Job 5 – Upgrade Cold Air Induction Kits
These vehicles utilise the Mitsubishi new style Hot Wire MAF sensor. These vehicles, as we know run very rich from factory.
There have been a lot of DYI customers fitting CAI (Cold Air Induction) and SRI (Short Ram Intake) kits to there vehicles with mixed results.
As can be seen from our own efforts, this is understandable when you look at the dramatic differences it makes to the Air Fuel Ratio’s of the vehicle.
We first after doing our back to back test on the baseline dyno run, fitted a K&N panel replacement air filter to the vehicle. We did not include a dyno printout, because essentially, we got no increase or decrease in power from the unit. We explain this, by the sheer fact the stock air intake box set-up, is quite restrictive in factory form.
It has a very small opening at the front, with holes drilled into the base around 1/3rd the way back as it sucks air from within the engine bay, and is also heated up by its proximity to the radiator.
The size of the set-up is virtually fixed in the amount of air it can pull at one time. The K&N panel filter, whilst it can flow better is being hampered by the fact that it cannot get any more air being pulled through the factory inlet setup.
The next step was to manufacture a new complete cold air kit for the vehicle. We did this by utilising the K&N Apollo Cold Air kit. We replaced the factory piping, with a new 90 degree silicon elbow which utilises smooth piping. We then cut out of the factory air box the piping that the MAF sensor screws into, giving us an easy 30cm of length of smooth piping.
This was cleaned and buffed, making it a very easy DIY job. This was fitted into the silicon elbow, and we then placed the enclosed K&N air box onto the end of this.
At this point we know have either a SRI system for those wanting that type of system, or can add the additional K&N piping to pull cold air from the front bumper location.
We did both systems, and surprisingly, found that both the SRI and CAI set-up produced the same horsepower levels. Below are the dyno graph printouts.
We tested three variations of air induction kits being
(1) Utilising the Apollo kit as a SRI system sucking from the larger air inlet, pulling air from the rear of the engine bay
(2) Adapting the pipe work from the K&N Apollo kit onto the factory air inlet tubing for a cold air feed
(3) Utilising the full setup of the K&N Apollo Kit and sucking form the inside guard of the vehicle for a complete cold air feed
The results were interesting, especially when you do a comparison against the same tests done on the 4B12 Mivec engine.
We also took the opportunity, utilising EvoScan data logging technology, to record the average air intake temperature from each test.
The first test resulted in a loss of horsepower and torque over factory with the short ram intake system.
The average air intake temperature was 40 degrees Celsius.
Looking at the dyno graphs it shows that the air/fuel ratio went richer overall which is more than likely the main reason why the vehicle lost power/tq.
With tuning there may be possible gains over a stock air box set-up but the high intake temperatures would never be an optimal situation.
The second test resulted in virtually an identical horsepower / torque result which is not surprising considering we have really just replicated the factory air box set-up.
The average air intake temperature with this system was 36 degrees, which we can take as the factory average as well.
We put part of this down to the factory system utilising heat off the radiator to provide a minimum / constant air temperature.
The third system, was with the full Apollo kit with the piping sucking air from inside the front guard.
The average air intake temperature dropped down to 30 degrees, even going as low as 28 degrees.
The vehicle produced a slight gain in power / torque.
Once again, the air fuel ratio’s richened up over the factory levels indicating that great power gains are obviously available.
What is interesting, is that in comparison to the overly rich tune on the 4B12 engines, which leaned out with the fitment of the very same cold air induction kits, the 4B11 motor richened up instead.
We believe this is due to the difference in the engine capacity with the larger engine pulling a greater volume of air with the less restrictive air intake system compared to the smaller 2.0 motor.