Dodge Cumming Turbo Diesel Tuning...

My friend is looking for some advice on how to get the most power out of his truck. Its an 02(I think) inline 6 Cummings.

The truck is totally stock other than an upgraded exhaust and some sort of tuning chip/logger (not sure what it is). The chip allows control of boost and also displays egts, boost, etc...

I have experience tuning gasoline turbo'd engine but not diesel engines. I have the understanding that its almost impossible to cause detonation. You are supposed to turn up the boost until you no longer notice smoke coming out of the tail pipe (this means its no longer running rich)?? If you turn it up past this point, you are not going to make anymore power.

Would turning it up past the rich point just increase the EGTs? What is the limit the EGTs should not exceed? How much boost does this truck run stock? Roughly, how much boost can the stock injectors keep up with? How much boost can the stock turbo hold?

To make more power, this will require: bigger injectors. To make even more power, he will probably have to get a bigger turbo and bigger injectors?

What are some other good supporting mods for this truck?

*EDIT*: Do you turn up the boost until it stops smoking @ WOT pull or while taking off from a stop? I would think it would be from a pull...but I haven't seen a truck constantly smoke @ WOT.

*EDIT*: Do you turn up the boost until it stops smoking @ WOT pull or while taking off from a stop? I would think it would be from a pull...but I haven't seen a truck constantly smoke @ WOT.

that's because stock trucks use a particulate filter, that removes most of the black "smoke" (it's actually soot, pure carbon) so truck that do pulling etc with major tunes run without them, so they blow constant streams of black smoke.

that's because stock trucks use a particulate filter, that removes most of the black "smoke" (it's actually soot, pure carbon) so truck that do pulling etc with major tunes run without them, so they blow constant streams of black smoke.


So, they take this filter out for tuning purposes? So they can tell when its no longer running rich?

I'm basically trying to figure out how to tune a diesel truck.

Try posting in the diesel engine section, it might have some more info you're looking for.Diesel Engines (http://www.automotiveforums.com/vbulletin/forumdisplay.php?f=1650)

Or you can always do a search on AF and you might find some info.

Try posting in the diesel engine section, it might have some more info you're looking for.Diesel Engines (http://www.automotiveforums.com/vbulletin/forumdisplay.php?f=1650)

Or you can always do a search on AF and you might find some info.

Ah! Thanks. I couldn't find that forum for some reason.

Well basically.
More fuel = higher EGT.
More boost = lower EGT.

It's also worth monitoring intake air temperature. This way you can figure out if the current turbo and intercooler are doing the job properly or not.
Without an intercooler, 15psi boost will run around 120 deg C on a 20 deg C day.
Intake temp changes translate very well to equivalent exhaust temp changes. So a good intercooler can let you run more fuel for more power without melting your engine.

More boost on a diesel can increase your efficiency through increasing the compression ratio. Of course it's a tradeoff between how much power it takes to deliver the extra boost and how much power you gain from the extra boost.

My truck runs the highest EGT's under sustained load. Full throttle at cruise (2500rpm) will only deliver 550 deg C, but full throttle at close to the rev limit (3600rpm) will cross the 700 deg C line.
I think it's a combination of heat soak (everything getting hotter), the turbo running into low efficiency zones (heating air more when it compresses it) and no intercooler.

So, they take this filter out for tuning purposes? So they can tell when its no longer running rich?

I'm basically trying to figure out how to tune a diesel truck.

yes and no. they take it out because it's restrictive. it causes back pressure between the exhaust ports and the open atmosphere.

for example, take a tube and blow through it, it's easy as there's no obstruction. now that a tube, and put a cloth over the other end, the cloth's like a filter, filtering dust and such and it's harder to blow through. this is a lot like the particulate filter, it's removed to let the exhaust get away from the engine easier. better flow = more power.

it's not taken out to see if it's running rich, it's taken out for the reasons above.

My truck runs the highest EGT's under sustained load. Full throttle at cruise (2500rpm) will only deliver 550 deg C, but full throttle at close to the rev limit (3600rpm) will cross the 700 deg C line.
I think it's a combination of heat soak (everything getting hotter), the turbo running into low efficiency zones (heating air more when it compresses it) and no intercooler.

:p Diesels don't have a throttle.

Here is diesel tuning in a nutshell (and these are generalizations but they hold true for most traditional turbo diesels)

Since there is no throttle, the intake is open to full atmospheric air all the time. At idle, the injectors are injecting just enough fuel to support idle operation. As you put more "foot" into it, the injector pump injects more fuel. As such, a diesel engine more or less operates between extremely lean at idle to borderline lean at full power. Soot and black smoke is basically unburned fuel that makes it out of the exhaust. Black smoke does not necessarily mean rich mixtures, it can mean late injection, poor efficiency, damaged injectors, or one of several things. But... since we're talking about a later, electronically-controlled diesel, we can rule out some of those things. Under normal operation, a 24v electronic Cummins doesn't belch black smoke thanks to efficient flame decks, accurate timing control, and good fuel atomization.

So, let's assume that the stock setup lets the engine operate between really lean up to a little bit lean at full power. Chips take advantage of the conservative factory tune and inject the extra fuel. Since there is still more air than fuel in the factory tune, giving it more fuel fills the gap without lapsing into black smoke territory. Also involved with that additional fuel is additional heat energy going through the turbo. In the case of some turbos (like early powerstrokes) there is no boost control other than the amount of exhaust, so increasing fuel increases boost. To an extent, in un-controlled turbos adding more fuel adds more air which allows you to add more fuel... etc. Of course you reach an inefficiency point with the turbo/intercooler which limits your streetability.

Other diesels with electronic or mechanical wastegates must be retuned to allow the extra boost or adding more fuel will simply create more black smoke and higher EGTs. For instance in the case of the Duramax you only have a small window to add more fuel at stock boost levels. After about 60hp you have to up the boost to get more air to go along with your extra fuel.

Basically, here's what you need to do. Small upgrades in fuel will give nice boosts to power. Keep EGTs in check and you'll be fine. If its a daily driver only, go ahead and juice it up a bit. An 80 hp chip should do fine on a stock truck. 100hp and more will require a careful eye on a pyrometer installed in the exhaust manifold. If you're going to tow with it, consider a better intercooler, a bigger downpipe, and a large-diameter exhaust to keep EGTs down. As a general rule, if you're going to get one of those switchable tuners that offer three or four HP levels, the hottest settings are fine for occasional street use, but a big no-no for towing. Upgrading intercooler and exhaust typically make the hottest settings fine on the street and OK for occasional light towing.

Its really pretty simple when you think about it. With gas you have to worry about VE and cam timing and all of the mechanics of how the engine ingests air. With diesel, that part is fixed. Its a simple matter of mass air vs. mass fuel. Increase the air and you can increase the fuel. Keep doing it until your pyrometer says stop. Then do things that reduce EGTs like exhaust and intercooler mods and add even more fuel. Your two biggest limiting factors are EGT and reliability of internal parts... and I guarantee you'll reach EGT limits before you even stress the guts of that Cummins. I have a link (on my other computer) to a dyno run of a 5.9 Cummins that makes over 1200 hp and 2131 lb-ft of torque AT THE WHEELS. Not kidding. Many Cummins owners are daily driving 5.9s that make 1200 lb-ft and 600+ hp at the wheels, so don't worry about the stock internals. You have a 360-cubic-inch motor that weighs nearly 1200 lbs. Its built for it :)

You are supposed to turn up the boost until you no longer notice smoke coming out of the tail pipe (this means its no longer running rich)?? If you turn it up past this point, you are not going to make anymore power.

For the most part that is true. Giving it more air doesn't help unless you give it more fuel. You may get a few more HP from the increased dynamic compression, but not worth it.

Would turning it up past the rich point just increase the EGTs? What is the limit the EGTs should not exceed? How much boost does this truck run stock? Roughly, how much boost can the stock injectors keep up with? How much boost can the stock turbo hold?

Adding more fuel past rich will cause EGTs to rise rapidly. The unburnt fuel would continue to burn once it encounters the manifold. EGTs spike, turbos cook, not pretty :). Can't tell you how much they run stock pressure, but think of it in the low 20s psi. I think I've read of owners running over 40 psi on stock injectors, but reliability becomes an issue at the fuel pressures required to deliver enough fuel. Just like with gas, injector size has trade offs; idle control vs mass capacity, pressure vs reliability... but at thousands of PSI fuel pressure, things get a bit more hairy. The stock turbo can usually be asked to go to about 40 psi. Its suggested to upgrade intercooler, hoses, etc since we are talking about exducer temps of 500 degrees or more at that level of boost. Typically the aftermarket advertises turbo upgrades starting at about 400-500 hp at the wheels, so I guess one could expect the stock spool to support 400 to the tires. At that level though I would expect you'd be spending more on EGT control measures than you would on a new turbo more suited to the application.

To make more power, this will require: bigger injectors. To make even more power, he will probably have to get a bigger turbo and bigger injectors?

Yep. Like I said in the other post... more fuel, more air, more fuel, more air.

What are some other good supporting mods for this truck?

Some serious help will be needed for that 48RE tranny (if its an automatic). They're pretty weak to start with, but after adding more torque it will be toast in short order. You can electronically beef it up, but that will mostly just increase line pressures and shorten shift times. The stock stamped steel converter will balloon and throw lots of heat at the fluid. An aftermarket billet TC might be in order as well as some serious fluid coolers. I'm not too well versed on which parts die first in Dodge autos so someone else will know better at what level these parts are required, but don't think that it will last without upgrades; even just for mild street use. Some complain about U-joints going fast, especially with firmer shifts. Not sure of the fix, but in my opinion (if I had a cummins) I'd drive it like I stole it and replace $30 U joints every 6000 miles :)

*EDIT*: Do you turn up the boost until it stops smoking @ WOT pull or while taking off from a stop? I would think it would be from a pull...but I haven't seen a truck constantly smoke @ WOT.

Its not quite that simple, but generally yes. Since mass fuel injection is controlled by your foot, tuning it for no smoke from a stop will leave room for more fuel at peak RPM. Tuning it for best fuel at peak RPM typically makes some smoke from a stop. That is up to the driver and the application. I personally don't like black smoke because I'm a little politically involved in diesel's place in society. John Q. Treelover and Mary Dolphinhugger don't like black smoke so I'd gladly give up 20 hp to get lower EGTs and be able to have more SMUG emissions than SMOG emissions. Nothing satisfies me more than taking an environmentalist for a ride in a 500-hp diesel and having them comment, "now this sounds like a diesel, but its too fast and I don't see any black smoke."

One of your questions I saved for last because I wanted to include my disclaimer. You asked about the EGT limit. I've personally never modified any of my diesels beyond the point where I felt I need a pyrometer, but if my memory serves me correctly most diesel EGTs are safe all day at 800F, pretty decent at 1000F, but more than that should be reserved for temporary splurges. My disclaimer is that I am VERY new to diesel. I'm incredibly interested and I'm soaking up info as fast as I can, but like you I'm most informed with gas stuff. I say that so you take my words with a BIG grain of salt because everything I just wrote is pretty loose stuff from an amateur in the diesel world. I just thought maybe I could give you a little kick start to help your friend out. Good luck and enjoy.

:p Diesels don't have a throttle.

Fine then, full pedal.:loser:

I have a link (on my other computer) to a dyno run of a 5.9 Cummins that makes over 1200 hp and 2131 lb-ft of torque AT THE WHEELS. Not kidding. Many Cummins owners are daily driving 5.9s that make 1200 lb-ft and 600+ hp at the wheels, so don't worry about the stock internals. You have a 360-cubic-inch motor that weighs nearly 1200 lbs. Its built for it :)

i believe we have a link to a site with a dyno print-out for a similar run in the diesel engines section.

a friend of mine is a diesel performance engineer. he's got a hilux with a 5.9 in it, ran about 2,320lb/ft at the flywheel. and something like 2,115lb/ft at the wheels. not sure about bhp numbers, but they're past the 1,100 mark.

scary stuff, i've driven it set to full-tilt on an industrial estate, it's fierce, very fierce.

grtn316, this is what a tuned 5.9 running with no particulate filter looks like at "full pedal" :p

http://www.dieselperformancemotorsports.com/gallery/main.php?g2_view=core.DownloadItem&g2_itemId=760&g2_serialNumber=2

My disclaimer is that I am VERY new to diesel. I'm incredibly interested and I'm soaking up info as fast as I can, but like you I'm most informed with gas stuff.
then passing it on to forums so that incredibly interested people like me can soak it up as well.

you know, the sae offers a course on diesels, i'm pretty sure you have to be an engineer though. i'll deffinitly take it after i get my degree.

but thanks for the info. i actually kinda wanted a diesel golf instead of my accord for the simple fact that i wanted to tune it, nobody would see it coming lol.

I personally don't like black smoke because I'm a little politically involved in diesel's place in society. John Q. Treelover and Mary Dolphinhugger don't like black smoke so I'd gladly give up 20 hp to get lower EGTs and be able to have more SMUG emissions than SMOG emissions.

Me too.
I see simply winding up the fuel and blowing black smoke as the cheats way to more power. I can only imagine what that much unburnt carbon does to your engine internals too.

The quest for more low end torque without smoke is leading me towards variable vane turbos right now. But they're not easy things to find in scrap yards.

If you're flexible on engine displacement and target boost range, 6.0 powerstrokes have a Variable vane blower that should be in the junkyards by now. Not cheap, but cheaper than new. There aren't many trims available for that setup but it might be a close enough trim for you.

If you're flexible on engine displacement and target boost range, 6.0 powerstrokes have a Variable vane blower that should be in the junkyards by now. Not cheap, but cheaper than new. There aren't many trims available for that setup but it might be a close enough trim for you.

The engine I'm running is an Isuzu 4BD1T, basically a japanese copy of the cummins 4BT at 3.9 litres. I'm in New Zealand where the vast majority of automotive stuff comes from japan (we import their cast-offs and drive them into the ground). American engines are almost non-existant.

A stock variable vane of a 6.0 might reach down to a lower range than my current turbo. But I've recently got a Gt2052V from a 2.5L audi diesel to play with. It's pretty small but the air requirements of a low speed 3.9L and medium-high speed 2.5L aren't too far off.

Here is diesel tuning in a nutshell (and these are generalizations but they hold true for most traditional turbo diesels)

Since there is no throttle, the intake is open to full atmospheric air all the time. At idle, the injectors are injecting just enough fuel to support idle operation. As you put more "foot" into it, the injector pump injects more fuel. As such, a diesel engine more or less operates between extremely lean at idle to borderline lean at full power. Soot and black smoke is basically unburned fuel that makes it out of the exhaust. Black smoke does not necessarily mean rich mixtures, it can mean late injection, poor efficiency, damaged injectors, or one of several things. But... since we're talking about a later, electronically-controlled diesel, we can rule out some of those things. Under normal operation, a 24v electronic Cummins doesn't belch black smoke thanks to efficient flame decks, accurate timing control, and good fuel atomization.

So, let's assume that the stock setup lets the engine operate between really lean up to a little bit lean at full power. Chips take advantage of the conservative factory tune and inject the extra fuel. Since there is still more air than fuel in the factory tune, giving it more fuel fills the gap without lapsing into black smoke territory. Also involved with that additional fuel is additional heat energy going through the turbo. In the case of some turbos (like early powerstrokes) there is no boost control other than the amount of exhaust, so increasing fuel increases boost. To an extent, in un-controlled turbos adding more fuel adds more air which allows you to add more fuel... etc. Of course you reach an inefficiency point with the turbo/intercooler which limits your streetability.

Other diesels with electronic or mechanical wastegates must be retuned to allow the extra boost or adding more fuel will simply create more black smoke and higher EGTs. For instance in the case of the Duramax you only have a small window to add more fuel at stock boost levels. After about 60hp you have to up the boost to get more air to go along with your extra fuel.

Basically, here's what you need to do. Small upgrades in fuel will give nice boosts to power. Keep EGTs in check and you'll be fine. If its a daily driver only, go ahead and juice it up a bit. An 80 hp chip should do fine on a stock truck. 100hp and more will require a careful eye on a pyrometer installed in the exhaust manifold. If you're going to tow with it, consider a better intercooler, a bigger downpipe, and a large-diameter exhaust to keep EGTs down. As a general rule, if you're going to get one of those switchable tuners that offer three or four HP levels, the hottest settings are fine for occasional street use, but a big no-no for towing. Upgrading intercooler and exhaust typically make the hottest settings fine on the street and OK for occasional light towing.

Its really pretty simple when you think about it. With gas you have to worry about VE and cam timing and all of the mechanics of how the engine ingests air. With diesel, that part is fixed. Its a simple matter of mass air vs. mass fuel. Increase the air and you can increase the fuel. Keep doing it until your pyrometer says stop. Then do things that reduce EGTs like exhaust and intercooler mods and add even more fuel. Your two biggest limiting factors are EGT and reliability of internal parts... and I guarantee you'll reach EGT limits before you even stress the guts of that Cummins. I have a link (on my other computer) to a dyno run of a 5.9 Cummins that makes over 1200 hp and 2131 lb-ft of torque AT THE WHEELS. Not kidding. Many Cummins owners are daily driving 5.9s that make 1200 lb-ft and 600+ hp at the wheels, so don't worry about the stock internals. You have a 360-cubic-inch motor that weighs nearly 1200 lbs. Its built for it :)

Thanks for all the great advice curtis!


Some other info I gathered is that his truck is actually a 2003 (I think I said 02) inline 6, it has 4" exhaust and a Edge Juice tuner.

What should be the next mods? Injectors, EGT gauge (I think this might come with the edge tuner though), open element filter?

I haven't got to get in the truck and mess with the tuner. I just spoke with him and he said he was only able to boost 25ish psi and his truck was bucking (he was hitting 30ish a week ago. fuel cut, i'd assume?). Anyways, the shop thats been putting the stuff on his truck is suggesting bigger exhaust (4.5 inch), meth injection etc...doesn't seem necessary just yet.


I'm going to see the truck tonight and mess with the tuner. I'm gonna check for boost leaks since hes peaking @ low 20 psi.


P.S. Its an auto tranny :(

**EDIT: Where can I find bigger injectors?

Update...


Last night, I took a look at the truck and found a few things...

1) oil ontop of the motor (I suspect its coming from the valve covers or pcv valve. Truck has 70k miles on it)
2) When the truck is in race or extreme mode, egts cleared 1000 F easy :eek7:. It would go up really fast as if it wasnt gonna stop. When he let off, it would go up to about 1200 F and then slowly drop off.
3) We set the boost to 35psi and it would peak at about 24psi. No visible boost leaks. Its sealed really good, so I kinda doubt theres a leak unless 1 of the pipes busted and theres a hole in the bottom that I didnt see.
4) He has a 4" tip and stock turbo back piping (3" ?)


Hes been driving to truck around for a couple weeks and I'm sure hes been beating on it. :disappoin Anyways, I let him know that his egts are really high and theres something wrong with his truck. @ cruise egts are around 600-700 F and @ cruise or full accel intake temperatures are @ 99 F.

I know that the 4" turbo back exhaust pipes may help his boost issue and EGTs but I kinda think theres something else going on since he was boosting 30ish psi a week ago.

Could those high temps have already damaged the new egt probe?

Anyone know what could be going on?

well, with any tunning ur going to have to make the truck reliable witch means he will have to by a tanny from ATC or some place, but the best tune for a dodge is a SMARTY, and he will dump smoke everyywere and he will notice a big big change in power, i can bet my life he will be happy with this too so trust me on that

well, with any tunning ur going to have to make the truck reliable witch means he will have to by a tanny from ATC or some place, but the best tune for a dodge is a SMARTY, and he will dump smoke everyywere and he will notice a big big change in power, i can bet my life he will be happy with this too so trust me on that

I can vouch for using Smarty. Good buy.

You need an electric motor!!