So as we all know the intake air temps get low enough in winter to hinder fuel economy and idle combustion efficiency. I have a winter front the helps out quite a bit, but I think they could stand being a little warmer.

I generally block off my home depot CAI in winter to keep snow/moisture from entering the airbox and maybe run a little warmer air.

I have been considering adding a 2" deck plate on the engine side of the air box. Close it in the summer when I don't want engine air, and open it in the winter when it's a good thing.

I considered a 3" opening because my HD CAI is 3" and the plug would work for both, but not sure I want/need that much hot engine bay air?

What do you guys think?

--- Update to the previous post...

Something like this.

No they weren't swings below the operating temp. I was seeing hotter running temps, and slower to open. It seemed like the spring was slow to react, and that I wasn't able to go full open. The excessive size of our cooling systems means that the thermostat's very rarely go full open (Mine doesn't go full open 10 times a year), so they develop wear spots and the springs fatigue easier than on other vehicles. This is also why I feel it's important to only run a Cummins stat (I bought mine directly from Cummins NW). I think a pair of thermostats would really increase thermostat life (Say a small one that cracks at 190, full open at 195 and a big one that cracks at 200 and full open at 205). You could also really improve the flow thru the block if you changed placement. But I don't think the cost benefit is there.

the ones i have been buying definately have no problem opening. they cant seem to stay closed long enough to get to operating temp. the one in here now seems to be working good after the trip over the mountains.it wasnt before the trip. it is holding better temp at idle and hits operating temp. it still fluctuates a little. we will see how well it works when it turns off cold here in tennessee.

I pulled my air filter out yesterday to see how much room I have for a winter opening in the box. I think I can fit a 2" deck plate pretty easily, and really I think that's all I want. With the winter front on my IAT's are about +20°-40° over where they are without it so I am already going in the right direction. I don't want to be opening and closing this thing based no IAT's getting too hot. I know 2nd gen's see over 100° pretty easily, but unless its 90°+ out or I am pulling a grade in 80°+ weather I don't see it.. So I don't want to be getting much over 110-120° with this mod.

This might be an idiot type of question, but this thread is of putting in a winter opening in the air box for warmer air during the cold, blocking off the CAI. With the industry demands for better mileage from engines, wouldn't they have engineer in a heating system of some sort for the air on the 'new' trucks if it would increase mpg, making them comply with the regulations set by the feds ? They said every mpg counts. I haven't seen anything for this on any new pickup truck or rig as of yet, or an aftermarket design, unless I missed it. (if there was a dollar profit in it, I would assume someone would have jump into it)

This might be an idiot type of question, but this thread is of putting in a winter opening in the air box for warmer air during the cold, blocking off the CAI. With the industry demands for better mileage from engines, wouldn't they have engineer in a heating system of some sort for the air on the 'new' trucks if it would increase mpg, making them comply with the regulations set by the feds ? They said every mpg counts. I haven't seen anything for this on any new pickup truck or rig as of yet, or an aftermarket design, unless I missed it. (if there was a dollar profit in it, I would assume someone would have jump into it)

No... Its all about EPA and CARB not performance or MPG. So like on my chainsaw (Sthl 046) I have the same setup a summer and winter shutter or pre-warm air or cold air. Since standard vehicle are under the EPA coverage they must tune to meet the lowest emissions... They don't care about MPG's... If the did half the garbage on our trucks would be here. (EGR, DPF, short exhaust lobe, etc)

This might be an idiot type of question, but this thread is of putting in a winter opening in the air box for warmer air during the cold, blocking off the CAI. With the industry demands for better mileage from engines, wouldn't they have engineer in a heating system of some sort for the air on the 'new' trucks if it would increase mpg, making them comply with the regulations set by the feds ? They said every mpg counts. I haven't seen anything for this on any new pickup truck or rig as of yet, or an aftermarket design, unless I missed it. (if there was a dollar profit in it, I would assume someone would have jump into it)

They kinda did in 08 when the shrank the intercooler. It had 2 effects, warmer air for mileage and warmer EGT's for fewer regen's (main reason I beleive). And because everybody thinks colder is better.. which is true in terms of power, just not so much in terms of fuel efficiency..

Ya, I'm old school in knowledge of this. It was always the cooler the air, the dryer the air, good filtered air and plenty of it is the best. As for the EGT, the lower the temp, the less of restriction ... the best basic for your vehicle. Then, what can be done to extract the 'most' energy from every ounce of fuel.But, per this thread, I haven't lived in an extremely cold area in over 40+ years.

From a power standpoint you are 100% correct, the colder the air the more o2 per cubic foot of air, thus more power potential. From an economy stand point the engine has an efficiency range, and with ECM's adjusting timing/fueling the economy can increase, but your total power may be hindered... if that makes any sense.

This thread started because he wanted to block off his CAI system because of the cold weather themps. I've been pondering this thread and on the news, they stated they were looking into salt reserves for the wintered roads in our state. They are generous with that liquid mixture to help prevent icy roads.Now the questions are;* how much sodium contamination / moisture can pass through the filter system to the turbo* and how much damage can it do ?Never thought about this before.Think I'll block off that big opening below my fender for the winter.

While I was changing my spare out to my winter spare and re-tuning my Smarty today I closed the opening on my HD CAI... now to look into installing that 2" deckplate.

Yesterday I modded both of my gas rigs.. and it was easy. The VW has a 2 piece ducting that direct airflow from the grill to the air box, I simply removed it and now it can draw air from the engine bay. I haven't driven it with the SGII yet to see if it made a difference. On the 4runner I just removed the 3" tube between the fender and air box, got about 10-15° rise over what it was. Instead of putting another hole in my OEM box I am going to modify my Home Depot CAI. I am going to put a "T" in it, that can be plugged in summer and open in winter. It's a little bigger hole than I wanted, but it will also be about 6" lower and the temp should be a little cooler down there. Best part is that I don't have to pull the air box to do the work. Pulling the air box sucks as I have my winch power solenoid bolted to it and it's a PITA to access those bolts.

I'm patiently waiting...

Home Depot, or Lowes.. this morning.

--- Update to the previous post...

Well my PVC cement is cement in the can.. but here is the pre-fit.. It will draw air from over the coolant and boost hose, both of which radiate some heat!

When I was pulling grades this summer and had a temp sensor outside the OEM airbox the under-hood temps would go up 40-50° with increased/sustained boost and more coolant flow from a closer, or fully, open thermostat.

--- Update to the previous post...

Finished, and quite an easy change.. I am going to call it the "HD Warm Air Mod"..

I'll get results this weekend.

were you seeing wild swings like me? what did you replace th oe with?

Do you have a high idle box? I was having swings like you, start at 180 and then drop to 150, back to 170 and cruise at 155. I changed t-stat 3 times and still same fluctuating. I unplugged my high idle box from my water sensor and it straightened out. I left it unplugged for a month and it never missed a beat. I plugged it back in for a test and it was back to the fluctuating. I unplugged the water sensor again but left the iat sensor plugged so I could still use it in cold weather. I dont know why it does it but it does.

nope, no high idle box. mine started doing it when i changed my tstat 2 or 3years ago. it has been that way until i drove over the mountains 6 weeks ago. temp spiked to 215* briefly and has been working pretty well since. still fluctuates, but only between 183 and 190 now.

I have put a few miles on it since getting it finished up. With both the WAI and OEM holes open there was a nice improvement at slow speeds, but at higher speed's there wasn't even a degree difference. So I then tried blocking off the OEM hole a little and it made a difference. I run about 5°-20° warmer under most diving, including at 65 mph. So between the WAI and winter front my IAT's think is early summer! Now to see if it makes a difference on mileage, but either way it will help the motor stay warmer on super cold days with a light load.

Winter front on too?

Of course!

Diesel_Dave on another forum has recently been tracking ambient air temps against fuel mileage over [80] days of work commutes (Indiana; within frost season). The relationship of air temp against mpg tracks, up or down:1-C = 1% changeHotter equals better.I thought it would level out at around 90F, but a gasser chart shows it climbing still at 105F (north Texas summer). For purposes of mpg it appears that there is no downside to heat. Now, under load and with elevation changes things might not be as clear.

I just happen to get a really good look at that this yesterday. I was heading down to Ontario, OR and Caldwell, ID for supplies. Well the start of the trip was at +10*F about and couldn't do much better than 17-19 MPG. By the time I got to Council, ID the weather start warming up start creeping towards 20 MPG. By the time I was running around in Caldwell, ID it was 56-59*F and the MPG was really rising up towards 22-23 MPG... No joke. I've also just verified my ScanGauge II is dead on the money now. So I've not seen any down side to warm air either... All pluses when it comes to MPG's...