Pyrometer

[harbormasterextra]

I don't hear much talk about Pyrometer gauges. Seems like having these gauges could help you save an engine that has a preignition/lean condition.

Comments??

Anyone have these gauges?

[Greg Maier]

From what I have seen, pyrometers seem to be used mostly on supercharged engines. I would imagine that this is because most supercharged engines are run closer to the edge and require more attention than a NA engine. Even if I had one, I'm not sure that I would be able to interpret the readings. What are the correct temperatures for exhaust gasses?

[gcarter]

I think the O2 sensor on fuel injected engines are really pyrometers. It might be possible to get a readout on the output.

George

[MOP]

Most all of the pyros I have seen were on diesel engines, I have seen them on a dyno setup at an engine shop, only a few on a gas motors. Quite a few guys run thiers boats on load vs pyro readings vary the rpm to get what they want. It would be real interesting to get some knowledgable input on how well they would work on gas.

Phil

[BUIZILLA]

You can use a pyrometer on literally anything.... how you interpret it is the key to it's value. When I raced go karts, it was a tool to let you know just before you seized a piston :bawling: There is NO correlation between on o2 sensor and a pyrometer. o2 sensors are voltage derivitive sensors.

J :propeller

[Ranman]

I've seen pyrometers (EGT's) on 4 stroke gas engines and though they may be helpful, they are not critical to the tuning process. Most people find it easer to read plug color, adjust the timing curve, etc.

Now on a two stroke (like a snowmobile) :bonk: EGT's are much more useful in my eyes. They are, however, just a tuning tool. Once a baseline is set by reading plug color and piston wash, EGT's can and will show how your carb jetting is affected by temperature. On a 2 stroke, if you're jetted perfect at 30F as the temp falls while riding at night, you will literally watch your EGT temps rise from say 1150 (good) to 1300+ (going lean) as the temp drops. If you keep that jetting and the temp goes much lower, you can easily have a lean burndown. Working in the other direction, if you're jetted for 0F (fatter) and it's 30F out, you can gain power by leaning out the jets.

TO answer another question, generally speaking aluminum (pistons) melts around 1400F. This may or may not be what the EGT's are reading when you burn down the motor. The temp that the EGT reports is very dependent on where the actual probe is placed in the exhaust stream. Think of a lit torch. If you place the probe right at the tip of the small blue "hot" flame, you'll get the highest reading. Move the probe closer or further away or have the probe off center and you get a lower reading. This means the exhaust gas can actually be 1500F and your gauge is reading 1250F. you think you're safe running at 1250F, but your in the process of burning down the motor. This is why the number alone is not important and proper plug and piston wash reading are. You have to tune the motor to optimal performance and use that reading as a baseline. Higher temp readings suggest danger (too lean), lower suggest safety (too fat).

Jamie, where are you bud. Jump in here...

[Rootsy]

i've used a pyrometer (thermocouple) in header pipes to monitor exhaust gas temps when drag racing... before inexpensive O2 equipment was available, or at least that i knew of... i don;t know if there is one good "temp" range for all motors... they are all different to an extent... there are a LOT of variables...

on the camaro we made the quickest passes with the best mph in the 1390 F range... once she would pass the 1400 mark we would begin to fall off.. getting lean... so say from 1380 - 1400 was optimal for us... 1420 - 1450 was lean... this was at the #2 header pipe... we didn't have 8 thermocouples.. just 1 channel.

i really prefer an O2 sensor for tuning... heads above a thermocouple setup. the reason being that on our setup you only really saw the MAX temperature on our DA equipment on 1 cylinder. a pyrometer gauge is a continuously updating instrument though. a motor will not make really HOT exhaust temps unless it is being run hard under load.. like drag racing or on a dyno. the O2 setup on the other hand will give you an A/F reading no matter what the load, engine speed, etc. is and it is gathering an "average" from each bank of cylinders (if it is placed in a collector).

Doug Lovins had GIL weld an 18mm thread bung in his gil riser and it works pretty well. i am going to get around to welding the two i made into my imco risers. you have to make sure that the sensor is not buried between the inner and outer pipes but that the element extends into the exhasut stream. Place them as close to the manifold to riser joint as possible to avoid damage from moisture since they really hate water... i am also placing it on the long turn radius (outside radius) of the pipe.. water will tend to trickle down the short turn radius if it does in fact get water in it. i am on the edge with my camshaft but the imco risers dump water another 4 or 6 inches rearward of the mercs... i have seen zero sign of reversion in my motor.

you CAN purchase an A/F gauge that aquires continuously form an O2 sensor, from autometer that goes in dash...

donno if that worked for or against ya randy ;)

i'd rather hear buz's take on it! so come on jim!

JR

[gcarter]

Jamie & Jim;
I've not worked on a F.I. marine engine, although I have a reasonable amount of experience from automotive engines some years ago.
So are marine F.I. engines run "open loop" with no exhaust feedback?

George

[Ed Donnelly]

My Criterion SS came with 2 pyrometers. One for each manifold. When running the twin turbo set up. I jetted to keep my exhaust temps under 1100F
Now that I am running NA, I see reading of 1075F with my o2 reading 12.5 to 1. Just remember if you are using a pyrometer over 900F,make sure you use K type thermocouple wire. I also use 2 o2 sensors, 1 for each manifold. One is heated, the other non. I was just too lazy to take the heated one off when I scrapped the electronic fuel injection(still for sale). I'm surprised MadPoodle doesn't have twin pyrometers on his SS.....Ed

[Ranman]

George,

Marine F.I. engines such as my 350 MAG MPI are open loop with no 02 sensors. They just use a preprogrammed set of values for fuel, spark, etc.

Jamie and DougL are talking about running o2 sensors on carb'ed applications to get the jetting and A/F ratio perfect.

[gcarter]

My Criterion SS came with 2 pyrometers. One for each manifold. When running the twin turbo set up. I jetted to keep my exhaust temps under 1100F
Now that I am running NA, I see reading of 1075F with my o2 reading 12.5 to 1. Just remember if you are using a pyrometer over 900F,make sure you use K type thermocouple wire. I also use 2 o2 sensors, 1 for each manifold. One is heated, the other non. I was just too lazy to take the heated one off when I scrapped the electronic fuel injection(still for sale). I'm surprised MadPoodle doesn't have twin pyrometers on his SS.....Ed
Hi Ed;
I'm trying to learn, Why did you you ditch the F.I.? :confused: :confused:

George

[Ed Donnelly]

3 years of trying to get the system to run right. Hundreds of programs.
Tried open loop, tried closed loop, nothing worked. So, last August, I pulled the system out. When we pulled the plugs,we found 2 plugs that had never fired. Defective right from the factory. The system uses 4 coil packs,but the bad plugs were from separate packs. I was so upset with my stupidity, I just put on a carb and distributor.I am going to supercharge the engine next year, so it will be easier with a carb.....Ed

[BUIZILLA]

I just wrote a very detailed, mutli-paragraph explanation, hit SUBMIT, and it went POOF. I'm not writing it again, it took about 20 minutes to type it. darn.

J :angryfire

[MOP]

Jim sorry your post got Poofed, this has been a good one. With marine running under load most all of the time I think if you watch your gauges you would spot a problem happening. But if not watching and it goes lean for instance things happen fairly quick. I was talking with my local machine shop guy, he thought that thermo couples on each exhaust was the ticket. When one went bad have the TC's hooked into the ignition to weaken spark a lot so engine would die down but not quit. Any thoughts along those lines.

Phil

[gcarter]

Has anyone tried something like a Z06 computer with O2 sensors? I've noticed most modern performance car engines have extremely flat torque curves, and should work on a boat. Gosh you might even get better gas mileage!! :) :)

George

[Rootsy]

much much much more complex than just doing that george... just taking a Z06 eprom and computer and trying to retro it to a boat engine is not impossible but way more trouble and money than it is worht... the torque curve is not defined souly by the puter either... many mechanical aspects of the motor determine that...

[gcarter]

Hey guys, I'm not beating a dead horse, but I wanted to explain the source of my first reply last night. This is from the Bosch Automotive Handbook 2nd edition. Now I hadn't read this since about 1990, and I just got the information kind of confused. Look at the left hand page and you'll see O2 sensors do measure exhaust temp and a lot more. They also measure ambient air temperature, and eventually oxygen ions, THEN they generate a current differential that can be interpreted as excess O2. So please pardon my faulty memory. The next time I won't post so soon.
Thanks again guys;

George Carter
This is a pretty large file so I hope you can read it.

[ToonaFish]

George, I must warn you that a few more posts like yours and Rootsy will feel compelled to post a graph!

[gcarter]

George, I must warn you that a few more posts like yours and Rootsy will feel compelled to post a graph!
Celine, I guess it just isn't your type of bed time reading? :yes: :yes:

George

[Rootsy]

just for that toona... i am gonna install an O2 and i am gonna post A/F readings every 500 rpm from idle to WOT... and then i am gonna make a change and do it again... i'll have a legend and everything... you can salivate in anticipation ;)

Root - logrythmic or expodential that is the question ;)

[ToonaFish]

Damn Engineers.

Bunches,

Celene 'just when I was getting a grip on synthetic oils...'

[gcarter]

Damn Engineers.

Bunches,

Celene 'just when I was getting a grip on synthetic oils...'
Celene, was that an oxymoron? :D :D

George