Experimenting with Intake Air Temp. Request for comments.
 

I'd like to do a little experimenting with the goal of lowering Intake Air Temperature with minimal modifications to the stock setup. This is not an attempt to increase HP or MPG (although it should help both, if successful), only to get IATs down to a reasonable level, to avoid having the ECU pull timing. Please make suggestions.

Any permanent mods should be easy to perform by an intermediate DIYer with "standard" home shop tools. Any temporary mods (eg, thermocouples) should be easy to put back to stock condition. I have ordered replacements for the filter boxes and ducts, so they can be modified extensively if need be.

I need to install some thermocouples to get a baseline and measure results. Measuring engine compartment temp shouldn't be difficult, but I'm not sure how to go about measuring the the temp of the air in or near the intake manifold.
At first glance, it looks like drilling a hole in the duct, just before it enters the manifold, would be easiest. Does anyone know of an easily un-doable way to get a t/c inside the manifold?

After getting some baseline readings, I plan to install some insulation on the filter box and ducts. Any suggestions on type of insulation to use? I'm thinking something that is flexible, less than 1" thick, and having a reflective outer cover would work best. Maybe something like an exhaust blanket, only lighter weight. Tentative budget for insulation is $25-50 per side.

From there, I may explore extending the filter box inlets to an area of cooler air. Depends on how well the insulation works.

Hints, tips, and suggestions are welcomed.

PS: Yes, this is another of my obsessive projects - much like trying to figure out what causes the occasional pause when starting. :)

Most excellent tip. Thanks. :tiphat:

That's a mod that I might implement as part of "extending the filter box inlets to an area of cooler air". It appears that most of the mods involved can be returned to factory condition easily; that's a plus.

So in my experience (hundreds of hours of logging on the street, on the dyno, on the track, on the strip, autocrossing) the number 1 heat buildup causing factor is the radiator.

When the car is not in motion, the radiator heats the air behind the bumper cover up to 30-40 degrees over ambient.

With metal intakes, even if you have aggressive insulation (like me) it still ends up heating up the interior of the pipe, leading to eventual heat soak.

Plumbing the intake snorkels through the bumper to the outside air would be the only truly effective treatment for this phenomenon, by my reckoning.

Thanks for the input. Some form of CAI is phase two.

Once you get "normal" air flow, about how long does it take to cool insulated metal tubes back down? Seconds? Minutes? Do you know if the stock plastic tubes would cool down faster or slower?

This I am curious about, as being boosted I generate more heat both from the engine and other moving parts.
Intake piping coating:
-Silver heat shield
-Gold heat shield
-Black coating (like GTM has done on a few FI cars)

Are any of these good at separating the heat away from the piping and keeping it cool? Is one better than another?

Depends entirely on ambient temp and how long the car sat and sucked in heated air. Sitting in traffic, I'd see 160+ degree air and it didn't matter how much I drove after that, unless I was doing WOT pulls one after another, temps would never get back down to ambient (100ish), they'd just hover around 130.

Plastic doesn't conduct heat worth a damn, even if they do heat up, they won't transfer much of that heat into the air in normal use. Again, if you're idling for a long time, it'll heat, but I'd expect your temps to return to something like 'normal' relatively quickly.

So, generally speaking:

Shiny = Reflects IR
Black = Absorbs IR

Gold is one of the best reflectors for IR, 'swhy satellites and whatnot are covered in it and why DEI's radiant heat protectant products are all gold.

If the major heat sources in the engine bay are already shielded, I could see why they'd use black.

GTM shields their manifolds (and perhaps turbines?) already, so radiant heat is less of an issue, so they'd run black because that will help move heat out of the hotter charge air into the cooler ambient air. It's all relative and all comes down to heat gradients. Heat moves from one place to another, if you understand what I mean.

Think of the Light/Dark paradigm, darkness is the absence of light, cold is the absence of heat.

So yeah, tangents aside, they'd use black so that heat is transferred through the charge pipe into the atmosphere rather than hanging out in the charge air and going into the engine.

Every little bit helps!

Also note that we are talking about two different things here. Radiant heat can be shielded against, convective heat can only be handled by replacing that heated air with fresh, cool air or by insulating what you want to protect.

This is why I have my intakes wrapped in both header wrap (for insulation) and DEI reflect-a-gold for radiant protection. (I have un-wrapped headers at present, they heat everything up, on the list for this season to get those taken care of)

Wow. This got long, quick.

I messed around with my stock filter boxes a while back for a similar reason. I documented most of it here: Lets cut our stock intakes to pieces

This isn't exactly what you're going for, but it might give you some more ideas. I'm probably going to add Modshack's mod to this eventually.

From what I've seen, the stock airbox intake temp is approx 10 degrees F hotter than ambient air temp while moving down the highway at speed. There's a lot of room for improvement here.

As far as measurement, any OBD2 device hooked into your android phone will be able to give you the car's intake temp. Cross-reference that with the ambient air temp from the trip computer and you're good to go.

That should come in very handy when I get to phase two. Great DIY. Repped.

I'm getting about 6°F difference between the ambient temp sensor and the IAT reading in cool weather (40-50°F) at highway speeds and 9-11°F when the outside temps rise.

I have a ScanGaugeII that I use to monitor IAT, but, I think that comes from the MAFs (if I'm wrong, please correct me) and I'd prefer to get a reading closer to (or inside) the manifold. I may end up using IAT if getting a t/c in there is too difficult.


Thanks to all for the info and suggestions. Keep 'em coming. This is going a lot better than my "pause on start" thread. :)

I expect to have the spare parts in tomorrow or Monday. I am trying to track down a small t/c that can be inserted into the ducts or manifold (I have an industrial panel meter and an inverter already).

At present, my plan is to get some engine compartment temp measurements, do some baseline measurements of the air in the tubes/manifold, insulate, take more readings. If all is going well at that point, I'll try some homebrew CAI.

Thanks again for all the help.

Yes it was, but lots of good info. Thanks.

what about swapping radiator fans? if there are stronger fans pulling in more cooler air from outside of the car, wouldnt that cool the radiator down a bit more, thus making cooler intake temps? i dont think it would lower it by much but it should help in theory

Great idea. Thanks!

It's one of the things on my list of things to investigate someday. But I was thinking of fans as primarily a water and oil temp solution.
It certainly sounds like a good theory. Maybe I need to change my thinking. :)

For now, I'm trying to keep any permanent mods to a minimum and as cheap as possible, so new fans may have to wait for phase three. I'm shooting for lower air temps on general principles, not any HP/MPG gains.

I was going to track down some insulation today, but Real Life intruded. I've been posting between chores. I have new front brake rotors now - got some mud in the grooves in one of the pads and it was starting to eat up one of the rotors. Replaced the other rotor "just because".

that sucks but i like the way you think, did you go to slotted rotors or stick with stock?

aside from that maybe even an oil cooler might help cut down radiator temps as well, cooler oil means cooler coolant in radiator which means cooler temps, again that is just a theory based off logic

also you might be able to modify the air box itself and relocate it to behind the wheel wells or something, that should allow the box itself to suck in cool air at all times even when not moving but im not sure how temps would be at the MAF or even the pipes before the MAF, heck you might be able to do that with some flexible plumbing hoses from home depot or something and a few hose clamps and scrap metal to use as brackets

Stock, but not Nissan. My "suspension guy" said he would get as good or better than OEM and I trust him. I do some occasional spirited driving, but seldom hard on the brakes. Defensive driving FTW.

Maybe. But the heat from the oil cooler is right in front of the radiator. When stopped, I don't think there would be any improvement without relocating the filter box inlet location (eg, using tubing as above). Something to look at during phase two.

Great idea, but waayyyy beyond the scope of this project. I'm hoping to limit heat gain from the engine compartment and then I'll probably do one of the CAI DIYs above (depending on how well insulation works). An oil cooler is a possibility much later on.


Wow! Lots of great input. Thanks. Now I need to get some insulation, find a thermocouple, and figure out the best place to locate the t/c. No rest for the wicked.

For the insulation, you might look into HVAC duct insulation since I think you could probably a foil backed insulation.

Not sure what thermocouple "type" (I'd recommend type J based on the temp range) you plan on using but just twisting the two leads tightly together to form the junction is more than sufficient.

There is an industrial insulating company about three miles from me. I don't have high hopes that they will have what I need, but, if they do, I might be able to get some free scraps. Then I'll try the HVAC place about 5 blocks away. If neither of them can help, the only other place I can think of is auto parts stores and see if they have some kind of thin, foiled exhaust blanket or header wrap with foil.

My panel meter will take J, K, & T; any of which should do the job (plus R and S, but those aren't a good choice). For what I'm doing, twisting some extension wire together would probably do the job; relative readings will be more important than absolute accuracy. I have a J or K that I use to measure temp in the garage, but it is in an industrial sheath and has a lot of lag. Will try to find a real t/c, but could strip the sheath if need be.

difference is 5.5 to 6 degres higher than the out side air temp. I have data logged it.
when driving at 100 kms. (stillen G3>)
Z

Yeah, when moving it's easy to keep close to ambient.

Mine is usually exactly the same as ambient when moving.

Got the intake air spare parts today. Everything from the radiator support to the throttle bodies.

Bought some insulation yesterday.

Took some preliminary temperature measurements last night. Six degrees difference between the VID and IAT readings! First guess is that VID is wrong.

Code:

---

Time  T/C  VID  IAT  Water
00:00  74  71  76  x
02:00  67  64  71  85
03:00  67  63  69  80
04:00  65  61  67  78
11:00  62  58  64  62

---

Stock setup. No mods made.
Had several fans blowing on radiator, air intake opening (removed filler plate between radiator support and bumper cover), and MAF area.
Unmounted ambient temp sensor and placed it and T/C together.
Car had to be started to get IAT and water temps.
T/C display was calibrated about 10 years ago, so absolute value may be off, but relative readings should be good. Will calibrate when I can find a standard.

Just curious, but what kind of insulation did you end up going with?

I checked with 3 HVAC shops and they didn't have anything. The industrial insulator didn't have time to talk. So off to the auto parts stores. All I could find was Thermo-Tech Thermo-Shield Tape and DEI Reflect-A-Cool. I have no idea how well they may insulate, but didn't have any choice. Neither seems to be particularly rugged, but should hold up long enough for my tests.

If you are looking for a recommendation, I don't know enough about either product, other than a perception of feeling "cheap" to the touch, to have an opinion. I'll post my findings as I go along.

Probably going to wrap my G3's with a material called refrasil. It's a ceramic fiber based cloth used in heat treat applications. Just hoping I have a enough scraps from work to fully wrap the intakes.

so what is the conlclusion to this test? I read a little bit when it first came out but ignored afterwards until I got my dongle in the mail for the obdII system and read it through my android. Im averaging 5-8* difference at night and about 10-15 during the day. I commute 50 miles one way and during the day time i noticed when it was 78 or so that Inlet Air Temp was up. I also noticed here that there is one owner who has g3's and has the same temp fluxuation as most of us do. So how or why is it benificial for the g3's in comparison to short ram air intakes? Please no character assasination, I might be missing out on a very valuable point but just want some clarification before I pull the trigger on modifying my intake systems. One is sucking from outside the engine bay and one from inside, but we all have collant lines running through the throttle body so that does warm up the air before going into the plenum. So clarification would be greatly appreciated.

No conclusions, yet. I'm waiting for a friend's daughter to insulate the spare air ducts I bought, but school and boys are slowing her down.

I would think that pulling cooler air from outside the engine compartment would be better.

From what I have read, yes, the TB coolant lines will warm up the air. If I can figure out a good way to measure the air temperature after the TB, I will collect that data also.

you could drill a hole in the top of the intake and use a expoxy to seal up the whole if you use a thermocouple. Which brings the question of where is the intake air temp being read at? I thought it was the maf but I may be wrong. I don't disagree when it comes to pulling air outside, but here is my stumbling block. We as a customer are spending 150bucks on 3 degrees of air for 3 or 4 hp (gen3, aem, injen, etc) compared to a k&n or takeda? Most of the times cruising down the hwy the difference would be an avg of 5 or 6* right? if you are stuck in traffic then they both seem to have the same heat soak.

Also some useful information, the other night I took the wife out on date night in the z. When we left the resturante from dinner my intake air temp was around 130 from being parked for dinner. After some city driving (ambient temp was 44) it dropped down to about 95. When I got on the hwy it plummeted in a matter of 20-45 seconds to 46.

I'd like to find a less permanent/destructive way to do it. There are several vacuum lines that I may be able to tee into (t/c through the run and current hose on the branch).
I still haven't found a good (ie, cheap) solution for taking 4-5 temperature readings at the same time. I have found a dual-channel t/c meter that I will be ordering this week or next, but at $9 I'm afraid that it will not be very be accurate. If it does turn out to be reasonably accurate, I'll order more.

The ECU uses the MAF temperature on bank 1 for IAT.

I'm trying to see what can be done to the stock setup. I'm not worried so much about an increase in HP, but rather keeping IAT below where the ECU starts pulling timing (which I suppose is, in effect, a boost in HP).
If the insulation works well enough, I won't need to spend money on a CAI. :)

I've noticed much the same. Takes forever to get temps back to normal at city speeds after a long stop.
Did coolant temp go way up, also? Was the big drop at the same time that coolant temp dropped? The TB coolant loop may be having a larger effect on IAT than I suspect.

I am not suggesting the hp gain merely the effect of the three degrees of differing temp. I suspect the same with the tb coolant lines but nissan tech stated it was for cooling the air prior to entering the plenum. My radiator does cool rather fast but ambient temp was 44 and had almost no traffic at night.. During warmer weather it is true for temps to take longer to drop, havent had my reader during summer or warm weather but am anxious for the results. However when it was 80* out on my way to work heat soak was apparent in a matter of 2 mins.

Also if it is reading from maf then thats not a accuate readi g due to the fact that there is a heat source at the tb. In my opinion this is a faulty design.

I gave up on getting my friend's daughter to insulate the intake ducts and started doing it myself. It's slow work and it ain't pretty. The insulation is not very thick, but the silvered cover should reflect a lot of heat. Will post some pics later this week.

getting a woman to do a mans job most of the time is a fail lol. I was able to purchase some gen3's. But still in it for the results. I think the most common problem is air flow. But we shall see. Good luck with the results!

Progress Update
 

I added two pics of how the insulating is going (Nissan 370Z Forum - SouthArk370Z's Album: Air Duct), but my camera died before I could get a shot of the front of the filter box.

Still trying to find a 4-6 channel thermometer at a reasonable price. If anybody runs across one for less than $200, please let me know.

your air boxes are looking like mine. i used 1.5 x 10m rolls of the foil insulation tape to do both completely. All wrapped up til the rubber post-MAF hoses. At the time i was too lazy to take the bumper off so i didnt wrap the pre-airbox duct but i might do that next time i have the bumper off.

The stock IAT sensor on the bank 1 MAF module suffers from heat soak, no doubt about that. Once you're stuck at one light and IAT rises, it will never go back to what it was prior to the red light. Could be due to a slow reacting sensor but from memory it's an exposed thermistor & that's as good as they get.

Before wrapping my airboxes and MAF housing tubes, the surfaces would be very hot to touch, almost dangerous to touch. After wrapping, the interior surfaces are warm to touch but not scalding like before so they make a difference, even if the effect on power is slight.

I've wrapped my MAF tubes in heat resistant mitt neoprene style material (buy an oven mitt made of this material & cut it up). This insulates against radiant heat, esp on the alternator side of the engine where that very hot coolant pipe is. With the finger parts of the mitt, i cut an opening in each and slipped it over the MAF connectors. Lots of zip ties ensured a snug fit around the cables and sensors. This helped delay heat soak but idling on a very hot day (35*c+) but it still suffered. Problem with this sort of insulation is that it also keeps the heat from escaping but i'd say its protection from radiant heat is worth this downside.

Biggest (and cheapest) improvement was relocating the IAT sensor by way of a separate thermister mounted in the pre-airbox duct. I can get IAT within 1*c while cruising at 60kmh on a 22*c night. While there might be some discrepancy between the actual air temp and the output of this sensor, i havent measured it & i'm not too fussed. It cant be that far off. Both the sensors have the same resistance at 20*c

Thanks for the input. :tiphat:

I'm wrapping mine with 1-1/2" wide Thermo-Tec Thermo-Shield (thin layer of insulation on a foil cover) and then covering that with DEI Reflect-A-Cool (no insulation to speak of, just a reflective barrier). Only reason I chose those particular products is because that's all I could find locally.

I was able to spend about a hour doing more insulating last night. I have the short filter inlet duct finished and most of the filter box/MAF tube is done. Now I just have to buy more insulation so I can do the other side. I like you idea of using a mitt - I'll probably use that on the flex tube.

Cheap header wrap + Reflect-a-cool/gold works too. That's what I've got mine wrapped in.

Yeah that's the same width tape i used. Stanley knife blade to cut it and trim it to fit over all those ridges.
I'll get some photos of the airboxes soon!

For the flex tube (i assume you mean the accordion tube) i am just going to replace it with a silicone one. Silicone should be more resistant to heat and insulate better, plus it smoothens out the airway for some slight gains. Only problem is they're much more expensive than oven mitts! and for me i'll have to wait about 2 weeks for them to arrive from the US.

I would advise against more than 1 layer of the foil reflective tape. Some parts of the airbox are quite close to nearby components so you don't want any rubbing or fitment issues if you make the airbox too fat

So I subscribed to this thread pretty much immediately for results, but I am now also wondering what kind of temperature difference you're hoping for and/or expecting, SouthArk.

I have R2C black nickel intakes, so unfortunately, there's no way I would consider any of the exterior wrap options. After I purchasing the intakes, I borrowed a friend's scangauge to monitor the IATs. They certainly get heat soak (I would guess worse than stock), but now I am wishing I had recorded my endeavor as I cannot remember exact numbers. I just remember that the results weren't too concerning after all my forum research. Do you know at what temps the ECU will interfere? Is the ECU using the same IAT reading I get from the scangauge?

I'm not looking for a big drop, 4-5°F would make me happy. I'd also like to get temps back to normal a lot quicker after sitting in traffic.

IIRC, the ECM starts pulling timing advance when IAT gets above 95°F.

Yes. The ECM uses the temp sensor in the bank 1 (right side) MAF and that is what you see on the ScanGauge. I wouldn't be too surprised to find out the sensor data is massaged a bit before being reported, but it should be close to what the sensor is seeing.

I did a visual check and didn't see any spots that would be problematic, but some places are impossible to see. I guess I'll find out when I go to do the install. :)
I tried to keep the overlap on the tape to a minimum and don't have a lot of overlap on the foil.

I used the last of the tape and foil earlier today and will have to make time to go to the auto parts store to get more.

:tiphat:

95 eh... That's less than ambient for about 6 months out of the year here in TX :ugh2: So I guess my timing is retarded in the summer :icon17:

Due to roof, plumbing, and bathroom repairs, this project is on hold for a few weeks. :(

I'm still looking for a multi-channel thermometer.