Turning Down The HEAT!
Summer winds down, bringing cool nights to Michigan. That means cool air in the mornings! The last few weeks I've notice the the Camaro is incredibly peppy in the morning. Cool air means increased performance, but the Camaro seems more responsive to cool air than previous cars I've owned. So I decided to do a little digging and a little testing!
So one fine morning with the outside air temperture at 50 degrees I plugged my Dashhawk in and found that the intake air temperture (IAT) was only 54 degrees. No wonder the car feels so peppy! Usually it seems like the IAT temps were in the 80's or 90's. But his morning the IAT was staying nice and low... So I decided to do a 0-60 test. And to my amazement instead of the 6.0 seconds I have always gotten with the car I got 5.6 seconds! WOW! No wonder the car felt so different on these cool mornings!
This kind of got me wondering why my IAT temperture was only 4 degrees above the acutal outside air temperture but at other times it would be 20 to almost 30 degrees above the outside air temperture. The stock air box does have a snorkel that reaches up to the front of the car bringing in fresh air and the fact that my IAT was only 4 degrees above the outside air showed that this design really did work! So why were there times when the IAT was so much higher? I started doing a little reading. I learned the the IAT sensor was actually integrated into the Mass Air Flow sensor (MAF) which is located in the intake tube right next the the air box and right next to the motor. I also learned that the MAF/IAT sensor was suseptible to "heat soak"... Now heat soak may not be the absolute correct term but I sure found a lot of people using the term and talking about how their MAF/IAT sensor was suffering from "heat soak".
What they were describing was how their MAF/IAT sensor would heat up and then give a very inflated IAT reading, telling the car's computer that the air coming into the engine was higher than it really was. The computer then does things like reduce the timing which in turns reduces performance! Hmmmm, that sounds kind of like was i was experiencing. Time to do a little testing.
I took the car out for a drive and then stopped the car. The IAT was reading 81 degrees on a 65 degree day. I turned off the car and the IAT and the engine coolant temperture (ECT) both begain to climb... and rather rapidly! I let the car sit for about 20 minutes from the the time I stopped. I checked the tempertures again. The ECT had actually come back down BUT the IAT temperture had shot up to 122 degrees. WOW. Starting the car brought the IAT temperture back down to 100 degrees. I then took the car for a drive and found that it took 3 to 4 miles of driving 45 MPH to bring the temps down into the lower 90s! Still a bit higher than the 81 degrees! This basically confirmed for me what I had been reading, that the MAF/IAT would get extremely hot sitting basically next to one very hot motor. Once the sensor is hot it would cause the IAT sensor to read higher than the actual air. It also appeared it does takes quite a while for the sensor to recover and give a more accurate reading of the intake air temperture.
Here's a little video I made later showing this...
After digging a bit more it seemed that the solution was to add a stand alone IAT and locate it in a more sensible spot. Sounded good to me... so at this point I decided to call an expert! Yep, I called Scott Hoag at MRT! I quickly explained the situation to Scott and he agreed that adding a stand alone IAT sensor made a lot of sense and could really improve peformance. I asked Scott if he would be willing help out. Again, Scott agreed and I was off to MRT!
The installation of the new IAT sensor was very straight forward. First thing was to decide where we should locate the new sensor. We decided on the far side of the air box lid. The new sensor was a "push-in" type, so we simply drilled a hole, installed a rubber groumet and installed the sensor. Next step was to locate the proper two wires for the stock IAT. I had found some references to the MAF sensor wiring so by process of elimination we determined that the stock IAT wires would be the Tan and Blue wires. So we snipped the two wires and verfied that the stock IAT sensor was no longer working. It was then just a matter of wiring up the new sensor!
Now during this time the car had been shut off for probably close to an hour. The hood had been open for 30 minutes. The temperture inside the shop was 65 degrees. Before we actually completely finished the wiring we decided to check the temperture reading from the stock IAT and the new IAT sensor..... The new sensor had been in place for while so it had come up to temperture... The results were pretty consistent with what I had been finding. The stock IAT sensor was still reading 97 degrees while the new sensor gave what appeared to be more accurate reading of the air temperture in the engine bay of 72 degrees! So my uneducated guess is the stock IAT sensor was reading the heat coming off the intake tube and MAF sensor while the new IAT sensor was in fact reading the actual air temperture.
 New sensor in air box lid |
 Actual sensor |
 Completed! |
 Stock IAT |
 New IAT sensor |
But now for the real question... does all of this REALLY MATTER? With my previous 0-60 tests I had shown that this car really responds to cool air, but would getting a more accurate reading of the actual air temperture really make a difference? While not a scientific method for determining if in fact the new sensor made a performance difference, I figured a good test would be to run the car at the drag strip. So off to the track I went!
Now on previous days at the track I've noticed that the IAT would be reading anywhere from 15 to 20 degrees above the outside air temperture even after letting the car sit for an hour! Also I found that as i sat in the staging lanes the IAT would quickly climb as the motor heated up the senor. This time however the IAT was reading only 5 degrees above the outside air temperture. I also found that the IAT temps did creep up but VERY SLOWLY as the air in the engine bay started to warm up, as opposed to the stock IAT which appeared to be reading some of the radiant heat from the motor.
So it was clear to me sitting at the tree that my new IAT was more accurately reflecting the air temperture but it still remained to be seen.... would it actually improve the cars performance? On this particular day the air was in fact a bit better than previous occcasions so I would have expected to see a small improvement over past times. The best I had managed at this particular venue was 14.69 @ 94 MPH, with a best 60' of 2.14 seconds. Based on the weather conditions I would have expected a .1 to .15 improvement in my ET. So sitting at the tree I'm thinking that anything below a 14.5 would be outstanding...
The 3rd amber light comes on and I go.... the car hooks and feels good! IAT is reading 70 degrees and running 27 degrees of timing! That's 4 to 5 degrees more timing that I typcially see on a run where the IAT is in the mid to upper 80's! I also listened closely to make sure I wasn't hearing any signs of pinging. (As a precaution I have been running premium gas. If only I could monitor the knock sensors! But that's another story.) So the car felt great the entire run... Heading down the return road a number of people gave me thumbs up... perhaps and omen that I had a good run? I sure hoped so!
I park the car and walk over to pick up my time slip. The whole time I'm hoping to see something, anything better than a 14.5... I get my slip and quickly find the 1/4 mile ET... 14.323! And the trap speed has shot up to 97.75 MPH! WOW! Needless to say I was PUMPED! I then looked at the 60' time. The car also pulled a new best 60' with a 2.08! That's on those big 20" stock RS wheels and tires! And that's just launching off of idle with the traction control on! WOW!
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Next step was to put the car on the dyno and see if there really is any measurable difference. Looking at the dyno sheet you can see a nice bump in the low end torque! No wonder the car feels more PEPPY!
 Before and After showing the increase in low end torque. |
Needless to say I think the verdict is clear, the IAT Relocation Experiment was a HUGE SUCCESS! I have to give a special thanks to Scott Hoag and MRT who really helped make this experiment happen! Thanks, Scott!!!
