Exhaust Gas Temperature Gauge - Need Input

rv_safetyman · February 22, 2010, 09:22:40 PM

Bob Belter has been beating me about the head on this subject. He has me convinced I need the gauge. It looks like the cost would be less than $200 and the protection/information would be worth a lot.

I have welded a bung just after the turbo (no good way to put it in the Series 60 Manifold that I can see) and now I need to find a good source. So far, Westach (http://westach.com/) seems to be the leading source (and Bob's recommendation). Anyone else want to offer another alternative source?

One of the big issues is the long length of the connecting cable. The thermal couple generates a small voltage that is a function of the temperature and the long wire length (resistance) poses a potential problem. I talked to the Westach folks and they can fabricate a special long-lead thermal couple for the bus application.

I would like to hear from others who have installed an EGT - especially anyone who has installed one downstream of the turbo.

Thanks, Jim

TomC · February 22, 2010, 10:39:40 PM

Jim- you do NOT need a pyrometer on a Series 60-or any electronically controlled engine. The electronics just plainly won't allow the engine exhaust temperature to get high enough to damage the engine. If this was a mechanically controlled engine like my Caterpillar 3406B-I would say yes go for it-it is useful. But please-save yourself a lot of work for nothing. We don't install pyrometers on new trucks unless requested-and even then they are only small 2" gauges. And besides-with the Autoshift, the transmission will not allow the engine to lug enough to raise the temperature up. If you would see 1,000 degrees, I'd be surprised. And always remembering what one boater told me "above 1200 degrees costs money". I sincerely doubt you'd EVER see 1200 degrees with a Series 60-the electronics will have reduced the power down well before that. Good Luck, TomC

JackConrad · February 23, 2010, 05:14:39 AM

Jim,
We installed a 2 1/8" pyrometer on our 8V71 NA, just because I like gauges and want as much info as possible while driving. I installed the thermocouple in the exhaust pipe shortly after the point where the left & right exhaust pipe converge. We connected the existing wires from the thermocouple to 2 empty terminals in the rear electrical panel. from there we ran 14 gauge wires to the front panel and from the front panel to the gauge.
Since the readings change so rapidly with engine load, I have not found a way to confirm accuracy. At idle the gauge is pegged on 300 (the lowest reading). When driving on flat roads at 60-65, the gauge reads about 450-550. Under a load, 550-750. As soon as the load is removed (topping the hill, lifting off the throttle), the gauge moves back into cruise range or lower if coasting within a few seconds.
I watch this gauge when climbing. The pyrometer and tach are inversely proportional. As the RPM drops, the temp increases. When the RPM hits 1500, I downshift. The RPM increases and the temp drops. I purchased our pyrometer (as well as all our other gauges)from Precision Speedometer in Phoenix, AZ. Great people to deal with and a very helpful tech department. Jack

luvrbus · February 23, 2010, 05:29:28 AM

Jim, I talked to Cole about the pyrometer on a DDEC series 60 and he agrees with Tom it is a waste of money that is one reason they don't pre drill the manifolds any longer for pyrometers. My 8v92 mech has a tap on each manifold for the probe fwiw

good luck

kyle4501 · February 23, 2010, 07:41:18 AM

If the engine was running properly, I'd agree the computer should protect the engine. BUT, that is not the case here, Jim's engine isn't performing as expected, so something is out of spec. . . .

Wouldn't the info from the pryo be of some use in diagnosing his problem of low power?

Also, wouldn't a pryo give faster feedback as to how hard you're working your engine? Like letting you know well in advance before your water temp goes up - thereby allowing you to modify your pace to ease the strain on your coach?

If the computer protects the engine, I have a question concerning Dad's Airstream 10 year old coach that was built on a freightliner chassis with a cat 330 hp. It can overheat in the mountains (even though it still has plenty of power to accelerate in hi gear) if you don't force the automatic to a lower gear - Does that mean there is something wrong? If it matters, Freightliner checks it every year & gives it a clean bill of health.

rv_safetyman · February 23, 2010, 07:49:56 AM

Thanks all for the great input.

As Kyle said, one of the factors that had me thinking about the EGT is my engine problem/troubleshooting effort.

The other reason is Bob Belter's post over here: http://www.busconversions.com/bbs/index.php?topic=14591.75. His comments are on page 6, in case it does not come automatically. Interesting observations.

Like Jack, I am a data freak. Can't have too many gauges! However, I don't want to spend the money if it is not worth it.

Jim

TomC · February 23, 2010, 07:50:35 AM

Coolant overheating compared to exhaust overheating are two completely different animals. Coolant overheating is a function of the air flow over the radiator and the capability of the radiator-which would not necessarily make the exhaust run hotter. At altitude it is common for engines to overheat since the air is thinner and many times much dryer. Dry air has a harder time transmitting the heat from the metal of the radiator to the air. For those few times that your Dad's Caterpillar overheats-I would consider installing radiator misters (if he doesn't want the expense of increasing the size of the radiator-which in this case means getting rid of the aluminum radiator and having a custom copper/brass radiator made-at a cost of pushing $2,000) just for those few times he is in altitude. I have them on my bus since I have had the largest radiator made and it still overheats. Good Luck, TomC

luvrbus · February 23, 2010, 08:11:02 AM

Jim, you would think if it was that important of a feature for the DDEC the Silver Leaf people would be all over it like white on rice.

good luck

kyle4501 · February 23, 2010, 09:23:30 AM

Quote from: TomC on February 23, 2010, 07:50:35 AM
Coolant overheating compared to exhaust overheating are two completely different animals. Coolant overheating is a function of the air flow over the radiator and the capability of the radiator-which would not necessarily make the exhaust run hotter. At altitude it is common for engines to overheat since the air is thinner and many times much dryer. Dry air has a harder time transmitting the heat from the metal of the radiator to the air. For those few times that your Dad's Caterpillar overheats-I would consider installing radiator misters (if he doesn't want the expense of increasing the size of the radiator-which in this case means getting rid of the aluminum radiator and having a custom copper/brass radiator made-at a cost of pushing $2,000) just for those few times he is in altitude. I have them on my bus since I have had the largest radiator made and it still overheats. Good Luck, TomC

I didn't mean to imply the coolant overheat was caused by overheated exhaust. Dad's exhaust hasn't ever overheated to my knowledge (the engine & exhaust show no discoloration).

Doesn't the EGT (kinda, sorta) follow the power output of the engine? The more power it is making, the hotter the EGT.
Coolant overheats when the engine is making more power than the cooling system can handle.

The exhaust temp will rise before the coolant does. With an EGT gauge, you can get a bit of warning so you can back off a little. Sometimes, you may not realize you're working the ole girl so hard.

For Dad's case, he simply drops down a gear & rides at the normal cruise rpm. ( He must be doing something right as he averages 10.5 mpg pulling a toad. )

rv_safetyman · February 23, 2010, 10:02:55 AM

Tom C, I have been struggling with the pre vs post turbo location. I just got a call from a good friend and he pointed out that most of the truck EGT applications are installed just downstream of the turbo. Assuming that is the case, what would be a good max temperature to shoot for? If you don't have direct experience, can you pick someone's brain at your shop? The reading I have done suggests the upstream temperature max should be 1300*. If that is the case and the rule of thumb of 250-400* drop through the turbo, that would suggest 900* max on a downstream EGT.

Clifford, I wish SilverLeaf could pick up sensors other than those that feed the engine ECM. Anything that is not an OEM sensor can't be displayed on the lower cost units. However, there is/was a big movement in the industry for aftermarket components to be designed to the RV-C (multiplex technology - http://www.rv-c.com/) specification/protocol. Most of the high price house systems (inverters, generators, etc) have or are moving in that direction. I am working on a second generation of my system that will be RV-C compatible. Once a system is compatible, SilverLeaf (or similar vendors) can read the information and create a gauge. Simple gauges don't lend themselves to that technology.

Another issue I am struggling with is the connection/cable between the thermal couple and the gauge. In talking to my friend we concluded that good old solid "communication" wire will probably be just fine. Westach publishes a table of temperature vs mV and I can check the voltage at the sensor connection and the gauge (to account for wire losses) and then do a "mental" recalibration.

Kyle, when I do my SilverLeaf seminar I preach to folks to use the digital temperature gauge that is displayed and watch for a trend in the rate of change of engine coolant temperature. If folks have an overheating problem, they can catch it early and drive by that very accurate gauge. In my case, I have a charge air cooler issue and have to drive the hills by the "air inlet temperature". I simply back off on the throttle and maintain a reasonable temperature. Surprisingly enough, that does not really mean all that much drop in speed. Your idea to use the EGT for the same purpose is a good idea. As you point out, the exhaust and engine coolant temperature should track pretty well.

So, I am still leaning towards installing an EGT. Not too much money and a pretty good "safety" tool for the engine.

Jim

bobofthenorth · February 23, 2010, 10:13:33 AM

Jim my experience with EGT probes is limited to Powerstrokes & 466 IHCs. On the Powerstrokes the favored location was pre-turbo but there was always a healthy debate about the risks of putting a probe through the turbo. The drop dead pre-turbo temp was generally 1300 degrees. On the IHCs that we ran in field applications the drop dead post-turbo temp that we were advised to use was 1100 degrees. In both those situations however the engines in question were working at the extreme upper limits of their design horsepower output and that was the reason for the EGT monitoring. I'll add my vote to the the list of those who don't think you need an EGT probe in your application. OTOH I don't think you can have too many gauges - doncha just love those Bluebird cockpits?