Intake insulation experiment, FJZ80


I recently purchased a Scangauge after reading about it on Mud and that thing is just awesome! Well, anyway after viewing the intake temps and reading a few threads on Mud, I wondered it would be possible to lower the intake temps by insulating the air filter canister and piping. This was largely motived by a thread by Landtank regarding his results after wrapping a winter coat around the canister.

I’m not really trying to gain h.p. per say, but I figured the intake system really just couldn’t be in the worst possible place or made of the worst possible material for heat. Considering it’s a metal can and it’s right next to the exhaust, it could probably use any help possible to keep temps somewhat reasonable.

So I removed the intake system and wrapped it up in insulation. I used some high temp wrap insulation around the air cleaner can where it faces the exhaust and some wrap around the intake tube. Then used some cheaper insulation around the rest of the intake can and then covered everything in reflective heat tape. I covered almost every exposed surface, including the bottom of the filter canister and the lid.

This is the test results and I’m curious how they compare to anyone else. Do you think this actually reduced the intake temp at all? I only ran once with my scangauge and no insulation. At 50 ambient, my highway temps were between 69-73 at highway speed, without insulation.

After wrapping everything up, outside temp was still 50. On the highway at speed, the intake hovered between 55-57 degrees, even after a few runs of getting on it and testing out the horse power feature on the scan gauge.

I then parked and left the engine running to see what the intake temps would do. It very slowly climbed over about 15 minutes until it got to up about 91 degree. Water temp started at 188 and dropped to 186 during this period.

I then opened the hood and see what affect it would have on the intake temperature. To my surprise, it didn’t lower it, and intake temp very slowly kept rising until it reached 96. The engine compartment didn’t seem very hot and the intake can was barely warm to the touch.

I closed the hood and headed back out on the highway. At speed, the temps began to steadily drop. After about 5 minutes of driving at 60mph the temp was back down to 58.

When I got home, I found that the intake piping and air filter canister was barely warm to the touch. The warmest part, not surprisingly was the front near the exhaust, but it wasn’t too hot to touch. The rear of the filter canister near the fender was barely warm at all.

By contrast everything else in the engine compartment was extremely hot. Wire looms and hoses that were right next to the intake tube were almost too hot to touch, while the intake tube was just warm.

I don’t have a snorkel. Everything about my engine and intake is stock.

I'm really curious what the combination of a snorkle and this heat wrap would do, since folks say that a snorkle also lowers intake temps.

Bella PSD

One thing I would like to add.

Although I drive do drive a Ford Super Duty, I have monitored under hood temps for over a year. Next to, inside and below the filter location. Also monitored temps at the center of the engine bay. What I discovered was that the under hood temps at the filter location is only about 10-20 degrees higher on average than the ambient temp. At the center of the bay was about 50 degrees hotter on average. That's at cruising speed. Really, anything above 25-30 mph and under hood temps at the air filter location are low.

What surprised me was the effect heat soak has on a closed "cold air" box style air intake system. This heat soaked condition takes place as soon as you stop forward movement or park for as little as 5 minutes. After forward movement has stopped, under hood temps rise quickly and everything under the hood is heat soaked and just stays hot. This heat soak condition continues long after you get back over 30 plus MPH. Any effect from the cooler air with the box style "closed" system was lost due to the heated up box that also took a loooong time to cool from the heat soak condition.

The open style filter I was comparing also suffered from heat soak but recovered much faster. This was do to less surface area to cool down on the open air filter, once forward movement resumes.

On long trips that were 300 miles plus, I could leave with a dead cold engine that was the same as the ambient temp. If I did not stop, the under hood temps would only rise above the ambient temp only 1-3 degrees over the 300 plus miles. Once I stopped and parked the heat soak would take effect. Even if I parked for only 5 min. I have popping the hood during stops and that helps some.

I think your insulation helped some as long as it does not become heat soaked. Once the intake box and tube is heat soaked, it just stays hot for a long time.

One thing I never experimented with was a double layer of insulation from the heat. One layer would be your tube insulation. The second could be a second insulation box or surround that has an air gap around the air filter. Like a box around your air box.


Grim Reaper

Expedition Leader
I think your measuring may not be what you think.

I think the reading is intentionally lethargic.

If the intake temp was to be an instantaneous change then it would be making excessive fuel rate changes every time you stopped in traffic and it picked up some exhaust heat from the car in front of you. I am sure it was designed to make slow changes to deal with running through heat pools like that.

I bet if you put a simple oven type of thermometer in the air box not touching the metal you would see an instant drop back down to near ambient temp, if the preheat pipe is fully closed, just bringing up the engine speed.

Just a FYI the ambient air temp sensor should be in the AFM right at the canister it looks like in the pictures.

That said I have seen where under hood temps make a BIG difference. My last rid was a 75 GMC Jimmy. in 75 they had under hood breathers with no snorkel to pick up fresh air. I had a ping problem in the summer in that truck. I totally cured it with a factory snorkel air cleaner off a newer truck. Picked up a full 1mpg in the summer and performance since I could advance the timing a little.

My thought on why people are saying they are picking up power with a safari snorkel is proably due to where the factory intake is. My guess is this is a low speed fenomenum where engine bay or radiator heat is pooling where the intake is from lack of forward movement. I know my Suburban with its monster 454 heat pump can melt snow all the away around it idling if it is a light cover right near freezing. Stand within a couple feet of it in the winter and you can feel a big rise in temp.

If you want to play hit target and get one of these. I piss my wife off with that. I am always dragging it out to the shop when I am playing with my home build 12v fridge. I also don't let her cook my meats anymore since I bought that. She tends to overcook but that lets me see just how done my steaks are when I am pan frying them. ;)
I might play with it on my truck as well. I have a F|AFM I was going to swap on my truck this week. You got me curious now so maybe it will mess with it some.


Heretic Car Camper
My thinking on the heat soak issue is that once the can does get warm, the insulation slows cooling it off as well. I would consider the previously mentioned air gap type heat shield placed btwn the exhaust and the filter can. If you can convince some of theunderhood airflow to flow btwn the shield & the can (even when sitting still) then the heat soak will take much longer if it can happen at all. Seek to delay the heat soak as much as possible.

Reminds me that I need to re-read Smokey's article(s) on his purportedly Aidiabatic engine.....


i noticed the heat soak will instantly drop once the truck is turned back on. The fan clutch engages at startup and blows all that stagnant hot air out.

The most engine heat is created at higher rpms (going up freeway grades for example). It takes a bit for that heat buildup to dissapate.

Slow driving does not hit max temps for me, even in traffic w/ AC on & 100+F.

I think the guys are on to something with a deflector plate rather than wrapping up the entire intake. It may have an unintentional insulating effect as everyone is saying. allowing air movement while deflecting the heat maybe the way??

nice experiment, it would be nice to see how your numbers turn out w/ continued use


I have a couple of additional thoughts.

First, I'm not sure how long term driving would affect the temps. Especially in hot weather. At some point, the engine and exhuast heat might overwhelm the insulation and air temps would end up being the same as without insulation. I'm not sure if that's possible, given the same conditions or not.

The other thing is that I'm wondering if the intake tube really isn't a huge source of hot air. It sits right above the exhaust and since heat rises, I would think it actually might soak up more heat than the filter can.

I look at it like this. I don't think it takes much to heat up air. An extreme example is any space heater or blow drier. Moving air through a hot tube, even a very short tube will heat it up very quickly when it comes to space heaters and blow driers. So, if the tube is insulated, it may in fact play a significant roll in keep temps down as it reaches the intake manifold.

My other thought is I wonder what affect this might have in serious freezing conditions during winter time. Aircraft have issues of carbs freezing up at altitude. Most cars with carburators have heaters built in, usually involving either exhaust heat or coolent running through the car and/or intake manifold. I've even seen that my CRX and I think mini-truck have coolent running through the throttle body to keep it from freezing up.

So, my question is this. My insulating the intake system am I risking freezing things up and also, if in fact the LC80's throttle body is pre-heated by coolent like other vehicles, maybe I'm wasting my time, since the air will heat up anyway. And then there's the issue of the sensor thinking the air is colder than it will be once it reaches the manifold and how that might affect the fuel mixture settings.

Just brain storming.


Dave Druck [KI6LBB]
Interesting idea.

Not a total hijack.. but i've been wanting (was gonna go 2 weeks ago) to pick up a Scangauge II .. but didn't know if they worked with OBDI? or even worth it with OBDI?

anyone know? Scanguage website doesnt say.

Grim Reaper

Expedition Leader
Insulating won't hurt it at all. It will help keeping the air cooler especially in the summer.

As far as freezing. It wont. There is a preheat pipe somewhere to warm up the charge when it is cold to prevent that. There is also a coolant line running through the throttle to warm it in the winter so it doesnt frost at the throttle blade.


Interesting idea.

Not a total hijack.. but i've been wanting (was gonna go 2 weeks ago) to pick up a Scangauge II .. but didn't know if they worked with OBDI? or even worth it with OBDI?

anyone know? Scanguage website doesnt say.
Sorry, OBD II only. I got lucky in that I have a later model '95 with both OBD I and OBD II systems and it does work. But when I go to DEQ to get tested, they treat me like I'm an OBD I car. 1996 model year was when it became a requirement. Toyota started implementing it sometime 1995 model year. But most rigs 1995 and older won't work with the Scan Gauge


Heretic Car Camper
Part of the reason that carb'd vehicles have some sort of heat riser is to vaporize the fuel coming out of the carb in cold weather. With EFI this isn't really needed since the injectors do a much better job of that than a carb does (assuming they're working as intended). Aircraft carbs have freezing issues in conditions that are outside of anything you can likely encounter on the ground (at any elevation) in the lower 48. While it's possible to freeze up an intake on a ground vehicle, I wouldn't use aircraft conditions as an example unless Alaska's North Shore in winter or similar conditions are expected to be encountered in the near future.

If you are driving the air is being cycled thru the engine compartment. There will little stagnant air to heat soak the intake tube or filter can. So as long as you can deflect it away or create a barrier of constantly replaced colder air btwn the intake bits and the exhaust heated air, the intake temp will be lowered.

When sitting still in hot weather is the bigger challenge. Your only ally in this case is the radiator fan. Which is why I suggested that any heat shield be shaped to capture some of the air coming out of the radiator & duct it btwn the shield and the intake bits. That air is still going to be cooler than air heated by the exhaust system.


As was stated before, preheat is for the carbs that need to vaporize fuel. Having heated water run through the throttle body does not heat the air, it keeps the throttle body from frosting and sticking open.

Now on to thermodynamics. Insulation slows the movement of heat. Insulation retains very little heat. It is not a heat sink, like a chunk of metal is. As soon as the ambient air is running through the duct, it will be ambient temp again, on the inside (the duct material will take a minute to cool down). The insulation is designed to slow the flow of heat through the duct wall. You wrapped it with reflective tape; so the radiant heat will be greatly reduced also.

The addition of metal shields, with air gaps, is very effective. You could use one of the heatshields that are placed above catalytic converters.

Moving your intake-opening away from the radiator and road, will allow for the coolest intake temps. Even a short snorkle, to get air from outside the engine compartment will help. If air comes from the space inside a fender, and the fender is dark green, the air will be hot. Solar heated air.

One layer of insulation tape, and one layer of heat-reflective tape, and one heat shield are enough under the hood. Now control your intake location.


Just thought I'd report my numbers as I test. Unfortunately I haven't had much time to drive it and test it, but on my way to work today...15 minute drive

Ambient temp was 51 degrees, average speed was about 30 mph

Intake temp was 51 degrees until the last few minutes when it went as high as 53. I sat in the parking lot for about 8 minutes with it idling and watched the temp climb to as high as 69.

At first, I thought maybe heat soak was playing a roll in the higher temps at idle, but I noticed that the air under the fender where it draws air is very warm. So now I think the issue is entirely just that it's drawing warm air that is being heated up by the engine. Which isn't an issue when you're driving down the highway.

I'll bet with a snorkle, this wouldn't be an issue at all. So far, this really does seem to work.

More testing though. I want to see how it performs driving on the highway for hours at a time.


Update in some experimentation the other night.

This was at night, ambient temps varied from 40-42 degrees.

After 15 minutes of city driving, the IA temp, started at and remained at 46 degrees. This was from a cold start up. Full WT warm up took a good 10 minutes.

I then parked it for 15 minutes. I was inside a covered area, so the ambient temp was slightly higher at 45. During that 15 minutes the IA went from 50-69 degrees. I then opened the hood, with no affect.

I then lightly sprayed water all over the intake filter and canister for about 15 seconds. The temp stopped climbing and very slowed came down to about 67 degrees after about 5 minutes.

I then closed the hood and took it out on the highway. Ambient temp was 42. Within 5 minutes on the highway, the IA was down to 46 where it stayed no matter how I drove or for how long, as long as I remained at highway speeds of 50-60 mph. As soon as I slowed down significantly or stopped, the IA started to climb very slowly.

So, far at highway speeds, this mod seems to keep IA temps to within a few degrees of Ambient temps, but slowing down or stopping really has a major affect on IA temps. I tend to this is almost entirely because its breathing in hot air from the engine area. I wish I had snorkel, because I suspect, temps could remain close to ambient even at low speeds with a snorkel and this insulation mod.


Expedition Leader
Brian894x4 said:
I wish I had snorkel, because I suspect, temps could remain close to ambient even at low speeds with a snorkel and this insulation mod.
That would be the interesting thing, to see if the insulation makes any difference w.r.t. ambient air temp outside the engine bay coming in through a snorkel. I'd have guessed that outside air would be a bigger effect.