When this article was originally written, it described how to fit a generic pod air filter to your Magna/Diamante. Mark Thomas of RPW wrote in, saying that fitting a generic filter was not a very good idea:
The Magna air mass sensor registers the amount of air coming into the motor and tells the computer to adjust the fuel curve accordingly richer or leaner. The MAS unit registers the air via ultrasonic waves that pass through the honeycombed section. There is also a section surrounding the honeycombe section which bypasses the honeycombe section which is not measured air.
The fitment of a traditional rampod cone / round shaped filter causes a swirling action of air which in any other application is beneficial to the air flow of the vehicle. Unfortunately this swirling action promotes a bad running problem on 90% of Mitsubishi’s.
In order for the air to be passed evenly between the honeycombed section of the MAS unit and the bypass sections the air must come through straight with no tumbling action. When it is being tumbled or swirled it tends to bypass the honecombe section and go through the path of no resistance - the bypass section which the computer then tells the car it is getting less air and in most circumstances the car runs lean or can sometimes run rich. The end result though is that it will eventually damage the engine.
K&N released a specific K&N Rampod filter to suit the Mitsubishi MAS sensor units which has a specific adapter plate that is not round but is Oval and is the same shape as the MAS unit. Secondly the filter is a very large and flat / oval shaped filter that smoothes the air out and promotes a more accurate MAS sensor system. This is 100% guaranteed to not cause problems with the MAS and does not harm emission controls.
If K&N had of thought a cone shaped filter would have done the job they would not have made a specific filter for this application that is not suitable for any other model vehicle.”
David Thomas
And indeed, the new filter, while altering the power distribution of the car, was not making the car run at it’s normal efficiency. While there was a stronger midrange surge and a slightly higher peak power change, the idling had deteriorated and the car was showing signs of running rich.
Original Filter:
New Filter:
After fitting the filter supplied by RPW the change was immediate - the idling had improved and the power flow was much better - a more steady curve. There was still a loss in low-end power (as happens with this sort of modification) but there was even more guts in the mod.
There are two real plusses about this kit - the first is obvious - as David explains, this is a filter specifically tailored for this sort of engine. The other is the adaptor - it’s a much better unit, which is much more air tight. The filter also looks a lot better - it is bigger, more purposeful looking and the top is finished in chrome.
(I think this one might be a few decibels louder than the last one…. and it does have a better bark to it). MkII - Thanks to RPW
How to fit: It’s very easy really. The stock airbox can be removed in no time - it’s a simple matter of unclipping it and removing a very screws. The adaptor then bolts into the place of the airbox. Slide the filter over the adaptor hose, tighten the zip tie - and you’re done. Well, not quite. The RPW kit comes with a universal bracket to hold the filter stationary (as it isn’t connected to the air intake - it will flop around and probably break something, or itself). We’re still making do with our trusty bit of tin - ’til we get around to making something a little more aesthetically pleasing.
You may note that I have left the front half of the airbox on. This was done for two reasons - 1. to use it as a heat shield, to deflect some of the hot air rising from the manifold, and 2. as I’d like to hope that the intake is still sucking in some cool air.
Some sort of alternate cold air induction system will be installed - possibly a combination of bonnet vents (flowing air into the filter, and out from the radiator area) and a pipe from the front of the car. I would even like to integrate this into the design of the front bar - if it can be done without ‘cheapening’ the looks of the car.
I have read a lot of discussion about the virtues of the original airbox and panel filter setup. I personally have my doubts about the stock cold air intake - as it draws air from above a hot radiator, under a very well sealed bonnet. If anyone has done some airflow testing I would love to see it.
What else? You could move the battery (to the boot for example) and run an inlet pipe to the area behind the headlight. Then add a heat shield (made of perspex or similar), and perhaps some cold air induction (from above, below, or both). The area behind the headlight should be good for air flow - it is where many other factory and aftermarket intakes draw their air. Once again, your only problem is finding an air flow sensor adaptor (or adapting the original - if possible) and not having an intake resonator. Intake resonators are something of an enigma (which I am trying to learn more about) - but seem to be better left ‘on’ (power may be lost when they are blocked or removed). Apparently some companies are now making intake pipes which include resonators.
What to expect from this modification: I didn’t have my car dynoed before and after, so I can’t give a precise kw/hp increase. In any case the effectiveness of the filter also has a lot to do with other mods - from air intake to exhaust to fuel modifications and so on. It would vary as to what your car has had done to it already. A change in engine management (aftermarket computer) is also required to get the best out of all your modifications - as they will change fuel/air delivery to suit.
You should expect to find at least a handful of extra kw/hp on the dyno chart.
David claims that the kits have been dyno proven to increase power by 5hp (at the wheels) - with no other mods (7-8hp with other mods).
There was a definite power increase (nothing huge), though, as I have noted, there was a definite change in power distribution - ie: when the power arrived. Air filters, like most ‘air’ modifications, rob from the ‘low’ and give to the ‘mid to high’. There is now a little less power at the beginning of the power curve (when you first put the foot down) and a strong ‘power band’ has developed (kicking in at around 3500rpm). I should add - this is in conjunction with a cat-back 2.5″ system (top muffler removed, hi-flo muffler at the rear).
Noise: louder, but hard for me to judge (as the noise of my exhaust would drown out a lot of it anyway!). With the bonnet up you can hear it - the filter is very ’slurpy’, and roars when a hefty dose of throttle is applied. The overall noise of the car now includes a hiss. Don’t expect the degree of intake roar you hear in many other cars - the Magna/Diamante has superior sound deadening under the bonnet so it cuts a lot out (if you’re really stupid you can remove this). Manual cars may notice it more - as higher revs can be sustained.
Please send me your input - I am more than happy to add to this article. Articles on other tech tips are especially welcomed.
I do not accept responsibility for any damage you to do yourself or your car after reading these tips. Please use your common sense when tinkering with your vehicle. If in doubt, consult a certified mechanic.