pyro gauge - why do we need one?

[glenn]

I was going to post this on the recent post about CVI where a discussion about pryo gauges occurred, but it is clearly off topic. There have been a few posts about how essential these gauges are. I have two questions about a pyro gauge:

while it is cool to know exactly what is going on in your engine at a given time, what is the big advantage to knowing this info? Assuming that one already lets the semis pass while climbing the Coquihalla, and keeps one's right foot away from the floor, why bother? I have a turbo timer which idles the van for up to 2 minutes or so if I have been on the highway, but this could be achieved by . . . letting the van idle for about 2 minutes after being on the freeway. Now that a few drivers have reported their exhaust temps we know not to push our vans for long, and to let them cool off before shutting down - aside from this what is to be gained?

Secondly, what damage is being prevented. I see lots of talk of alarming exhaust temperatures, but what can happen? And I don't mean what can happen if you say, floor it through the mountains with a couple yards of rocks in a trailer with clouds of black smoke trailing behind you, but more from normal conditions? Have there been many problems with our delicas that can be associated with high temps?

Basically, I fail to see what all the hype is about - but I am very willing to admit that I am blissfully ignorant.

Thanks

[Green1]

while it is cool to know exactly what is going on in your engine at a given time, what is the big advantage to knowing this info? Assuming that one already lets the semis pass while climbing the Coquihalla, and keeps one's right foot away from the floor, why bother? I have a turbo timer which idles the van for up to 2 minutes or so if I have been on the highway, but this could be achieved by . . . letting the van idle for about 2 minutes after being on the freeway. Now that a few drivers have reported their exhaust temps we know not to push our vans for long, and to let them cool off before shutting down - aside from this what is to be gained?

Secondly, what damage is being prevented. I see lots of talk of alarming exhaust temperatures, but what can happen? And I don't mean what can happen if you say, floor it through the mountains with a couple yards of rocks in a trailer with clouds of black smoke trailing behind you, but more from normal conditions? Have there been many problems with our delicas that can be associated with high temps?

Let me speak briefly from experience here, climbing the coquihalla after I first got the van, I didn't think I was pushing the van too much, but I overheated anyway, the stock temp gauge was at the bottom, and then a couple seconds later was pegged off the top and the rad hose had split open due to a cracked head, there was no time to react, by the time the temp gauge registered a problem it was already too late. If I had had a pyro gauge I would have had much earlier warning of a problem.
In my case the cause of the whole problem was a fully clogged radiator, however the same problem could happen if your thermostat jams shut, or you have a coolant leak, or various other cooling issues.

I guess to answer your questions:
- driving carefully is a good first step, however that only takes care of the "routine" part, if anything goes wrong you wouldn't have any indication util it is too late
- what damage can be prevented? this is the biggy, overheating cracks heads... so while the odds of it happening are low, the cost of dealing with it if it happens is quite high, a pyrometer is cheap insurance.

[mararmeisto]

This is what I understand:

The turbo is driven with exhaust - this is what makes it spin in order to compress incoming air before supplying it to the intake. Exhaust heats the turbo, so there is some transfer of exhaust-heat-to-intake-temperature increase, perpetuating a cycle of increase the engine's temperature.

Liquid cooled engines are quite efficient, but liquid cooling can be 'slow' - it takes a while for the liquid to heat up and transfer away the heat from the block. The bigger problem is the dissipating of the heat from the coolant, and this is where bad lines and a clogged radiator will kill your engine. As Green1 indicated, by the time the water temperature gauge on your dash indicates the engine is too hot, it's actually way too hot.

So, an EGT gauge will indicate directly the temperature of exhaust gases, with about a 200 degree F difference before/after the turbo. Preferences vary for placement before/after the turbo, I'm going to install mine after because I have a nice and shiny blanking plate where my EGR valve used to be just begging to have a probe inserted into it.

How does one use it? Backing off the accelerator even a bit will drop the temperature a couple hundred degrees (F, of course), and one can generally see a drop in temperature before there is a noticeable drop in rpms. Or, down-shift will have a similar effect. And that, apparently is where the magic happens: by keeping the rpms up, the engine becomes an air pump, thereby cooling it instead of cooking it.

But that's just the way I understand it. If I've got it wrong, I would appreciate someone clarifying...

[delicat]

Mine tells me when my engine needs servicing (plugged injectors) as the EGT gets higher than normal but hard to tell just from the feel of it.

It also tells me to slow down when I think I'm doing fine, surprising at time what a head wind can do...

On my recent drive across Canada I found that little gauge extremely useful! Up to you...

[flyfishn]

I really want to install a pyro-gauge as I tow a trailer. what is the install cost?

[Mephisto]

Installing one yourself is easy, especially if you have done the EGR block off mod. My basic understanding is that high EGTs crack heads, just a little at a time though, whenever I have taken a diesel head off and it has seen sustained high EGT action, you can see little cracks in all the thinner areas of the combustion chamber. These will grow with continued high heat until you get into a water passage, etc..... On gas engines, which see much higher EGTs, the exhaust valve is set with a bigger gap so that burning out a valve is less likely, on our 2.5 the inlet and exhaust valves are set the same. Don't ask me why gas heads don't crack as easy as diesels, I can't answer that, although I will be sure to ask next time I'm around someone with that knowledge. So back to the valves, metal obviously expands with added heat so the hotter your EGTs the smaller your valve lash is going to be untill you reach the point where the valve no longer seats completely. The valve gets much hotter than the head and cools itself when the valve is closed, by dissipating heat to the head. If a valve isn't seating properly it can't cool itself off and exasperates the situation, resulting in a burnt valve (chunks fall off). Diesels burn more efficiently at cooler temps, once you pass a certain temp you start emitting all those nasty chemicals that gassers puke out, look into the new tech from mercedes on compression ignition gas engines and how they don't need catalytic converters because their emissions are so much lower from keeping combustion temps low. As a follow up, your EGR block off plate is located before your turbo (not after, as someone previously stated), some people suggest to put your probe after your turbo so if it burns and drops a chunk it won't go into your turbo. I think that only applies to gassers seeing extreme exhaust temps and have not heard of it happening to a diesel, I suggest putting it pre-turbo for the added accuracy.

[Green1]

Don't ask me why gas heads don't crack as easy as diesels, I can't answer that, although I will be sure to ask next time I'm around someone with that knowledge.

quick guess... pressure... Diesels operate at MUCH higher pressures than Gasoline engines.

[mararmeisto]

Don't ask me why gas heads don't crack as easy as diesels, I can't answer that, although I will be sure to ask next time I'm around someone with that knowledge.

quick guess... pressure... Diesels operate at MUCH higher pressures than Gasoline engines.

Gasoline compression is usually 8-12:1, while diesel is 14-25:1. Much higher pressures.

[glenn]

Ok, I was blissfully ignorant. Great information, now I understand why I want to know what the EGT is (notice the use of this newly aquired jargon). What convinced me I need to get one is delicat's post

It also tells me to slow down when I think I'm doing fine, surprising at time what a head wind can do...

Thanks everyone for the replies

[TardisDeli]

I have not installed a pyro as I saw all the work involved to get Delicat's installed, but it might get on my HoneyDo list. Delicat is a good resource for your questions.

Cost, dunno, as it is usually mechanically inclined people who do it themselves. I just saw the MANY hours the guys spent lying under the deli while drilling holes in the poor deli, and making brackets to fit after finally finding a spot to mount on already very crowded delis, and running wires after testing many wires to find a wire that would work for the load and on/off etc, and cursing in both official languages, and drinking, and discussing hockey and generally enjoying themselves.

I baby my deli, and drive by sound, and know exactly what sweet spots and rpm and speed I go, and thought my choices were perfect for fuel economy. When Delicat installed his pyro, I went for a drive with him up the hills. But watching the pyro guage at the shift points I had thought were perfect were actually too hot, as I was lugging the engine up the hills ie driving at too LOW a rev. Technically the engine wants to rev higher to enable it to cool down. Very interesting. So, now I rev a bit more on the uphills (eeek, does that use more fuel maybe).

My two bits worth, Christine.

[delicat]

Glad to help!

Cost is purchase (around $220) and install the easier way is simply to drill a hole in you down pipe (after turbo), fit the supplied probe into your new hole and run the wire back to your cab where you'll attach them to your gauge. Quite easy. As for all the swearing in both official languages... must have been while working on something else! (Too funny, glad to see you're back on line Christine!)

[Fishtank]

Two questions for you David, or anyone else who can answer;

1. Do you have your EGT probe pre or post turbo?

and

2. What are the temps that we should see both pre & post turbo?

[Profister]

My setup is the same as robinimpey's: http://www.delica.ca/forum/traded-clock ... ight=clock and the temp numbers are similar. The nice thing about Auber 1812 gauge is that it is programmable, has a warning light and connectors for an external buzzer. Also it can be used as a pressure/boost gauge with an appropriate probe.
This little gadget affected my driving habits (when driving Delica ); it was really surprising to see how much EGT changes depending on driving style and conditions.

I have a turbo timer which idles the van for up to 2 minutes or so if I have been on the highway

2 minutes is a guess but if you had a gauge you would learn that it was not enough time for EGT to go down from 600F to 350F when you can safely shut the engine.

[Green1]

pre-turbo is better, however I recommend post-turbo for 2 very important reasons:
1) it's usually much easier to mount it post-turbo
2) drilling holes in the exhaust system generates metal shavings inside the system, I'd rather those were blown out the exhaust pipe rather than in to the turbo!

[Fishtank]

pre-turbo is better, however I recommend post-turbo for 2 very important reasons:
1) it's usually much easier to mount it post-turbo
2) drilling holes in the exhaust system generates metal shavings inside the system, I'd rather those were blown out the exhaust pipe rather than in to the turbo!

What about pulling the turbo to drill the hole? Does this not solve these two issues?