I just changed my K&N drop in filter out for a 'custom' K&N cone filter and noticed something interesting.

First off with the drop in filter I had my A/F tuned to a solid 11.5:1 in forth gear from about 5k -7.5k. I pulled the airbox and added an adapter to my MAF sensor and through on a fresh 4" K&N cone filter. I kept the black plastic accordian section that connects the compressor inlet to the MAF housing because I heard stories about the vibrations screwing with the MAF sensor readings. So I just have an open air filter on now, with the stock airbox scoop, no other changes were made.

I went out to do some logging and noticed right away that my A/F ratio which used to be a solid 11.5:1 @ WOT was now in the mid-high 10s. This to me means I'm not getting as much air with the open cone filter as the stock box & drop in... is that a correct assumption?

So I did a couple of tuning runs and made some adjustments. Got the A/F back up to around low 11s but I wasn't feeling the power like with the stock air box. The weird thing was that I wasn't getting ANY knock either so I added some timing.

Even with the additional timing and leaning the car out it still felt soft and weaker then previously.

Another interesting thing I noticed was that my boost was now HIGHER then with the stock airbox (as recorded by my GM 3bar map sensor). I even turned the boost down before I started logging because I was expecting to be leaner with the intake. Normally I run 23psi spike setteling down to mid 20's by 7k. Now its spiking to mid-high 23's, sometimes 24.5 and ending up at the same mid 20s by 7k. Again this was after turning the boost DOWN before driving and having no knock either.

DOes anyone have a simular experience?

 

I had the AEM intake and I went back to stock with an HKS drop in and I noticed better idle and it seems to pull better.

 

You are likely not only flowing more air, but the conical intake is making more karman vortecies which in turn run you up higher in the MAF load cells. Conical intakes will likely stick you in 260-300kpa cells even at only 21psi.

 

What octane gas are you using in order to run @ 11.5:1 in 4th gear?

 

Thats exactly what happens.. I logged this earlier on..

What is even more odd is its not a linear increase.. It happens at low to midrange RPM's, and gets "back to normal" at the higher RPMs.. So you'll very easily overrun the load at low rpms and peak torque, and then drop down to something normal as you get upstairs..

This is what makes some intakes difficult to tune, as the airflow rate changes, its behavior changes, and can be a little unpredictable.. (this is something Tuners are ALWAYS fighting with aftermarket intakes, and which many recommend specific intakes that they already have tuned before, or the stock Airbox)

The stock Airbox is good to over 400whp.. Same with the stock Intake pipe.. So generally most of us who have been through this before tell people to just leave it stock until there's a specific need to change it. At the least get a better higher flowing air filter..

 

The stock airbox lid on mine approximately doubles the inlet restriction as measured by the barometer, so on the stock setup it is probably worth cutting it back and keeping some shielding from the radiator fan and the exhaust manifold.

There was data published on the MLR which showed that K&N cone showed the highest airflow reading, followed by stock airbox, followed by APS cold air kit. As above, I don't think this reflected actual airflow changes, just change in calibration of the airflow meter. Interesting that the increase in readings with a K&N cone onto an adapter is reproduced here. There are conversely threads on the MLR with dangerously lean AFRs with HKS induction cones.

 

Yep, Thats actually an accurate statement, the cone filters and MAF pipes alter the airflow readings, the increase in power actually is because in some cases the upper ranges are actually lower than stock, and in turn cause the car to run leaner.. BUt in the low to midrange region, it reads higher, and therefore runs richer.. so you feel the car loses power down low, and gains power up top.. Whats worse is there are several things going on that will affect the airflow through a cone filter.. The location of the filter is in a low pressure area as it is, so driving and other factors affect that low pressure area and an affect the readings accordingly.

The baro readings in the airbox don't really measure a true restriction, only that its effectively drawing air into the box, without the airbox the baro sensor isn't really effected, but the restriction in reality is not a concern until you are moving more air than the MAF is calibrated for anyway... It definitely isn't a big enough restriction until your making over 400whp And the easy solution is to use a holesaw and cut a few 2" holes in the cover so it can draw air in from something other than the snorkle.. Unfortunately you end up drawing hot air into the mix from the radiator wash..

 

Also larger MAF pipes tend to decelerate the rate of airflow, so it moves slower through the metered portion of the MAF, hence the severely leaner readings on some setups..

 

Hahah I noticed the same thing, but unfortunately I could not put stock box back on because of my custom upper pipe to fit stock battery so I had to stay with the cone. Some days I come out car feels fast as hell and other days I am like who the hell changed my map lol, but since winter is coming that cone filter will feel really good hehe

 

MalibuJack, why doesn't the baro reading measure restriction? It is a classic method to use a barometer pre-turbo and at stages through the inlet tract to the fresh air to see where the pressure is being reduced and to avoid reductions as much as possible. If you remove an upstream restriction (and it is only the lid not the base of the box) and you get a higher pressure in the pipe then it appears to me that I have at the same temperature a 5% higher air density. Although the temperature might go a bit higher, I don't think when moving it is enough to offset a 5KPa increase in pressure pre-turbo.

To get 280 KPa post turbo, then the compressor has to work at the following pressure ratios:

91 KPa with lid on... 280/91=3.08
96 KPa with lid off... 280/95=2.95

So I spin the turbo slower to charge my engine with the same air mass, I run the compressor in a more efficient area, I open the wastegate more and improve VE. I probably move the knock threshold favourably for a given air mass too and might get more timing.

By removing the airbox lid I had to reduce my wastegate duty cycle to keep the same boost level, all across the range, but most noticed at the top end.

Whilst a chassis dyno isn't ideal for comparing air inlets, removing the lid of the airbox gave about +15 BHP with the same AFR.

There was a thread on here that showed pressure readings in the inlet with no deflection at something like 500 WHP. I don't think the results are valid - look at every Evoscan log - the baro drops as the airflow increases because the stock setup is restrictive. A bigger turbo may still be efficient to cope, but maxxing out the stock turbo's airflow really reveals the inlet restriction I reckon.

 

The gains are always good when you remove a restriction, but you will get a measurement anywhere you put that sensor where there's an inlet and outlet.. Only the airflow through the box is matched to the capability of the MAF, thats what I had meant..

My entire point was more intended to say its really not worth putting on an intake or cone filter until you need it.. If your producing 350whp, You probably won't see any significant gain by switching.. If your producing 400whp or so, you will see more gain because you are at the point where it begins to act as a restriction.

But the MAF system is calibrated for these components, and changing it does throw it off.. I would prefer to draw cold air from the snorkle than low-pressure and hot air from under the hood..

The reality is it doesnt matter, its just $150 spent thats not necessary as an early mod..

 

Thanks for the info guys.

I am going to see if I can tune the higher load cells like suggested and get the A/F curve I'm looking for, then run the car at the track. If I don't see track results I'll put the stock box back on there.

 

http://www.lancershop.com/customer/p...8&cat=2&page=1

This is the Blitz induction "lid". I am sure you have all seen it, basically its the stock airbox lid minus the top. I saw this and thought like Jack pointed out, why spend money on a cone filter if I can just cut the top of the lid off like this. I have been running my filter assembly (with K&N filter panel) this way since the car was new. Logging I dont seem to get any odd AFR changes which is consistent with a lack of extra vortices as pointed out. I do notice an increase in power and I am not logging higher IAT than anyone else seems to. In fact down a recent 1/4 mile run the temp was dropping all through the run. Just I thought I would share and stir things up a bit.

 

what about something like the Kasani service air box.....its carbon fiber (reflects engine heat to a degree)...it uses a stock like snorkel....and uses a cone type filter....wouldnt this be Ideal?

 

Would be the same as stock or perhaps a tad better. Big $$$.