lakemg

The real issue is that the IAT sensor/intake duct becomes heat soaked and indicates a false positive intake air temperature. We had the same issue in the Pontiac G8 community and actually would split out and relocate the air intake temperature sensor closer to the air filter intake charge where it was less prone to heat soak. Worked really well.

Bob U

Great point.
Some folks have wrap the intake tube and sensor with insulation material to keep the high engine bay heat out of the intake track.

BJ67

A tutorial sounds formal and I am a informal guy so here goes. On a non Z51 car, the left and right ends of the grill have covers on the inside (4) upper and lower. You need to get access to the back of the grille thru the rf wheel house panel by removing almost all of the clip's and screws so you can pull it out of your way. Stick you head in there and remove the lower plastic cover. Its only heat welded in spots and it comes loose no problem. After, If you lie on your back and look thru the opening that's toward the rear of the underside of the right headlamp, you will actually see the tip of the air filter itself. The trick is to direct air flow up to that opening. Buy a z51 brake duct that attaches behind the grille opening you just removed the cover from. Before you mount that duct you have to cut the rear section off so you can fabricate a tube to go from the brake duct to the opening where you can see the air filter tip. Make sure its as leak proof (air) as possible so the air doesn't just spill into that lower cavity behind the grill.

BJ67

The air intake is high on top of and to the rear of the right headlight. Engine heat, outside heat leach in the that area because there is no sealed direct path to the rf lower grille area and there are openings for such air to be sucked on. Suction from the air filter housing right there just pull's air from everywhere it can.

BJ67

The air filter housing and tube to the throttle body heat soak badly, heating the intake charge. Magnify that by the insulation on top of the intake manifold keeping it hot is also heating the intake charge. Cool intake, cool air = more power.

BrunoTheMellow

https://www.corvetteforum.com/forums...-cold-air.html

BrunoTheMellow

I know where the intake is. There is a giant hole on the frame right where the intake is... A stock car pulls from inside the fender. So does a Halltech intake. You don't need a sealed path to the brake duct. That's also adding debris and water. So much that halltech tells you not to drive in the rain unless you have the back part of the ram air open, that's just annoying.

davekp78

Doing some rough calculations, the air spends less than 1/10 of a second in the whole intake system. How much can it really heat up in that amount of time?

Higgs Boson

it doesnt. the iat heatsoaks at idle and gives what is essentially a false reading. this doesn't mean the air itself is heating up, it means the sensor is heating up.

the computer biases fueling on ECT and IAT and adjusts automatically based on airflow through the MAF. Low airmass is biased towards coolant temps and high airmass is biased towards intake air temps because GM knows that with low engine/vehicle speeds the IAT readout is not reliable (as opposed to it being hot). so they bias to coolant temps as they are more steady (but also less important at heavy loads/high airmass where IAT is more important).

we have to remember that we are not scanning and reading the temp of the air, only the output of the sensor which is based on a voltage slope. the slower you go (RPMs and air flow correlated with vehicle speed) the less accurate the IAT sensor is, that doesn't necessarily mean the intake air is hotter. (although I am sure it isn't cooler either).

it would be fun to see that chart again but replace vehicle speed with engine rpm.

at the end of the day we use the tools we have and in this case it is the IAT sensor. if there was a way to measure the air temp inside the intake tube without being influenced by underhood temps that would be much better but humanity isn't that advanced yet. maybe the Homo Futurians will figure it out as we Sapiens don't get it.

davekp78

Yes, this makes perfect sense.

BJ67

And because the Halltech brake duct part is mostly sealed, and pulls air from the massive grill opening , it creates a positive air flow to the opening that is there under the inside of the fender. They even say ram air effect at speed. The other issue there is if you look on the upper side of that opening and the opposite side of where the air filter box mounts you will see many openings that allow a draw of air from the hood hinge area(under the hood) and around the underside of the headlamp.. areas not cooled but heated . The closer you can draw air thru the grille opening the closer you will be to a true ambient temp air source. The cooler you can keep the iat sensor is a plus.

BJ67

On a 65 degree night after a local drive ( not in stop and go traffic) , park the car, shut down the engine, open the hood and wrap your hand around the throttle body. Is it hot to touch, warm to touch? because of my set up, its cold.

Higgs Boson

cold? not sure about cold....with wrapped headers I am sure you can touch it without burning yourself...its attached to a plastic intake manifold and a plastic intake tube.....

we know it's not going to be below 65 on a 65 degree day even sitting all day. after driving I am sure it's quite a bit over 65 which I am not sure I would call "cold."

you should do a video of you driving, show the coolant and iat temps on the scanner and then get out and shoot the TB with a temp gun so we can get some real data instead of "cold."

not that the temp of your TB is really even relevant to rwhp anyways. I'll give it 3rwhp.

also, I haven't seen anything in this thread that is free....lower iat = free hp? seems like everything so far costs money....coatings, wraps, etc. ;-)

BJ67

Cold meaning as cold as apiece of metal being held out the window for a while on a 65 degree night drive. All it means is my intake air temp is cold enough to cool all the way to the throttle body versus being heated. Even the top of the intake with the plastic cover and insulator off is of the same coolness. Better than warm or hot like the water pump directly under the throttle body. I realize a cool throttle body does nothing for hp, I am trying to explain how cool the air is being ingested and that equals HP.

Higgs Boson

Gotcha. I am not saying no one should do anything to contain and manage heat, I think it's important, too.

dovervold

The graphs show IAT's climbing 30-50 degrees after some heat soak. Higgs, you are talking 3 rwhp at the TB. I am talking the entire intake path. At 30 degrees increased IAT's I'm saying the loss in rwhp is significant based on pulled timing and increased air temps. It was Fasterprom's that posted the results from the changes I made. I will find that thread for your reading pleasure.

Higgs Boson

the rule is 1% HP for every 10 degree actual reduction in IAT (rather than (potentially false) reported temps).

40 degrees is 4% power increase which is 460*.04 = 18 HP which is great as long as your data is good....If you reduce temps when you are full tilt then that's a real increase in power.

I am not too sure why you are worried about IAT at idle. A spike in IAT it idle is normal from a heatsoaked sensor, which is misreporting true IAT, like the end of those logs where IAT spikes.

The issue is you are counting a reduction in a heat soaked IAT sensor to a non heat soaked IAT sensor rather than a change in actual air temps, which are not reliably "sensed" at low engine speeds. This is nothing new and is compensated for in the tune, as mentioned above, since I don't know.....1997?

The graph shows ambient going from about 70 to about 105, 35 degrees increase in ambient? Something is wrong with the data in the graph.

ilivas

You guys are getting 10 degree above ambient? Wow, I wonder what's going on with mine then. 147 degrees. Lol

Higgs Boson

Z06 or boosted? logging IAT2 or Manifold Air Temp?

RussM05

All the data was logged using HP Tuners. The data shows ambient starts at ~75°F and at the end ~105°F so the raise is 30° not 50°.

My garage is much cooler than ambient, so that explains why the increase was this much.

As far as I know, I am the only person to post actual data like this. Lots of theory about what is going on. The last third of the data shows vehicle speed decreasing and IAT increasing. Makes sense that as vehicle speed decreases, less outside air is moving thru the engine compartment, so less heat from the engine and exhaust system is being displaced.

Without data from a second sensor placed inside the air intake tube, I can not agree with the factory IAT sensor giving false readings. Its good to create a theory, but without data to support it, its just a theory.

One thing my test shows for sure is the coolant hoses are so close to the Halltech air box, it contributed to the increase in IAT. I went back to the stock air intake system, and the data showed an immediate reduction in IATs.

As an experiment, I made my own intake system from tubing and aftermarket air filter. I placed the air filter on the driver's side just above the anti lock brake system. IATs were between 150° and 160°. More than stock but close.

Lets face it guys.....the area where the filter and intake tube are going to get very hot. The less air moving thru the radiator, the hotter it will be under the hood. The slower you are moving the hotter its going to be.

We can insulate the filter box, tube from the filter to the throttle body, and MAF sensor. That will probably help some. I did insulate my filter box and added sleeves over the coolant hoses. But the motor still radiates a lot of heat especially when the vehicle speed drops below 60 mph. But it still gets very hot under the hood. By the way, since the filter is pulling air from behind the passenger's fender, dark coolers heat the fender up more in the day with a bright sun out so the air there will be warm than, say, a white car.

Its been suggested to remove the baffle between the radiator shroud and the hood to allow cooler air into the engine compartment that is now directed out the hood.

The best solution...and I haven't figured out a way to do it... is to get air to the throttle body directly from the outside and avoid all the plumbing under the hood. The C5 and C6 have a shorter and straighter path from the filter in front of the radiator to the throttle body so they don't have a big a issue as the C7.