Pre-Turbo EGT Installed

[GM Smitty]

Well, for about a year now I've been running regular Juice with my post turbo EGT gauge. I've recently upgraded to the Hot version (and some experimenting with Predator stacking) and decided I better install one pre turbo due to the differences in temps. I'm using Autometer gauges.
If anyone is running a performance chip of any sort, I strongly suggest the pre-turbo set-up. Just running around tonight with the hot juice on level 3, it wasn't all that hard to hit 1200. Pedal to the floor, it would hit 1150-1200 around 90mph. This is totally empty, although my truck does weigh in at 7800lbs with my 210lbs on board. I've never seen temps above 800 on my post turbo gauge, except when towing (I can hit 900, then I usually hit the go pedal to drop down to fourth). It's amazing to see the difference in how fast the needle sweeps between the two gauges. Now that I have both installed, I have a good comparison between the two. I'm anxious to see what she'll get up to while towing.
For the install, I removed the manifold from the truck. Not really that hard at all. It was nice to be able to drill and tap on the bench, and take my time. I know me, and I know I would feel rushed with the truck running.
Just though I'd pass on the info, I feel a bit better now, plus the triple gauge pillar looks extra cool. :D
Josh

[Bullseye54]

GM Smitty

How much heat does the turbo realy eat up?Is the difference constant throughout the rpm range or is there an area where it spikes.

[DMax_Doug]

GM Smitty,

You write:
"I've recently upgraded to the Hot version (and some experimenting with Predator stacking) and decided I better install one pre turbo due to the differences in temps."

I'm about to setup a post-turbo Autometer pyro, and am curious if and why a pre-turbo EGT setup is better than a post-turbo EGT setup.

I understand the readings may differ pre and post turbo, but couldn't you factor the temp difference to monitor safe EGT levels based upon the gauge location you are using?

One last question (okay it's really two): Is the more common application for diesel trucks pre or post turbo? And for post-turbo setups, what is the safe upper limit?

Thanks,
Doug

[GM Smitty]

Bullseye - The difference in temps is not consistent at all. I did quite a bit of mixed driving today (town & highway), but no towing. For the most part, temps were about 200-300 degrees different. However, accelerating hard the pre-turbo gauge rockets up, and the post-turbo seems real lazy. In the past, I had to try pretty hard while towing to get my post-turbo gauge to read 900, and it never went above 800 with empty driving. I got the pre-turbo to 1250 without too much effort today (remember I'm running juice at 90HP), post-turbo gauge reading about 800, so right there is 450 degrees difference. This was during accelerating rather hard on the highway.
I think the pre-turbo just gives you a more accurate and instant reading.

Doug - That's what I was doing...adding about 300 degrees to my post-turbo gauge, but sometimes it's alot more. It seems most fellas here (TDP) with EGT gauges have them mounted pre-turbo. It's not hard to do at all, and if you're only going to have one, I'd suggest doing it that way.
It's hard to say I guess what a safe post-turbo limit is. I always kept mine below 900 degrees, but now that I have both gauges installed, that could have been too high in certain situations.

Josh

[GMC-2002-Dmax]

UH OH!!!!!!!!! :eek:

Took a little ride tonight after I went post turbo to Pre-Turbo with the EGT Probe. Mounted in the passenger side "HOOT" location.

I used to see 800-850 post turbo with the Hot Juice, but I saw 1250 with L3 and buried the guage on 1600 :eek: for a split second running hard on L4 HOT stacked with the Predator 40hp Tow Tune.

It got a little too late and dark out for some more runs so tomorrow I will load in the stock tune and run the truck with just the Hot Juice.

I want a baseline EGT for all the Hot Juice settings and the 4 tunes in the Predator so I will hopefully post some results.

If anyone is still running a post turbo guage and any kind of box you really should pre turbo your EGT guage probe. ;)

GMC :D

Guess a 4" exhaust is next.

[DieselDixon]

Hey Smitty,

Did you have to change any gaskets when you pulled the manifold off?

I have a totally stock truck and was going to mount it post turbo, but now you got me thinking again.

[GM Smitty]

DieselDixon - The gaskets are re-useable. If you're going to install one, do it pre-turbo. It's not any harder, and a lot more useful. ;)

GMC - I had that UH-OH feeling in my stomach too after seeing that gauge move as quickly as it did. I'm hoping I didn't cause any damage in the past. :eek:

Josh

[GMC-2002-Dmax]

Originally posted by GM Smitty:
DieselDixon - The gaskets are re-useable. If you're going to install one, do it pre-turbo. It's not any harder, and a lot more useful. ;)

GMC - I had that UH-OH feeling in my stomach too after seeing that gauge move as quickly as it did. I'm hoping I didn't cause any damage in the past. :eek:

Josh YUP !!!!! :(

I don't run it hard like that usually, I was trying the PredatorTow Tune with the Hot Juice. I am thinking that the Hot Juice only is gonna be 200 deg. less, I hope.

BANKS 4" exhaust will be here by next week, too late to get by the weekend

Hey my heads didn't melt yet :eek:

GMC ;)

[DieselDixon]

DieselDixon - The gaskets are re-useable. If you're going to install one, do it pre-turbo. It's not any harder, and a lot more useful. Anything I should be warned about? Do any of the bolts go into a water jacket? How long did it take you?

Looking at other photo's it looks like most people mount the pre-turbo probe at the rear portion of the passenger side manifold?

Does anyone know why all the big rigs always put these probes post-turbo?


Thanks

[ 06-11-2003, 09:55 AM: Message edited by: DieselDixon ]

[DalDMax]

Been thinking about this...and what is it in the turbo that removes that much heat?

The compressed intake air is cooled with the intercooler up front, but the exhaust gases don't go through any type of cooling device.

I know the turbo is oil and water cooled, but that ain't going to remove a couple hundred degrees from the exhaust temps.

If a turbo removed that much heat from the exhaust, a gas turbo car's cat converter would have a heck of a time getting hot enough to work properly.

Is it possible that the pre-turbo probe reacts faster to the exhaust temp swings then the post-turbo probe does?

Does the probe mounting make a difference in the temp readings?

[Idle_Chatter]

DalDMax, what removes the heat from the gases in the turbo is the work that the turbo is performing. The hot flowing gases expand (and thereby cool) in the turbine vanes of the turbo thereby providing the rotary energy to spin the compressor and charge the intake. Heat energy is also absorbed in the turbo snail and rotor material (with additional heat being soaked up by the water cooled barrier between the turbine and the compressor. Post turbo is just not good for monitoring temperatures, especially when you have added fuel and timing that may produce damaging results. Not only is it slower to warn of high egt's at the heads and pistons - but the variance shifts as the load on the turbo changes. Post turbo would be fine for a stock engine, but pre-turbo is the ONLY way to go with any modifications!

[TBC]

Dieseldixon

No need to pull the exhaust manifold to drill for pre-turbo installation. Pull the wheel well shield and it is a snap to do. Run the engine while drilling. You can be finished hours before you can pull the exhaust manifold. There are lots of folks on this site that have done it like I did. This is where I got all the info for performing the task.

Tom

[DieselDixon]

No need to pull the exhaust manifold to drill for pre-turbo installation. Pull the wheel well shield and it is a snap to do. Run the engine while drilling. You can be finished hours before you can pull the exhaust manifold. There are lots of folks on this site that have done it like I did. This is where I got all the info for performing the task.

Tom
I know, I have read this all over the forum, but I think I am in the same boat as Smitty and just have to pull the manifold to be extra safe.

Thanks for the input though.

[GM Smitty]

It might have taken me 2-3 hours to remove the manifold, tap it, install probe, and put it back on the truck. That was taking my good old time. I'm sure I could do it now in 1-2 hours....tops. It's not hard. I have crappy luck, and I'm high strung. Removing the manifold made me fell a heck of a lot better, and I could take my time tapping.
I've read the instructions in past discussions (thanks hoot), and things didn't go exactly like I though they would. It was nice to be able to work on the bench, not inhaling diesel fumes in the gargage. My opinion...take it for what it's worth.

Josh

[hoot]

To each his own own. I pulled the wheel well liner, drilled and tapped with the engine running and was done with it.

Pulling the exhaust manifold only adds the chance of something else not going right.

Even if a small chip blew through, at idle a soft cast iron chip going past the turbo at idle and blowing out the exhaust ain't no big thin.