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post #1 of 28 Old 08-09-2019, 11:54 AM Thread Starter
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Reducing engine temperature with exhaust wrap

In this thread I will show my results of wrapping my muffler with lava wrap to reduce under the temperatures on a 1981 JD 400, with 23HP Vanguard repower. I noticed my headlight wires were starting to melt. I also had a lot of valve train noise when hot after mowing, it didn't seem normal to me. Noise is not there when the engine is cold. I might switch to a heavier oil.

I used my cheap laser pointed infrared thermometer gun. With the before and after measurements of different parts of my tractor. I use $15 lava wrap from Amazon, in a 50 foot roll I only used maybe half. The readings were taken after mowing half an acre on ~90 degree days with the engine still running.

Link:
ARTR Titanium Lava Fiber 2 Inch x 50 Feet Exhaust Header Wrap Kit with 10pcs 11.8 Inch Stainless Locking Ties https://www.amazon.com/dp/B012C5FOLK..._.BztDbW7S7TXT



Hood: before 142°. After 116°

Muffler: before 521°. After 487°

Left valve cover: before 215°. After 190°

Muffler heat shield: before 330°. After 235°

Battery: before 130°. After 120°

Left side panel near tail pipe: before 165°. After 217°

Other Temperatures without comparison: Rear diff 119 and hydraulic cooler 143. Deck spindles 117.

I am happy with the outcome especially of the cost and only taking an hour of my time.


1981 400- Vanguard 23 HP, 54C deck, 56 blade, 50 snow blower
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Last edited by Merc1973; 08-09-2019 at 12:05 PM.
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post #2 of 28 Old 08-09-2019, 11:36 PM
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Re: Reducing engine temperature with exhaust wrap

Interesting. What exactly were you trying to achieve?

If the engine is basically running the same before and after, then it is producing the same amount of BTU's with and without that wrap in place, so the heat has to go somewhere.

One thing I note from your measurements is this:

Left side panel near tail pipe: before 165°. After 217°

So the exhaust gasses coming out of the tail pipe are hotter, which means that the internal temperature of the exhaust system is increasing, which means that the exhaust manifold and exhaust valves, and probably the entire combustion chamber, are all running at temperatures hotter than they weres designed to run at.

A team of engineers at JD designed that entire tractor, including the engine and exhaust system to run as it was originally designed. The "before" temperatures that you posted seem reasonable to me.

So back to my first question, what exactly were you trying to achieve?

My guess is that if you run it like that for an extended period of time you will have some sort of premature internal engine part failure. Possible a burnt exhaust valve or possibly rings going bad, or any other type of failure associated with the exhaust system and/or the combustion chamber running too hot.

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post #3 of 28 Old 08-10-2019, 03:40 AM
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Re: Reducing engine temperature with exhaust wrap

Quote:
Originally Posted by Merc1973 View Post
In this thread I will show my results of wrapping my muffler with lava wrap to reduce under the temperatures on a 1981 JD 400, with 23HP Vanguard repower. I noticed my headlight wires were starting to melt. I also had a lot of valve train noise when hot after mowing, it didn't seem normal to me. Noise is not there when the engine is cold. I might switch to a heavier oil.
If the wires are melting, install shielding to protect them. Pop cans are cheap. The rest of the heat is not really a problem.

Does anyone know at what temperature the side panels begin to degrade?

Check the temps under the hood of your car or truck after a shopping expedition downtown for comparison.

Bob

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Last edited by TUDOR; 08-10-2019 at 03:50 AM.
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post #4 of 28 Old 08-10-2019, 07:31 AM
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Re: Reducing engine temperature with exhaust wrap

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Originally Posted by TUDOR View Post
Check the temps under the hood of your car or truck after a shopping expedition downtown for comparison.
The temps under the hood work great to bake freshly painted small parts. When the wife gets home I place the parts in the engine bay and lower the hood. A couple of hours later I have hard durable paint.
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post #5 of 28 Old 08-10-2019, 07:33 AM
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Re: Reducing engine temperature with exhaust wrap

I DO think that JD compromises engineering to accommodate styling. I think the OP should run his temp tests with the side panels left off. I would bet money that my "hot rod hood" set up lowers the temps around the motor.
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post #6 of 28 Old 08-10-2019, 07:36 AM
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Re: Reducing engine temperature with exhaust wrap

I've never used exhaust wrap personally but people that I know that used it on mild steel exhaust headers ended up with drastically shorted life of the headers. Works good on stainless steel iirc.
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post #7 of 28 Old 08-10-2019, 09:40 AM
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Re: Reducing engine temperature with exhaust wrap

I think you are looking at this backwards.
You repowered the JD 400 from a 19.9HP engine to a 23HP engine. Both of these engines are air-cooled which means that any heat generated from the internal combustion process is dissipated by the flow of the surrounding air. With the repower, you noticed that the temperatures under the hood had increased to the point that melting of the insulation on wiring was occurring. You thought that by wrapping the muffler with insulation would lessen the heat output of the engine. Not going to happen as the heat output is a constant for that engine. Wrapping the hottest part of the engine you can access with insulation only makes the heat travel elsewhere, possibly to areas that can't handle the increase for long periods of time.
About the only thing you can do is increase the amount of the ventilation to the engine. You can also shield sensitive items from that heat increase. Wire looms around wires are great for that as the increase they surface area allowing for more heat dissipation.

The JD 400 was designed around the heat output of the 19.9HP engine.
The original engine was 19.9HP which can be converted to 14,839.43 Watts or 50,634.236 Btu's/hour
The new engine is 23HP which can be converted to 17,151.1 Watts or 58,521.982 Btu's/hour
Horsepower can be converted to other terms. One horsepower = 745.7 Watts = 2544.43 Btu's/hour
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post #8 of 28 Old 08-10-2019, 10:25 AM
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Re: Reducing engine temperature with exhaust wrap

There may be some blockage in the cooling fins or blower housing (mouse nest,etc)--or the timing may be off ,or the mixture too lean,all these will increase operating temperature..muffler shouldn't get hot enough to melt wires unless they are almost touching it..the oil thinning out and valves clattering indicate it is overheating or very close to it..


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post #9 of 28 Old 08-10-2019, 12:06 PM
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Re: Reducing engine temperature with exhaust wrap

My take on exhaust wrapping is to keep the engine bay cooler because of conditions that cannot be changed. Like a hot rod stuck in heavy traffic and thus low to no airflow. But there are downsides to everything. The exhaust gas is much hotter and the heat that was once dissipated at the head along the header is now having to travel all the way to the end of the exhaust pipe to be eliminated. As mentioned above, this puts more heat in the head and its components. I would apply heat shields to anything under the hood that I had a concern about like the underside of the hood or fuel pump or carb and any wires or plastic items. Even the heat shield could be shielded if necessary but forget about the wrap. I built an AC Cobra kit car with side pipes and thought about wrapping the headers. I asked around and was told the side pipes would become red hot and disintegrate in short order and the fiberglass lower body would be affected. I didn't use the wrap.
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post #10 of 28 Old 08-10-2019, 12:10 PM
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Re: Reducing engine temperature with exhaust wrap

Quote:
Originally Posted by Flaken View Post
The JD 400 was designed around the heat output of the 19.9HP engine.
The original engine was 19.9HP which can be converted to 14,839.43 Watts or 50,634.236 Btu's/hour
The new engine is 23HP which can be converted to 17,151.1 Watts or 58,521.982 Btu's/hour
Horsepower can be converted to other terms. One horsepower = 745.7 Watts = 2544.43 Btu's/hour
This is a good thought but assumes that the OP is pushing the engine to its horsepower limit. If doing equal work, the engines will be putting out similar amounts out heat.

People heat wrap the exhaust on performance engines all the time. I do remember from my performance tinkering days that it will void the warranty on most headers.

In theory, retaining as much of the heat as possible increases exhaust gas velocity which should decrease temps at the exhaust valve. I think it's a great solution. However if it were me, I would just wrap the muffler and leave the header section open. There might be some decreased life of the muffler but seems to be a fair trade-off.

Also, I assume the OP has thought of this, but if this is a new problem, you might have an engine issue as tractor-holic suggested.

Last edited by denverguy; 08-10-2019 at 01:22 PM.
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post #11 of 28 Old 08-10-2019, 12:33 PM
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Re: Reducing engine temperature with exhaust wrap

I think, if the same engine is running under identical conditions, it is going to produce the same amount of heat in terms of BTUs if you want to use a measurement. That heat has to go somewhere.

Before wrapping, I suggest that a portion of the BTUs was being radiated off the exhaust inside the hood area per your observations of melting wires and such.

After wrapping, I'd think the same BTUs, not being able to radiate as much from the exhaust, are now being pushed out in the exhaust gas stream. Likely you should see hotter exhaust gas exit temps as a result.

Regardless, wrapping certainly helps keep the engine cooler by pushing most of the generated heat out the exhaust stream. The only down side might be that the exhaust system likely runs hotter, so watch the place where it exits the head for any heat related issues. A well adjusted engine, valves, fuel, etc., shouldn't suffer from a wrapped exhaust system.

Just my humble opinion.

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post #12 of 28 Old 08-10-2019, 01:34 PM
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Re: Reducing engine temperature with exhaust wrap

There always got to be a test subject (aka guinea pig, canary in the coal mine). Worst case the OP will be putting another engine in or the hood and side panels will be reshaped by the heat.

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post #13 of 28 Old 08-10-2019, 01:46 PM
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Re: Reducing engine temperature with exhaust wrap

Watch, now the muffler will melt! LOL: Disgus:

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post #14 of 28 Old 08-10-2019, 02:32 PM
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Re: Reducing engine temperature with exhaust wrap

Most mowing is done at wide open throttle. A larger engine at WOT will burn more fuel and produce more heat over the same time span than a smaller engine.

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post #15 of 28 Old 08-10-2019, 02:49 PM
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Re: Reducing engine temperature with exhaust wrap

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Originally Posted by blkwtr View Post
Most mowing is done at wide open throttle. A larger engine at WOT will burn more fuel and produce more heat over the same time span than a smaller engine.
These engines are governed which adjusts throttle position to the load and maintains a relatively constant RPM. While you should be mowing at full throttle, it's likely far from WOT if you were looking at the throttle position on the carburetor.

If you are pushing the engine hard by cutting thick/tall grass and/or at high speeds, you might end up at WOT but in most circumstances, you are not at WOT when cutting grass.

Last edited by denverguy; 08-10-2019 at 03:00 PM.
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