EGT/Pyrometer gauge, worth while or not?

Originally posted by Swazo:
OK, I went ahead and got an pyrometer gauge (lunar series to match my gauge overlays )

Should it come with a bung for the sensor?

Yup, thats the same one im running.

Originally posted by warmonger:
Well, the accuracy isn't really the way to look at this one. The gauge will accurately measure temp wherever it is but if you want to know combustion temps then you'll want it close to the head. On the other hand, the probe will wear out faster. I've been running one since '02.
I currently have it in my y-collector where both banks combine. It is still very sensitive there. If you want to compare it to other peoples temps then you would have to mount it where they have it.
If you put it in a header then you only reflect the temp for one bank, i.e. if it goes lean on the other bank you'll never know. Still, overall that is rare. I'd mount it in the collector of your header or on the bottom of the precat chamber of the stock manifold in an easy location.

It will be more accurate to the combustion chamber which is the whole point of using it. If you use it after a bend you will be picking up the temp of the metal, not the exhaust.

I mounted mine too low, right where the 3 collectors join up on the back header - so it reads really hot as it's constantly being blasted by one cylinder at any time - so in effect it's not really useful where it is right now. I need to remount it right up next to the head, which I will do when I rework the motor this winter.

Is there any safe way I could try to install this while the header is installed?

1. I was thinking about drilling most of the way through, clearing the shards before it punches through.
2. Greasing up the drill bit to catch the remaining bits.
3. Weld in bung as close to the head as I can.

Uninstall turbo, start car to blow out misc s*%^ out the crossover pipe?

Any truly safe way? No.

Do it right once.

Sure. You do it in the collector of one of the banks, The shards will mostly fall out and if you do as you say with grease then you should catch them all. Don't worry they'll fall down by gravity. You can unbolt the y-pipe first and then take a vacuum to it to be sure or let the exhaust blow anything else downstream.

I'm disagreeing with you on an academic level.

It will read the temp of the exhaust minus however much it cooled between the head and the probe. Wherever the probe is at, this is what it reads. This is always the case since the exhaust temp is soooo much hotter than the metal temp, even the metal around the combustion chamber. If the metal in the combustion chamber ever approached the temp of the flame temp...it would melt. The heat just flows so quickly through the metal that it never reaches the temp of the exhaust.

So no matter where you are putting it you get the temp of the exhaust at that point.
All you do is determine how far you are from the combustion chamber and adjust your expectations of exhaust temperature accordingly.
For example, in the clamshell header of the stock exhuast manifold next to the factory O2 sensor I would run 650 C in cruise and approach 850 C under full throttle.
Mounting it in the last set of mild steel pipes I used in the y-collector it would read around 500 C cruise, 700's under full throttle.
Now with stainless piping and full header wrap, the heat is not conducted out of the exhaust that quickly so it retains its heat. I cruise at 600-650 c, Idle at 350 C or so, and full throttle around 800-850 C.
So it doesn't really matter what the temp or location is, assuming it is close to the source of combustion; relatively speaking as compared to the whole length of the exhaust. It matters more that you determine your "Calibration".
The way to do this is to test your car's air fuel with a wideband at cruise, idle, and wot and record the wot measurements at several rpm points.
Then as long as you know that your air fuel is spot on, then the temperature "has meaning" no matter where you put the probe because it will now be your reference temp at that ambient temperature. As long as you don't change the type of pipe, wrapping, or location of the probe. Otherwise you just adjust your expected temps accordingly.

The temperature never remains constant under wot, it will constantly increase as the rpms increase, so he will need to watch how it climbs and learn what is normal.
After having it for a while and knowing what the temps mean, it becomes second nature to know that combustion temps and therefore A/F is correct... just by watching that one gauge.

Originally posted by warmonger:

For example, in the clamshell header of the stock exhuast manifold next to the factory O2 sensor I would run 650 C in cruise and approach 850 C under full throttle.

850 celcius? Thats 1123K, or 1562F. The manifolds are cast iron, right? Cast iron melts at 1420K. Thats dang hot, and pretty close to melting.

Is that right?

You can mount it further than 1" from the head, but just make sure it's reading ONLY ONE CYLINDER. I f'ed up and mounterdit in the collector so it reads all three cylinders. Hence my temp are too high, even though it's not really running hot. Think of it this way - rather than being hit by one exhaust pulse every 4 revolutions it's getting hit 3 times - so it doesn't have time to cool ever and thus reads high. Make sense?

Here isd the diagramatic representaiton of what I am trying to get across:
http://www.stevetek.com/R-EGTprobeLocation.html

OK, that shows that it ran 150* hotter when in the collector and it was more or less an average temp. Their theory is that a lean condition can be over looked and unnoticed if the sensor is tapped in the collector as it'd average out the temps from the combined runners.

Now from a novice POV, I could see having every runner tapped to be able to see which every bank temp is and having it worth while. But, to only have one out of six banks tapped in hopes of catching THAT bank running lean doesn't seem optimal.

Teamed with good upstream o2's and the wideband o2... shouldn't I be able to accuratly use an EGT for tuning if it's mounted in a header collector?

No. If you read what I am saying - I get good umbers on my A/F ratio (i.e. rich enough) yet cos I have it mounted in the collector it says it's too lean >1600�?°F on WOT.

When I remount it it will be in either cylinder 1 or 4 as they are the furthest down the fuel rail from the inlet of the fuel rail, thus more prone to getting less fuel then cylinders 6 or 3, thus more prone to being leaner.

Hence you want to mount it in the header tube of 1 or 4. OK?

You could always weld in 6 bungs and close off 5 and then move the probe from cylinder to cylinder

Originally posted by KingpinSVT:

Originally posted by warmonger:

For example, in the clamshell header of the stock exhuast manifold next to the factory O2 sensor I would run 650 C in cruise and approach 850 C under full throttle.

850 celcius? Thats 1123K, or 1562F. The manifolds are cast iron, right? Cast iron melts at 1420K. Thats dang hot, and pretty close to melting. Is that right?

Yes. The temps are correct but you missed the part about the metal temps NOT being at the same temp because they conduct the heat through them and away. That is the exhaust temp in the middle of the stream and that is with the probe sinking some heat as well. The temperature drops off rapidly as you go from the center of the exhaust stream toward the walls of the pipe.
Weird Huh?? How about this example: You take a match and you put it on the bottom of a steel pan. The match flame is pretty darn hot, it sets wood on fire, paper wax, etc. It doesn't even change the overal temp of the steel pan because the heat is conducted so rapidly throughout the pan. It will have what is called a heat gradient from the point where the flame touches the pan and radiating outward. Once everything reaches a steady state you take a temperature probe and measure from the point of the flame then outward from that point at even, radial distances and you will see that the temps drop down as a function of distance. IF the material structure is the same in all directions then it drops the same at all radial distances. This is used to determine the temperature gradient and then the heat transfer coefficient of that material.

Take paper.. It never feels cold to the touch because it doesn't transfer heat fast. Instead it lights on fire at the localized point where the flame hits it. That is because the paper temp at the point the flame touches rapidly approaches the flame temp due to the fact that it can't conduct the heat away. On top of that it is flammable.

So that is why your engine doesn't melt down...that and the coolant that transfers heat to the radiator and then the outside air.

These kind of concepts are why I love materials science and why I got my degree in it.

BTW, the manifolds are some form of stainless steel or high grade steel on our cars. There isn't anything cast iron on our cars that I know of, just low and high grade steels.
I think the manifolds are some form of stainless to resist corrosion as long as they do.

Originally posted by Stazi:
No. If you read what I am saying - I get good umbers on my A/F ratio (i.e. rich enough) yet cos I have it mounted in the collector it says it's too lean >1600�?°F on WOT.

When I remount it it will be in either cylinder 1 or 4 as they are the furthest down the fuel rail from the inlet of the fuel rail, thus more prone to getting less fuel then cylinders 6 or 3, thus more prone to being leaner.

Hence you want to mount it in the header tube of 1 or 4. OK?

I read what you said, that your median tempurature for your rear banks indicate that you're running lean by single bank sampling guidelines. Since Chris did your tune, I know it is highly unlikely to be doing so.

I do agree that it is ideal to sample from a single bank, and when I can afford the time to rip apart my car just to cut into the header and weld it in, I will. That's just a major PITA right now, and I wish I had considered getting this gauge sooner in my build up.

It's hard to warrant tearing back into a project when you're fine tuning part throttle and WOT apects of your tune

Originally posted by Stazi:
No. If you read what I am saying - I get good umbers on my A/F ratio (i.e. rich enough) yet cos I have it mounted in the collector it says it's too lean >1600�?°F on WOT.

When I remount it it will be in either cylinder 1 or 4 as they are the furthest down the fuel rail from the inlet of the fuel rail, thus more prone to getting less fuel then cylinders 6 or 3, thus more prone to being leaner.

Hence you want to mount it in the header tube of 1 or 4. OK?

I don't really get this one. This would only happen if your fuel pressure were insufficient to carry the load. Fuel pressure and fuel to each injector should be much larger that what the injector can dump...again, unless there is insufficient volume or pressure. THe pressure will drop but the the regulator (or pcm via fuel pump voltage) should increase the volume flow as the pressure begins to drop and effectively preventing the pressure form falling.

As far as sampling one tube:
I'm thinking if you sample one tube then you will only be accurate for that one tube but it would reflect what the whole bank is seeing unless you get a fault in one cylinder.
If you mount it in one tube and closer to the ports then the temps will rise even higher than they are now no matter what you do.
It is best to sample all three if you are only using one device, in case one runner is going lean.

Originally posted by Stazi:
You can mount it further than 1" from the head, but just make sure it's reading ONLY ONE CYLINDER. I f'ed up and mounterdit in the collector so it reads all three cylinders. Hence my temp are too high, even though it's not really running hot. Think of it this way - rather than being hit by one exhaust pulse every 4 revolutions it's getting hit 3 times - so it doesn't have time to cool ever and thus reads high. Make sense?

Here isd the diagramatic representaiton of what I am trying to get across:
http://www.stevetek.com/R-EGTprobeLocation.html

Ok, you have an egt.

I have to reiterate the point that our engines run leaner than engines of the old days. The combustion temps are higher yet they still resist detonation and pinging better.
I have always run much higher EGT temps. I always made my best power when my car was NA with 13.2:1 A/F at WOT without any worries of pinging.
With the turbo this engine is comfortable with 12.5:1 A/F without detonation...on 91 ocatne no less!
These engines have better materials than the engines of old and people don't realize it; especially the 'old time' hot rodders. THey'll tell you the engine will blow up on a NA engine with a 13.5:1 A/F ratio. That isn't the case at all and it has been proven bymore than just myself.
With the turbo, old school turbo people say to run 11.5:1 or even 11:1. THat is pig rich for this engine. AF with my turbo as I said earlier is comfortable at 12:1 and fine on 12.5:1 with moderate boost. I have no fear running my engine at 12:1 and 12-14 pounds of boost! That is because this engine is well designed and it is very efficient.

I'm saying all this because the temps being high are not an error, they are the result of a more efficient engine running at a higher temp and making more power because of it.

If anyone really wants to be serious about their EGT's AEM has a 4 channel thermocouple amplifier with a serial output so you can log the temps with your PC.... and that would be the reason why my new headers have 4 bungs, one for each cylinder.

Yeah but we have six cylinders.

Your engine is 33.3% deficient and I'd need two of those devices to make it work.

Well obviously you'd need 2 of them :-P I'm sure you could find somewhere to put another 2 thermocouples.

Tom, the only plac eI se it worth measur on entire bank, is further down the header, maybe right before it merges with the header from the opposite bank. Right now I'm at the center of the collector of the rear three headers tubes. So it's reading silly high. If I move it further down it'll probably read lower and more realistic.

On my returnless setup, there is probably less chance of heaving one cylinder leaner than another due to a dead head setup in the fuel rail, but for return-style rails, I bet money that the last injector before the pressure reg is a smidge leaner than the first injector on the rail - this is because unless the FPR clamps shut under boost (thus creating a dead head) the allowed fuel flow out of the rail will cause the pressure at the last njector to be lower than the first - there' no way around that - otherwise you defy fluid dynamic ansd physics. I.e. you have to have a low and high pressure variation to cause the fuel to flow into the rail and out again.

Well I know i am no expert at this but I mounted my EGT at the number one header the hotest cylinder and my highest recording was 850 C on wide open throttle with load. I never burnt a piston yet and I would think that you are really looking to just catch problems like fuel problems and tuning. If you have a injector go out you might not catch it but the odds of that is less. I mounted it an inch off the head works well seems to adjust quick to temp changes.

Stazi, well that makes sense when you explain it like that. But in my case the FPR diaphragm recieves positive boost pressure so it should be clamping it shut.

That also reminds me that injector pressure would be reduced by the boost pressure present in the intake.

I wonder if it balances out. The FPR keeps fuel pressure a rock steady 55psi without boost under WOT. If it adds 10psi boost to both the diaphragm and the intake system, does it balance out and still inject at 55psi?

Originally posted by warmonger:
Stazi, well that makes sense when you explain it like that. But in my case the FPR diaphragm recieves positive boost pressure so it should be clamping it shut.

That also reminds me that injector pressure would be reduced by the boost pressure present in the intake.

I wonder if it balances out. The FPR keeps fuel pressure a rock steady 55psi without boost under WOT. If it adds 10psi boost to both the diaphragm and the intake system, does it balance out and still inject at 55psi?

Theoretically yes, assuming there is no pumping loss through the injector.