Air Intake Revisions and Performance Filters - Do They Work?


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Before getting into the topic I want to make clear that I have no intention to start an argument.

I am working with 5 different chassis dynos in the UK as well as other in other countries.

Additionally, me and my associates conduct real time testing on the track and drags trips as well as 1/4 mile tests on different public places. The public places used are not used as 1/4 mile references even when the average used of 2 opposing runs. The reference value is in so far that changes before and after can be evaluated on the absolute changes as well percentage changes.

All runs are repeated a number of times in order for the driver to get his best result before and after as well as the ECU adjusting to the ambient conditions.

When doing the testing before and after we try to do this in the shortest possible time frame to be able to lock out as many variables as possible.

When testing competitors product we have independent observers present. we do this in our own interest as we do not want any misrepresentation of facts and/or being accused of being biased or trying to fake figures.

All the above is general procedure in Europe.

Coming to the questions. The first question is whether air intake revisions and performance filter increase performance.

This question can't be answered with a straight 'yes' or a straight 'no'. Also the impression one might have after changing is subjective,which can be proven with acceleration metering equipment. And some of the before and after 'tests' made are of no relevance because they are made under different conditions.

It is also noteworthy that in the industries changes below 2% are not considered as improvements or losses due to tolerances that affect the reciprication.

Air intake revisions can be split generally into 5 different groups.

1. Replacement panel or cylindrical filter elements
2. Universal filters/air intakes
3. Model specific induction kits/CAIs/AIRs
4. Bespoke AIRs
5. Custom AIRs

1. Replacement panel or cylindrical filter elements

Depending on the make and material the replacement filters can improve overall performance. However this will be marginal.

Usually when people report about the improvement they have seen when replacing the original filter with the replacement filter is the fact that in virtually all cases the original filter was not new and therefore the flow rate was decreased. Changing a used original filter with a new original filter will also show an increase in performance.

Over the years we have conducted many tests with these filters and accept that they can improve performance by anything up to 1.5% (usually cotton gauze) on small engines, but less on bigger engines. Some of the foam filters or sponges have actually lost performance.


2. Universal filters/air intakes

They will work on some turbo air intakes, but will on normally aspirated engines reduce torque the further down the rpm range the more. This usually results in poor driveability and often an increased fuel consumption. Placing the universal filter on the throttle body or at the end of a pipe does not consider some of the important points to gain performance.

Near the throttle body usually the air is usually rather hot. Adding a cold air feed will in very few cases change this for reasons I am not discussing here as it would lead too far. One thing cold air feeds do adversly is helping to throw a lot of dirt at the filter.

Another aspect is the turbulent air. The faster the vehicle moves the more the turbulences affect air intake.

In case the universal filter is attached to some part of the factory air intake additional flow losses might be observed at the filter mouth and throat, which add to the system specific ones.

Here is 2 pictures of what a cold air feed can do when installed as BMC specified:
 

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Thread Starter #2
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Continuing from previous post:

3. Model specific induction kits/CAIs/AIRs

These can be quite good but also appalling.

Whenever we tested any pipercross product we had not a single occasion where they did not lose power and torque against the stock intakes.

BMC usually fares better but some of the kits showed very little improvement and needed much better piping to show full potential.

K&N kits with the exceptions of the typhoons will lose low end performance. With the Apollos we never saw ant improvement. The 57is can gain top end.

Most other systems tested showed peak power and in a number of cases low end torque improvement.

4. Bespoke AIRs

Although the bespoke intakes are model specific they need to be separated from the other model specific ones as they are more likely custom intakes than anything else.

The bespoke intakes are optimised in virtually all aspects without changing any other component than the air intake.

The K&N Typhoons are the best of the mass production manufacturers. They are moderate on torque increases and good on peak power.

Some smaller manufacturers who design bespoke intakes improve not only peak power but also improve low end torque dramatically, which is on normally aspirated engines a big task.

Important is on the normally aspirated engines to get the entry going right for temeperature reasons but even more so high pressure zones and turbulences around the filter and the filter mouth and throat. Torque can be gained on normally aspirated engines by having an appropriate intake length and the right diameters in order to achieve the best compromise between inertia and mass.

In force induced intakes the inertia problem can be fully neglected in favour of the mass.

5. Custom AIRs

Custom intakes are bespoke intakes of a special kind. The customer usually will allow to go much further than making it an easy to fit air intake. such installations look first of all into the performance point of view with minimising the compromises. This might necessitate alterations to other components. Such changes have a big impact on performance but in most cases far to expensive to be considered by the enthusiast.

To sum up the improvement on air intake revisions.

We have seen system designed without compromise other than what chassis restriction and engine location dictated that improved on small normally aspirated petrol engines in heavy modern cars low end torque to a degree that it is possible to drive up on inclines in top gear with driver and passenger at under 1500rpm and gaining speed.

The other extreme was that power was lost due to the poor general design losing power. And some designs showed some improvements, but lost soon against stock because they were just dust traps. One of these we compared against another revised intake, which was much better located picking up less dirt showing 27% peak power difference on the same car.

The 2 post are only on overview of the topic highlighting the complexity of the problem for finding an air intake revision that does desired improvements. It also is meant to show that there is much more to it and that it is necessary to look at every car individually to achieve improvements.

As time is going on I hope to be able to provide more model specific guide lines specifically for the Indian conditions.
 
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That was a brilliant write up, sir. I am sure other rev crazy and mod happy users will throw tremendous questions on this subject.
 
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Nicely written and very informative ,sir..
Please do post such informative threads in the future.
Eager to hear more from you.[:)]
 
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Nicely written and very informative ,sir..
Please do post such informative threads in the future.
Eager to hear more from you.[:)]
Thank you ACMohan and fusion_defusion.

I certainly will add more technical info, but also would like to hear from you guys what your specific questions are and what I can do to help solving issues you might have or project queries.
 
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I've a doubt.I own a Swift DDIS and now it runs on stock air filter.I haven't replaced it during last service but had just cleaned it as I had a green cotton Wind filter kit(along with the dynamisation kit) in my mind.Is it a good choice or should I stick to the stock one or even a replacement filter?[confused]
 
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I've a doubt.I own a Swift DDIS and now it runs on stock air filter.I haven't replaced it during last service but had just cleaned it as I had a green cotton Wind filter kit(along with the dynamisation kit) in my mind.Is it a good choice or should I stick to the stock one or even a replacement filter?[confused]
The replacement filter on your engine is from the performance point of view of very little use. The green kit is the better option. However, the Green kit is not the best option. Practically it is only half a kit. Much more can be extracted with a purpose designed that connects to the turbo.
 
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The replacement filter on your engine is from the performance point of view of very little use. The green kit is the better option. However, the Green kit is not the best option. Practically it is only half a kit. Much more can be extracted with a purpose designed that connects to the turbo.
Can you please make it more clear.And what are the other options?
And please do post the approx. prices.[:)]
 
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Hey drifter,is it possible to fit an Air filter like the green cotton wind as a DIY?
Do we need to tune the car after that?And I've seen a video in which petes is installing the same filter on a Swift.But somewhere I've read that the fitting of air filter took more than 1hr.Advice needed![:D]
 
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A little update from our second test mule, which is a Lines T-Jet. After fitting a dedicated AIR the mileage increased on average by nearly 1km per liter, which is 12.3kpl.On long runs the fuel consumption is 14kpl. This is an average saving of about 8%.

Such savings apply to turbo charged engines when AIRs are designed correctly.
 
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Hi, can you post performance figures of t-jet and any other mods planned on it ?
I will start a T-Jet thread for this soon. Performance figures aren't available as yet as we haven't got the right conditions at the moment because of the monsoon. As soon as the weather allows we start before and after testing again.

The planned modifications are AIR, exhaust, hoses/pipind (to and from inter cooler), cam shafts, turbo, intercooler and re-map.
 
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K&N offers much more performance improvement. Had it in Zen mpfi.The pickup increased drastically and also the average. Even my friend is having in his Fabia and he feels the same.

Thanks for details information,very helpful.
 
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