Engine/Transmission (1998.5 - 2002) 24v why less idle torque???

[Cummins Cowboy]

I have been driving my 02 of a few years now, I had a first gen before, and drove a '95 12valver, on thing that is annoying at times with my truck is it has way way less off idel torque than the other trucks, my old first gen could prolly start out in 4th and not die, sometimes on really really steep streets with my trailer, my truck almost wants to die, my first gen would just lug down and get the job done. I was wondering why the 24valve engines are this way.



My theory, the 24valve has way more advanced injection timing at idle, thats why the idle is so much louder, and also why it doesn't cold start quite as well as the old first gen. if this is the case, why couldn't they make the electronics retard the timing more at low rpm??

 

[Supermod56]

I dunno, but mine quieted down at idle a ton once I stuffed the Don's Sticks in it. My neighbor has a 1st Gen, and his is a lot louder, at all speeds. And you look at the key and it starts in cold weather, and off idle torque is just fine, I start off in 2nd and never step on the gas, just let the clutch out, same thing with the trailer hooked up, cept I use 1st. You are probably right on the timing thing, I would assume the ECU retards it at start, but I dunno!



Tom

 

[2-ND TIME]

less torque

Does your engine idle smooth or does it thump ????

 

[Vaughn MacKenzie]

Cummins Cowboy, a comment Marco made once was the VP44 can't deliver the fuel when you start dropping below idle RPM like the P pump can. That's why the ECM adds fueling to try and force the engine up to idle speed.



As for the rattle I believe it has more to do with the injection process than the timing. The 24v system delivers the fuel faster meaning more fuel is present when it ignites, making a louder clatter. There is always a delay between the point injection begins and when it starts to burn. If it gets quieter with Don's sticks that's probably because they atomize better and light off faster.



Vaughn

 

[Hohn]

An Marco ECM should take care of that off-idle problem. They respond a lot like a 12V just off idle.

 

[HookMeUp]

Cummins Cowboy, a comment Marco made once was the VP44 can't deliver the fuel when you start dropping below idle RPM like the P pump can. That's why the ECM adds fueling to try and force the engine up to idle speed.

Try this in an empty parking lot, suprised me the first time. Put it gear and let out the clutch and let it idle across the lot. Now step on the brake and what happens, that's right it over-powers the braking!

 

[Cummins Cowboy]

I have noticed that it will add fuel to speed up the engine. but it still does not seem to have the rotating mass like the first gen did.