egt's pre/post turbo - Diesel Forum

calland1 · 04-11-2007, 12:52 AM

What is the difference in egt's pre turbo versus post turbo. I got the EGT probe right behind the turbo in the downtube of the exhaust. i was just curious if anyone out there had any experience pre vs. post turbo egt's..

thanks

teamroper60 · 04-11-2007, 01:18 AM

Pre-turbo readings will tell you how hot the exhaust gases are as they exit the engine and head toward your turbo. This tells you how hot your engine is running and is handy for preventing catastrophic failure to the engine and turbo.

Folks with pyros in both locations on the same truck have reported some very drastic differentials in the two readings with the post-turbo readings being well below that of pre-turbo. They also report that the differences are not linear. So nothing of significant value can be obtained from a post-turbo reading that would help prevent a catastrophic failure. It might be handy for knowing when your turbo has cooled enough to shut down, but that's about it.....

guardrail22 · 04-11-2007, 09:23 AM

send a PM to GeorgeC - he had both on his 03 and kept track of the numbers

diesel67 · 04-11-2007, 10:33 AM

post turbo climbing grade 800 degrees
pre turbo climbing hill 1200 degrees and climbing if I let it.

if your sensor is after the turbo i would recommend you move it to the manifold

UNBROKEN · 04-11-2007, 05:17 PM

I run one in each manifold and one post-turbo....the post pyro generally runs 250 degrees cooler than the pre's

tjigger · 04-11-2007, 07:39 PM

I agree, post 250-300deg cooler.
I like having the post turbo to see the temps drop for cooldown.
The pre turbo(manifold) temp drops way faster than the post at cooldown.

Marks6.OH · 04-13-2007, 08:38 PM

I am currently installing my gauges and was wondering the same. On the large marine applications all cylinders plus "stack"/post turbo/turbos are monitored. On some vee blocks its left and right bank plus post turbo/s.

Why is post turbo bad on the 6.0? Isspro sells gauges for both pre and post turbo readings.

I guess I just don't like having the probe so close to a cylinder outlet only on one side of the engine. What if the other side has a problem?

I don't mind pre turbo, but it seems the current location is #8 cyl. (I think) vs. pre turbo.

I'm interested in hearing more pros/cons.

Mark

davidg5252 · 04-13-2007, 08:59 PM

I don't think post turbo is a bad thing. I just think most people want a reading of the hottest part of the engine and that would be pre-turbo

Marks6.OH · 04-14-2007, 11:01 AM

"I don't think post turbo is a bad thing. I just think most people want a reading of the hottest part of the engine and that would be pre-turbo"

I agree, my only thought is having the reading only representing one side of the engine. Ideally we should be reading both "banks" vs one side only. If not sensing both, it should be sensing all. Maybe I need to get a "dual" pyro.

Does anyone know it the down pipe is "thick" enough to TAP?

Mark

mtnbiktn · 04-14-2007, 11:53 AM

I think they make a clamp on setup for the down pipe as one option.

kenkillsr · 04-17-2007, 10:17 AM

My EGT probe is installed post turbo.
However I'm considering a pre turbo also.
Correct me if I'm way off base here.
My idea is mounting the pre turbo probe into the opposing exhaust pipe?
You'd get nearly the same reading as in the manifold with greater ease of installation.
All 8 cylinder and dual bank probe installations along with post turbo seems like OVERKILL to me.

Ken Kill Sr.
2005 E350SD 6.0L PSTD
SMB RB15 Modified
All Electric

MJPliska · 04-21-2007, 01:44 PM

[ QUOTE ]
I think they make a clamp on setup for the down pipe as one option.

[/ QUOTE ]
Yes, ISSPRO makes clamp-on thermocouples (R650A-HT is a popular one).

As far as drilling and tapping downpipes, I can't speak for factory 6.0L pipes, but I can confirm that I was able to do it on the Tymar downpipe on my OBS. I recently installed a post-turbo thermocouple and gauge. So far it appears to work as I expected. When temps are going up, it lags the pre-turbo by as much as 400 degrees. When running steady-state, it tends to slowly approach the pre-turbo readings (but never getting quite as hot when the temperatures are high). When cooling down rapidly (like driving downhill after cresting a hill) the post-turbo is hotter by 150-200 degrees. I would be interested to hear anyone else's data, to see if the truck type and set-up has much influence on these readings.

Thanks,
Michael Pliska

brahamfireman · 04-21-2007, 02:36 PM

[ QUOTE ]
I guess I just don't like having the probe so close to a cylinder outlet only on one side of the engine. What if the other side has a problem? Mark

[/ QUOTE ]

if there is enough of a problem with your fuel delivery that you notice it on the pyro you will FOR SURE notice it in the SOTP meter.

there realy is no reason to monitor both sides, if there is significant variance you will feel it in the lose of power.

Diesel Rod

My427stang · 04-21-2007, 09:22 PM

I wouldnt even consider post turbo.

The reason being is that the farther away you go from the heat source the less sensitive to changes it will be.

In addition, you are checking EGT to keep chamber and exhaust valve temps in check, if you measure post-turbo, you are measuring the temp AFTER all the pieces have had a chance to deal with that heat

Just my opinion but drilling and tapping an exh manifold is so easy, I dont see any reason not to go that route