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jauguston · 03-12-2013, 10:33 AM

Airstreamer,

If we are talking about Cat 3126/C-7 engines they have steel not aluminum pistons. For that reason they are able to tolerate higher EGT's than engines with aluminum pistons.

TS Performance that makes the MP-8 programmer ran a C-7 on their chassis dyno for one hour at 1500 degrees EGT with no ill effects.

Jim

mbrandt1402 · 03-12-2013, 11:43 PM

Do you happen to know exactly where their EGT probe was situated? If so, 1500 sounds like a benchmark.

jauguston · 03-13-2013, 09:40 AM

No. That was a test with their MP-8 turned up to beyond the maximum power setting for what they sell. That information is not furnished or authorized by Cat and I posted FYI only. Most don't know these engines have steel pistons.

Jim

Airstreamer6 · 03-21-2013, 11:40 AM

Quote:

Originally Posted by calhyatt

If you have installed a pyrometer pre-turbo you are still not reading the actual exhaust gas temperature. It is too far from the actual cylinders themelves. You are reading a number that means nothing because there is nothing to compare it with. As far as I know, there is no chart, no performance /planning data sheets that tell you what a proper value is where you plan on mounting the thermocouple. You are just reading a temperature of the mixed gasses from all cylinders at that point. To read true exhaust gas temperature you must sample each cylinder at the closest point to the actual exhaust port of each cylinder. Even if you did this, I doubt you will find a data sheet that gives you values to compare with your readings at various rpm, load values ect. I hope I have not hopelessly confused this issue but that is the sum of my knowledge on EGT. I watched it daily for my 42 year aviation career.
Seeya on the road.

I became sold on knowing the general manifold-derived EGTs when I first got my pyrometer. I was horrified at how fast the EGTs rose when climbing hills in high gear.

With the aid of my pyrometer, I now gear down my automatic transmission before the EGTs begin to exceed 1300F or so. By the simple act of dropping one gear, the EGTs immediately fall as the RPMs rise. For me, this is well worth the $200 for the gauge, and is worth my time to read it on ascents while towing.

Surely, having a general EGT reading in the manifold is not as valuable as having individual readings from each cylinder port, but for our purposes, it is still quite valuable. Anyway, unlike aviation applications, we have no ability to adjust fueling etc while underway if any one cylinder begins to overheat although this knowledge may be valuable to an aviator reading individual cylinder EGT values when he can enrichen the fuel mix or whatever to improve things.

I did learn in this thread that the pistons are made of steel in the engine under discussion. I suppose this could raise the acceptable EGT limits, but surely not 1500F for lenghtly periods of time. Even if the pistons or manifolds do not melt, what happens to the turbos, valves, etc and etc under such conditions?

For me, I've set a limit of 1300F while towing for any sustained period of time, and only with the pyrometer can I achieve this. Perhaps my engine can take more, but I see no reason to push my engine to such extremes for what, to beat the Mustang up the hill?

Tony Lee · 03-21-2013, 08:59 PM

Seems as if the outcome of all these posts is not to bother installing a system and instead drive conservatively to your coolant temperature gauge - which seems to be what most chassis manufacturers decided on years ago.

wb7auk · 03-22-2013, 05:14 AM

In most cases unless you are going to operate at or near GVW on grades or with the
added power chips I agree with you.
Any gauge is only as good as what the driver understands about it in the vehicle it
is installed in.
About all gauges are a general information source who's accuracy is general.

mbrandt1402 · 03-22-2013, 07:00 AM

Quote:

Originally Posted by Tony Lee

Seems as if the outcome of all these posts is not to bother installing a system and instead drive conservatively to your coolant temperature gauge - which seems to be what most chassis manufacturers decided on years ago.

"drive conservatively to your coolant temperature gauge" should not be taken literally. It takes a lot longer for temperature to build in the coolant than it does for excessive EGT to start doing damage. It takes something else going wrong (failed wastegate actuator, for example) or modifications such as an MP-8, but IMHO you could do some major damage if you put your foot down on a long, long grade and only watch the coolant temp.

The lack of an EGT gauge from the manufacturer does not invalidate its usefulness. Manufacturers use a lot of criteria that an owner does not when deciding how to equip a vehicle. For example, the Mazda Miata had a real oil pressure gauge for the first 4 years of production. The result was a lot of service calls (read: cost for Mazda) when unenlightened owners thought their car had dangerously low oil pressure. Mazda's response was to make the gauge work like an idiot light. If you had more than a few psi of oil pressure, the gauge read mid-scale. Otherwise, it read ~ zero.

For mainstream mh manufacturers, the decision was probably more along the lines of cost/benefit. I suspect only 5% of mh owners would understand how to alter their operation of the mh based on EGT. Installing a gauge that won't be used by the vast majority doesn't make much sense.

Tony Lee · 03-22-2013, 08:32 AM

Point I didn't make clearly was to drive conservatively - and use the temperature gauges as a guide as to whether you are driving conservatively.

The point others made was if you buy a exhaust temperature gauge and install it in a non-standard spot (and that too seems open to debate), exactly what temperatures should one regard as alarming. Since the answer seems to be "who knows", why install the gauge.

wb7auk · 03-22-2013, 09:03 AM

Tony,
Your point is well taken, any install of the EGT probe other than at the cylinder
exhaust port is non-standard.
All of the do not exceed temp's the engine builders talk about is the cylinder exhaust
port temp.( not exhaust manifold pre turbo or further down stream)
The other problem is a lot of the EGT kits might have the wrong probe size for a
proper install.(I have seen as much as 400 degrees difference in the wrong one
and the right one)

mbrandt1402 · 03-23-2013, 10:11 AM

I agree 100% about driving conservatively, I just don't agree that the temp gauge gives you fast enough feedback to know you are taking a grade at a conservative speed/rpm.

It simply takes too long to increase water or oil temp to show that you have a problem. EGT could rise to dangerous levels and it won't show on the temp gauges for at least a couple of minutes. There is too much water and too much oil volume to change the temp that fast.

Trust me on this - I've had plenty of heat related engine damage on my race cars that never showed up on the oil or water temps.

jauguston · 03-23-2013, 11:10 AM

For those of you that for one reason or another don't think a pyrometer installed like they have been for 50 years or more in the manifold near the turbo if you have one is a good idea the answer is simple. Don't install one and skip the threads that discuss them. These are NOT airplane engines that have pilot controlled fuel mixture.

If you have not added a performance programmer a pyrometer provides "interesting" information while the ECM protects the engine from damage. If you have a programmer it can provide "valuable" information.

Jim

doorguy · 03-26-2013, 06:31 PM

Duecenut, we have the same coach along with 1Ciderdog and we installed our pyros post turbo; there is a fitting with plug there that will accommodate the probe. I know it is not the prime location and knew that before, so I kind of allow a 300 deg. difference on my pyro as a guide to the temp. I just haven't got the gumption to drill into the exhaust manifold, although there are many posts on how to do it properly w/o getting drillings in the turbo.

1ciderdog · 03-26-2013, 06:46 PM

Kind of a plus to installing the probe after turbo is you are reading a combined temperature from all six cylinders not just the three if you drill into the manifold. My thought is if you monitor the EGT reasonably consistently you know where the needle should rest under most driving conditions. If it is out of the "normal" reading it is time back off the throttle or to shut it down. I agree not the best solution but I think a reasonable one.