Engine Bay Heat Insulation Blanket

A note... I think Mods posts should be placed under the Technical category instead of Parts, but heck thats what the main topics suggest, so here it is. This is about an engine heat reduction mod.

I was riding the other day in about 95 degree heat. The humidity was very high and the air seemed very stagnate, even at 65 mph. I was wearing shorts. I could not touch the tank. Usually I wear jeans and really don't notice the heat, but when I slowed down, the FJR kept hitting four bars. The heat was just pouring out and roasting my legs. And I could barely touch the tank, even when there was a bunch of fuel in it.

As some of you may know, I'm building an airplane. I bought scads of different types of heat and sound insulation for the project. I figured, what the heck, it'll work on the bike, too. I had read many posts about guys gluing new insulation to the bottom of the tank to at least keep that more under control. Well, I tried a bit of a different tack. And it worked quit well.

I had some aluminum faced, fire retardant, thermal insulation matting. You can get this stuff for cars. It's got fairly thick cloth matting behind the metal film, and there is stitching in the fabric. I used 3/8 inch thick material.

I popped off the black plastic tank skirts and took the tank bolts out. I put a stool on the left side of the bike and then flipped the tank over on it's side onto the stool. Poor thing looks like a drunken turtle over there! Anyway, I left everything hooked up fuel and electrical line-wise. The wires to the tank weren't run conveniently for what I was doing, so I disconnected them and re-ran them with the left main fuel line. Not a big change, but significant. The fewer cuts in the insulation, the better...

I cut some cardboard for a template and got an idea how much matting I would need. This matting is not rigid, but holds it's shape well. I shaped the carboard template on the bike and then sheared the insulation matting to match the shape I chose. I had to mark it and cut both a few times, but I finally got what I wanted.

I decided I did not want to glue parts, I just decided to make an engine bay "blanket". My goal was to cover everything over the engine and under the tank from the seat pan to the front of the frame where the tank bolts down. Well, I couldn't really cover everything and leave the ugly blanket sticking out, but I did get it to cover the vast majority of the places where heat was getting to the tank and out to my legs.

This idea is pretty simple. Start with a flat piece that is actually too big, then cut it back so it doesn't show. I did have to make 4 slices in it to get around the fuel lines and wires, as well as the rear tabs for the long bolt holding the tank down.

Once I got the general shape, I cut slots in the insulation for the fuel lines and fished the sheet of insulation through the middle. Surprisingly, it sits there quite well. NOTE: The left fuel lines are slightly aft of the right fuel line, so the cuts are not directly across form one another.



I thought about taping these slices closed, but I think there will be some overlap as well as the tank mashing them down. I want the blanket to be easily removable, too. I want to sync my throttle bodies again pretty soon, so I gotta get that thing off easily. Also, in the winter I WANT the heat!

With the flat sheet of insulation rough trimmed in place, I flipped the tank back into postion and simply mashed it down. I worked the tank back to postion and loosely bolted it back down. Then I marked the matting for trimming again. Much of the trimming could be accomplished with the tank in place.

I left the rear corners of the insulation matting square. I then folded the corners and tucked them down and a bit under the painted panels that are under the black tank skirts. I trimmed the matting so it would not show under the black tanks skirts and re-bolted everything. Worked like a charm! Took about 1 hour.

In addition to the engine bay blanket, I also closed off a bunch of the gaps in the rear upper area of the fairing. It looks kind of silly, but it was just a test. I bought $2.17 worth of 1/2 inch hot water pipe insulation. There were four of those thick foam tubes that you tape over the pipes in each package. I used two of them. Now the packaging says the stuff works to about 240 degrees F, so I was concerned about the stuff melting. So far so good, but you may not want to try this, it could be disastrous!

Again, I wanted something just to test, and something removeable. First thing I did was cut a piece to put between the fairing and the bike along the upper rear boarder of the fairing. The insulation tubes are slotted, so I just slid the slot along the fairing and the round tube insulation is held in place nicely. It shows, and it looks a little geeky, but its just a test. Next, I fed more pieces up under there to close off as much airflow back to my legs as possible. I used three additional cut sections of the foam behind the fairing to block the airflow to the rear area escaping to my things as much as possible. All the pieces are at the top and kind of in the rear "apex" of the fairing, aft of the vent slots. Once I had the insulation pieces tucked into place, I went out for a 100 mile test ride.

The results of all this is excellent. Pros: cheap and easy, removable, and it works. Cons: the pipe insulation looks dorky where you can see it (which you do have to look for it), and the engine does get to 3 bars a little easier. I did not block the side vents, the air can still go from the radiator to the engine, then out the sides and bottom. But it is substantially blocked the heat to my legs and the tank.

The frame still gets very hot. Those black rubber covers under the lower sides of the tank at the level of the frame are still extremely hot. I notice hot airflow from them. I will remove the tank again and try to get some matting or something else under there to improve that sitution.

The insulation material I used is called The Insulator. I used the single sided material, with foil on one side only.

Come on man, we need more pics!

Sounds like an excellent idea, but I wonder what effect the elevated temp will have on the motor? You mentioned that it got to three bars quicker than before. It's definitely something to think about though. :blink:

But again, we need more pics!!

I took a bunch of pics, but only the one turned out worth a hoot. When I lift the tank off again, I'll try to snap some more of the blanket. The insulation tubing just can't be photographed. I tried. You can see the insulation between the frame and the fairing in the one picture though.

The temp does go right back to two bars when you start moving. But I did notice that it was quicker to achieve 3 bars, and perhaps slower to resume 2 bars. And it was about 90 out. Humidity was way down, thank goodness. It was a beautiful ride. I went all the way to reserve on fuel in stop and go traffic and the tank never got THAT hot. Sweet!

In my very unknowledgable opinion, as long as the temps go back down, and the indicator doesn't show the bike freaking out at 4 or more bars (never seen more than four!), I don't think there would be a problem with the engine. The mod doesn't make that dramatic of a temp change with the radiator system.

Nice job Rocket. Where did you get the insulation? I'd be interested in this mod for sure.

Mike

All my aircraft insulation came from Aircraft Spruce and Specialty. You can probably get similar laminated/multi layer "blankets" from JC Whitney or JEGS ( and a bunch cheaper). Just about any engine firewall insulation material will work, you just can't get it too thick. I like the metal side down to reflect the heat away from the tank. There's a lot of variations on the theme out there.

Another 200 mile run today and my cobbled setup works pretty well. No melted foam insulation. Tank got warm, but never hot. I do need to open the tank back up and put some insulation under those floppy rubber covers. Those dudes get REAL hot. It only got up to 86 today, so perhaps the test wasn't stressed enough. But I'm happy with the results. I should be even happier if I can cool down those rubber caps under the tank.

Come on man, we need more pics!

Click to expand...

Will these pics work?

Sounds like an excellent idea, but I wonder what effect the elevated temp will have on the motor?  You mentioned that it got to three bars quicker than before.  It's definitely something to think about though.

Click to expand...

I find that, since this article was done back in April of 2003, there have been no adverse affects.

I went back under the tank and added anoother layer of insulation blanket. This layer went under the black rubber caps. It extended in one piece from side to side, and as far forward as I could work it. Sorry no pics. Now for another 90+ degree test ride.

I don't know... I just keep thinking that it may not be a good idea (for the engine's sake) to insulate anything in its bay. Smarter airflow and expulsion seem the more appropriate path to me. Just my $0.02.

-BD

The black rubber caps block the stock "airflow", but mostly look like rain or cosmetic covers to me . The tank aleady has insulation from the factory, and all I'm doing is making it thicker with the blanket. So the "engine bay blanket" is not really blocking the flow, just blocking the heat.

I am blocking the flow with the foam insulation, but not from the factory vents, just around the upper and rear perimeter of the fairing. And it works great. Not perfect, but a nice improvement over stock. And an easily reversible change.

Still, the water temp gets to 3 bars easier, but it goes right back down to 2 bars once I get moving more than 30 - 40. And temps were in the low 90s here. I don't think I ever hit 4 bars yesterday.

Having said that, the added layer of insulation from side to side under the rubber caps really didn't help much. It's to the point where the maximum heat I'm getting is generated by the frame, so there's not much hope of reducing that heat. I'll probably leave the insulation under the tank, which got warm, not hot. But next time the tank is up, I'll probably remove the other layer.

Happy to report that yesterday, cruising around at about 60 or so most of the afternoon and evening, I got about 48 mpg! That was a nice surprise. I've ran two tanks through and got over 45 both times. I was getting nervous yesterday when I stopped for gas. Odometer was something like 230 and the reserve had not stopped flashing. I thought it was broken! Turns out I had almost a 1.5 gallons remaining when I fueled up! SWEET!

I can't believe it got to 99 degrees yesterday. At about 3 in the aifternoon, I got stuck at one of those 5 minute stop lights on a side street intersecting a main slab. I'm hear to tell you that it was HOT! The bike went 4 bars pretty quick, but back to 3 in a jiffy. I was sweltering in bright sunshine, and so was the bike. The tank even got hot. Riding around an unfamiliar town behind "Sunday drivers" was a bad move on my part.

Once the light changed, I pulled out onto the slab and eased up to about 65. The bike never got back down to 2 bars the rest of the ride home. That was about 60 miles, mostly 4 lane highway.

My feet went out to the highway pegs, and my knees went out as far as I could get them. The shield was as far down as I could get it without it whistling. The bike cooled down reasonably well. The tank went back to being just warm quite quickly, but it was WAY too hot. I don't see how you guys in the SW do it!

I also understand why those of you in stop and go traffic in hot metro areas complain. It was not pleasant. I'm not sure it would have been on any bike, though.

At any rate, I'm still happy with my insulation results. I rode 300 miles yesterday, and except for the last bit of stop and go starting a nasty hot streak in near 100 degree heat, it was a beautiful ride. I think my mods have cut down on the heat, certainly not eliminated it. It seems that I was able to warm down the bike fairly quickly after it got hot, too. When it's hot enough out to keep the engine to 3 bars, I think there's only so much you can do. Most of the ride, the tank never even got that warm, but I also never slowed down or ran the bike balls to the walls.