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Old 04-26-2016, 09:12 PM   #21
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I would drastically like more power, but I've had to admit it's best if I don't take things apart anymore. I think I'll probably ride this slow boat (hey that might be a good name) stock the way it is until one of us gives up. Is there a bus name registry around here where I can check that? This was a lucky buy for me in a lot of ways considering I didn't have the benefit of reading the pain of other to learn what to get until several months after my purchase. I liked this brick shape. Got a decent rear end, but stuck with the 545 like so many here. Just dumb luck. I've learned a lot.
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Old 04-26-2016, 09:32 PM   #22
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most engines can be "turned up".. transmission swaps are possible, of course theres usually some fabrication involved and need to handl the issue of which mounting plate adapters you need..

I was reading on here where the allison 5th gen transmissions no longer need an external control box.. simply a throttle position sensor.. if I remember right the 6th gear on a 6 speed 2000 series is a health .61.. your AT545 or MT643 4 speed auto is a 1.00 so you can see thats quite an overdirve.. if you limit it to 5 speed you get .71...
-Christopher
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Old 04-26-2016, 10:39 PM   #23
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All right. Time for Terminology.

Any "cooler" is a "heat exchanger". It's not an exchange is the sense of a barter transaction. What happens is that heat takes the opportunity to transfer from the hotter place to the colder place.

Engines and transmissions both generate surplus heat. In the engine, most of it comes from combustion, but some also from friction. In the transmission it's all friction, both mechanical and hydraulic.
Excess heat would damage the unit if that heat is not given a way out. For the engine, we put water right smack dab next to the hot metal, and the heat transfers to the water. Now the water becomes too hot. So we put that water right smack dab next to a bunch of outside air -- in the radiator.
The water passages in the engine function as a heat exchanger -- metal to water. Then the radiator does the same -- water-to-air.

We don't use water inside the transmission itself, but we do put water right smack dab next to the hot transmission fluid. On some vehicles this happens inside the bottom tank of the engine's radiator. The transmission fluid runs thru a separate passage -- heat exchanger -- inside the radiator. The heat transfers to the water, and we know the rest.

On other vehicles, the transmission heat exchanger is free-standing. On Millicent, it is a rectangular steel box fastened to the bus frame. Transmission fluid runs thru one passage in that box, and engine water runs thru an other passage thru that box. (The box has four hoses attached.)
Same thing happens... heat transfers from hotter transmission fluid to less hot engine water, and the rest.

You can add a separate radiator to the transmission fluid circuit. But you may not need to, if the engine radiator-and-fan has enough capacity to handle all of the transmission's excess heat.
That's what I discovered when I installed a manual switch on Millicent's (water) radiator fan clutch. (A toggle switch on the dashboard.) By sucking extra air thru the radiator, the water at the bottom of the radiator became colder, AND THAT'S THE WATER THAT GOES THRU THE TRANSMISSION COOLER, whether it is inside that bottom tank or mounted separately. That's the water that the transmission "sees".

Why did the reading on the engine temperature gauge not show much change? Because the temperature at the top of the engine is regulated by the thermostat. The engine wants a minimum temperature for proper operation, and the thermostat restricts the flow of water out of the engine as needed.

When I sucked more heat out of the transmission with the colder water at the bottom of the radiator, the thermostat simply opened a bit more.

More in a moment. I gotta take a breath. lol
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Old 04-26-2016, 10:46 PM   #24
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One more thing about transmission temperature.
Like the engine, the transmission ALSO wants a minimum temperature for proper operation.

This is handled in the same heat exchanger as the cooling. That is... when the transmission fluid is too cold, it gets heated by the engine water. Brilliant!
At a cold start, the engine warms up much faster than the transmission would on its own, so at a cold start, the engine heats the transmission.

This is why.... If you install an auxiliary transmission cooler, it goes in the hose FROM THE TRANSMISSION TO THE COOLER, so the engine water can heat the fluid going back to the transmission if necessary.

More coming.
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Old 04-26-2016, 11:07 PM   #25
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Now we are going to talk about something ENTIRELY DIFFERENT.

ABSOLUTELY SOMETHING TOTALLY ELSE.

An engine converts stored energy (in the form of fuel) into movement of the vehicle. The more fuel we can burn with each piston stroke, the snappier that movement will be.

But fuel needs air in order to burn. (Oxygen, actually.) We can always pump plenty of fuel into the engine. The difficult thing is to get enough air in there.

So... since we are PUMPING the fuel, why not PUMP the air in there?
No reason not to! And that's what a Turbocharger does. The turbocharger sits midway between the engine's air filter and its intake manifold. And it pumps -- compresses -- the air going into the engine.

"Compresses"? Yes. The standard terminology is that when this pump is driven by a belt or a shaft, it is called a compressor. And when it is driven by exhaust from the engine, it is called a turbocharger.

Inside a turbocharger there are turbines, which rotate very fast.
Inside a mechanical compressor there are rotors, which rotate relatively slowly.
But a compressor (also called a blower) and a turbo PERFORM THE SAME JOB. They pump more air into the engine than atmospheric pressure can do.

A quick break again.
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Old 04-26-2016, 11:23 PM   #26
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And now, ladies and gentlemen, we arrive at the Feature Attraction;
The INTERCOOLER, or AFTERCOOLER, or CHARGE COOLER.

In school we learned that when we compress something, such as a gas, it becomes warmer.

We also learned that when we heat a gas, it becomes less dense -- fewer molecules per cubic inch.

So... while the turbo gives the engine more oxygen molecules per piston stroke by compressing the air, this process is partly sabotaged by the heating of the air. In other words, the engine could receive EVEN MORE oxygen, if only we could cool that compressed air down before it reaches the engine.

Bingo.

We plumb that compressed air thru a radiator of its very own. These hoses are big -- maybe four inches diameter. That air-to-air heat exchanger usually sits right in front of the engine-water-radiator, for convenience and efficiency. (But it could be located anywhere.)

Into this inter-cooler/charge-cooler/after-cooler goes warm air from the turbo, and out comes colder (well, less warm) air going to the intake manifold. And colder air has more oxygen molecules per fist-full (piston stroke), so we can burn more fuel for more power.

What was the question, again?
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Old 04-27-2016, 12:20 AM   #27
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While we are at it.

Excess heat will damage the engine. This can happen in a general sort of way, by the whole engine becoming too hot; and it can happen locally, by a specific part in the engine becoming too hot.

When the whole engine becomes too hot, the water boils, and boiling water does a lousy job of transferring heat, so now the engine rapidly becomes even hotter, and maybe the head gasket fails, and the head itself can become twisted (warped), and Dog knows what. In the 1970s, I saw a set of piston rings from a car engine that could be twisted like bailing wire. The man had kept driving until the car would. Not. Go. Another. Inch. The heat wiped out the factory heat treatment (hardening) of the piston rings.

Then there is local. What goes first is usually the pistons, which are made of aluminum, which melts at a lower temperature than steel. Where might we have aluminum-melting temperature in an engine? In the combustion chamber. The very flame of the combusting fuel.

How would that happen? Essentially, by burning too much fuel.

That's why we have an instrument called a pyrometer. Pyro means heat or flame or some such. The "official" word for fireworks is pyrotechnics.

The pyrometer measures the temperature of the exhaust fumes IMMEDIATELY after those fumes exit from the combustion chamber. That's as close as we can get. So far, nobody has invented a sensor that can live thru the actual fire in the chamber. Something like 1,200 degrees Fahrenheit in the exhaust manifold corresponds to a safe temperature on top of the pistons.

There is a second spot we can install the sensor for the pyrometer, and that spot is immediately after the turbocharger. Why would we do that, and get a less accurate reading? It's about what is practical.

When I installed a pyrometer in Millicent, I needed to drill a hole for the sensor.
Ideally, I would drill the hole in the exhaust manifold and get the closest reading. But that means that the chips from the drilling would be upstream from the turbocharger, and would ENTER THE TURBO. Turbos are rather finicky about swallowing metal chips, and turbos are expensive.

I could have removed the turbo, and reinstalled it after drilling and cleaning, but that opens the door to all the Oooops Stuff that can happen.

So I drilled the hole in the pipe downstream from the turbo.
The whole point of the turbo is to capture and make use of the energy in the exhaust fumes. So those fumes are cooler when they come out of the turbo. I even telephoned Isspro, the manufacturer of the pyrometer, for advice. Word was, to subtract 250 or 300 degrees from the 1,200. So I use 900 as the max.

When Millicent climbs a hill, I watch the pyrometer. When it hits 900, I either lift my foot, or downshift. Typically, after lifting my foot, I soon need to downshift! The good news is, that higher RPMs allow "more foot".
Why? Well... as I believe I perhaps understand it... more RPM means more air per second, and... while we are now burning more fuel with the additional air, that more air also has a cooling effect as it enters the combustion chamber.
Or something like that.
I have read that a larger turbocharger may also help -- and can contribute to making more power at the same time. But we have now exited my realm of actual knowledge.

Except that... I can mention that there are "heavy duty" pistons with a thin layer of steel on top. This is very desirable. Such pistons are available for the IH DT466, and that's all I know about that.

Annnnd.... I was supposed to be doing something else this evening. Which I will now do.
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Old 04-27-2016, 08:28 AM   #28
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Elliot, thanks for the step by step on the cooling of the motor. I didn't know that a turbo actually helps cool as it boosts power!

As far as a pyrometer, that is a bit out of reach for me. I will just remember to downshift when my rpms are too low and I am not moving very fast uphill!!
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Old 04-27-2016, 09:01 AM   #29
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Elliot, thank you for that detailed explanation. Yes, apparently I've had some terminology problems here. I had thought some people were hooking up an extra odd shaped radiator that cooled the transmission fluid for those of us who tend to overheat the tranny. I do have a trans temp gauge but no pyrometer. I live in the mountains so every time I go shopping (actually about once a month) the transmission will get hot in the last few miles on my way home which involve some steep hill climbing to get back to the sheep ranch. Steep like pulling the hill in second or even first. The problem is this is not the top of the mountain, and one of the main purposes of this bus aside from travel was to get me to high mountain lakes so I can demonstrate how lousy I am at fishing.
I haven't been up the mountain because of the heating issue. It would seem that I'm going slow enough while climbing hills that there isn't a lot of air passing over the radiator. The engine does not overheat but the transmission is showing a tendency to overheat fairly quickly while I'm slowly pulling a hill.
This is becoming complicated with intercoolers and aftercoolers. I actually haven't had the transmission serviced since I got the bus, just doing minimal driving until this bus, I mean van, gets set up right. The transmission fluid does smell a little burnt and has since I picked up the bus. It may be possible that a good trans service, fluid and filter, would improve the hill climbing issue. I was thinking that with the hill climbing that I like to do to get to my favorite locations the trans would probably continue to heat up on these long hill climbs.
So was I getting my threads mixed up or is there actually an extra cooling system some people add for the transmission? Also how much tranny fluid does a 545 take?
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Old 04-27-2016, 09:15 AM   #30
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this is a great read! Love it!..

one thing about the pyrometer.. if you install it AFTER the turbo.. you are on the "low pressure" side of your exhaust and will be getting cooler readings..

when you install on the Exhaust manifold itself you get the temperature reading with the higher pressure and hotter exhaust gasses...

to install in the manifold, take an old shop-vac attachment and drill a hole in it bigger than the biggest drill bit you will use to drill your manifold..

Use BRAND NEW drill bits and tap for drilling the sensor holes..

grease your drill bit, place through the hole in the shop vac attachment.. place shop vac attachment over area where you are going to drill and turn on the vac.. now drill your PILOT.. you will suck nearly all of your shavings up and what does not will get caught by the grease..

with vacuum hose nearby brush shavings off of around the hole...

go to next drill bit and repeat above..

same with tapping the hole.. use the vac. you will get nearly no shavings into your manifold and your turbo will be fine..

-Christopher
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