Engine/Transmission (1998.5 - 2002) two tell the truth egt sensors ?

[jhyatt]

with two egt sensors one before one after turbo the one before reads 1400 but one after reads750 at wot wich one is right? also i have 14cm non waste gate does that matter thanks

 

[KLockliear]

Always use the hotter reading for safety... but generally all you need is a pre-turbo pyro. As you can see, the difference can be huge.

 

[15w40]

Here is another idea.



You don’t say if you are switching between the two probes or are using two independent gauges. If using a switch there may be a problem with the error a switch may introduce by creating a thermal EMF. This error will cause the two probes to read differently. To check if this is a problem try running the truck at low boost (less than 4 psi) pressure on a flat road for several minutes. This should make the pre-and-post thermocouples see the same temperature. If the readings now agree, there is not a problem and you can trust what you see. If the post turbo reading is still much lower than the pre turbo reading, there is a problem in the switch or one of your gauges needs calibration.



Hope this helps.

 

[jhyatt]

thanks keith and dave ill try that today. i have two senders and gauges. one is a gauge and one is blue chip box should the pre turbo be in front or rear bank or does it matter

 

[College Cummins]

From my understanding, the rear bank of the exhaust manifold run the hottest, because of the lack of air flow to the number six cylinder. Anyways, that's where mine is James

 

[Gary - K7GLD]

"with two egt sensors one before one after turbo the one before reads 1400 but one after reads750 at wot wich one is right?"



That's easy - they BOTH are probably right!



There's ALWAYS a substantial difference under normal load between pre/post turbo EGT - otherwise, why even bother with 2 probes?



The difference is due to heat loss thru the turbo, and is a normal function of turbo operation - most of us prefer to place the probe in front of the turbo, and if possible closer in exhaust flow to the rear cylinder banks which typically run hotter than the front cylinders - that way we get a truer picture of actual maximum EGT as the combustion chambers and turbo see them - since THAT is the main reason for monitoring EGT to begin with...

 

[jhyatt]

my sender pre turbo is in the rear bank. how long can u run at 1400 or should i ask where do i get a set of pistons. does runnig nonwaste gate turbo make more heat?

 

[WestTN]

2 sensors

I think something is wrong. 1400-750=650. That is too much temperature drop. I would be surprised if you really have much more than 300 degrees drop. 650 degrees F would indicate a tremendous amount of work being taken out of the exhaust stream, and I really doubt you would have that much efficiency. I think a bit of calibration would be in order to determine if your measuring systems are accurate.

 

[Cooker]

Re: 2 sensors

Originally posted by WestTN

I think something is wrong. 1400-750=650. That is too much temperature drop. I would be surprised if you really have much more than 300 degrees drop. 650 degrees F would indicate a tremendous amount of work being taken out of the exhaust stream

I don't think this is correct. It is entirely possible for EGT's to vary well over 300 degrees especially under WOT situations. The myth of 300 degress difference between the two is just that, a myth. Under normal driving the 300 degrees is realistic but not during heavy right foot driving



Under WOT my pre and post turbo EGTs will easily vary over 500 degrees.

 

[y-knot]

I guess this want go down as being the popular response but, I also monitor pre and post EGT. And to be as fair and accurate I use tow of the same type gages (Autometer) And two identical probes. The wires are are the exact same length and are are as I can tell both accurate. First I had always heard of the tremendous difference between pre and post turbo temperatures, and wanted to see for my self what the difference is and how my modification affect this temperature difference.

I was surprised to find that there is actually very little difference, I have yet to see a greater difference then 200 degrees. I have had this arrangement for sometime now, and there really doesn't seem to be such a big split. Even at WOT the two stay pretty close, and at idle they are about the same.

 

[Cooker]

I think it depends a little bit on fueling and turbo selection as far as the variations on pre and post turbo temps.



With the stock turbo, the more fuel I added the farther apart the numbers became.



I will shortly be installing a new turbo and losing my probe in the OEM exhaust elbow. I will have to figure out a way to mount it in the pipe itself to see how the pre/post temps change with a larger turbo.

 

[SMorneau]

I can see more than 300 easily.



Why not swap the positions of your probes and if they read similar numbers under similar conditions?

 

[CFast]

I've never seen a big, over the road truck with the egt probe in the ex manifold, so why do you guys do it? Everything I've ever seen was in the pipe elbow after the turbo. i guess it just depends on what you're used to reading.

I've even read posts where someone drilled the ex manifold before the turbo, and didn't bother to pull the turbo! It's only 4 bolts to pull the turbo, and the price of a gasket is alot less than the price of a turbo.

 

[jhyatt]

thanks every one i tryed daves idea and they both read the same but with blue box at 15% fueling wot 1400 and 750 what is the fix to lower egts

 

[JFinke]

more air, less fuel, better flow from the exhaust manifold to the end of the pipe, or a combination of all the above