HPCR fuel system.........

[V6power87]

Hey guy's,





Are there any problems yet with this system? Any lift pump troubles like with my truck?



Has the aftermarket came out with any fueling boxes yet?



I test drove an '03 today and noticed that when I shifted the RPM kinda hung around and did not fall down very fast... ... why?





Thanks.

 

[lschultz]

Thanks to your(our)great engineers thats the way they have it set up. I notice it more on mind from 2>3.

 

[V6power87]

I wonder what the purpose is for the RPM to stay up, better trans shifting?



I noticed it the second I shifted... ... I am so used to the way my '01 is.



The '03 ETH felt MUCH stronger than my ETH stock for stock. I also drove a new Duramax with the Allison, It was VERY slow. The sales guy could not even tell that I was hot rodding it.

 

[RSnaith]

Originally posted by V6power87

I test drove an '03 today and noticed that when I shifted the RPM kinda hung around and did not fall down very fast... ... why?

We've been discussing this, as Cummins/Dodge has been very tight lipped about why they maintain the RPMs between shifts. So far we've got two viable theories:



1) Emissions. Keep the RPMs up, boost doesn't fall as much between shifts, less emissions. Some cars in the 70s and 80s were programmed like this.



2) Clutch saving. The 03 clutch appears to be identical to the 02 clutch, and since an HO is running pretty close to ragged edge on what the clutch is capable of handling, keeping the RPMs up between shifts will be easier on the clutch.



Keep in mind, these are only theories.

 

[kaffine krazed]

I think the reason the rpms don't drop off is for shift quality.

 

[Prairie Dog]

I've noticed it mostly only does it from 1-2 and 2-3 shifts and is worse if I use a very light throttle setting. I've also noticed the engine does not stumble rite after I shift anymore and the transmission shifts much smoother. As for the revs hanging up, I've learned just to delay letting out the clutch slightly and the truck pulls very smoothly. I am a little concerned as to what this mite be like on ice or snow though.

 

[DPKetchum]

My two cents worth is its emmissions releated. A afterburn type affect to plurge left over fuel off of cyl. walls etc. Thats way autos in late 80s and 90s did this,more so with throttle bodys then port injection. Older port stuff also did this to such as Datsun Z in mid 70s to early 80s. It was called a BCDD Boost control deaccelartion device ans was totaly emission releated.

 

[Vaughn MacKenzie]

My theory is it's intended to smooth out drivetrain slop when going from acceleration to deceleration, and eliminate the rebounding effect when revving up and letting off completely in lower gears.



Vaughn

 

[TxDieselKid]

Originally posted by V6power87

Has the aftermarket came out with any fueling boxes yet?

Yes!!!

 

[V6power87]

Andrew,



Who? How much? how much power?

 

[kbarlow]

Originally posted by Prairie Dog

... . As for the revs hanging up...

Mine did the same till 2000 miles. Now at 3000 miles it appears to operate normal. I wonder if the high mileage guys are still getting the slow spool down?



Cheers Ken

 

[DIESELMAN]

Barlow - Your just gettin used to it, mine still is slow to unwind, but I'm used to it too now.

 

[yogibear]

27,221 miles on mine, and it hasen't changed.



Larry

 

[DIESELMAN]

Go Larry!

 

[kbarlow]

Thanks Larry



It must be my old timers disease, I'll pay attention the next time I use the truck.



Ken

 

[yogibear]

Kbarlow, old timers disease, whats that?!? I'm 64 and rolling!! I can do that because I'm pretty round!



Larry

 

[KLockliear]

Re: Re: HPCR fuel system.........

Originally posted by RSnaith

We've been discussing this, as Cummins/Dodge has been very tight lipped about why they maintain the RPMs between shifts. So far we've got two viable theories:

Both wrong, but I'll give you a hint... think turbo.

 

[krabman]

Cmon, give it up, is it to help keep from barking it or what? Inquiring minds wanna know...

 

[RSnaith]

Re: Re: Re: HPCR fuel system.........

Originally posted by KLockliear

Both wrong, but I'll give you a hint... think turbo.

Maintaining RPMS helps keep the boost levels up, that much is obvious. This in turn helps reduce emissions. Is there something else to add?

 

[JHansen]

My guess is that keeping the turbo spooled up by letting the RPM drop slower reduces lag thereby making the engine feel more powerful yet... ... . plus as an added side benefit you get to think you're driving a big old Cat instead of a Cummins pup engine



Someone let me know what I win if my guess is right!



Jason