Thinking of installing a lower thermostat 160 in LLY to keep temps down a little longer when pulling my trailer over grades.......good idea/bad idea.......opinions please........Rick

I was told that doing that would get worse fuel mileage and less power by my dealer mechanic. I'm not sure, but thats what he says. I had one overheating drasticly, but it has not done it since the reflash.

Thanks Rick,.... kinda figured that. It be neet just to try it and see what happens!!........Brutis

Depending where you live I think you would find that you wouldn't get enough heat in winter.

Since a diesel motor runs more efficiently at operating temp if it stayed cooler you probably would get worse mileage.

This has been discussed before on the site. If I recall correctly there were issues with the PCM possibly being affected by the different operating temps and changing fuel delivery, etc. Best to check it out. Agree with previous post that the LLY runs better at normal operating temps. JJ :)

I don't think you would benefit nearly as much as what you would lose. You would only have slightly more reserve when hitting a hill, because once the engine output reaches the capacity of the cooling system, the thermostats are wide open anyway. The downside is fuel dilution of the oil because of cool temps, more soot, dirtier oil, cold cabin in winter, etc.

The thermostat controls the time at which the system STARTS cooling the engine. By the time you get to that hill, this temp has already been reached, and coolant is already flowing through the engine.

Make the cooling system more efficient with greater airflow (grill, fan, etc.), larger coolant-to-air heat exchanger (radiator), or cooler combustion temperatures (fuel mixture, EGR valve) and you've got the ticket.
Wait.... you guys are disabling the EGR valve and boosting the horsepower...
How about a cooling tower mounted in the bed?):h

I've also observed that the LLY dash temp gauge is particularly inaccurate as compared to the data on the Tech 2. Warm as it may seem by the gauge, mine presently runs 181-187°f and if it happens to hit 19o° or so, the gauge is saying 210°

Since the dash gauge now reads the ECT sensor, it is absolutely ridiculous to not have an accurate, scaled gauge for coolant temp...

Brutis - I've looked into this a bit, and perhaps I'm missing something but....I'm not sure you can find a different temp thermostat for the lly if you wanted to....At least by application anyway....:confused: Having said that, like the other guys said before me, I don't think you would see a benefit anyway......

If anything, you reduce the cooling capacity of the radiator. The higher the temp of the coolant in the rad, the more BTU's the air will remove.

I know the dash coolant temp. guage is not that accurate and I wanted to install another coolant temp guage on my 2004.5 lly but no one seems to beable to tell me where to install the sensor any help will be appreciated

AutoEd states: Make the cooling system more efficient with greater airflow (grill, fan, etc.), larger coolant-to-air heat exchanger (radiator), or cooler combustion temperatures (fuel mixture, EGR valve) and you've got the ticket.
Wait.... you guys are disabling the EGR valve and boosting the horsepower...

JJ needs clarification AutoEd.:confused: Are you stating the EGR actually aids in cooling combustion temperatures? I always thought they raised combustion temperatures since these are hot exhaust gasses being recirculated for combustion again. Thanks. JJ :)

JJ- good point.

Think about combustion- requires fuel and air(oxygen- O2). If you replace a portion of that air with something else that won't support combustion, like exhaust gas (carbon monoxide- CO)* the process changes- LESS COMBUSTION- cooler exhaust temps are the result, and consequentially, lower amounts of Nitrogen Oxides. The result is cleaner exhaust. Now I'm not saying that it doesn't also lower your horsepower and torque. The engineers thought of that too, and tied it into a computer which only allows it to open when you don't need the power, and won't notice the change.( i.e. steady cruise speed, etc.)
Ain't those guys smart!!!
The real problem as I see it is keeping the thing working properly with all that soot (which is produced in the combustion chamber) running through it.
What can we cure by removing or disabling a properly functioning EGR valve?
Ed

*(OK actually: nitrous oxide, nitrogen dioxide, formaldehyde, benzene, sulfur dioxide, hydrogen sulfide, carbon dioxide, and carbon monoxide):h )

What is the optimum coolant temperature for fuel mileage and performance? I run an old DB-1 Isuzu 4 cylinder diesel in my pick-up and it specifies a 180 degree thermostat. She runs great, no problem heating or over-heating and gets 29to 30 MPG unloaded.

AutoEd, great intel bro', thanks. I had that totally backwards. JJ ):h

What is the optimum coolant temperature for fuel mileage and performance? Please

What is the optimum coolant temperature for fuel mileage and performance? Please
operating temp is 180 or 185 and they perform the best at that temp. don't hot rod a cold diesel either, not good for it.

just like a gasser...putting in a lower temp thermostat fools the ecu to thinking its cold all the time and for lack of better terms, runs rich or uses choke. you would use more fuel doing this. I am sure its the same behavior on a diesel, but I am no diesel pro.

wgroat2, that's more of a technical question, way above my techie level. You might post on the "Ask the Techs" forum or you might get lucky and a techie type may read this thread. I would post on the ***. :)


FWIW, years ago I worked with a mechanical engineer. He explained that engines actually run more efficiently at higher temps.:confused: Why, I dunno! JJ :)

I've also observed that the LLY dash temp gauge is particularly inaccurate as compared to the data on the Tech 2. Warm as it may seem by the gauge, mine presently runs 181-187°f and if it happens to hit 19o° or so, the gauge is saying 210°

Since the dash gauge now reads the ECT sensor, it is absolutely ridiculous to not have an accurate, scaled gauge for coolant temp...
John, how close is the attitude temp to the tech II?

I bet they read the same temp.

I see 10-15* cooler temps on the attitude over stock dial.

GM should offer these trucks with their POS gauges-:t as options so we can purchase aftermarket gauges in their place. My aftermarket gauge package has an "attitude"! JJ ):h

Not to beat a dead horse but, I to have a new 04 lly and am trying to sort out what modifications were made to the lly for emissions. Most changes for emissions compromise performance & economy. In Smokey Yunick's Power Secrets he says, "Running an engine at 180 degrees will drop the horsepower by 2-3 %. For maximum power the coolant temperature in a racing engine should be at least 200-210 degree range, measured at the point where the coolant is returned to the radiator.” He is talking about smallblock Chevy’s. I know from the racing we've done with cars and motorcycles that 180-190 degrees worked well. That 1978 DB-1 diesel I run uses a 180 degree thermostat which like most pre smog cars of the seventies used. I have on order a finger stick and plan on blocking the EGR also plan on a new turbo back exhaust. Then maybe I‘ll add a torque converter and a Predator. From what I’ve read on this form, which I’ve truly enjoyed, we’re all searching for similar information. Should I try posting elsewhere?

I still would like to know how we can hook up an addtional temperature guage and no one has the answer. I know someone out there has to have the answer as where ans how ro hook up the guage and where to install the new sender. Please help

wrgoat, from my previous post "wgroat2, that's more of a technical question, way above my techie level. You might post on the "Ask the Techs" forum or you might get lucky and a techie type may read this thread. I would post on the ***. :) ". Ask the Techs bro! ):h

Jimbo, you might want to *** as well. JJ :)

I believe a lot of the efficiency change with ECT change has to do with the temperature differential between the engine parts in contact with the fire, and the fire. A warmer engine will leave more heat in the fire where it belongs.

Watch your DIC mpg go in the toilet on a cold engine once...

The Hotter the Better!

JJ- good point.

Think about combustion- requires fuel and air(oxygen- O2). If you replace a portion of that air with something else that won't support combustion, like exhaust gas (carbon monoxide- CO)* the process changes- LESS COMBUSTION- cooler exhaust temps are the result, and consequentially, lower amounts of Nitrogen Oxides. The result is cleaner exhaust. Now I'm not saying that it doesn't also lower your horsepower and torque. The engineers thought of that too, and tied it into a computer which only allows it to open when you don't need the power, and won't notice the change.( i.e. steady cruise speed, etc.)
Ain't those guys smart!!!

Autoed,

Not to add to JJ's confusion, and mine, but ............

When the discussion of blocking EGR flow started last summer, one of the techs posted a service write-up describing the operation of the EGR valve. Unfortuneately, I think some of post got cut off during the database conversion last December, but here is part of what is said aobut the operation of the EGR valve:

http://dieselplace.com/forum/showthread.php?t=12054

Conditions for Running
-The barometric pressure (BARO) is more than 74 kPa.
-The engine coolant temperature (ECT) is between 60-96.75°C (140-206.2°F).
-The intake air temperature (IAT) is more than 5.25°C (41.5°F).
-The battery voltage is between 11-18 volts.

I am assuming that "running" means the valve is open. So, when the coolant temp exceeds 206 degrees, then the valve closes, meaning no EGR flow.

If EGR flow lowers combustion temp, then I would think the engineers would want to keep the valve open (running) as the coolant exceeded 206 degrees. Wouldn't this lower the engine block temp, which in turn would lower the coolant temp?

Do you know what the reason is for closing the EGR valve when the coolant temp exceeds 206 degrees? I originally thought it was to reduce overheating, but that is not consistent with the explanation you posted.

JJ - I feel your pain.

Thanks.

Autoed,



If EGR flow lowers combustion temp, then I would think the engineers would want to keep the valve open (running) as the coolant exceeded 206 degrees. Wouldn't this lower the engine block temp, which in turn would lower the coolant temp?

Do you know what the reason is for closing the EGR valve when the coolant temp exceeds 206 degrees? I originally thought it was to reduce overheating, but that is not consistent with the explanation you posted.

JJ - I feel your pain.

Thanks.


The Dmax EGR is cooled by engine coolant...

From the reading I have done, the EGR is about reducing the emissions. The EGR closes above 206 degrees because the pollutants are being burnt off above that temperature. So no need to recycle the exhaust gases for further burn.

Good information I have a better understanding of the need for heat and why the EGR valve is closed at 206 degrees, but combustion temperatures and exhaust gas temps don't run parallel, an efficient diesel will transmit the combustion chamber temp to the crank? Reduce fueling to reduce exhaust gas temp?

wgroat2,

I would suggest posting this question to "autojim" on the dieselstop.com. Please post what you learn here.

BH,
"conditions for running" is a common term in GM service information and refers to the parameters required to run a particular test. In this case it likely refers to one of a few tests which the PCM runs on the EGR valve to determine if it is operating normally. These parameters could be part of the list of conditions which must ALL be satisfied before the valve is put into operation during any given drive cycle.
Ed