Engine/Transmission (1994 - 1998) Pyro- pre? post? good and bad

[lpearson]

Piers mods came the other day and it's time to install the gages. I have spent some time searching out information on this, but I would like to get the pro's and con's on where to install the pyro probe and the Transmission temp. sensor? Any input would be much appriciated.



Ramifications,

Lowell

 

[esommer2500]

With the goodies you got, you better put it pre-turbo to make sure you don't melt something down. The main advantages to post turbo are 1. ) it's easier to do (I think) and 2. ) you can monitor turbo cool-down temps better. However, once you start gettin some serious fuel in there, which you are, you really need to keep an eye in the manifold.



I currently have mine post-turbo, for the reason's mentioned above. When I go to a hotter plate and 370's, I am going to get another probe in the manifold and try to put both pre and post-turbo on the same guage through some kind of switch. Anybody done this?



Eric

 

[Oil Burner]

Eric,

Do a search for "pyrometer switch" then select the thread that says "wiring 2 pyro's to 1 guage". It has everything you are looking for. (sorry I couldn't import the thread).

-Jason

 

[Dkevdog]

This is alot like the :-{} "tastes great less filling" debate . On my 96, I had both pre/post gauges. No switch, two gauges. I had it like that for a little over a year, and towed a 9000lb fiver with it setup like that.



I did it more than anything just to see what kind of differences under different circumstances the gauges would reveal. Under normal empty driving after accellerating to a given speed, the guages would read nearly the same, maybe 150* difference between the two, post being the lower of the two. Under accelleration and just plain driving, the post would generally be about 300* cooler. However... ... ..... the biggest surprize was that after pulling a good grade under load, the post would remain as much as 500* higher than the pre gauge would and often would take 5 minutes or more to cool off to the "shutdown" temp.



Conclusion?? You don't really need both- Run the gauge pre, get faster more accurate readings, and after pulling hard, let it cool down for 5 minutes if I'm gonna shut it down.



Kev

 

[illflem]

If you're only going to use one pyro, definitely go pre-turbo

 

[DBCooper]

Lowell, I know this is off the subject, but how do you like the #10 and 370s in an auto truck? How's the power, egt's and smoke? I just had the #10 recomended to me this week and have thought a little about it along with the 370s after my exhaust mods. Thanks.

Dan

 

[rfcom]

For the most accuracy and best response time, you must be pre-turbo. However, for longevity of the pyro probe, the cooler, post-turbo position is preferred. Plus, if for some reason, the probe breaks off, your turbo won't eat it. I'm putting mine in the elbow of the exhaust brake.



Jim

 

[illflem]

Turbo damage from a breaking probe is a non-issue. The question has been asked here several times in the past years if anyone has experienced it, no one has reported they have. I'm not saying it isn't possible, but it's extremely rare.

 

[cmonroe]

Pre-turbo with one guage is the only way to go. I first installed mine post turbo and after switching noticed 175* difference between the two. It is more important to monitor the temperture of the pistons (from the exhaust manifold) than anything else. Hope this is of help.

 

[Forrest]

Bombed = Pre turbo ... end of discussion

& here's why. HX35-12, 32psi, 950 to 1000 degrees post turbo.



Moved the probe to pre-turbo, I backed off @ 1500 degrees.

 

[lpearson]

Thanks for the replys

I think from what has been posted I will go pre on the pryo. Which brings up a question I know has been asked before. Do you need to remove the turbo during the installation or are minor shavings no big deal?



Ramifications,

Lowell

 

[BillGotthelf]

Take a shop vac and vacum the hole as you drill. Put some anti-sieze on drill bit after you get in about 1/8". After you drill through put anti-sieze on tap and vacum it as you tap. 99% should not end up in manifold the rest won't hurt turbo.

As for your trans sensor-the easiest place to mount 1/8" sensor is on the pass side front corner of the trans. Looks like a can protruding fromthe trans and it has a 1/8" plug-Handy-take out plug (when cool) and insert sensor. You will get same readings here as in the cooler line going to the cooler.

 

[illflem]

Although not too common all it takes is one chip jammed between the housing and turbine to stop it dead. I find it faster to remove the turbo rather than fool around with grease and magnets that might not get all the debris out. Here's the instructions I pretty much follow, I've always been able to reuse the turbo to manifold gasket.

http://www.dieselpage.com/gipda.htm

 

[rfcom]

I know you guys are right about going pre-turbo, but I can't get over drilling a hole into a perfectly good manifold. If I screw up, it's a $700 repair. (CDN) Oh well, it's my problem, I'll deal with it.



Jim

 

[cmonroe]

rfcom, if you make a mistake all you have to do is weld it back up.

 

[DBCooper]

You could always go with a 1/8" npt probe and if that gets dorked up move up the the 1/4". I know it's not much, but at least all is not lost. The manifold is pretty soft, so not a pain to work with. Shouldn't be a problem if you take your time.

 

[bmoeller]

Originally posted by rfcom

I know you guys are right about going pre-turbo, but I can't get over drilling a hole into a perfectly good manifold. If I screw up, it's a $700 repair. (CDN) Oh well, it's my problem, I'll deal with it.



Jim

Just installed the thermocouple today. Went pre-turbo. Piece of cake. Make sure you have sharp bits. Used a 1/4" bit first and then a 7/16" bit. All I did was stick the bits and tap to a strong magnet. Had a small tipped magnet to fish around in the hole. Never got anything from drilling. All stuck to the bits. Not so with the tap. It only held maybe half. Magnet got the rest. If you miss anything it is VERY small. All is well and working perfectly.

 

[scotmartin]

Before I installed my first pyro, in my 93, I walked over and looked at the CAT, Cummins, and Detroit engines on test stands at work. These engines are used by students in the local Community College. I noticed that all of them had the pyro after the turbo. I was informed that almost all of the bigger engines were using this setup. The pyro tends to last longer. So I went with that. Now that I have read about some of the people here on TDR having their stock manifolds crack. (I know it's rare), but I feel better not having another weak point in my manifold. Besides, it sure is an easy install after the turbo. I don't mean to throw flames onto the debate fire, but that is my two cents.



Scot

 

[Champane Flight]

Pre-post-pre-post-pre-post!

After all the years of debate, I have found this to be true.

If you are running a bunch of fuel and competition, run pre. If you are running slightly modified or stock run post.



If you are really worried about EGTs mount a thermocouple to each cylinder, then you will get a true idea of how warm your internals are getting. I still hold to the old rule of thumb, post turbo add approx 100' to every inch behind turbo for actual turbo temp. It has held true for several people that have both pre and post thermocouples. This taken after complete warmup and on steady pull.



If we did see what each cylinder was doing during a pull (have seen actual computer read outs from internal thermocouples on industrial engines) you would see a WIDE difference in temps flucuating quickly between 200' to 2800' . These thermocouples come in handy for setting fueling levels. They flucuate and in most cases have no bearing on engine failure. Most of the time internals fail for other reasons, such as lack of lubrication, unbalanced injection, engine coolant failures, or introduction of foreign object. I am not saying you can't melt one down. With the fueling that some of the "Good ole boys" are running here, they could burn down an asbestos building!



I am not sayin that not having any pyrometer is the way to go either. but, if you are looking for internal temp of engine don't completly rely on pre thermocouple. If you are looking for turbo cooldown temps go post. If you want both, go for it, the mo the better.

 

[fortunate1]

Pre- vs Post

Well, here's another stir for the pot. If pre-turbo is more accurate, then which cylinders are you going to monitor? You can only place one thermocouple in one location: measure exhaust temps at the collection point for 1,2,&3 OR for 4,5,&6. Drilling into the middle of the manifold outlet will only get you into the wall separating the 2 collection points. The exhaust for ALL of the cylinders only comes together completely in the turbo. And as mentioned before, the temps of each cylinder can vary too. Most ship's diesel engines and aircraft piston engines have a thermocouple on each cylinder head and a rotary switch to one guage, or a guage for each cylinder. That's the only way to have complete anal-retentive accuracy. Otherwise, it's an "average" of 3 cylinders. Or measure post-turbo and estimate 10 degrees hotter per pound of boost. And make sure that you don't push too close to the limits in case your estimates are off.



So, is 1-3 the best, or 4-6? Or post-turbo and do the math? Maybe it's just a matter of personal preference. :-{}