pyrometer location question
 

i believe to have asked this before, but upon inspection it looks to me like a good spot to drill for the pyrometer, i got my egr blocking plate kit and where the tube used to come out of the exhaust manifold for the egr; right where that little circular manifold block off cap goes looks to me like a great spot as its right by one of the cylinder exhaust ports and the pyrometer probe i have is about 3 inches long so it would be right by the #1? exhaust port which should be a good spot i would think to grab the exhaust temps... please let me kno if u guys think this would work, i really want to install this thing and i dont want to have to take off the exhaust manifold and turbo in order to do it, this sounds like a much better spot to me, thanks- J

That spot which might look to be an easy place to connect the probe. You wll not get the true reading of the heat going through the Turbo charger.
You are only getting the temp from that one cylinder.

To get the true temp, you will have to remove the manifolds, and drill & tap into the exhaust manifold where the exhaust goes into the turbo.

I have seen some drilled into the header pipe (down pipe) post turbo, but the temp will be a couple hunderd degrees lower.

this was just discussed on a thread a week or two ago. FORCEDINDUCTION might have a thread on it. I do remember BGKAST showing some pictures doing it when I first registered a couple yrs ago.

Charlie

Right after the turbo is a good enough spot., but you can certainly put it before as long as like charmalu says, all the cylinders exhaust needs to be present.

how much lower are the readings right after the turbo tho? or are they about the same?

charmalu's right

here is a picture of my install.

http://i131.photobucket.com/albums/p...g?t=1240355735

http://i131.photobucket.com/albums/p...g?t=1240355897

It needs to be pre-turbo to get an accurate reading. I know a few people that did experiments and the post-turbo temps would vary over 200 F, not to mention read lower.
Just before the turbo is best.

The EGT gauge is there to help prevent melting your turbo.

You absolutely cannot put the probe at this location. There is no exhaust flow at that point and the temperature is meaningless.

The probe must go between the head and the turbo............as close to the head as possible.

The EGR port is a separate tube about 8" long. It has no flow and the temperature readings would be grossly inaccurate.

The area where all the exhaust collect to go into the turbo is the best area. You can also install it into the turbo housing if you don't want to remove the manifolds.

Don't try to drill/tap with it still on the engine, the metal shavings will damage the turbo.

It should look something like the attached picture when installed.

I'm sure others will disagree (someone always does) but the real purpose of an EGT probe is to protect your pistons from melting down. Generally I believe the blades of the turbo (impeller and compressor) are made from steel. Not very likely that you will produce exhaust gasses hot enough to melt steel.

The pistons on the other hand are made of aluminum and the point at which the aluminum alloy used in manufacturing pistons begins to melt is right around 1275*F (690*C). That temperature is easily reached, especially if your running a little heavy on the fuel.

Ideally you want to measure the exhaust gas temperatures as close as possible to where they exit the exhaust port - to have a little time and opportunity as possible for the gasses to cool. The perfect thing would be to acutally measure the temperature inside the combustion chambers at the top of the piston. The problem with measuring the temps there is that you'd need a separate probe for each cylinder since even minor variations in air flow and fuel injected will cause the combustion temps to vary somewhat. The same thing applys to measuring the temps at one of the exhaust ports. That might be your coolest running cylinder and while it is running at 1250*F, one of the others might be closer to 1350*F - resulting in the hotter piston getting slagged - even though your gauge showed the temps being below the critical 1275*F.

So you definitely want to mount the probe where it can/will be exposed to the combined flow of gasses from all the cylinders. It still isn't going to be measuring the exact temp of the hottest one, but it will be measuring an average of all of them - which is better than measuring the temp of the coolest one (which you could end up doing measuring the temp right at one port - if you're unlucky enough to pick the wrong one).

When you move the probe to a post turbo location the variation in temperature becomes even larger. Depending on design, flow, RPMs, etc. the temp of the gasses exiting the turbo will generally be in the range of 200*F-300*F lower than they were when they went into the turbo. The turbo housing itself absorbs and dissapates a lot of heat and the gasses expanding inside the turbo causes them to cool as well. The good news is that the EGT temp drop for a given turbo is a pretty consistent number, or more precisely a consistent percentage.

So, as Forced stated, measuring the temps where the exhaust exits the manifold (into the turbo) is about the best you can do to get the most accurate measurement of the average exhaust temp. It works just fine to install the probe post turbo BUT you have to find out what the temp drop is across your turbo is at max EGT (assume around 1250*F to use a "safe" number with a little margin for error), and then set your "upper limit" on your EGT gauge that much lower.

For example, if the EGT drop across your turbo is 250*F when the incoming gasses are at 1250*F (a 20% heat loss), and you have your EGT probe installed post-turbo, you have to remember that the safe limit on your gauge will be 1000*F. This works just fine and as long as you make the proper compensation for your application it is plenty accurate enough to provide the needed protection from slagging pistions. Just about all piston-engined aircraft have their EGT probes installed post-turbo, and that is definintely an application where accuracy is critically important. A slagged piston at 20,000 feet has a little more serious repercussions than having one slagged in the engine of your car beside the road...

Like most things in life, having one probe in the collector area is a compromise. Its not 100% accurate but its close enough to be acceptable for daily driver people like us. "Driving by temperature" is a great way to maintain maximum efficiency.
If you're serious and willing to spend the dough, $400-600, there are several models of aviation pyrometers that have 4-6 inputs in a single gauge. Most can be set to automatically display the hottest cylinder and even have a high limit alert.

The exhaust will be cooler after the turbo, but I wouldnt risk drilling into any manafold. Like others have said, it will be accurate enough for what you are trying to do. Here is what I did, and I know I've posted this before.

That looks pretty good to me. One question: how much temp drop are you allowing for across the turbo (to determine max temp limit on your gauge) , and how did you figure out what the temp drop is?

I was thinking of using one of those non-contact infrared thermometers to measure the temp of the manifold pre-turbo and the downpipe post-turbo and use that to caculate the (approximate) percentage of temp drop across the turbo and then multiply that percentage by 1250 to determine my max EGT number for a post-turbo installation.

The only problem is figuring how to measure the two temps while under load & boost. I don't have ready access to a dyno...

The commonly allowed post-turbo temperature is 950*F.

If you are squeamish about drilling and tapping your manifold, go to the junk yard and get one there, if you some how destroy it you are out $20 or whatever they charge these days for a manifold.

pulling it at the yard will give you valuable experience, making it easier to install it once you have drilled and tapped it. If you can find a 78 SD you will find an exhaust manifold without the EGR. so you will never have to worry about that leaking.

Drilling and Tapping the manifold is safe, its cast iron. Cast iron is used in making engines because it is easy to machine, softer then steel.

It sounds like a lot of work to remove then manifold but trust me its an after noons work, and even faster if you practice on a car at the junk yard. and your pyrometer is in the correct location.

300* drop is a good rule of thumb to be sure, but as I'm sure you know, every model of turbo/turbo setup is different, and I'd like to be a little more precise if possible...

Quite a bit more than $20 in the Seattle area, I can assure you. Plus you're forgetting the cost of the gaskets & other little anciliary items...

I'd think actually just removing the turbo would do, if you have a close-quarters right angle drill and a short bit. I don't see where removing the entire manifold would even be required.

On another note, if you use a donut-shaped magnet and put it against the manifold around your drill bit when you're drilling and around your thread tap when you're cutting the threads you'll catch 99% of the shavings, so I don't see where you'd really even HAVE to take the turbo off.

The few tiny filings that might escape to the inside of the manifold would only be from that last fraction of an inch when you actually break through with the drill. I'd think that many little filings would be able pass safely through the turbo impeller and out the exhaust in about the first 30 seconds of idling the very first time you start the engine when the impeller wheel is barely even turning. Can't see where that would cause any damage worth being concerned about. Heck the impeller chews up flakes of carbon that get blown out the exhaust at WOT - when its spinning at tens of thousands of RPMS - without being damaged...

Is there a flaw in my logic here somewhere?

Only way to do that is to know the temperature drop for your climate, engine and driving style and that means a probe pre and post turbo. If you're going to do that, might as well just go with a pre turbo probe and be done with it.

Post turbo probes are mainly for maximizing economy, "driving by temperature", as I said earlier.

Removing the turbo and manifolds is very easy and a gasket set costs $35. If you can weld a bung onto an exhaust pipe I know you can use a drill and tap.

That 1% is all it takes to do damage. A wheel spinning at 120,000rpm doesn't take much to get off balance and take out the bearings. Iron is much harder than carbon and soot. A shaving can easily get wedged between the wheel and housing.

Some "lazy" shops drill and tap with the engine running around 2000rpm. The idea being exhaust pressure will blow any shavings out before it can drop in.

Umm, yeah, I'm a pretty experienced fabricator - so doing this job wouldn't be much of a challenge for me.

However, everyone reading this might not be in that same boat so to speak...

I agree - if the turbine is spinning at 120k RPMs when the shavings pass through it. If they pass through at idle when its barely turning its a different story. If one got wedged like you describe, it would stop the wheel, right? That should be pretty easy to determine and fix before it does real damage.

Harbor Freight sells tap sets, drills and bits. Its not impossible to get a good pyro system finished DIY for under $300. I've done it once and I've got another pyrometer coming for my 300D.

I bought this gauge and probe from these people.

http://www.egauges.com/vdo_mult.asp?Type=Pyrometer&Series=Vision

works great and cheap! and VDO to match the car. I borrowed the tools, but they could be had from harbor freight for around $20

In my opinion doing it anyway other then the manifold on the bench is just asking for problems. and its really not that hard to remove and install. swapping to a pre EGR manifold was a plus.

I would say the EGT is there to detect poor conditions of combustion resulting from
-Poor atomization (Bad Injector or Delivery Valve)
-Leaking Valve
-Bad Compression
-Overload
-Bad timing
-Poor air supply

I have a question. When i drilled my diesel ram. I started the hole then started the engine & finished the job. Shavings blew out from the hole. Shut the engine off, tapped the hole & installed the sender. How is the 300SD different?

It isnt. Doing it that way is a good way to cause damage. Shops with good mechanics won't allow shortcuts like that.

I like the idea - pretty much no way for even one filing to go inside against constant positive pressure...

Agreed. There's almost no risk if the engine is running while the hole is drilled.

That is the lazy/improper way to do it. Do it right.

In your opinion. I think it is the easier/simpler and therefore more effcient way to do it.

Feel free to do things the hard way if you like. I have a life so I prefer to do things more simply and efficiently.

ok so this is what im thinking... i got a saab 900 intercooler coming to me soon so im going to do the pyrometer and the intercooler and the full load fuel screw all in the same weekend hopfully, i was going to take the turbo off and while im drilling im going to put a big magnet on the other side of where the hole will be and while im drilling the hole i will have my brother hold a shop vac by the drill bit grabbing any metal flake that will be present and then running the vac inside the manifold before i put it back together, what do u guys think?

Way more than adequate...

No, in fact. This is no different than the "bubble method" deal, made up by somebody too lazy to take the time to do things right.

Take the turbo off. When its off the chances of debris getting into the engine is almost nil. The turbo gasket set costs about $10 and $35 for the entire manifold set.

Lance, we all know that in your infinite wisdom, you already know all there is to know and that any way of doing anything OTHER than the FSM way is dead wrong.

Please explain, in technical terms, exactly why drilling the manifold with the engine running is risky and/or a bad thing to do. And because that isn't the way some book or instruction sheet says to do it is not a good enough explanation. Neither is the fact that it is an easier, quicker, cheaper or even the "lazy" way to do it. Tell us what is really wrong with finding simpler easier ways to do things.

Pulling the manifold is the correct way to do the job to ensure no metal is introduced into the engine/exhaust and the hole is drilled/tapped straight.

Its very simple...there is a right way and wrong way to do a job.

Pretty much what I thought - you can't explain or give any technical reasons why it isn't an acceptable method - it just isn't the "right" way to do it. Just like any timing method OTHER than the FSM "drip" method.

How good the results are doesn't matter, or how much time/effort can be saved (even if it reduces the time & effort to half or less - as would be in this case), it just "isn't right".

With that kind of thinking then NONE of the alternative repair methods that innovative people around here have come up with are acceptable. Things like pool noodle seat repairs, odo repairs using loctite, etc. would all be unacceptable because they aren't written down in an official manual somewhere. :rolleyes:

Sure glad you're in such a minority around here.

Blah blah blah blah blah. How about actually contributing something instead of just being combative?

In the books thou mayest read what to do and when, but only the voice of experience may tell thee why and how, else thy reading of what and when shall but plague thee with smoke.

i said i was going to take the turbo off, i just dont want to take the manifold off because im aftraid of breaking a bolt off as the nuts/ bolts look pretty rusted.

I know. rcounts just can't seem to understand how easy doing it right actually is.

Leave him alone, eh?
 

Leave the poor guy alone. So what if he is only twenty three years old and has no experience. So what if he hasn’t passed a single ASE test, much less all of them to be a Certified Master, like our moderators. After all, he has over 14,000 posts on this board, except for the Techs Only forum, where it takes proof that you have professional credentials. So what if he misleads people with his opinions.

I think you should believe every word he says…………. Just like I do.

Thank you for demonstrating your ignorance. :) Clearly you haven't the slightest clue about me, my life or my experiences. I can easily pass several ASE tests and fulfill their experience requirements but I do not attempt the tests because the shop I work at does not provide any benefits or incentives for attaining certification (other than paying for the test itself), I would have to do it for personal gratification alone.

Thank you for confirmation of your ignorance. If you take the time to read the forum descriptions, you'll see your "Techs Only forum" is nothing more than the g@soline counterpart of this forum. I have no interest in dirty, sloppy g@soline engines which is why I rarely look in that sub-forum, just as there are long-term members in that sub-forum that never come into here for the exact opposite reason.

Is this your personal motto?

:eek: ENGINE RUNNING? While you are in there, I hear pouring a cup of sand into the intake will polish your manifold.

lets not argue and fight in these forums, its rediculas and seems to always happen in all of the forums i have been in and it takes the focus away from the origional issue at hand...

so do u think i should just pull the manifold along with the turbo or is just pulling the turbo enough while i run the shopvac and put a magnet on the otherside, i figured once the drillbit started to penetrate that i would move the shopvac to the inside of the manifold

Can't we all just get along? :D

That would work fine. If you set the magnet inside the manifold it should attract any shavings.

I don't see how your gonna get a suitable drill in there. I'd pull it and put it on a press.

If you can get the drill in, you only need to pull the turbo then vacuum.

When I put my turbo setup together I made my exhaust gaskets from brass shim stock (exhaust still holds 40 psi) plus $5 Mercedes gasket on the oil delivery, $5 gasket on the oil drain. YMMV

Read the whole thread winmutt. We're talking about tapping the exhaust manifold for a pyro thermocouple. Running the engine at idle was suggested as a way of ensuring through positive pressure that all the chips/slivers/filings end up on the outside and don't get sucked into the turbo. As with all things, Lance insists that HE knows better than everyone else and that there is only one way to skin a cat. As usual, I disagree with his condescending know-it-all tone. He hasn't been able to provide any technical reason why it wouldn't work - just that it isn't the "right" way to do it.

Do you have a more technical reason to suggest why doing it this way would not be safe? If so, post up. Otherwise....

BTW, I will most likely pull the turbo off when I install mine. Unless I just decide not to to prove Mr. Know-It-All wrong. I'm sorry, but I just have a hard time with people who take a sef-righteous I'm the only one who knows what is right and anyone who disagrees is simply wrong attitude. Unfortunately, that seems to be Lance's only posture on any and every subject. It gets old - know what I mean?

Anybody who's been around the block a time or two knows there is more than one way to do almost any job, and saying - self righteously - that doing things an easier way simply means that others are lazy or incompetent (compared to yourself) just rubs me the wrong way.

The truth finally comes out. You don't have a problem with doing the job right, you have a problem with ME telling somebody how to do the job right and you're just being argumentative or, possibly, jealous. You're acting like nothing more than a child intentionally disobeying a parent just to be spiteful.

You're more than welcome to stay out of it and ignore my posts.
In fact, I'll make it very easy for you so this forum can be a better place without your useless and pointless arguing. Click here: http://www.peachparts.com/shopforum/profile.php?do=addlist&userlist=ignore&u=11901

That ignore list trick works both ways pard, and feel free to add me to yours.

You're partially right about one thing Lance. The biggest problem I have is with you and your attitude. Whenever someone suggests something you disagree with you immediately begin making condescending statements.

Funny thing is you have the exact same kind of run-ins with multiple people - including moderators. Try reading the thread from the last time you got banned. On the other hand I have never been banned or even received an infraction. Generally, I only seem to have these conflicts with one person - you. What does that say?

The very thought of me (as the child) "disobeying" you (as a parent figure) is too ludicrous for words. Don't flatter yourself. Yes, I initially planned on taking the turbo off. But certainly not the whole manifold - as you initially suggested was the only "right" way to do it. This thread got me to thinking about whether there might not be an easier way. The collective knowledge here came up with a couple of suggestions of easier ways. See, I have a life, so finding ways to do things simpler and with less time investment is something I'm interested in. So, I'm seriously considering the alternatives, and the fact that doing it a different way would save time and effort - AND prove you wrong (again) at the same time would just be a bonus.

BUT N-O-O-O! We can't even discuss finding easier more efficient ways to do things - we all have to do it Lance's way - either that or listen to him harangue us about how lazy and "wrong" we all are - because Lance knows everything and knows it better than everyone else put together!

Think about the way you come across man. I know it is pointless to even suggest that, since so many others have already done so many, MANY, MANY times, but I figure if you hear it enough times, maybe someday the message will get through...

ya thats what i was going to do. i cant wait til i have some time to do it.:cool: