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I originally posted this on TDR but also thought this might be of interest to some of you guys.

I have always wondered about what people have said about the difference in the readings before and after the turbo. I had to see for myself. Was hard to believe that the readings could be that different in a span of about 8". I know about expanding gasses and all that but seemed hard to accept that kind of difference. I originally had a direct reading (thermocouple)US Gear pyro located after the turbo and just last week installed a new ISSPRO electronic pyro in the ATS manifold (in front of the turbo) I put on last year. I went on a trip to Washington last Friday and returned Monday. Pulled a 5500 pound load up, came back with an empty trailer at 2250 pounds. Took a series of reading both directions and only took "stable state" readings. some were pulling a grade and some were on flat ground. Found some scary things and thought I'd pass them along.

The direct reading pyro is very slow to respond when compared to the new ISSPRO pyro. I could put the new pyro into the red and then cool back down before the old pyro hardly moved.

Also took readings with the tranny in OD going up a hill. Got the pre turbo temp up to 1200 degrees then shifted out of OD to get the RPM's up a little. Saw an immediate 150 degree drop in the EGT. This alone is a good reason to shift out of OD when towing up a hill!

Here are the readings I took pre and post turbo-at idle the readings were basically the same as the turbo wasn't working at all.

PRE POST TURBO
600 400
700 500
750 550
800 580
875 620
900 640
1000 700
1100 750
1150 800

As you can see, there is a 350 degree difference at the upper end of the scale. Based on this, I would try to keep the post readings at 900 or less if that was the only reading I had. I used to push it to 950 and a little higher when towing which put me up at 1300 degrees. Sure glad I put the new unit on as it is a much more realistic reading!
 
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