What happened to all the hub bub over aluminum heads and diesels? I
have heard rumours and second hand BS but I think I've come to the
conclusion that GM/Isuzu did one heck of a job making aluminum heads
work on a diesel. Not only did they make it happen, they went even
further and turned it into an advantage!



GM/Isuzu/Dmax deserves some credit for coming up with a basic design
that has proven to hold up quite well with not only stock power but
with all the crazy power mods on top of it.



Looks like all the naysayers bought one.

Thanks for the kind words hoot yah dodgerhttp://www.dieselplace.com/forum/smileys/smiley36.gif

Where is the report post button? Nick, someone has hijacked hoot's (aka MR. cummins) account info. Suspend it immediately until you contact the real hoot. http://www.dieselplace.com/forum/smileys/hihi.gif Edited by: Max Power

Actually Hoot brings up a good point.


Very early on all the Camps of the competition were signaling out the worst thing GM could have done was put Aluminum heads on a diesel.


They all had it failing right out of the gate,failing bad.Funny thing how the Bosch injector has been the sore heal.


The Aluminum heads have been a winner and the crowd has gone hush and they must be humbled.Wonder how long we see this technology expand out.





Mac Edited by: Mackin

The aluminum heads don't work. They cause high injector failure rates. And I'm not really sure about those aluminum pistons. Really flimsy for a diesel. Give me solid cast iron any day.

Jim

Jim......... put the crack pipe down.....you're out there. LOL http://www.dieselplace.com/forum/smileys/smiley36.gif

Even when the Dmax first came out it didn't make sense.There have been high peak cylinder pressure, turbo and supercharged high horsepower aluminum headed engines since WW II. Aircraft engines. I was surprised that the Dmax was the first Diesel. I thought there had been several before it. The only drawback to an aluminum head is paying for it. Everything else is an advantage. The head on this engine goes beyond the material it's made out of. Ever think the reason a Dmax can make so much HP on so little boost is because the head is such a good design?

Hoot,


When I decided to order a DMAX in July, 2001, I searched all the forums to find out what others had to say about the DMAX and the other two brands (Ford and Dodge). My choice came down to a Dodge or Chevy. For my personal situation, I eliminated to Dodge mainly due to the excessive engine noise of the vehicle and the lack of a robust factory automatic tranny. What I noticed at the time, was that the DMAX was being slammed in a major way on the other forums for Aluminum Heads (like you mention), being too quiet (real trucks make a lot of noise) and for the fact that the engine was a "Jap" design.


Fast forward today, and I find it rather ironic that the aluminum heads are really a "no issue" and may actually be an advantage (as you mention). The Dodge, which used to have the "loudest" engine, now has possibly the most quite engine. One reads the various Dodge forums and you get the feeling a lot of owners really appreciate the fact that the engine is quiet (I guess real trucks can be quit, right?). The engine is still a Japanese design (no getting away from that), but in reality, the part content that makes up the final product is global, much like other products we buy everyday.


I also note, that the one item that haunts the DMAX's reputation today (INJECTORS), was not mentioned back then as an issue, nor did anyone realize that the replacement cost was approximately $4,000. To me, this $4,000 replacement cost is the single biggest liability/drawback of the DMAX design and the various forums ALL missed that at the time.





Time goes on,


Alan


Edited by: OC_DMAX

You don't realize how many times I get some ill-advised redneck wandering into my stall, to ask me, "how them 'luminum heads for replacin'?" I've gotten to the point I just ask if they can find "luminum" on the periodic table of elements because I don't know what it ishttp://www.dieselplace.com/forum/smileys/smiley23.gif

A friend of mine that owns a powercroak warned me against the dreaded aluminum heads. After owning one and joining the forum, I tell him that the injectors are the problem. And even that isn't a problem for someone like me who doesn't us my truck to work with-especially if they extend the warranties on the 03's and 04's like they did on the 01's and 02's. Heck, he even offered me to race him title for title. I told him I would race him payment for title and that is the best that I could do.


All in all your right Hoot. BTW, I sure am glad you didn't leave this forum after you bought a cummins. Good luck with your new truck!

Alan, I think you hit it for me. I can live with the fact that maybe I'm going to replace my injectors sometime. But between the cost of the injector and the design of the engine to get to it that is one BIG http://www.dieselplace.com/forum/smileys/smiley19.gif I'm just hoping they can beyound the injector issue in the next 4-5 years because when that warranty runs out, 4-6 thousand is a major concern both for keeping and selling......Bill

Dmax wasn't the first diesel with aluminum heads. I think there have been other manufacturers, but I know the Mercedes diesels from 86 on had aluminum heads. Unfortunately, the Al head on that motor was a doomed design (I know, I just spent about 3 grand replacing mine). Cracking is somewhat attributed to overheating, but even that is in some doubt. More likely is just a design that used too thin of casting between the prechamber and the valves where they all end up cracking. The good thing is, though, that Mercedes fixed the problem and the next head design seems bulletproof. Of course those engines were notorious rod-benders, but we won't get into that now.

Hoot,


.................................... The Dodge, which used to have the "loudest" engine, now has possibly the most quite engine. One reads the various Dodge forums and you get the feeling a lot of owners really appreciate the fact that the engine is quiet (I guess real trucks can be quit, right?). .................................


Time goes on,


Alan





Noticed lately what seems like more and more owners are looking for 'quiet' exhaust systems too. Things and preference evolves w/time.

Jim......... put the crack pipe down.....you're out there. LOL http://www.dieselplace.com/forum/smileys/smiley36.gif

Got one! Now Richard, don't your reconize a good troll when you see one?

Jim

A fellow worker purchased a new Dodge the other day based on the information he received from the Sales Pro stating that the DMax had an aluminum engine that fails under heavy loads. He has a really nice truck but is angered by the misinformation he received to draw him to the sale.

I heard from a "short-bus" rider that aluminum heads cause high silicon levels in the oil.



http://www.dieselplace.com/forum/smileys/smiley2.gif

....and baldness and maybe erectile dysfunction too.....http://www.dieselplace.com/forum/smileys/smiley3.gif

The main reasons that these heads survive is the alloy they use that can take the heat. The second item are the special head gaskets that can handle the different expansion rates.

I ran into a fellow at a NJ gas station driving a 6.5TD dually. Nice loking truck. I had my GMC at the time. He asked me how my truck was doing and proceeded to tell a story of a friend of his in New York that had a bunch of Dmaxes that were going through multiple head gasket replacements.


I told him I was very involved with info sources including dealer service dept's and I did not read a head gasket or head issue as being a standout problem. He simply shrugged.


There still are a lot of unbelievers in the Dmax due to alum heads. Being involved in Cummins I can tell you they don't have stock head gasket isues but they do blow head gaskets at lower power levels than the Dmax does. Cummins hot rodders get o-rings installed around the cylinders when they go high power.

I can't find the website but isn't there a guy running an all aluminum DD 6-53 from a M113 APC in a drag truck? I thought his downfall was the headbolts holding the 66 psi he was putting to it.

at 98000 I'm still waiting for my injectors to go, the headgaskets to blow and the aluminum heads to melt. I do have a blown speaker in the PS door, maybe I should trade it in before all heLL breaks loose at 100K http://www.dieselplace.com/forum/smileys/smiley36.gif

Time will tell.......... I noticed some oxidization on some of
the aluminum parts. Wonder how salt will affect things, in the
long run.....?

at 98000 I'm still waiting for my injectors to go, the headgaskets to blow and the aluminum heads to melt. I do have a blown speaker in the PS door, maybe I should trade it in before all heLL breaks loose at 100K http://www.dieselplace.com/forum/smileys/smiley36.gif


I hear you, Michael! I'm over half way to 93,000 myself and waiting for the axe to fall!http://www.dieselplace.com/forum/smileys/smiley3.gif Still running like a champ and looks like it will continue! http://www.dieselplace.com/forum/smileys/hihi.gif

Does anyone have an idea about how much boost pressure the stock head-gaskets will take? I was just wondering if anything will need to be done when the big turbos, and hopefully twinshttp://www.dieselplace.com/forum/smileys/smiley4.gif become available.

More boost equalls more heat. How mush more heat do you want this powerplant to withstand? My boost gauge shows about 24-25 Lbs. at times. Unless GM/Izsusu are going to redesign the heads, intake, & exhaust systems to get the heat out and hold the boost in, how much more power do you want out of this beast?





Brad

You can never have too much power. Hohohohohoho (in manly grunting voice)

Micheal T


Is this the truck you are draggin an pullin. If so you doin just fine, keep it uphttp://www.dieselplace.com/forum/smileys/smiley32.gif

geno, yes it is

More boost equalls more heat. How mush more heat do you want this powerplant to withstand? My boost gauge shows about 24-25 Lbs. at times. Unless GM/Izsusu are going to redesign the heads, intake, & exhaust systems to get the heat out and hold the boost in, how much more power do you want out of this beast?





Brad





Brad,


I disagree a bit... more fuel equals more heat.. if we can get turbo designed to move more air, the the effect of adding boost (air) should reduce our heat.. example- with my tts extreme, if i set the actuator to 28 lbs max it runs much hotter EGT wise than if i set it to 32 or 34lbs max.. same amount of fuel, just shoving more air in at the same time...

The competition seems to be talking less and less about the heads. Now that they are a proven non issue they have become beneficial which is good and you know they don't want to mention that. http://www.dieselplace.com/forum/smileys/smiley2.gif

I dont think that aluminum has any real advantage performance wise other than being liter weight(and thats good for me too since I can run a bigger blade on a chevy with its "weak" IFS than a ford or a dodge even though they have a higher fawr) The design of the duramax heads appears to be excellent for making power though. Aluminum is nice becasue its much easier to machine too. That and the weight issue is probably why they went with aluminum. JMO


In a gasser all else being equal an iron head will make more power than an aluminum head.

Weight and heat dissipation. Heat removal has a positive impact on performance.http://www.dieselplace.com/forum/smileys/smiley2.gif

...

In a gasser all else being equal an iron head will make more power than an aluminum head.

Why?

I was just at our local dealer yesterday, having the tailgate straps replaced (first time back for anything), I asked the service manager how many Dmax's are coming in with injector problems? His reply was "We don't see many back with any problems". Either he's blowing smoke or the number of injector failures is small compared to the number of units out there. http://www.dieselplace.com/forum/smileys/smiley4.gif

I was just at our local dealer yesterday, having the tailgate straps replaced (first time back for anything), I asked the service manager how many Dmax's are coming in with injector problems? His reply was "We don't see many back with any problems". Either he's blowing smoke or the number of injector failures is small compared to the number of units out there. http://www.dieselplace.com/forum/smileys/smiley4.gif


My dealer says the same as do the DMax owners I speak to on the road. http://www.dieselplace.com/forum/smileys/smiley4.gif

Heat removal has a positive impact on performance.http://www.dieselplace.com/forum/smileys/smiley2.gif


You know your stuff so I'm curious about this statement.http://www.dieselplace.com/forum/smileys/smiley5.gif

My Bad Rat,


Sorry for the typo. Actually the Removal of heat has a neg impact in relation to making power This impact is however offset and then some by the performance gains realized by being able to machine the alum heads to better performance tolerances. (Due to the workability of the material itself) Cast Iron heads would normally require blueprinting to acheive what is easily attained by the alum head machining.


Edited by: a bear

Heat removal has a positive impact on performance.http://www.dieselplace.com/forum/smileys/smiley2.gif


I think you were right the first time, sort of. Yes heat removal is bad for efficiency, maybe not so bad for performance. Heat of course, not any explosion is what drives the piston, so removal of it would seem to remove some of the power. But, the ability to rapidly transfer heat to the cooling jacket and therefore be able to tolerate higher combustion temps may be one of the reasons that the Dmax is seemingly able to tolerate much higher EGT's than other engines.

What is considered safe higher EGT for the Dmax. I try and limit my beast to about 1250* That's why I changed the intake and exhaust systems, to get the heat out. I had always been led to believe that cast iron had a higher melting point and could stand more heat. Am I wrong on this point?





Brad

What is considered safe higher EGT for the Dmax. I try and limit my beast to about 1250* That's why I changed the intake and exhaust systems, to get the heat out. I had always been led to believe that cast iron had a higher melting point and could stand more heat. Am I wrong on this point?





Brad











Cast iron has a higher melting point. another strategy to keep something from melting is to get rid of the heat before it get's hot enough to melt. Aluminum will get rid of heat much better than cast iron will. Iron cookware works much better than aluminum, the iron holds the heat while aluminum cools easily. Don't forget the pistons, eventhough they are oil cooled I bet they will let go before the heads will. As far as EGT, 1250 is safe but some are going north of 2,000 I believe. I go a little higher than 1700 frequently. Spikes of course it drops at each shift point. 1700 is the highest that my TST comp will allow.

Aluminum has a better heat transfer than cast. If you were welding on an aluminum boat, you can't set your hand within 3' of the place that you are welding. Therefore it cools quicker.

What is considered safe higher EGT for the Dmax. I try and
limit my beast to about 1250* That's why I changed the intake and
exhaust systems, to get the heat out. I had always been led to
believe that cast iron had a higher melting point and could stand more
heat. Am I wrong on this point?






Brad





The beauty of a properly designed aluminum head is it's ability to
dissapate the heat quickly. Even though alumuinum has a melting point
in the 900-100 degree range, it cannot reach those temps because of the
liquid cooling and the mass it's bolted to is drawing away the heat. An
insider told me that in testing they would blow a turbo because the
clamp that held the two halves (compressor/turbine) together would
loosen from the heat before they had ANY engine problems. Worry more
about the turbo than the rest of the engine.



I would venture to guess the Dmax has probably a 200 deg or so
advantage over the norm... that's maintained heat. The heads simply
don't retain the heat because they transfer it so quickly to the
coolant.



Some mentioned heat is good for performance. Yes and no. Cold intake
air increases charge density which adds oxygen. Remember, hot air has
molecules farther apart. Once ignition takes place you get more heat
because of the added O2. That's why they use cold cans and
intercoolers. Combustion will be hotter but you don't want the physical
engine parts to exceed their max usable temps.



The old boil water in a paper cup.... you can with an open flame
directly on the paper cup because the water will not allow the paper to
go over 212 deg. Do not try this with a waxed cup.http://www.dieselplace.com/forum/smileys/smiley2.gif



Cold intake air.... controlled head/block/piston/valve temps.






Edited by: hoot

Well after all of this discussion over heat I have my pyrometer probe plugged into the passenger side exhaust manafold. I try to limit the exhaust heat to 1250* The question is this the safe limit before I can damage the engine, is it too high, or can I allow it to go higher. I assume because of the past discussion that the heads won't go first, it would probably be the exhaust valves that would suffer the most damage right?





Brad

Turbo damage first, I believe.....

according to the engineer I talked to at IHI awhile back the turbo was designed for continuous operation at 800 degrees C (1472 degrees F)

Holly CRAP!......... are you sure about that? Man, that's pretty toasty. http://www.dieselplace.com/forum/smileys/smiley4.gif





Burner-------------> http://www.dieselplace.com/forum/smileys/smiley4.gif

according to the engineer I talked to at IHI awhile back
the turbo was designed for continuous operation at 800 degrees C (1472
degrees F)



Makes sense for durability reasons.

don't forget the turbo is water and oil cooled

I think it is alien technology.

Alot of good stuff going on hear. Yes heat dissapation is good and bad. To a certain temp, heat retention is good. Take a blow torch to two heads of equil configuration, one being aliminum and one being cast iron and run coolant through them. See which one melts first. The cast will because it can't get rid of the heat as quickly as the aluminum does. The pistons will melt before the heads or the turbo. You can melt the bearing surface (bushing) in the turbo quickly as well with high temps. The pistons are at the worst disadvantage because they are at the mercy of the oil temp and how quickly it removes the heat from them. I have melted these things in a quest for power out of these engines. Never melted the heads though. Some have to learn through carnage.

Why have I read from this forum that high exhaust temps, for the turbo
are bad? Or are exhaust temps a different topic than heat in
general?

Years ago I installed a complete ATS turbo system on my 93 Ford. I first put the pyrometer probe just after the turbo. Max temp was up about 1000* so the 800* temp internal to the turbo I believe must be bogus. I later moved the probe to the crosover pipe just outside the passenger side exhaust header and it was peaking out at about 1300* with the fuel turned up (mechanical pump). Most of the truckers and heavy equipment operaters that I've known have told me that 1200* to 1250* is about as hot as you want to let get else you run the risk of cooking the motor. If the Durmax can go higher, we all would like to know. At this point I believe that 1250* is about as far as I want to run the engine safely for any period of time and not run the risk of perminate damage. Before I changed the intake and exhaust systems I saw temps as high as 1400* and had to back out of it for fear of cooking the engine, turbo or whatever.


So far on this posting if you look back there have been numbers spouted out all over the place. Is there an expert out there that can give us the limits to which this power plant operate over a long period of time like 30 minutes or more with out risk of perminate damage.


Brad

I duno what you can run one at continiuosly and I dont think any one here knows or has the balls to load thier truck down and run it for a 1/2 hour at 1200....."ok it held together.....lets try 1300.......ok still going strong.....1400......going good for 25.5 minutes and pop. OK I recomend 1350 for long term usage."


I would say that the old rule of thumb is probably a pretty good one and very safe since I think we have proven that the duramax can handle higher EGT's pretty well. Also look at it this way, what are guys seeing stock? You said 1400*. How many people are out there running the dog piss outa thier truck stock without having a clue what the EGT's are and they havent nuked towing stuff. GM probably had some clue what things could handle and didnt build it to go out of that range.


I know short term there are guys(me included) have watched thier pyrometer swinging faster than the tach needel and staying pegged in the red for a 1/4 mile blast. So short term i would say we know about as hot as you think you can get it.


If you want to become an expert I'm sure we will all take up a collection for you but other wise you will just have to live with speculation and everybodys WAGs.


Max, just another WAG but I would say that subjecting anything to a temp it melts at or boils and cooks and breaks down at is bad. I duno though, i aint an experthttp://www.dieselplace.com/forum/smileys/hihi.gif Actually I dont think 1800* is good on anything long term but I could be wronghttp://www.dieselplace.com/forum/smileys/smiley2.gif Edit: not quite sure if i am following you actually. the heat a turbo gets is from the exhaust gasses blowing through it. Its like stick a hair drier on your hand...well the turbo would pick up temp from the oil and or coolant if they were warmer than the exhast. Stuff is always trying to equalize, thats the main thing to remeber with heat transferEdited by: ratlover

Why have I read from this forum that high exhaust temps, for the turbo
are bad? Or are exhaust temps a different topic than heat in
general?




Two different animals but related. Heat is expansion is power. Heat
also turns solids into liquids. Ultimately you want no heat left after
the power stroke. That means it all turned into work. Unfortunately
that leaves nothing to run the turbo. The turbo needs the same
expansion characteristics as the power stroke of the piston. Somebody
came up with the turbocharger as a means of using wasted heat energy to
drive a compressor. It works well but there is a balance that needs to
be maintained to keep the physical parts from weakening. This assumes we are happy wasting heat to run the turbo.



Cold air coming in = denser, more oxygen rich charge



Add lots of fuel and you get a bigger explosion.



Add good flow through intake and exhaust and you can reduce the
transfer of heat to the physical parts by moving it through quickly.



That's kinda what Diesel Power was suggesting.



Hope that helps.

Edited by: hoot

hmmmmm that does bring up another though of mine.


is aluminum a plus or a minus for us over all since we are running diesels from a perf stand point? I would imagin our egt's would be quite a bit higher if it wernt for the aluminum and the weight savings is nice. Do we have all the heat we want in a diesel so it sucking heat outa the chamber not really a hinderance(albeit small and mostly on paper? machinability and ease of cleaning it up is nice. All in theory of course......

I goofed in my post.....



Damage from heat would show up first in the turbo? Without
overheating the engine. High temps would cause the turbo to crap
out first, before anything else occurred? Guess what I'm trying
to say is the turbo is the weekest point in the equasion.
??? (for heat)

I believe on the Dmax specifically the turbo is the weakest link EGT wise.



Forget overheating the engine... that's not even in the equation in
this conversation. Most of the cooling systems today have plenty of
excess cooling capacity.

Gents,


I'm trying to seek some answers from GM Engineering through a source of mine. As soon as I receive an answer on what the design limits for EGT and what fails first when the limits are exceeded, I'll post the answers.





Brad