Diesel lope...

[horse123]

After looking into this, I've found that the general consensus is that most people think it's very stupid and pointless, but that's beside the point. If someone wants to lower their civic until it's an inch off the ground and give a 45º camber then that's their business, I figure it's the same for any modification. Do what you want, and as long as it's not damaging your vehicle significantly, don't care what other people think.

That brings me to my next point. I also found you can get lope in (at least) 2 ways, either changing out cams or a tune. I've found some people saying it's bad for valves, some people saying it couldn't possibly hurt valves, I even saw one or two people say it causes a runaway in high idle sometimes. So I decided to ask here for the mechanical facts. What is happening in a diesel engine mechanically when you cause it to lope at idle, and how bad is it actually? Other than the extra vibration possibly causing things to rattle/fall off faster in the interior.

You can PM me if you want to tell me how stupid lope is, I'm just asking for facts, not what people think about it. I don't even have a diesel truck so don't worry about it.

 

[bullwinkle]

Would think lope would be a misfire, timing incorrect at idle. Not sure why one would want an engine to lope, would be a lot of unburned fuel smoke & weird noises, like my 6.0 PSD used to with a sub 30F start with 15W40, sounded like an idling lawn mower, LOTS of blue smoke.

 

[oilpsi2high]

If there was any benefit then trucks would come stock with a lopey idle.

If you change cam duration and lift then it'll lope. Not sure if there is any benefit to doing that on a diesel.

 

[horse123]

There's a benefit to tuning trucks, and yet trucks come with awful factory tunes most/all of the time. It could cause no damage but is unnecessary/wastes fuel or something, which is why I'm asking and could be why trucks don't ship with lope if it's true. But again I'm asking for someone to explain what is actually happening in the engine and reasonable proof whether it's bad or not harmful to diesel engines.

 

[OVERKILL]

Most gas cams that give you "lope" have a narrow LSA and some decent overlap. This is done to allow the exhaust to "draw" the intake charge into the chamber, which makes more power at higher RPM.

Boosted engine cams tend to have wider LSA's and no overlap because you don't want to boost going out the exhaust valve. Due to this, even having more duration and more lift, they tend to sound very docile.

I can't imagine a well designed aftermarket diesel cam giving you any overlap, and ergo, would not expect it to give you any real "lope" either.

Most power with a diesel is gained with more boost and more fuel.

 

[horse123]

I knew it wouldn't give much/any power, but I was just wondering mostly is it really that bad for valves like people seem to think, or is it just worse for fuel economy?

 

[tom slick]

Just rig a switch that kills one fuel injector, that'll make it lope. Then you can flip that switch when you need to impress others.

 

[horse123]

Originally Posted By: tom slick
Just rig a switch that kills one fuel injector, that'll make it lope. Then you can flip that switch when you need to impress others.



You mean fuel injectors on one cylinder, or one injector on all cylinders, or one injector on one cylinder? I'm not even sure if any diesels have more than 2 valves per cylinder, never looked very much into diesel engines until recently...

 

[meep]

Originally Posted By: OVERKILL
Most gas cams that give you "lope" have a narrow LSA and some decent overlap. This is done to allow the exhaust to "draw" the intake charge into the chamber, which makes more power at higher RPM.

Boosted engine cams tend to have wider LSA's and no overlap because you don't want to boost going out the exhaust valve. Due to this, even having more duration and more lift, they tend to sound very docile.

I can't imagine a well designed aftermarket diesel cam giving you any overlap, and ergo, would not expect it to give you any real "lope" either.

Most power with a diesel is gained with more boost and more fuel.


^^^^great answer^^^^

I can't see how it would hurt valves if the cam is set up properly and the springs are appropriate, but any cam mods like this in a diesel would be counter-productive and frankly pointless in my opinion.

Camming a gas engine, otoh, can have its benefits, as well as compromises. Just depends on what the owner is after. A cammed V8 can be loads of fun, and a little pesky as a DD, all at the same time.

 

[tom slick]

Originally Posted By: horse123
Originally Posted By: tom slick
Just rig a switch that kills one fuel injector, that'll make it lope. Then you can flip that switch when you need to impress others.



You mean fuel injectors on one cylinder, or one injector on all cylinders, or one injector on one cylinder? I'm not even sure if any diesels have more than 2 valves per cylinder, never looked very much into diesel engines until recently...


That's for you to figure out. I just know a diesel with a bad injector lopes at idle.

 

[1 FMF]

Originally Posted By: horse123
I've found some people saying it's bad for valves, some people saying it couldn't possibly hurt valves, I even saw one or two people say it causes a runaway in high idle sometimes. So I decided to ask here for the mechanical facts. What is happening in a diesel engine mechanically when you cause it to lope at idle, and how bad is it actually? Other than the extra vibration possibly causing things to rattle/fall off faster in the interior.


people can say/claim anything, do they back it up with any kind of logical rationale?
i would first ask what is causing the lope, because in a diesel (compression ignition) it is not natural or normal. so whether loping is hurting anything may depend on what's causing the lope. But at idle under no power, there's no heat and no extra forces that aren't normally there so i can't see valves getting hurt. as for runaway, what causes runaway is unregulated fuel added to the combustion chamber either diesel from injectors or injector pump or engine oil. I don't see how loping can cause runaway, unless you rationalize the up/down rpm causes the turbo to spool up/down somehow causing a seal failure and oil leakage from the turbo into the intake, which i would then disagree with.

if the lope drops idle rpm down to 400-500 rpm then i would start to worry about lack of oil pressure and oil flow because the oil pump is not turning. and with a lope if incomplete combustion is happening as a result, or what's causing the lope is resulting in excess fuel in the cylinder causing wash down then yeah the lope can be causing damage. diesel is compression ignition, relying on heat upon compression to ignite fuel. you want to maintain a stable and warm cylinder temperature, you don't want it cooling off and evidence of that would be white exhaust where there isn't a catalytic converter and other emissions devices.

 

[Fleetmon]

What engine? A two-stroke loping idle is typically erased with a simple adjustment.

Another cause of loping can be a suction leak at a fuel filter, fuel line, etc....they will lope badly at idle but will straighten out and run fine until it returns to idle and begins sucking air again.

A loping fuel system requires a good look to avoid another problem......sometimes a loping/erratic idle can be a sign the fuel pump/governor drive is near failing.

 

[Silk]

In older diesels it was just the idle speed being too low, which makes the governor lift speed,then it drops and it lifts it again. I used to like driving an old Leyland or similar and having it lope at the lights - has it become the in thing for young guys to do now?

 

[circuitsmith]

Wanting a diesel to lope makes about as much sense as trying to get an electric motor to lope.
Race car drivers would be quite happy with an engine that made good power at 10,000+ rpm AND idled smoothly.

 

[CDX825]

Lope tunes are popular with the lifted and stacked to the max diesel crowd. Yes they are actually tuning them to lope at idle.

It sounds terrible if you ask me. Sounds like an engine with several bad injectors.

Get on youtube and look it up.

I seen a couple young kid at the gas station one day with a lope tune. Whole truck was shaking as a result of said "tune".

I can't imagine it being good for the engine or transmission.

 

[SHOZ]

When I was much younger one of my jobs was starting the trucks for a fuel delivery company on the 3rd shift Sunday night. When it was really cold we would give them a grape shaped ether pill and crank them up. They would lope and clatter so bad I wondered how they ever stayed in one piece.