly with higher pressures. The power it takes to drive the CR pump. Higher pressures mean more power needed to drive the pump. This translates into higher fuel consumption.



I'd like to mention also that higher pressures mean higher fuel temps in the system and added stress to the system as a whole.



I'm not saying don't buy a box. I know how hard the BOMBing bug can bite...

All I want to do is to shear the experience we've had here with such kinda boxes.

You play, you pay...



Marco.

 

[Parshal]

Originally posted by Marco

Higher pressures mean more power needed to drive the pump. This translates into higher fuel consumption.

This makes sense to me. What doesn't make sense is that I've seen an increase in mileage since adding my EZ. I have not heard a good explanation as to why.

 

[Chace TX]

EZ

I have been told by Edge that the increase in fuel pressure and delivery caused by the EZ, causes the ecm to compensate by automatically advancing timing. Most EZ users are seeing a 1-1. 5 mpg gain.

 

[Marco]

Urban legend

Increased timing = 1. 5-2. 0 better MPG is an Urban Legend.



I've tested that with the Cummins and the Duramax on the engine

dyno. Optimized timing for performance gives a 2% ( TWO percent!) lower fuel consumption and a 60% higher NOx output.

Power increase is nothing worth to mention.



The better mileage several people claim to see after mods is related with thermal efficency.



Since emission laws have been introduced all diesel engines have been "detuned" in their most efficient thermal range. The part throttle. That's been done because they otherwise would produce more particulates than the law permits them.



In other words better mileage is gained with a slight increase of fuel @ part throttle ranges.



That makes the operation @ part thorttle more efficient thus the better mileage.



Maybe it's not all that clear...



If you have to move a big load, with an engine that's "detuned" @ part throttle you have to rev the engine higher to produce the power to move that load.



On the other side, if the engine produces all the power it can @ part throttle you'll get the load moving without reving the engine as high.



Clear as mud?



Marco

Marco

 

[Chace TX]

Makes sense to me.

Thanks Marco,

It seems too simple really. Is it not true for basically all detuned engines? You have to find the "happy medium" between power and efficiency.

 

[Marco]

I would rather say the happy medium between Emissions-Power-Efficency.