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Old 19th November 2004, 12:56   #1
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Hi guys

Until recently, i had been running my carb zen on a K&N filter encased in the stock filter box. And then i went ahead and replaced the stock filter box with a set of parallel round plates that exposed the filter's sides to open air. Ever since i have done this, the car's performance at low rpms has decreased. I mean, at low rpms, now it accelerates slowly as compared to earlier.
The earlier stock intake had a small black box attached to the pipe of the box through which air used to flow. Was this used to cool the air? Is this the reason i am seeing this decrease in performance? Can the engine be tuned to get that peppiness back?
Or are there any intakes that i can use that will cool the air thats going in??

Haaaaallllpppp!!!!
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Old 19th November 2004, 14:10   #2
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Here is a snap from the K&N website showing the stock filter that i had earlier and the new one that i have now...
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Old 19th November 2004, 14:26   #3
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i had a similar experience with my vectra.

The car responds better now when I put the stock filter and box back, than when I had put a K&N cone filter.

Don't know why!

Maybe the cone filter was not balanced to the size of engine and location???
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Old 19th November 2004, 14:30   #4
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Well, in my case, at least replacing the stock filter with the K&N filter did increase the performance a bit. But when i replaced the stock filter box also, then things went a bit worse.
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Old 19th November 2004, 14:56   #5
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put up pics of before and after!
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Old 19th November 2004, 23:33   #6
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Correct me if i'm wrong here guys, but, could it be due to the fact that since the filter is fully exposed, more amount of hot air (air heated due to the heat of the engine) is being taken in.
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Old 20th November 2004, 01:12   #7
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thats what am also afraid of , shravan.... that could very well be the reason.
Dom.... ur expertise required...
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Old 20th November 2004, 02:50   #8
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guys ,
but most of us have the exposed conical K&N filters.but the performance has only improved.technically ur filter is drawing more air now,so its performance shud not drop at all.
if the hot air is cuming into the picture now,where was it previously.
but i do feel that ,the performance may vary in the day time when the surrounding temp is also hotter as compared to performance in cooler times of the day.
this is my guess, which cannot be perfect as k&n filters are used for racing even in the deserts .
Dom wats ur say???
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Old 20th November 2004, 13:11   #9
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Quote:
Originally Posted by [b
Quote[/b] (speedsatya @ Nov. 20 2004,00:20)]if the hot air is cuming into the picture now,where was it previously.
Satya, the stock air intake in my car had a rectangular black box connected to the intake pipe, before the filter. The box is empty. Probably it played some part in cooling the air? Also, the intake pipe's open end was pointed away from the engine, pointing downwards, thus reducing the chances of warm air coming in. Thats my theory.
I am also waiting for Dom to throw some light on this...
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Old 21st November 2004, 01:35   #10
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Quote:
Originally Posted by [b
Quote[/b] (amitoj @ Nov. 20 2004,10:41)]Satya, the stock air intake in my car had a rectangular black box connected to the intake pipe, before the filter. The box is empty. Probably it played some part in cooling the air?
the black box is knows as the helmholtz resonators or Acoustic resonators they DO NOT cool the air, however their primary aim is to control the sound pressure level inside cavities but they also act like reservoirs of air.

In the dia below you can see the intake path,the arrows indicate the direction of flow of air from the atmosphere to the engine.



as it can be seen the amount of air present is represented by the colour blue now what happens when you press the accellerator
1) The butterfly flap or throttle body opens
2) The engine demands air, the quantity of air which it requires depends upon how much accelerator you press.
3) The air demanded by the engine may be less than the air present in the intake path (which is blue in colour), so more air is sucked from the atmosphere this leads to a delay lets refer this delay of air as *reduced mass flow (sounds a little cool)so this reduced mass flow decreses acceleration or in other words leads to a low pick up.
4) note : mass flow or rate at which air from the atmosphere reaches the engine increases once you are above crawling speeds because of the RAM air effect.



NOW THE INTAKE PATH WITH THE RESONATOR OR BLACK BOX or whatever you call it

*

as it can be seen the amount of air present (blue colour) has increased due to the addition of a hollow box which is nothing but our friendly resonator
1) now when you press the accelerator the engine demands air
2) the extra air in the hollow box should be more than enough to fulfill the engine needs there is no delay
3) even if the air in the intake path is less the delay is minimal
4) which leads to better acceleration

So car manufacturers arent that stupid after all, so if u have a naturally aspirated car keep those resonators ON


NOTE : Please feel free to sue me if im wrong
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Old 21st November 2004, 02:51   #11
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Thank you Kinetic!

Although it is true that manufactuers do limit their cars because of cost issues & driveability, it should not be assumed that they do not know what they are doing, or that they have badly designed components. Most manufacturers probably put in tons of more hours and much higher quality research and testing than most aftermarket suppliers.
Point being, dont believe the hype...almost everything has a tradeoff.

cheers
R



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Old 21st November 2004, 14:47   #12
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awesome explanation there Kinetic, thanks!
But tell me something... if there is no stock intake and the engine has all the air around the filter to suck in during acceleration, should it not enhance the pick up? I mean in this case, the question of there not being enough air during acceleration shouldnt arise as the filter is exposed 360 degrees to get as much air as is required.
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Old 21st November 2004, 17:44   #13
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Quote:
Originally Posted by [b
Quote[/b] (amitoj @ Nov. 21 2004,12:17)]awesome explanation there Kinetic, thanks!
But tell me something... if there is no stock intake and the engine has all the air around the filter to suck in during acceleration, should it not enhance the pick up? I mean in this case, the question of there not being enough air during acceleration *shouldnt arise as the filter is exposed 360 degrees to get as much air as is required.
thanks rehaan,amitoj


im not sure if i understood your query spot on amitoj, but here goes anyways..

I assume when you say"there is no stock intake" you mean that *the oem (rectangular) air filter along with its filter box is removed and at that end you have mounted a conical filter something like the diagram below ...



as seen above we will face the same problem of a reduced air mass flow due to the volume of the intake path, so why not remove the original intake path completly and mount that conical k&n filter directly onto the engine throttle body, there will hardly be any intake path restricting the flow of air from the atmosphere to the engine , someting like the dia below (please excuse the diagrams im not as good as many of our fellow team-bhpians when it comes to imaging softwares)




so now evrything looks great you have a conical filter mounted right on top, no delay no lag, engine wants air, engine ges air directly, ready to burn some rubber well im kinda sceptical about that cozzz
1)our old friend Mr Heat is now showing up .. since the filter is so close to the engine more hot air than usual is sucked leading to u know what
2) once you have gained vehicle speed where is the ram air advantage ? which again leads to the u know what

so for the above setup on the plus side u have near zero restriction for the intake air flow but in the con side u have heat and no ram air !

But if you can achieve shortest distance of the conical filter from the engine and at the same time get cooler air and a dash of ram air to spice up things then i guess u have one hella of a dish

there maybe a lot of other parametrs also but i aint that good enuff i reckon u require dedicated scientific trial and error methods to get the optimum setup for your ride



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Old 21st November 2004, 18:39   #14
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Ur diagrams are quite helpful. But in my case, i have a round filter sitting on a carb engine. refer the diagram i posted in this thread with my second message.
But i can apply the same principal that you mentioned above to my case anyways. You are also endorsing what shravan, satya and i have been thinking... that the warm air can be the culprit here.
Am i correct?
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Old 21st November 2004, 21:30   #15
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yup infact there is a thumbrule that for every 11 degrees Fahrenheit drop in temp you get a 1% horse powergain,
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