I keep reading about people doing this mod or that, and it lowers their exhaust temp by 50-100*.

What's the point of that? Better mileage? More power? increased component life?

Obviously, you don't want your temp at 1,500*. But what do you gain by going from 1,200* to 1,150*? Or 1,000* to 900*?

 

My reason was so I can add more power and keep the engine has happy as possible. These CR engines can create some incredible piston crown temps so I figure the lower I can keep it, the long it will last with the added power I run.

 

Across ALL technologies, mechanical or electronic, heat kills! Lower the temps and components will last longer. In the this case turbos, oils, seals, pistons, valves, etc.

Tony

 

So it increases longevity? By how much? Does 100* in an essentially stock truck make a noticable differance?

 

I'm sure it would. If 100° help things last an extra 50k miles for example, it would be worth it to lower the temps as much as possible.

 

Metals will melt when it reaches a certain temp, i.e aluminum melts at 1218 degrees.

 

Thank you, Mr. Obvious.

 

Tryin to just point something out to try and help somebody and someone always had to get smart

 

the lower the egt the more efficient the engine runs, on your 07 you can get a 40% increase in mpg and lower egt by 300* by removing the in-cylinder egr, restore timing and shorten duration. they had to do this to meet emissions.

 

While that may be true, the pistons are not pure aluminum. The actual direct heat melting point of the piston is considerably higher than aluminum.

In-cylinder temps can frequently exceed 2500 degrees in normal use. What we measure for EGT's is just an indicator of combustion temps influenced by other variables so comparisons don't really work well.

That statement is is by definition false and terribly misleading. Because the EGT gauge drops does not mean combustion temps are lower, it just means more heat has been extracted from the exhaust flow PRIOR to it hitting the probe. Guess where that drop in heat actually went?

Efficiency of the use of available fuel by nature will increase combustion temps and given nothing else changes, the EGT's. Even that is misleading because to increase efficiency you MUST make other changes, specifically injection timing. Increasing timing will increase efficiency, increase the combustion temps and heat soak in the cylinder. EGT's by nature will go down BECAUSE of where its being read, not becuase of increasing the efficiency. Subtle distinction but it makes all the differences in how far you can push the envelope.

It is entirely possible to melt a piston while the EGT gauge never reads over 1200 degrees. Depending on other variables, 1200 may be too hot and 1600 just fine.

Ultimately it is a balance of air, fuel, combustion dwell time, and the ability of the engine to absord heat without damage. The relationships are NOT linear so basing decisions on one aspect is DANGEROUS.

 

What Oh-no said above is correct.

I melted pistons at 1400* at a much lower HP level than I am now. I can see 1600* now at a much higher HP level without adverse effect. I know of a few duramaxes that are dedicated pullers and see 2000*....

It is, as explained above, a combo of the relationships involved. EGTs as measured by a probe in the exhaust manifold are just a relative indication of what is going on in the cylinder and a poor one at that. But, that is what we have.

 

that would be constant

 

Actually CR's, especially 04.5-07's, run much lower piston temps than other trucks. The retarded timing on the CR puts the heat out the exhaust and thus the high EGT's, this gives you lower power, lower efficiency, but mainly lower emissions.

What oh-no and soulezoo stated is absolutely correct.

In stock trim my 05 was capable of 1450°, if I tried to run at 1450° with my the advanced timing of my Smarty Jr I would melt something, now I try not to go over 1250° continuous.

There are many factors to determine efficiency, but simply put the most efficient motor will go the furthest on 1 gallon of fuel. The things we do to improve that efficiency will normally reduce the EGT's, because more work is being put into driving the piston down and less into heating the Cat/DPF. The mods that just drop EGT's (not modify fueling parameters) generally have very little overall effect on efficiency. Such as a 50° drop from a intake (which is generally false), or other bolt on mod...

If I added up all the temp drops I should have from my mods then I would never break 800°, but that just doesn't happen.. Heat is power, we just have to control it. Also depending on your turbo they may need a certain amount of heat to become as efficient as possible, for my turbo that number is 1000°. Above 1000° the drive pressure to boost ratio really drops, it goes from a high of about 1.1:1 to a low of 0.8:1.

What all of my mods have done is allow me to run efficiently at partial or full throttle and maintain decent cylinder temps at all loads. The only mod I have done to "drop" EGT's was the initial purchase of the Smarty Jr, which I only used on SW1, timing only, for the first 40K miles.. The rest of my mods were to improve airflow and general efficiency, yes some drop the EGT's but main I just removed restrictions and less restriction meant higher flow and a cooler fire in the cylinder.

 

Pretty sure piston temps are cooler due to the cooling enhancements, not the fueling. They have to be because the piston is thinner and the bowl design much shallower giving less surface and volume to heat. The actual combustion temps are probably higher because they make so much more power, power IS heat, and the heat cycle is much longer due to the multiple events. Thats why timing can be a huge downfall.

Its not neccessarily the combustion temp that causes emissions but the big short spikes that raise havoc with NOX formation.

Ah, ah, ah!! Be careful there! A drop in EGT's is not always preceded by a drop in combustion temps. Again, all these other factors come into play.

By design modern diesel are running fuel rich to limit temps. It is much easier to trap and burn soot created by incomplete combustion than it is to remove NOX. Thats what the CAT is on these trucks is, a big soot filter not really a catalyst.

The air filter, air tract, turbo, etc, all play into keeping the combustion events from spiking and stretching it into the exhaust cycle. Removing restrictions will give better air for the combustion event in the cylinder to burn hotter and faster.

Adding ONLY a boost fooler and 5 psi of boost will take up to 200 degrees off of observed EGT's. We did not change timing, fueling, etc, but still see a drop in EGT's. That heat went somewhere. Yes, SOME went to heating that extra volume of air but the bulk went into powering the engine in the mid to upper range.

 

I thought the cooling enhancements (we're talking piston cooling nozzles correct?) were due to the increase in power and thus more heat. However the retarded timing that the 04.5-07 has kept the cylinder pressure and temperatures lower for emissions.. fewer hotter higher pressure spikes and lower emissions.

Look at the SW1 setting on the Smarty and Smarty Jr, it's timing only. It gives up to 50 hp in the mid range on stock fueling with 200°+ lower EGT's, there is going to be a lot more piston/cylinder heat with that timing that stock (which I can see when towing on the coolant temps). It goes to show how the stock setup is geared towards emissions and not power.

They do make a lot more power but a lot of that power is from the 3rd event as well, which makes power but at the cost of high EGT's, but the timing of the 3rd event means lower cylinder temps and pressures.

The 325 motor does have a higher peak cylinder pressure stock than the 03-04, but there is also an increase in power.

With the release of EFILive and the ability to delete the 3rd event and maintain good power I wonder if there will be fewer melted pistons on the 04.5-07. A single longer main event will probably allow for less heat soak and the same power output.


Yeah, that wasn't what I was trying to get across... Depending on what caused the EGT drop there may be an increase in combustion temp, or a decrease.

I am not sure it will be hotter, but I do buy faster since the more air that is compressed the more heat you get. But more air for the same fuel should burn cooler on a diesel, maybe not recordable on modifications to stock plumbing, but leaner is cooler right? Idle is the leanest we run and WOT is the richest.