Here’s one for the techhies amongst you:
After the decatted manifold & Y-pipe were fitted to my car, two problems were apparent:
1) The induction pipe was being heated by the manifold.
2) Hot air was being blown towards the filter head by the radiator cooling fans.
The result of this was that at lower speeds, the IAT was as much as 40°C above the ambient (outside) air temperature. It was not until speeds of 60-70 mph were achieved that the difference in temperature (ΔT) was reduced to below 10°C. These temperatures were recorded using a diagnostic meter plugged into the OBD2 port. Ambient air temperature (AAT) was read directly from the dash thermometer.
Following Boyle’s Law, the effect of the intake drawing in hot rather than cold air is therefore to reduce engine performance.
In order to isolate the induction from as much hot air as possible, I made the following modifications:
Using a roll of aluminium foil coated insulating mat, I made a double thickness heat shield between the manifold, radiator fans and the filter. I also wrapped the induction pipe in a layer of foil, doubling on each wrap to ensure maximum coverage. In order to further insulate the induction I then fully covered the induction with the exception of an opening for the air scoop before taking readings The foil was secured in place using ordinary bathroom silicone sealant.
THIS IS NOT MEANT TO BE PERMANENT AND "SCRAPHEAP CHALLENGE COMMENTS ARE WELCOME!
To quantify the effect of the insulation, a thermocouple was installed into the intake pipe close to the MAF sensor and connected to a digital readout located inside the vehicle.
![]()
![]()
For the stationary readings, the car was warmed up to full operating temperature and driven until the IAT stabilized. The car was then parked with the engine running and readings taken every 15 seconds. After the final temperature had stabilized, the car was again driven for a short period until the temperature stabilized and the test repeated.
For given speeds of zero, 20, 30, 40, 50, 60 and 70 mph, temperature reading of AAT and IAT were recorded at 15 second intervals over a 5 minute journey. For accuracy, each test was carried out 3 times, with 1-2 mins between runs. The engine was running at a temperature of 25° at the start of all of the tests and a constant speed was achieved by setting the cruise control (not possible under 30mph).
An average for each of the 3 tests for each given speed was calculated and graphs were plotted for ΔT.
The results are as follows. For low speeds up to 40mph the IAT took as long as 2 minutes to stabilize to 2-3° ΔT. For higher speed, the ΔT dropped very rapidly and stability occurred within a minute, and only 1° ΔT.
So, in conclusion, the benefits of insulating the intake with a heat shield are overwhelming.
![]()
![]()
After the decatted manifold & Y-pipe were fitted to my car, two problems were apparent:
1) The induction pipe was being heated by the manifold.
2) Hot air was being blown towards the filter head by the radiator cooling fans.
The result of this was that at lower speeds, the IAT was as much as 40°C above the ambient (outside) air temperature. It was not until speeds of 60-70 mph were achieved that the difference in temperature (ΔT) was reduced to below 10°C. These temperatures were recorded using a diagnostic meter plugged into the OBD2 port. Ambient air temperature (AAT) was read directly from the dash thermometer.
Following Boyle’s Law, the effect of the intake drawing in hot rather than cold air is therefore to reduce engine performance.
In order to isolate the induction from as much hot air as possible, I made the following modifications:
Using a roll of aluminium foil coated insulating mat, I made a double thickness heat shield between the manifold, radiator fans and the filter. I also wrapped the induction pipe in a layer of foil, doubling on each wrap to ensure maximum coverage. In order to further insulate the induction I then fully covered the induction with the exception of an opening for the air scoop before taking readings The foil was secured in place using ordinary bathroom silicone sealant.
THIS IS NOT MEANT TO BE PERMANENT AND "SCRAPHEAP CHALLENGE COMMENTS ARE WELCOME!
To quantify the effect of the insulation, a thermocouple was installed into the intake pipe close to the MAF sensor and connected to a digital readout located inside the vehicle.
For the stationary readings, the car was warmed up to full operating temperature and driven until the IAT stabilized. The car was then parked with the engine running and readings taken every 15 seconds. After the final temperature had stabilized, the car was again driven for a short period until the temperature stabilized and the test repeated.
For given speeds of zero, 20, 30, 40, 50, 60 and 70 mph, temperature reading of AAT and IAT were recorded at 15 second intervals over a 5 minute journey. For accuracy, each test was carried out 3 times, with 1-2 mins between runs. The engine was running at a temperature of 25° at the start of all of the tests and a constant speed was achieved by setting the cruise control (not possible under 30mph).
An average for each of the 3 tests for each given speed was calculated and graphs were plotted for ΔT.
The results are as follows. For low speeds up to 40mph the IAT took as long as 2 minutes to stabilize to 2-3° ΔT. For higher speed, the ΔT dropped very rapidly and stability occurred within a minute, and only 1° ΔT.
So, in conclusion, the benefits of insulating the intake with a heat shield are overwhelming.
