Diesel Questions

As you guys know I jumped into the diesel world in January and have been doing non-stop reading since. I want my truck to be reliable, have an extremely long life, and be powerful. In doing this I do most of my reading in how to care for the engine and bring the power out wisely. I have a few questions for you guys...

1.) Can someone explain to me what "rough idling" is and what causes it?

2.) When idling the truck are supposed to throw it in neutral with the parking brake or does it not make any difference being in park?

3.) I plan on running 100HP nozzles and plan on upgrading the turbo prior to. For power and efficiency was size Industrial Injection turbo would be the the wisest to go with 62, 64, or 66?

I've read 100s max out the 62, don't hear much about the 64, and the 66 has stellar reviews, but just not sure about the efficiency for daily driving and towing.

Thanks for the input guys.

Roughly idling is when the injectors are not spraying properly creating a shaky idle. Also could be air issues with the fuel if air is in the fuel it harder for the CP3 to pressurise the fuel rail.

Shouldn't have to place it in park or neutral while going from light to light. Drive it just like a gasser.

Be careful how far your going. The higher up the HP/TQ number you go the less reliable the truck will be as well as how low you'll push the MPG's making the truck a pig to drive.

Thanks for the help man!

When I say idling, I mean parked in a lot, not driving. In this 100 degree heat, when waiting in the truck, leaving the AC on is a must lol.

Now I don't plan on pushing huge power, probably around average. I plan on upgrading the tranny, airdog 150 lift pump, bag o parts cp3 mod, not sure on the turbo, and 100HP nozzles....should be from 500-600HP. I know 50hp nozzles are primarily for MPG, and 100s help a little or have no affect from the research I've done. With those mods, would te reliability of the truck be hindered significantly or would it be the same with proper maintenance?

You limitation is going to be head gasket and transmission...

Roughly speaking you need 1 PSI of boost for 10 horsepower. So you would need 55-60 PSI of boost, turbos capable of, exhaust system, intake, etc. Plus on top of it the head work to support such...

Then with driveline its not the HP that hurts but the torque. So the drivieline would have to upgraded to hold roughly 1000-1200 ft lbs of torque... Roughly speaking again.

For a reliable daily driver I would limit to 400-450 HP tops. That will produce close to 1000 ft lbs of torque.

So then it'd be smart to just stop with the lift pump and transmission? No need to Mod the CP3 if i stay with stock sticks. I've seen CR's dyno'd with the same/similar set up I have right now pushing 400-440HP and 800-900lb/ft of torque

1.) Can someone explain to me what "rough idling" is and what causes it?

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Could be anything from dirty fuel(a bit more water in than normal but not enough to trip the sensor) to a electronic glitch.

2.) When idling the truck are supposed to throw it in neutral with the parking brake or does it not make any difference being in park?

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No need to idle in neutral and I NEVER trust a parking brake alone.

3.) I plan on running 100HP nozzles and plan on upgrading the turbo prior to. For power and efficiency was size Industrial Injection turbo would be the the wisest to go with 62, 64, or 66?

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There are many good turbo shops out there to taylor make you one to fit your needs.II,Forced Inductions,High Tech Turbo,River City Turbo,Garrett,Turbonetics and Engineered Diesel.Its a pick a shop your confident with and go with them.Personally running a 90hp or a 120hp injector I would not run any charger smaller than a 64mm.

I would also slip a little fuel additive throough your system to help with the roughness.The two I would reccomend are Almagated or Standyne.Good Luck.....Andy

P.S.-I would not step up the charger and nozzles without studding the head.

I don't have rough idling, I was just curious to what it was lol..but thanks for the info! What's your opinion of the reliability of a 500-600HP truck?

I plan on studding it also

infernoredram said:

I don't have rough idling, I was just curious to what it was lol..but thanks for the info! What's your opinion of the reliability of a 500-600HP truck?

I plan on studding it also

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If done properly, you can make a reliable 500-600HP truck, it just take money. Like said above, you're weaknesses are going to be transmission, headgaskets, and with the torque that you will have, the driveline will become a weakness. So driveshaft, rearend, and rear axle will need strengthening.

You can only ever have 2 of the 3: Power, Reliability, Low Cost.

You can have a reliable powerful truck, but it's gonna cost ya.
You can have a reliable low cost truck, but it's not gonna be powerful.
You can have a powerful low cost truck, but it's not gonna be reliable.

You can have a reliable powerful truck, but it's gonna cost ya.

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But driveablity will be a factor. Now will you be able to control you smoke from light to light? These kind of truck should be built for track use not daily drivers because that why we now have strict diesel smoke laws.

You can have a powerful low cost truck, but it's not gonna be reliable.

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This is the most common you see out on the street some tosses a performance box in a truck without the supporting mods and end up tearing up a engine in no time flat.

The last one is still going to cost you, in repairs and eventually a new truck.


I have always found that when it comes to performance you need to do it right, and that is invest in quality products and strengthening the weak parts on the truck first.

For every mod there is a supporting mod. I know I built a reliable yet powerful cummins.


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RYAN66 said:

The last one is still going to cost you, in repairs and eventually a new truck.

I have always found that when it comes to performance you need to do it right, and that is invest in quality products and strengthening the weak parts on the truck first.

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ramhunter9 said:

For every mod there is a supporting mod. I know I built a reliable yet powerful cummins.

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So very true... But when do you say enough is a enough to street power without driving a truck that blacks out the street from light to light? This is a issue that most nobody ever looks at. I talk to hundred if not thousands of people that claim to have 800-1000 HP daily driver truck but can never control the smoke from light to light. I end up hear all the juicy stories about blacking out State Cops, to smoke tickets, etc. Most of this never makes it to the forums but is all very common with truck over the 400-500 HP mark. And you all wonder where all the smoke laws come from?

The other side of the coin I never never seen a truck over +500 HP that was capable of holding consistent 20 MPG and above as daily driver. Not even my truck is absolutely right there above 20 all the time but I hold my own. Little tougher for me in the mountains of Idaho.

Making a high power truck is one thing but economic and good manner daily driver is another thing.

Just more food for thought...

As is my girlfriends dads 6.7 is somewhere around 450-490hp according to H&S with zero smoke
Hoping to get it on a dyno this Friday!

Stangshcky12 said:

As is my girlfriends dads 6.7 is somewhere around 450-490hp according to H&S with zero smoke
Hoping to get it on a dyno this Friday!

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Sad to say I'm a dying breed... I've haven't seen a 6.7L yet. So I can't judge them.

Drove my buddies 2012 Laramie longhorn mega cab Cummins for a good while today. Nicest truck I've ever seen/driven/been in...the interior is ridiculous. To be honest though, I wasn't too impressed with the stock power...but it is a big truck, and on 35s lol