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2007 AWD 3SS
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Discussion Starter #1
I did a little bit of data logging today combined with measuring temperatures with my Solomat Type K thermocouple Thermometer.

-The stock Cold air induction on the TBSS sucks, badly.
-The stock IAT temp readings are accurate, they really do tell you the temperature of the intake air charge.

I relocated my MAF inside the airbox a while back, but with not much insulation added. The outside temp was 87ºF verified by thermocouple. IAT temp at idle cold was 91º. After a 45 minite drive, IAT went up to 99º or so driving on the highway and 133º parked back in the yard.

My job was to find out why, and I did. This is what I found:

First I measured the temperature of the inside of the cold air box while the car was running, I did this by inserting the thermocouple sensor into the air inlet openings:
- - Idling in the driveway the temperature of the inside of the air box was 130º
- -MAF body temperature was 132º by thermocouple contact.
- -IAT reading was 132º
- -actual air inlet temperature, from the thermocouple wire inserted into air duct between MAF and engine, was 132º.
- -Ambient temperature was 89º
Under hood temperature with hood open at idle was around 140º +


Here is an amusing thing as well: The temperature of the windshield washer fluid was 120º.

I realized I had to isolate the heat sources from the AF body better. I went out and bought some thermo insulation tape and air duct insulation.

I plan to completely isolate as many heat sources from the MAF and filter as I can, including openings to the engine compartment as well as lining the top of the washer tank with reflective air duct insulation.

We will see what I can get from this, but I will not be able to mess with it until this weekend (superchips is using it for testing tomorrow til Saturday)

BTW: All the folks who say IAT only effects timing- they are full of shit. The table for Cylinder Charge Temperature Bias determines how much of the charge temperature is biased toward the ECT or IAT. The higher numbers bias the resultant temperature towards ECT.

The Cylinder Charge Temperature effects all kinds of fuel control and MAF signal parameters.

Basically, I was right waaaaay back at the TBSS forum when I said IAT readings effect fuel and timing, but I was blasted by the idiots who sell the HSRK telling me I was full of shit.

All I have to say to them: :fu::asshole:
 

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Yes but...

I think the benefit to the HSRK was the rate in which the sensor reacted to temp changes. What I mean is this...

Your intake temps will be +/- the underhood temps at idle as the air is just 'sitting' in the intake. Once the throttle is cracked open - it starts to pull air in. With a true CAI - this should be the ambient air temp. But we all know that all materials hold on to heat - some do it better than others.

Now HSRK will react to the temp changes faster than what the stock sensor does. So - when you have the ambient air moving across the sensor it will add timing/fuel as needed/safe.

I would be curious what the ambient air temp was if you held the throttle open for 15 seconds @ 2500rpm (or whatever RPM of your choice). I imagine it would also be different if you were in motion. I have a feeling the higher the RPM the closer to ambient you'll be yet the AIT will be higher as it is slower to react than your testing equipment.

Again - this is my understanding of the HSRK. I can't imagine there are so many other LSx people using them if they didn't make a difference.
 

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2007 AWD 3SS
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Discussion Starter #4 (Edited)
I would be curious what the ambient air temp was if you held the throttle open for 15 seconds @ 2500rpm (or whatever RPM of your choice). I imagine it would also be different if you were in motion. I have a feeling the higher the RPM the closer to ambient you'll be yet the AIT will be higher as it is slower to react than your testing equipment.
Ummm...ambient air temp doesn't change except with the weather. :D

But: I did several burst of WOT runs on the highway to see where the IAT would go, it went down to 91-94º. Considering the ambient temp was near 90º in the first place, I'd say it went down pretty well for the stock IAT sensor. I also don;t think you can find a faster reacting IAT sensor than the design GM uses, a simple epoxy protected bare thermistor. I can tell you the thermistor the HRSK uses (as well as other metal can mounted thermistors) will not react until the metal package it is built in changes temperature, and the metal of the packaging itself retains heat.

I think most people buy the HSRK because of marketing and word of mouth effect. I'm not saying it does not make a difference in power, but all it does is simply fool the computer to thinking the intake air is cooler than it actually is, leading to more timing and any other effect the Cylinder Charge Bias provides (the bias factor is higher at lower mass flow and miles per hour, meaning the HSRK IAT signals timing retard and cylinder charge temperature bias will have less power robbing effects at low speeds)

Now...I feel I need to study the effects of cylinder charge temperature bias to learn a little more about it all and see what else I uncover.

I'll get this all down in short order here I think.
 

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2007 AWD 3SS
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Discussion Starter #5
All in all, I did find that my AC system external temperature readout reads 5º lower than actual temperature, something I suspected for a while since it never agreed with any of the bulletin billboard signs that have temperature readings that I pass on my daily travels.
 

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2007 TBSS
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Ummm...ambient air temp doesn't change except with the weather. :D


Heres the key to this... its not an ambient air temperature sensor.. it is a intake air temp sensor. so when your sitting still your engine is not injesting ambient air.. its taking hot air off the car infront of you and what is leaked in from the engine bay... etc etc. further the intake piping is getting a chance to get heat soaked and scrubbing off heat into the intake charge.

A faster acting sensor is a great idea.. moving the IAT to the fender well to get a cooler or closer to ambient reading is nothing more than wishful thinking.
 

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'07 TBSS 2WD
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The reason I purchased an HSRK is that the maker of the one I bought has video of him logging the data with the stock set up and with his HSRK. The temperature change is almost instant... it begins to climb while sitting at a light and when he takes off the temp lowers again... I think getting the correct reading to the computer faster is a big help in opening some normally lost power due to temp readings.

BBA- I definately agree with you on the insulation for the washer fluid, it acts like a heater for the air that crosses over it, not to mention heat soaking the air filter. Good idea! Let us know if it makes a difference!
 

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2006 TBSS 3SS
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I can see the new track mod now is to drain the washer fluid. Hahaha. Never thought about the airbox sitting on a preheated tank ! But makes sense.

Thanks for the numbers and I would have to agree with what your results.

I personally dont think relocating the IAT sensor makes much difference. I do think having a faster IAT does. But you a really cant get a faster IAT without relocating it anyway.

The big issue if you look at the design of the airbox is that there is not enough inlet area behind the grill. Even if you open it up I think the truck has to suck air from other "hot" locations. If you went to the trouble of creating a sealed intake and ported it to the factory cold air opening (behind grill) you would starve the motor for air.

Its just a bad design !

I am either going to get a ram air hood or build a custom airbox with a duct down to the passenger front SS air inlet. I dont see any way to get clean air to the stock SS airbox.

Having accurate IAT readings is important. Does no good to trick it. Just need to get colder air to the box.
 

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2007 AWD 3SS
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Discussion Starter #10
The big issue if you look at the design of the airbox is that there is not enough inlet area behind the grill. Even if you open it up I think the truck has to suck air from other "hot" locations. If you went to the trouble of creating a sealed intake and ported it to the factory cold air opening (behind grill) you would starve the motor for air.

Its just a bad design !

I am either going to get a ram air hood or build a custom airbox with a duct down to the passenger front SS air inlet. I dont see any way to get clean air to the stock SS airbox.

Having accurate IAT readings is important. Does no good to trick it. Just need to get colder air to the box.
My thoughts exactly. I removed the little gasket between the passenger side radiator and the grille. I can look straight at the air filter from in front of the truck through the radiator inlet. The back side of the radiator is still isolated, if you were curious.

Short of buying hood with a scoop and air duct to the filter box, my next thought is to open the side of the air box and cut an opening in the fender wall and mate it to the air box, as well as cutting a vent in the inside wheel well liner to match. The thought is it will allow air to flow through the entire airbox from the radiator inlet to the wheel well, to keep from building up a static amount of hot air inside the air box.

Thoughts?
 

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Discussion Starter #11 (Edited)
Heres the key to this... its not an ambient air temperature sensor.. it is a intake air temp sensor.

We know this. This is why I was comparing real ambient temperature to the IAT reading.

The problem with the HSRK is still the air in the air duct is exactly the temp the stock IAT sensor says it is (and I verified that by inserting the thermocouple into the air duct while reading both the IAT sensor reading and comparing it to the thermocouple). This is because of heat transfer from the engine compartment air to the MAF sensor aluminum housing, then to the MAF screen and finally to the incoming air charge going into the plenum.

The HSRK only fools the computer to think the incoming air is not as hot as it really is.

One interesting thing, on the whighway trip this morning to drop off the TBSS at superchips, I was logging the whole trip, and the IAT eventually dropped to about 4º higher than outside ambient temp. Just means we need more flow from outside to the air box to keep things cool when we are not on the highway.

Short of relocating or insulating the washer fluid container, drain the washer tank if you want a little cooler temp to the motor.
 

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2006 TBSS 3SS
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BBA,

My experience with the HSRK (at least the one Vector sells) is that the temps are the same as the stock IAT as long as there is air moving. So I think its an accurate device and is not really tricking the computer. I just noticed the stock IAT gets soaked easier and because it reacts slower does ot work as well.


But your comment "Just means we need more flow from outside to the air box to keep things cool when we are not on the highway" is right on target.

We have a serious flow problems. The engines intake is going to pull air from the path of least resistance. There are more holes in this airbox into the engine compartment than there is opening to the headlight. Even if sealed off I dont think we can pull enough air from that headlight area. If I thought for a second I could get enough air through that front opening I would build a cool airbox in a second.

All our problems are based on not enough flow from where GM designed it to pull from !

Rich
 

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Short of buying hood with a scoop and air duct to the filter box, my next thought is to open the side of the air box and cut an opening in the fender wall and mate it to the air box, as well as cutting a vent in the inside wheel well liner to match. The thought is it will allow air to flow through the entire air box from the radiator inlet to the wheel well, to keep from building up a static amount of hot air inside the air box.

Thoughts?
BBA:you are like a Bloodhound on the trail...you are definitely doing some homework...I have nothing technical to add as this is way above my pay grade
except one thing...use some caution with the location of the air intake... you are thinking one option is the wheel well...I had a 99 Ford F-350 that was an early design...being they had four different air boxes for it...anyway...the one I had drew it's air from the wheel well and ultimately took the motor out at 24 thousand miles...from what Ford said was contaminated air (dirty water) from when it rains,snows Ect, these were their findings not mine...I gotta believe they would have said or done anything to duck out of replacing a Diesel motor at 24/k.


:2cents:
 

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2007 AWD 3SS
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Discussion Starter #14
BBA,

My experience with the HSRK (at least the one Vector sells) is that the temps are the same as the stock IAT as long as there is air moving. So I think its an accurate device and is not really tricking the computer. I just noticed the stock IAT gets soaked easier and because it reacts slower does ot work as well.
The main point I am driving is the GM unit is accurate, the thermistor itself is not getting heat soaked, the MAF housing is and that is the heat going into the intake.

The aftermarket unit is accurate, the difference being the GM one actually tells you the air temperature as it goes into the motor, after the MAF while the relcated one tells you the accurate temperature of the air before it goes into the MAF. That is where the problem lies...the aftermarket thermistor is not telling you what the real temperature is going to the motor.
How much that matters? Well, that's the point, and I would like to reduce the actual air temperature going into the motor as opposed to getting a different reading from a less accurate but more dynamic location.

I guess the hood scoop way is the best, but I really don't want to change the looks of the body work, not to mention how difficult it would be for a painter to completely match the metal flake and color of the imperial blue paint I have.
 

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That is where the problem lies...the aftermarket thermistor is not telling you what the real temperature is going to the motor.
How much that matters? Well, that's the point, and I would like to reduce the actual air temperature going into the motor as opposed to getting a different reading from a less accurate but more dynamic location.

.
Well I cant prove or disprove this theory but I cant imagine there is a significant temp different in moving the IAT uh?? 6 inches from the MAF to the location inside the airbox. There is a lot of air moving through that intake. I am 'guessing' if you measured temps at the filter and at the throttle body you would not find much difference above idle.

Just my theory though and happy to admit I dont have anything concrete to back it up.
 

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Discussion Starter #17
Well I cant prove or disprove this theory but I cant imagine there is a significant temp different in moving the IAT uh?? 6 inches from the MAF to the location inside the airbox. There is a lot of air moving through that intake. I am 'guessing' if you measured temps at the filter and at the throttle body you would not find much difference above idle.

Just my theory though and happy to admit I dont have anything concrete to back it up.
I would believe your theory had I not measured the temperature of the air inside the air duct to the throttle body. It was exactly the same as the IAT reading. (Thermocouples are great, just stick the wire in and measure.)
 

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Discussion Starter #18
Oh, another thought I had was just replacing the MAF sensor with one of the plastic bodied ones like Lingenfelter sells. I think that would definitely reduce the heat transfer effect of the stock aluminum body MAF sensor.
 

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I would believe your theory had I not measured the temperature of the air inside the air duct to the throttle body. It was exactly the same as the IAT reading. (Thermocouples are great, just stick the wire in and measure.)

Well what you just said is not contradicting what I am getting at. You just validated the air at the TB is the same shown on the IAT.

My point is no matter where you put that IAT as long as there is flow, its gonna read the same. So the computer is not being tricked by moving it.
 
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