EGT's Pre & Post Turbo - Diesel Forum

nivrig · 10-01-2006, 08:00 AM

Just wondering, I have a post turbo sensor and I understand your not suppose to exceed about 1250. What about the pre turbo sensor that goes on the exhaust manifold, is that 1250 as well???

I'm putting a 4" exhaust on and was considering moving the sensor. I understand that the pre turbo location is suppose to be better or does it really make any big differeence??

ltfox · 10-01-2006, 09:12 AM

1250 is too hot post turbo in my opinion. 1000-1100 post turbo is pushing it. Move your probe to the exhaust manifold and then stick to your 1250 limit. Pre-turbo is alot more accurate.

BlueMule · 10-01-2006, 10:25 AM

Have you actually had it up 1250º post turbo? Thats way to hot! For several years I had both post pre and post themocouplers and have seen the pyro in the manifold read 400º over the the one in the EBPV many times.

nivrig · 10-01-2006, 08:27 PM

When I tow my camper, which is 10K, and going uphill, when I start getting above 1100 I back out of it. No, I have never hit 1250.

I was just looking for some info on what I should not exceed. Thanks for your info.

WormDrowner · 10-02-2006, 12:35 PM

I have an Isspro post-turbo gauge. It gets into the yellow around 850 degrees and red at 1050. Sounds like backing off at 1100 is a good idea.

Allister73 · 10-02-2006, 03:21 PM

I have heard that if the pyro is post turbo, you would only want to see about 950 on it. It was mentioned that the post reads differently under different conditions, and it certainly reacts to the temp much slower than the pre turbo install. I would really be careful with those temps!!! [img]/ubbthreads/images/graemlins/shocked.gif[/img] I think that running 1100 is probobly in my opinion way, way too hot for more than a second or two. If it is off by 500 deg's, like some have seen, then that means you are running a sustained 1600 pre turbo. [img]/ubbthreads/images/graemlins/eek.gif[/img] Talk about piston melting or cracking, or even a bent exhaust valve!! Just my thought, but I would either keep it lower, around 950 max, or better yet, move the thermo probe to pre turbo. [img]/ubbthreads/images/graemlins/cool.gif[/img] Colin

FordJunky · 10-03-2006, 09:52 AM

Has anybody had any problems with the probe breaking off in a pre turbo application?That used to happen on the big trucks,and was often catastrophic.Now they all run post turbo.If even a small piece of that probe gets to the turbo,not only will the turbo be ruined,but it will more than likely put pieces into the rest of the motor.It sounds like an awful big chance to take.I'll be installing my Autometers this week and Im leanin pretty heavy to post turbo probe.

Allister73 · 10-03-2006, 10:21 AM

There is always a chance that the probe coulg break off. I was in Marine diesels for 4 years, and around them all my life, and have never seen one let go. I have heard of someones cousins, sisters brothers, dogs, ex-roommate having one break and go through. Will it is true that should a piece break off, it would be ugly, the risk is better than not knowing what the temps are exactly going into the turbo, and what the exhaust valves are running at. I will therefor be leaving mine pre turbo so I know for sure what I am doing!!! MY .02

WormDrowner · 10-03-2006, 12:11 PM

According to some, if you don't immediately stop what you're doing right now and move your probe to pre-turbo, you're engine will blow up your wife will run off with the mailman, your dog will die and your best friend will turn gay. [img]/ubbthreads/images/graemlins/rolleyes.gif[/img]

..or you could just learn to read the gauge and leave the probe post-turbo like the vast majority of heavy engines.....

TimMiller · 10-03-2006, 01:21 PM

[ QUOTE ]
According to some, if you don't immediately stop what you're doing right now and move your probe to pre-turbo, you're engine will blow up your wife will run off with the mailman, your dog will die and your best friend will turn gay. [img]/ubbthreads/images/graemlins/rolleyes.gif[/img]

..or you could just learn to read the gauge and leave the probe post-turbo like the vast majority of heavy engines.....

[/ QUOTE ]

Um.... Thats what happened to me [img]/ubbthreads/images/graemlins/rolleyes.gif[/img] [img]/ubbthreads/images/graemlins/rolleyes.gif[/img] [img]/ubbthreads/images/graemlins/rolleyes.gif[/img]

1fstfrd · 10-03-2006, 02:26 PM

[ QUOTE ]
If even a small piece of that probe gets to the turbo,not only will the turbo be ruined,but it will more than likely put pieces into the rest of the motor.

[/ QUOTE ]

Where did you get this info? There are a lot of variables but if a very small piece goes through if you aren't on it hard making 30 psi of boost it will most likely just go through. If you are running hard when it goes through it might dammage some of the turbine blades. HOWEVER how is it going to put turbo parts through the engine when this is all happening in the exhaust? It would be nearly if not impossible for a small or even a decent sized piece of the probe to go through the turbine side and have the turbo grenade to the point that the intake side would come apart and go through the engine.

[ QUOTE ]
..or you could just learn to read the gauge and leave the probe post-turbo like the vast majority of heavy engines.....

[/ QUOTE ]

The problem is as was mentioned above there isn't a consistant difference in temps. There is a huge range of difference in temps and the ONLY way you could "learn" to read it is to have two gauges to compare at what circumstance there is what difference.

All that being said I have NEVER heard of ANYONE who has ever had one break off and go through a turbo and dammage it. I think a lot of people don't understand the systems they are dealing with or how resiliant a turbo really is and are afraid of what they don't know. Besides I'd rather risk a $1500 turbo than a $7,000 engine. Hands down bottom line preturbo IS where your probe should be and where it will give the most accurate reading. Gauges don't matter if you they don't give you and accurate reading for what it is supposed to be telling you.

TimMiller · 10-03-2006, 03:59 PM

I've worked on industrial ovens for years. We have had the same type of thermocouples right there with the burner (they are reading much hotter temps than what our trucks will ever read) I have never seen any part of a thermocouple come apart. I have seen goobers run stuff into the thermocouple and bend it, and very rarely breaking it off. (Industial ovens have at least too thermocouples burner box side, to keep the burner from buring its self up and then on on the product side, the one that gets broke off from goobers running into it)

nivrig · 10-04-2006, 08:44 PM

OK guys, back to my original question

"Just wondering, I have a post turbo sensor and I understand your not suppose to exceed about 1250. What about the pre turbo sensor that goes on the exhaust manifold, is that 1250 as well???

I'm putting a 4" exhaust on and was considering moving the sensor. I understand that the pre turbo location is suppose to be better or does it really make any big difference??"

From the responses I found out:
1) Most like pre turbo and some like post turbo. It's all preference.

2) Max temps are, 1250 pre turbo and 1100 post.

3) Now I have to decide if I should change my probe from post to pre turbo when I put my 4" exhaust on

and

4)I was not trying to start a debate, I was just curious about the temps. Now I'm gona go get a cold one and think about it:-)))

thanks for your responses.

johndeerebones · 10-04-2006, 08:55 PM

[ QUOTE ]
OK guys, back to my original question

"Just wondering, I have a post turbo sensor and I understand your not suppose to exceed about 1250. What about the pre turbo sensor that goes on the exhaust manifold, is that 1250 as well???

I'm putting a 4" exhaust on and was considering moving the sensor. I understand that the pre turbo location is suppose to be better or does it really make any big difference??"

From the responses I found out:
1) Most like pre turbo and some like post turbo. It's all preference.

2) Max temps are, 1250 pre turbo and 1100 post.

3) Now I have to decide if I should change my probe from post to pre turbo when I put my 4" exhaust on

and

4)I was not trying to start a debate, I was just curious about the temps. Now I'm gona go get a cold one and think about it:-)))

thanks for your responses.

[/ QUOTE ]

Yes, you should move the turbo to the manifold, like said even if it does break off, rather replace and turbo for a screwed up turbine wheel and housing, than an engine cause it got to hot and melted down. The only downfall for manifold installation is that you are only reading one bank, could I guess put one in each bank and have two pryos, or you could also put your thermo couple in the collector right before the turbo, in the manifold is definitly gonna be the most responsive to actual temps though. Unless one cylinder is misfiring or dead on the side your thermocouple is on though, the other side will never be hotter then the side your reading, could only be cooler because it was down a cylinder or something, so by reading the one side, it is a safe bet the other side is cooler or about the same. The problem with post turbo as said is that the temps may only be 200 degrees different than pre or may be 500 degrees different, you won't know until you smoke the tops of your pistons then Know it was too hot, not debating, just trying to stress that pre turbo is MUCH safer location for the probe.

Allister73 · 10-09-2006, 12:58 PM

When in the service, the Hummer manual called for, when a glow plug broke off but was under so much of an inch long, run engine at idle, and let the tip blow out the exhaust and through the turbo and out the down pipe with the rest of the exhaust removed. Maybe GM builds there stuff better than Ford, do not think so!!!!. Maybe it is just that when operating things in the jungles, you do what you can to be mobile again. I would not intentionally do this to my baby, but it illistrates that things are tougher on the exhaust side of the engine than some may think. I drilled the hole in the manifild, then threaded it, and then started the engine and let it idle and blow the shavings out. Removed the turbo first time since then last week, low and behold, not even and mark on the exhaust fins. It is a stated better to risk the trubo than the engine. When you are at 1250 in the manifild, cumbustion zone temps and therefor exhaust valves are around 1800f. Do you want to risk blowing the piston, warping a valve, or such. You will never really know what the temp difference is between the manifold and the turbo outlet, unless you have two gauges all the time. 1150 is too hot on the post turbo pyro anyway. If you have done this already, I promise you have cracked the edges on the piston dish already, and will only continue to do more damage running this way. 950 is the only safe post emp. That way, when the thermal soak on the turbo is at 500 delta T you are around1450 before, which is still too hot, but that temp range is a bare minimum for use. Colin