The Myth about HP Gain with Aftermarket Airfilter

Not uncommon, on my TR when I was looking at changing, some mech, and of course the delaer said you will find no change. The key ( I was told) to have it changed often to make sure it was clean and clear for the air to flow through.

 

In a carburated engine a K&N can increase hp IF you rejet the carburator(s) when you change from stock to K&N. I now that for a fact as a result of dyno-tuning on several motorcycles I have owned over the years. Without the jet change, you will get a decrease in power as the mixture is then too lean. In a computer controlled FI engine,you will need to run the engine a sufficient period of time for the fuel mixture to adjust itself to the increased airflow after installing the K&Ns before dyno testing. If you didn't, thats why the stock filter showed a little more power. Next time, after intalling the K&N, run the engine at various RPM for at least 30 minutes before pulling a dyno test.

 

Ok, get a driver that can lap consistently within 2or 3 tenths of a second to go and do some laps in your car.

Then fit the filters, and send him out again..........

I have done this on several occasions with 360C cars, and the times get better by a tenth or two per 60 sec.

 

Air filtration is not Rocket Science. The only way to increase airflow (and therefore bhp) is to:
a) increase the surface area of the element
b) reduce the filtration of the element

Be very wary of smaller than standard air filters.

 

Let me shed a bit of light from a different angle. As I am in the process of developing a different filter housing fot the 2 valve 308 and Mondy, and the 4 valve 308, I did quite an extensive flow bemnch test, with the following results:
Both air filter houseings had K&N filte elements. Testing was carefully done, running the tests back to back, double checking, etc. I'm bankrolling this venture, so I damn sure want to knowif the tests are valid!
Useing a common test range, mounted on an adaptor that simulated the Bosch Distributor top, the ilters came up with the following result:
4 valve '85 308 with a 3/8" spacer between the element and lid (I learned this produced 3CFM in previuos testing on the TB's ) Flowed 89%
the 2 valve Mondy (same as the 308) flowed 71%
Now is where it gets interesting. I had not liked the looks of the 2 valve set up, as I felt the element was crowding the Bosch opening. Testing seemed to show that to be true.
Now the differance between the elements is, the 4 valve is about 5/8" longer, but half as thick, same width.
So to test the elements against each other, as part of the learning, I placed the 4 valve element in the lower houseing, leaving the top off. It flowed 96% with a 20 degree rise in temperature seen in the intake air.
Pulling that out, I was ready with the 2 valve element, and a foam strip to seal the short end. It flowed 96.5%! but was 23 degrees on the intake temp, which indicated it had to workmore to get thru the deeper pleats.
The point of this rant, is it may not be the filter. It may be the way it is mounted, the air source, etc.

 

Matt: Interesting stuff! Thanks for sharing.

 

Of course engineering isn't quite that simple as there can be multiple ways to achieve the same goal. It's like my Dad used to tell me that growing up, people said that everything that could be invented had been invented. Fortunately, since the 40s a couple of people have found better mousetraps. hence there are foam air filters, paper air filters, cotton gauze air filters and those crazy UFI fuzzy filters. Surely you don't think that all of these operate on the same restriction vs. filtration curve.....

 

If i had a Ferrari i would keep everything stock. But in any other car, maby you don't get too many extra horsepoer, but the sound improves! That makes it wourth the 100-200 dollars.

 

Like I said in another thread on this issue, we got similar results with several Jaguars -- no difference in HP between the "high flow" air filters and stock. It ain't there. With all due respect to the MC crowd, it's probably the re-jetting that is giving you the HP boost, not the air filter. Plus, as someone else noted, if you are not increasing the size of the filter, the only way to get more air flow is to decrease the amount of filtration. That means more dirt gets into the engine -- not a good thing for precision engines like Ferraris.

IMHO, I'd just stick with the regular air filter and look for more HP somewhere else.

 

duh? Even a mental midget can figure out that more airflow alone will not give you more HP without more fuel added to that increased air. More airflow alone will result in a too lean mixture which will not only decrease power, but will also cause extra heat and possible burnt valves. The classic proper air to fuel ratio has been 12.5 parts air to 1 part fuel for decades. Leaner running modern engines tend to use between 12.8 to 13 parts air to 1 part fuel for an optimal ratio. So, if you change anything that increases the air flow into the combustion chamber, whether it be a K&N filter, port and polished intake, plenum or runners, bigger valves or whatever, you also have to increase the fuel in order to maintain the optimal air/fuel mixture. With carburated engines its easy, increase jet sizes and adjust the mixture. In mechanical FI cars, there are several adjustments you can make to obtain the proper air/fuel ratio. In modern electronic FI cars, it is more difficult as their range of adjustments are limited for emission purposes and has to be done through chips and/or reprograming.

 

That dyno run was done on a 360, right?
The 360 has a mass air flow sensors, fuel injection, and a computer to adjust the mixture between the two.
It wasn't running lean; otherwise a fault code would trigger the check engine light indicating that a stoichiometric ratio couldn't be met.

Aftermarket air filter manufacturers put a lot more money in their own pockets than they do horsepower under the hood. And I have 3 K&N's on my 330.

 

I agree that K&N, Airhog and other aftermarket companies stretch the truth on their claims for increase HP. However, increased airflow accompanied with the proper amount of increased fuel will give you some increase HP, but probably not as much as claimed by the company selling the filter.

 

I wouldn´t be to sure on this. I can only vaguely remember my lectures in thermodynamics, but there was this h,t-Diagram .... .... huhm, if your combustion takes place at a higher pressure than the amount of energy that is used for propulsion instead of directly heating the environment is higher. For the same reason 100 mph at 4.000 rpm require less mpg than 100 mph at 8.000 rpm (in addition to the lower friction...).

Well, the only thing I remember for sure is

higher temperature of combustion = more mechanical power
higher pressure of combustion = more mechanical power

 

A guy at EuroStyling (UK importers of BMC) told me that a pair of BMC Carbon Fibre Airboxes will guarantee me at least an extra 20HP. Ive compared the dimensions of these airboxes with the stock ones on my 512TR and it turns out that the BMC's are the same length as the stock, but only three quarters the width. Surely this would suffocate my engine?

 

the hp gain with air filter could be verify only while driving because of dynamic effect.

i also have bmc air filter on my 348, and i feel a little difference while driving fast...

 

It appears from your graph that the air fuel ratio (AFR) on your car is running at 12.0 to 1, way to rich for a NA motor. It suggests that either there was insufficient air flow (fan capacity), or the 360's are programmed way to rich, or a problem with with your car. Either way, there is a significant power increase to be had getting the AFR right. The ideal ratio for a NA motor is 13.2-13.6 to 1. Leaner doesn't impact power much, but can cause the motor to seize/detonate, while a richer mix kills power noticebly.

 

For some reason 360's are programmed to run at 0.800 lambda at WOT.

Michelotto re-set the N-GT cars to run at around 0.888 at WOT.

I've sat in both 360C and N-GT with SD2 in my lap to verify this too.

Some cars respond better than others, but I urge anyone to try a 550 before and after. Even the most cushioned buttometer can detect the difference.......

 

Ah, I suspected as much. The 550's earlier ECU gives the desired result and leans out the mix, resulting in a noticeable and demonstrable increase in power. I my case it was almost 15kW at the rear wheel.

 

Stephens, if the K&N gives increased airflow, then the ECU will need to richen the mixture, not lean it! More air allows you to mix in more fuel to get a bigger bang and thus more HP.

 

I had an experience with a K& N in a Chevy Tahoe. It was just seat of the pants, no dyno involved but I did notice that the engine hp curve shifted lower by about 200 rpm so it started making more power sooner

 

Maybe not on a 360, but that is more a function of the stupidly rich mixture that is being run.

 

The ECU on the 550 is not that sophisticated, thankfully. It doesn't richen up the mixture, so produces more power. if I have time I will post the printouts showing what happens on the 550 to the AFR.