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Pre-Turbo VS. Aft-Turbo temps...

Mezmorized

Mezmorized

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Hope I have this thread in the correct section...

I have a 95 C2500 ECLB 2WD. I installed a 4" D.E. exhaust and had the E.G.T. probe installed in the turbo down pipe.

The readings I'm getting so far under normal driving are between 400-600 degrees F. I haven't had the chance to tow with it yet this season but will post those temps when I get them.

Where is your probe located and what temps are you getting? :)
 
I put my thermocouple right above the exhaust flange on the turbo. The highest temps I've seen are around 1050F, -but I'm running mediocre fuel with 18-20 PSI on a 19:1 engine, -so EGT's stay pretty reasonable.

I'm not getting near the amount of fuel that a lot of the DS4 folks are (I'm running a .310" plunger DB2).
 
I would plug the down turbo probe hole and move it to the crossover. With the easy access to the crossover there is zero reason to use an inaccurate down turbo probe location. (Probes are expensive, may as well install it to get the best reading possible from it.)

Best location as described above is just below the turbo. Otherwise you are guessing what the temperature drop across the turbo is. When you are pushing it, and you will push it on a hill towing, you need to know as close as possible to the ragged edge you are getting.

Keep in mind that pistons are not the only failure point at high EGT's. Glow plugs and injectors also fail. Also timing has a lot to do with EGT limits aka more advanced timing will do damage at lower EGT's.
 
Best location is pre-turbo. Best diesel mechanic I ever knew told me to keep EGT 1050 or below continuous, NEVER exceed 1200.
 
1998 K2500, L65, 4:11, 4l80E, ECLB.

Pre turbo in the manifold, 4" diamond eye exhaust, stock vacuum wastegate. 2.5" crossover, tuning is sometimes.....ahem....."adjusted"... but the following info is from stock configuration:

Around 250-300F at idle.

Around 500-550 on the highway empty.

Can spike 1100 climbing a VERY steep hill, empty and a VERY heavy throttle. Can't get it much higher when empty.

Loaded (35 foot travel trailer), can spike 1100-1200 anytime I feel like it with throttle.

Post turbo is not really the best location, you're never really sure what you're getting. As mentioned, the crossover pipe would be a far more preferable postion to ANY post turbo location....
 
I believe ideally, temp should be taken right at the turbo impellers, but since this is not possible, I put mine right at the turn down of the turbo. Would you not want to know what the temperature is on your turbo? You are getting all of the benefits. You put it in the crossover and you find out how much temp DROPS to the turbo. So IMHO and very humbly, I put mine post turbo to find out total temps from cooler gasses coming from the drivers side mixing with all hot straight from the manifold turbo side. I am not, and do not claim to be a mechanic, just my 2 cents.
 
I've never heard of a turbo failure from overheating (not that it can't) but I have heard of many an engine die from overheating
 
The issue is not how hot the turbo gets, but how hot the combustion chamber gets.

Since direct comb chamber readings are impractical, exhaust gasses at thier hottest possible point is the best indicator of whats going on during combustion.

The turbo causes a temperature drop which may or may not be consistent dependent on numerous factors, hense, inaccurate readings and an increased risk of cracking heads, blocks, etc.

Some would argue the crossover pipe is a better location than right before the turbo, to me it's basically little difference as long it's pre turbo.
 
Ok, I had started this thread to find out who has them where and what their temps were. Installing it on the turbo down pipe was my only option at the time. I am fully aware of the debate on where it should be located. I plan on getting a mandrel bent crossover pipe in the future and will relocate at that point. All I was asking was what the temps were pre or post that people are running.

I find it strange then that the big rigs have it mounted aft?

P.S. I will not install the probe in the manifold though. It will wind up in the crossover pipe. :)
 
You're getting the info you wanted, there's just a bit of extra "chatter" which is common in an open forum.

Where the probe is located is not as important as knowing what the safe egt range is.

For example:

It's a well established number for a 6.5 that 1000f pre turbo will keep the engine alive and happy. 1100 is getting into the danger zone an 1200 is to be avoided if possible except for spiking it a bit. Above 1200 you're kind of in dangerous territory and the longer you stay there the greater the risk

Post turbo readings are lower, but it's uncommon enough that it's uncertain where the limits are. No one really has much experience with it to say for sure.

If a "full size" rig has a post turbo or pre turbo sensor, it's usually known from the oe what a safe range to operate in is.

So, I don't think anyone is really knocking where your sensor is, there's justnot enough experience (ie data) to five you good solid numbers.

But we do know the pre turbo numbers.

;)

Ps.

Most guys ( myself included) mount it in the manifold for a reason. Believe it or not, it easier and a more solid/permanent/reliable solution...
 
great white said:
not a problem....
Click to expand...

BJ, are you telling me doing it is not a problem? I was already looking at getting one of the mandrel bent crossover pipes and would install the probe at the same time. I'm concerned about cracking the manifold and also (even though I know I would be careful) would be worried about leaving shavings in the manifold and take out the turbo.

Other thing that came to mind... Could one put a switch/relay on 2 separate probes and use only one gauge? I know the length of the wire is critical but I don't know if setting it up that way would affect the read out.
 
I don't know of anyone that has cracked a manifold putting in a probe. There's a boss in the casting that's tailor made for a probe. I'l try and get a pic of mine later.

Some guys have even installed it on the truck. They let the engine idle and "chips" are blown out while tapping.

I pulled my manifold off, I didn't like the whole idea. Plus, I was changing injectors anyways....
 
I am one who drilled and tapped the manifold on the motor. I started with a cold motor and started drilling. When I got about 1/8"+ deep I started the motor and also put grease on the tip of the bit. When the bit breaks through the exhaust pressure inside the manifold blows the chips out and the grease also catches some chips. I then greased the tap and frequently turned the tap back out and cleaned and re-greased it, again with the motor running. It went good and with absolutely no problems.

Don
 
My plan is to use one of those special hose clamps designed to hold the probe to a pipe. Just drill the hole no tapping required. Want to put it in the xover near driver side.
You will only read those 4 cylinders though, so best place is pre turbo as close to turbo as you can get. My last truck I drilled and tapped the same boss GW is using.
 
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