Thursday, September 5, 2013

Installing K&N Drop in Air Filters into the Q50

Don't do it!!! K&N filters do nothing but allow more silicon /dust / sand into the engine, they turn the engine oil darker sooner and wear out the engine components quicker. I have been an idiot all these years and have fallen to marketing hype. Bravo K&N. I removed all K&N filters from all vehicles last year. Not only has is my oil lasting longer before turning darker, but Blackstone Labs Oil analysis on the Q50 and my GT-R have revealed that the silicon has gone down considerable.

Read this:
and this:

and feel free to draw your own conclusions. As for me engine life is more important than 2-3 more HP at the top of the curve near red line, which is impractical.

Don't waste your time and money, simply buy paper filters the Q50 HEV or non-turbo engine gets no benefit from these these terrible things.

I have been using K&N Air Filters for the last 10 years in all of our cars. In most cases such as the G35 Coupe, EX35, and GT-R, I have found that using the drop-in air filter (like this) is much better than any after-market intake piping + conical air filter combination (like this).

I have tired, compared and contrasted the "intake piping+filter" on the G35 Coupe, Pathfinder, Altima, and GT-R over very long period of time to give them a fair shake, but in most cases, and in all cases of Infiniti cars, the net effect of using an aftermarket air intake + filter has been:

- Engine sound and exhaust sound gets louder increasing the perception of more HP. The reason for this is really because all the baffles are lost by swapping out the stock intake.
- Most of them lose the ability to "ram air" into the engine intake manifold, which the Q50 is actually designed to do.  This is of course unless the aftermarket pipes and air filter drop past the radiator (often called "long ram air intake") and come just behind the front grill. If not, then HP is lost rather than gained.
- Most of these after-market ones (especially the shiny ones that sit completely in the engine called "short ram air intake") soak up more heat than the stock plastic piping and thus make the air hotter going into the car, which actually reduces HP and mpg.
- If the filters are positioned just behind the grill, then get dirtier quicker defeating the purpose of longer lasting filters, end up getting completely soaked in rain, the car wash and ice/snow. Worst case for me has been a carwash in winter, where a filter was wet and froze in seconds, denying air to the engine.
- Most of them do not have an alternate emergency by-pass opening so that if the above were to happen, they could let out the water before it gets to the engine and also serve as an alternate intake for air.

Example of Short RAM Air Intake:
Great to make the engine and exhaust sound louder, lots of heat soak into intake air, reduced ram air effect, Ran those on the VQ35HR engine and net effect I noticed was 1mpg loss and reduced but HP and mpg.

Example of a Long Air Intake:

This one actually genuinely generates more HP, more mpg, and has the RAM effect. Heat soak is reduced. However susceptible to getting soaked in rain, car wash and ice/snow denying air to engine or worse sucking water into engine and causing a blown up block. Notice no by-pass in this setup.
Ran those and noticed considerable butt HP gain, increased engine & exhaust sound, I liked them, but the risk was too great for engine loss.

Example of a good By-Pass built to the mid-pipe joint:

After years of experimenting the best course for me has been to use drop-in air filters for reasons including:

- They let in more air than the stock filters. More air = more oxygen = more fuel = better combustion = more efficiency = more HP when needed or More mpg. More mog is my reason for replacing the stock filters. The nay sayers state that more air = more dust which can pollute the engine. I have run multiple engine oil analysis through and found no increased silicon (sand) in the reports.
- I recharge K&N filters once a year all filters and they all have out lasted the life of the lease or car, which means they pay for themselves at the first recharge.
- Easy to install.
- I trust the army of Nissan engineers with degrees in fluid dynamics and access to wind tunnels over an aftermarket company's pipe bending and welding technician. Besides, it is not the piping that is letting in more air, it is the conical or drop-in air filter.
- 1mpg gain at the least is expected.

Now that the history lesson is over, let explore workings of the intake of the Q50 AWD Sport with the 3.5L engine before making any conclusions. How is the air injected to the car, and how twisted is the path to the air intake manifold.

Remove these 8 clips using a tool or flat head screwdriver and then lift the entire panel upwards.

The first thing noticed is that it is a closed system. The air comes in from the front grill, just above the radiator, but it is angled such that no direct water can shoot into the intake.

Turning the whole intake to the side and upside down we notice the flow pattern for air and the baffles that keep the engine quiet.

The Q50 design has done a good job building the stock air boxes to be closed from the engine side and letting the air take the shortest path to the intake collector above the manifold to avoid heat soak and maximize the ram air effect.

Removing the engine cover, I noticed that there are more cross-balance tubes and also air baffles for to reduce sound, but it is still a straight shot into the engine.

So based on this what are my conclusions? (You are welcome to formulate your own.)

- Infiniti has done a good job with the air flow to ensure that there is a cold ram air effect without the chance of engine flooding with water.
- I could have done without the baffles, but being a hybrid they were going to a quiet engine sound (much like the EX35) as opposed to say the G37 Coupe or FX37. I will compare to a Q50 3.7s later on this week.
- Installing the drop-in air filters made me recognize the need for the intake piping to be extremely flexible.
- The only way to give this car more HP would have been using 3.5" intake piping instead of 3". Also if you stick your head under the back of the car, you will notice that the exhaust piping is 2.5" instead of 3.5" used on G37xS for example. The limitation on this 360HP car is the exhaust, not the intake.
- Therefore, it is drop-in filters for my Q50 unless an aftermarket manufacturer can prove that Drop-in (not stock) vs. Long Ram Air Intake with proper by-pass will be better in both summer and winter.

How to Install K&N Drop-in Air Filters.

K&N's website does not list any filters compatible with the Q50 Hybrid. However upon removal of the stock air filter, I noticed it is the same filter used in the Versa & Cube. Therefore the K&N Replacement Filter number is 33-2375 and the cheapest place to purchase them is on Amazon at $39 a piece. You will need 2 of them.

Comparison of stock & K&N Filter size.
33-2375 is a ft for Q50 Hybrid

Comparison of stock vs K&N Filter looking into the sun.
Light comparison of Stock vs K&N filter

Step 1: Make sure the engine is completely cool. Really, Wait for this! Open the hood. You do not have to remove the intake plastic as shown above or the engine cover, I did that after the fact. Unsnap the 2 clips on the air box.
Open these snaps

Step 2:  Push the top of the intake piping side backwards from the top and let the intake piping bend down considerable, but not so much that it pulls on the MAF connection. You will need some force.
Removing airbox cover

Step 3. Lift the entire assembly up, as it is secure by 2 plastic tabs that slot into loops at the bottom, make sure that the tabs do not tear the filter, this is important while reinstalling them. Place it on the engine cover. Examine the 2 tabs and 2 loops and think about refitting.
2 tabs on the airbox cover

Step 4. Remove the stock filter and place the k&n filter into the air box with the fins side into the airbox.
2 loops into which tabs go.

Step 5. Bend the air intake piping down again and bring the cover back at an angle. Without letting the tabs scratch the filter, make sure the tabs go into the 2 loops first. Both if them. This is not very easy it requires some wiggling. Then work the filter and airbox cover back into place.

Step 6: Snap the clips back on. Note that the rubber used on the K&N air filter surround is stiffer than the one on the stock filter, so the clip might snap open immediately. Wiggle the filter a little bit and snap them.

Repeat procedure on other side.

K&N Drop- in Filter installed.