Air Filter

[Dean_0]

Been looking at a few of the air filter modifications that people make especially around the air filters. The main contenders are the K&N air filter replacement which fits within the OEM airbox and the Ram air filter which replaces the OEM filter and drives the air straight down into the engine:

These pictures were taken from other people from the internet and are not mine. I currently have the K&N air filter fitted and have the second ram air filter arriving shortly for testing. From the readings I have done so far both seem to have pros and cons however, I was wondering from people that have tried either style which they feel will have the most benefit to performance? I know the differences are extremely small however, feedback from other users would be appreciated. 

 

 

Edited 27 May, 2019 by Dean_0

[KenONeill]

Neither will make any difference to "new filter, engine bay cold" performance. The K&N will lose less performance after 20k miles and/or when the engine is hot.

[Dean_0]

5 minutes ago, KenONeill said:

Neither will make any difference to "new filter, engine bay cold" performance. The K&N will lose less performance after 20k miles and/or when the engine is hot.

For the Ram Air I would look to fit a heat shield around the filter as the coolant bottle next to runs around 80C after checking with a heat gun. I would like to fit something like this:

Even if it keeps the filter itself around 10C cooler it would make a difference I think.

 

My aim is not to make a fun economical car into something it can't be. But with a few tweaks, I hope to make it a bit more peppy!

[Vitas]

The issue I'd see with the heat shield is down to the unusual size of the ram air filter. The hole isnt central. Might be a custom job. It may be worth trying to route your own intake into the grill so it gets cooler air but that comes with the risk of getting wet.

[Blackcountryman]

My experience with these afterfit filters is mixed.The original ducting and filter tend to give the best compromise on performance throughout the rev range.

Some of the afterfit filters may draw more air in ,but give a weaker fuel performance and less response at some throttle openings.

Having fittted some to cars were you could alter the fuel/air ratio on carbs ,meant you could adjust most of it out,but not possible with todays equipment installed on cars......

Edited 29 May, 2019 by Blackcountryman

[Dean_0]

2 hours ago, Vitas said:

The issue I'd see with the heat shield is down to the unusual size of the ram air filter. The hole isnt central. Might be a custom job. It may be worth trying to route your own intake into the grill so it gets cooler air but that comes with the risk of getting wet.

Yep this is something I have noticed from the pictures, I'll have to see what I can do on that. But since the Ram air is directly at the front of the car I feel that it should naturally receive a nice flow of air from under the bonnet and around the front radiator. I had considered removing the OEM snorkel with the resonance chamber and piping a duct to the front behind the grille, similar to another member on this forum as that looked good however I was not keen on chopping away the plastic trim behind that area as it runs close to an air con line and also the car is brand new, right now it's plug and play nothing is permanent. 

On a side note, I hooked up the PC to the car and got my father to drive I reviewed the intake temps as I feel that this is somewhat the most important deciding factor on whether one style is better than another. While running the K&N you can see the peak temps on the intake:

This screenshot is after driving two short loops near where I live to get the car to temp and then we let the car idle to see the heat soak in the manifold and then drive out again to see whether this temperature would decrease under the coming flow. I did not save all the trip data as it was just an initial test run.

Edited 29 May, 2019 by Dean_0

[Dean_0]

So I bought the Ram Air filter and tested it against the K&N air filter and collected data through the VCDS software to prove which design would be more optimal for performance. After two days of testing both designs in varied conditions the data was grouped together and has the following trend:

From the data and the driving sensation, the Ram Air filter seems to have a slight edge on low-end torque versus the K&N filter. But, the data seems to narrow this margin down. The test was on the same stretch of road driving in a similar manor conducting controlled pulls on the car. This was done once the car was fully up to temperature monitoring the oil and coolant temperatures. The graphs contain logged data from over 1000 sample points. The K&N filter using the OEM air box did produce the overall peak torque value however the margins were so fine that it amounted to roughly 0.5-1.5 N.m or torque difference according to the calculated value from the ECU. Some users said that the OEM filter box would keep cooler and although this is true the difference measured was not of huge significance. The K&N proved to be between 2-4 C cooler and seemed to be able to dissipate heat more effectively than the Ram Air filter after a heat soak cycle (5mins of idle).

In terms of how much air each filter and intake took they were effectively the same, turns out the OEM airbox is pretty decent and doesn't starve the engine as I had thought:

Edited 31 May, 2019 by Dean_0

[Breezy_Pete]

37 minutes ago, Dean_0 said:

After two days of testing both designs in varied conditions

Was that one day on each or two days on each?

Ambient temperatures recorded?

 

Great work btw. 

[Dean_0]

17 minutes ago, Wino said:

Was that one day on each or two days on each?

Ambient temperatures recorded?

 

Great work btw. 

Nope did back to backs each day, so day 1 I started with the OEM filter to warm up the car to full temp, the data recorded on that is not very good I will be doing that again soon although I'm scared that the results will not be good for the performance filters! Then I place on the Ram Air did a run with ambient staying steady at 22C according to the ECU, then took that off and ran the K&N panel filter. I repeated the same this morning but without the OEM filter, I ran the car with the Ram Air to warm up as I wanted a longer run time as I believe the ECU was beginning to adapt to the Ram Air filter. Then once warm did another run recording data with the Ram air then switched to the K&N. Today had a cooler ambient today of 20C. Tomorrow, I might run another back to back with the OEM paper filter against the Ram Air. However, I personally prefer the drivability of the Ram Air already, and the fuel economy is actually best with is which is something I did not expect! 

[Breezy_Pete]

19 minutes ago, Dean_0 said:

I might run another back to back with the OEM paper filter against the Ram Air

Good idea.

Thanks for the clarification about the order of proceedings.

[Dean_0]

1 hour ago, Wino said:

Good idea.

Thanks for the clarification about the order of proceedings.

Thanks, I'm having a lot of fun with this car I'm starting to learn a lot about how she drives and behaves. 

[Dean_0]

Found some more time to analyse the data here is a 15 point average showing the manifold intake temperature with respect to time. The green line is the Ram Air and the black is the K&N filter. The runs are almost identical in every way, in fact, the run time from one to the other differs by about 15 seconds. 

I definitely believe some form of heat shield and cold air feed could further increase the performance of the Ram Air filter.

[Vitas]

I'd run some ducting from the grill into the filter tbh, that might drop temps a little. But a heat shield would definitely make a difference.

[Dean_0]

18 hours ago, Vitas said:

I'd run some ducting from the grill into the filter tbh, that might drop temps a little. But a heat shield would definitely make a difference.

I didn't really want to splash more money into a heat shield when only a simple solution is required. My father had some left of aluminium food trays left so we cut and folded a semi-air catcher/ heat deflected. A lot of the heat originates from the base, the air is stagnant and can be drawn in through the cone with this solution albeit not the prettiest I believe this will solve this issue:

After a run, I used a heat sensor laser on the inside of the shield. The temps remain considerably cooler on the inside and can be touched even after a long heat soaking cycle whereas around the back and underneath the temps are around 70C. 

 

The red staining is from leftover red oxide paint I've been told.

 

Edit: ran to the shops today and the driving sensation with this is definitely noticeable compared to the OEM airbox, after 2000RPM this feels so much more lively and enjoyable to drive. With an ECU remap which I hope to get done it could add a few more % of driving fun!

Edited 6 June, 2019 by Dean_0

[J.R.]

On 29/05/2019 at 16:24, Blackcountryman said:

 

Some of the afterfit filters may draw more air in ,but give a weaker fuel performance and less response at some throttle openings.

Having fittted some to cars were you could alter the fuel/air ratio on carbs ,meant you could adjust most of it out,but not possible with todays equipment installed on cars......

 

That is simply wrong,  petrol engines since the early 90's have had closed loop mixture control driven by the 02 Lamda sensor in order to protect the catalytic convertor, the calculate and adjust the mixture to run at Lamda 1.0 many times per second and will instantly adapt to any change in air filtration.

 

[Tim1631]

What a load of crap. No point waste of money 

[dylanthomasuk]

That's some intensive research! Did you ever get a heatshield made up?

[freemansteve]

All these mods will change the sound of the induction noise, and will create the illusion of more power. In reality, on a fairly puny city car, you won't be able to actually measure any perceived performance gain. Changing the standard air filter for a similar good quality one every so many thousand miles is as good as it gets. I'm willing to be proved wrong by any genuine apples-for-apples, back-to-back dyno test result graphs (but not the usual advertising-faked-up-but-still-cleverly-legal rubbish published by K&N). Fun to see advertising wins in the end though!