Good and bad temp in the ext temp (Pyrometer)

[mocpac]

We have a doubt, what will be a good or average temp in the pyrometer (exhaust temperature) and what will be bad or to worry.



My gauge mark up to 24 average temp is 8 to 10 in my car and some times up to 11. B ut we are not sure what is good or bad. Some people said if I don't get to 12 everything is all right.

so any help with this?

[exist3nce]

I don't know the safe range myself, but I do know the numbers are quite variable depending on where you place your pyrometer. If you place it right at the exhaust port, you would be getting the highest (and most realistic temps), but if you place it say after the turbo, the temps would be lower and not as accurate. I think most people would place it in the manifold between the turbo and exhaust ports.

[PrecisionBoost]

The maximum temperature for each engine is slightly different due to factors to do with cooling.

That is to say a head that has really good cooling could manage 1300 deg F where as a head that doesn't remove the heat very well or one where there is a hot spot may only take 1100 deg F

At this point I think your ok..... 800 to 1000 deg F should be fine..... even 1100 deg F

I run about 600 deg C which is about 1100 deg F at full boost and throttle.

It's a bit on the hot side considering how rich the car runs, which is why I'm installing a water/methanol injection system.


Keep in mind that aluminum melts at just over 1200 deg F

The engine coolant inside your cylinder head cycles very quickly so it pulls lots of heat away from the aluminum, even at the surface where the exhaust is leaving.

Typically there is a buildup of carbon deposits in the exhaust port, so it acts to insulate the aluminum slightly.

So even though the melting point is 1200 deg F it is possible to push 1400 to 1500 deg F exhaust through without melting anything as long as it's for a short period of time.

If temperatures are kept above 1200 deg F for a significant amount of time the heat will eventually find a spot where the cooling isn't as good and cause some damage.

Another thing to consider is the fact that the aluminum looses strength as you approach the melting point.

This becomes a problem with Aluminum pistons..... which is why they have "quench pads" and many factory turbo cars have oil squirters that shoot oil at the bottom of the piston.

If one were to decrease compression by simply adding a really thick cylinder head gasket the pistons would not come up close enough to the cylinder head to transfer heat. ( called quench pads )

The net result is that the pistons will eventually fail under high load and high temperature.

Some people will redesign the cylinder head to give more surface area where the cylinder head and pistons come up very close to each other to maximize the amount of heat the hot pistons transfers to the much cooler cylinder head

I know I'm rambling a bit, but I wanted you to know the reasons for the " max EGT temperature" as opposed to just saying "1200 is a good maximum EGT"

[PrecisionBoost]

I don't know the safe range myself, but I do know the numbers are quite variable depending on where you place your pyrometer. If you place it right at the exhaust port, you would be getting the highest (and most realistic temps), but if you place it say after the turbo, the temps would be lower and not as accurate. I think most people would place it in the manifold between the turbo and exhaust ports.

After your turbo will usually be 200 to 300 degrees lower than in the manifold.

In the GSI the pyrometer is dead center where all four runners merge and go into the top of the turbo.

In order to do a better job of monitoring, I'd like to install four probes.... one in each runner so that I can tune each and every cylinder differently.

People don't realize that your typical EGT and Air/Fuel is based upon the mixture of all four cylinders.

For example.... you could have:

Cylinder #1 : 900 deg F & 11:1
Cylinder #2 : 1050 deg F & 12.0:1
Cylinder #3 : 1075 deg F & 12.3:1
Cylinder #4 : 1295 deg F & 15:1

Your net temperature at the EGT would be 1080 deg F and your Air/Fuel monitor would show a nice 12.6:1 ratio

In reality cylinder #4 is in big trouble.... it's running way too hot and way too high of an Air/Fuel for a turbo car.

In the end the engine might seem nice and stable, but eventually Cylinder #4 will fail.

When this happens people will often blame a "bad injector" but in many cases it's due to the intake manifold.

That is to say that cylinder #1 sees the least amount of air (and therefore is rich )

Cylinder #2 & #3 see an "average" amount of air

And Cylinder #4 is seeing way more air compared to the other three.


Most of the time the car manufacturer will try to balance the cylinders within reason, but they won't spend a pile of time and money on it.

So lets say one cylinder flows 10% more than the others.... for the manufacturer of a naturally aspirated engine that might be just fine.

Once you turbo the car..... your multiplying that factor because your shoving more air through the manifold.

So my point is that many race engine designers spend a pile of time designing things so that each and every cylinder is matched in power..... that is to say they tune each cylinder to get perfect air/fuel ratios in each cylinder

[exist3nce]

Good posts as usual Chris..... my shop is actually revamping their 1994 turbo Camry V6 with new custom manifolds and twin GT28s. They've put an O2 bung on each runner so that during tuning, he can switch around the wideband and see how the air is getting distributed.

[mocpac]

Ok, the sensor in my nubira is where you said in the center of the manifold. We run yesterday never pass 1200 I think the top temp at the moment was 1100 average and 8000 to 1000 cruising. Any way I will take the car to the Dyno the be sure that the mix is ok almost perfect. Breaking period stop yesterday @ 500 miles from day one.

Again thanks for the info, now Im not that worry.