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Offline Odie

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Re: Air Shroud and Engine Cooling
« Reply #15 on: May 30, 2016, 09:39:46 AM »
So polyester resin, abs, fiberglass and a little sandpaper? That concludes my class! Perfect timing, I'm tired of watching the rain come down.  :)

Offline Fishlover

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Re: Air Shroud and Engine Cooling
« Reply #16 on: May 30, 2016, 02:04:45 PM »
It's interesting that we are coming back to this issue.
Ref: see my post here:

Re: Primary mechanism of perfomance loss due to heat
Reply #3 on: January 10, 2016, 02:48:24 AM

I am still busy building all my "transportation equipment" for hauling and launching my boat and had not enough time to address this myself.
Very glad, Tom, that you are tackling this and are apparently able to validate what we suspected all along.

Actually, in my own concept, I was planning to modify the engine cover such that the NEW air scoop opening starts well toward the front edge of the engine cover and angling down over the fuel tank towards the fan intake. This will be a significant air flow improvement and, together with a larger volume tunnel, provide substantially better cooling.
BUT, in isolation, this mod is likely still hampered by the higher compartment back pressure. To solve this, a larger exhaust flow for the hot air is also very likely needed (about 2x vs stock openings).

Tom, have you tried welding the HDPE for the air scoop at all? Would that not be better/easier than to deal with the messy fiberglass? Just wondering.
Regards

Offline Painlesstom

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Re: Air Shroud and Engine Cooling
« Reply #17 on: May 30, 2016, 05:52:59 PM »
Welding HDPE is like any other process that requires equipment and skill. I don't have the equipment to properly weld plastic, it can be done though. On my plenum I did weld in a strip, but it took over an hour and I still ended up wrapping the whole thing in fiberglass to reinforce it. The average person could do this the fiberglass way as shown in my last post, not everyone could pull off the welding method.
Tom

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Offline The Man

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« Last Edit: May 30, 2016, 07:27:01 PM by The Man »

Offline Painlesstom

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Re: Air Shroud and Engine Cooling
« Reply #19 on: May 30, 2016, 07:44:39 PM »
I've made a "how to" on simple HDPE welding with a soldering gun and torch... This project of enlarging the plenum is a little too big for that to work well long term. Heat, vibration, expansion and contraction and you will end up with a plenum that is falling apart unless it is welded correctly. Wrapped with fiberglass ensures a permanent union and something anyone can do with materials bought at Walmart..  ;)
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Offline happul3

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Re: Air Shroud and Engine Cooling
« Reply #20 on: June 03, 2016, 09:22:17 PM »
The top opening of the plenum is quite a bit more narrow than the rest. Do you think cutting the top portion of plenum would significantly help with air supply? Your solution to make the whole plenum wider is certainly more effective, but I am not quite ready for something as drastic yet.

Offline Painlesstom

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Re: Air Shroud and Engine Cooling
« Reply #21 on: June 03, 2016, 09:59:50 PM »
While the opening is more narrow than the rest, removing it is still not enough to make much difference. I ran mine without the top on and still had lots of heat issues, all that went away once I widened the whole thing. It's the only way to let the engine breath, no band aid for this problem, either you fix it or you don't.
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Offline happul3

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Re: Air Shroud and Engine Cooling
« Reply #22 on: June 05, 2016, 05:46:07 PM »
On a related subject, could you explain power reduction when engine gets hot? 

Offline Painlesstom

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Re: Air Shroud and Engine Cooling
« Reply #23 on: June 05, 2016, 05:53:33 PM »
When the engine gets hot the incoming air/fuel charge looses it's density, volumetric efficiency become very low. Heat also causes parts to expand which closes up clearances and can cause more power robbing friction. If the engine continued to heat up, eventually the piston would seize in the cylinder, but since there is some air passing over the cylinder/head that wouldn't be a concern in the Mokai. But the power loss is a sign that the engine is getting hotter than it was designed to handle. No rpm should be lost once the engine reaches operating temperature, and my enlarged plenum proves that the engine was overheating with the stock setup.
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Offline happul3

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Re: Air Shroud and Engine Cooling
« Reply #24 on: June 05, 2016, 11:07:09 PM »
When the engine gets hot the incoming air/fuel charge looses it's density, volumetric efficiency become very low. Heat also causes parts to expand which closes up clearances and can cause more power robbing friction. If the engine continued to heat up, eventually the piston would seize in the cylinder, but since there is some air passing over the cylinder/head that wouldn't be a concern in the Mokai. But the power loss is a sign that the engine is getting hotter than it was designed to handle. No rpm should be lost once the engine reaches operating temperature, and my enlarged plenum proves that the engine was overheating with the stock setup.

Nice explanation, thanks! Better heat removal, that's what needed. Staying with reversible modifications for now, suppose I put couple of layers of fiberglass tape on muffler and connecting pipes. That would reduce heating in engine compartment, would it not? Any drawbacks you can think of? 

Offline Painlesstom

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Re: Air Shroud and Engine Cooling
« Reply #25 on: June 05, 2016, 11:57:55 PM »
Nope, none of that is going to do any good. More airflow is needed over the cylinder and head, no matter how much insulation you put on the muffler the engine is still generating heat and needs to be cooled. Imagine putting a cover over the radiator of your car so only 30% of the air made it through, your engine would overheat and it doesn't matter how much you vent the engine compartment when the radiator is what needs the airflow. Our engines need air flowing over the cylinder and head, enlarging the plenum is the only way to make that happen. There is no alternative.  ;)
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Offline happul3

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Re: Air Shroud and Engine Cooling
« Reply #26 on: June 06, 2016, 07:25:53 PM »
Nope, none of that is going to do any good. More airflow is needed over the cylinder and head, no matter how much insulation you put on the muffler the engine is still generating heat and needs to be cooled. Imagine putting a cover over the radiator of your car so only 30% of the air made it through, your engine would overheat and it doesn't matter how much you vent the engine compartment when the radiator is what needs the airflow. Our engines need air flowing over the cylinder and head, enlarging the plenum is the only way to make that happen. There is no alternative.  ;)

A little hard to believe that the improved muffler insulation would not reduce temperature in the engine compartment and consequently of the engine itself. It may be not be as effective as your solution, but it should have some significant effect, shouldn't it?   

Offline Painlesstom

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Re: Air Shroud and Engine Cooling
« Reply #27 on: June 06, 2016, 07:47:11 PM »
If my water cooled muffler didn't help, adding insulation to your stock one isn't going to make any difference at all.  ;)

My water cooled muffler stays cool, so the only heat coming off it is from the 3" long header, the rest you can put your hand on after 10 miles. It didn't have any effect on engine cooling. I've spent the last 9 months chasing my tail with cooling on this boat, the ONLY thing that fixed the heat issue was enlarging the plenum. I know that's not what you want to hear, but there is no easy quick idea to get the engine to run cooler. It needs air, plain and simple. I've tried it all to know what works and what doesn't, so you don't have to, and the result speaks for itself. There really is no easy alternative....
Tom

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Offline happul3

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Re: Air Shroud and Engine Cooling
« Reply #28 on: June 06, 2016, 09:29:00 PM »
If my water cooled muffler didn't help, adding insulation to your stock one isn't going to make any difference at all.  ;)

My water cooled muffler stays cool, so the only heat coming off it is from the 3" long header, the rest you can put your hand on after 10 miles. It didn't have any effect on engine cooling. I've spent the last 9 months chasing my tail with cooling on this boat, the ONLY thing that fixed the heat issue was enlarging the plenum. I know that's not what you want to hear, but there is no easy quick idea to get the engine to run cooler. It needs air, plain and simple. I've tried it all to know what works and what doesn't, so you don't have to, and the result speaks for itself. There really is no easy alternative....

Your water cooled muffler case does make a strong point. Certainly surprising to me, but so are many things. Do you suppose that bulkiness or some other feature that comes with it impedes or redirects the airflow thereby negating its heat removal benefit? Does it fit under the regular cover?

Offline Painlesstom

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Re: Air Shroud and Engine Cooling
« Reply #29 on: June 07, 2016, 12:08:06 AM »
Muffler size, shape, position etc.. has/ had nothing to do with airflow. If it did then the enlarged plenum wouldn't have worked because the muffler was blocking airflow if what you suggested was happening. I cut out the hood so my muffler sticks up through and then my fiberglass muffler cover bolts to the hood. The finished result is twice the exit area than the factory had. But all the venting in the world won't make a difference if the air coming in is being choked off.
Tom

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