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Discussion Starter #1
Hi.
2 months ago I bought Opel Corsa C 1,7 CDTI 2005 and I´d like to start modding it.
The first mod on my list would be an air filter.
I´ve read a couple of threads and still don't know what to do half of them say that it's better just to buy a high flow panel filter (Pipercross or K&N)
and the other half says that it's better to buy a cone filter (K&N) but with a proper cold air intake done
So if anyone could help me which would be better and the differences between them:
1.high flow panel filter (Pipercross or K&N)
or
2.cone filter (K&N) with cold air intake done
And the second mod would be a remap or a chip.
Thanks!!!
 

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Panel filter


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Or pipercross viper induction

As with cones they tend to suck in the hot air


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Something approaching a scientific investigation was done on this. I might be able to link it back again if you don't find it in a search. In this test, panel filters had a barely significant increase in air throughput compared to paper ones and, given that faffing around with washing and reapplying some expensive proprietary oil doesn't appeal half as much as chucking some dirty folded paper away (when Greta's not looking), I have stayed with paper. Cone filters, as you and Pugh have already noted, require a cold intake, but they did, when tested, have a significantly higher throughput (K+N was disappointingly poor - they might be the best known, but not the best if high throughput is your top criterion).

The problem is, with cotton or whatever, is that higher air throughput simply means more particles getting through (and this was measured to be the case). It's a simple trade off and there's no getting away from it when paper, fibre, foam or other random stuff is used as the filtering medium. The best way to achieve high throughput (until it blocks up) while maintaining particle retention is to have regular, precise holes. I found this in the lab with high-pressure liquid flows where we needed <0.1μm filtration, high fluid flow and minimal filter changeovers. Random layers of fibres were dismal in comparison to regular, ordered structures. For some reason, it's not really developed in automotive use (I don't count those AliExpress gimmicks).
 

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Something approaching a scientific investigation was done on this. I might be able to link it back again if you don't find it in a search. In this test, panel filters had a barely significant increase in air throughput compared to paper ones and, given that faffing around with washing and reapplying some expensive proprietary oil doesn't appeal half as much as chucking some dirty folded paper away (when Greta's not looking), I have stayed with paper. Cone filters, as you and Pugh have already noted, require a cold intake, but they did, when tested, have a significantly higher throughput (K+N was disappointingly poor - they might be the best known, but not the best if high throughput is your top criterion).

The problem is, with cotton or whatever, is that higher air throughput simply means more particles getting through (and this was measured to be the case). It's a simple trade off and there's no getting away from it when paper, fibre, foam or other random stuff is used as the filtering medium. The best way to achieve high throughput (until it blocks up) while maintaining particle retention is to have regular, precise holes. I found this in the lab with high-pressure liquid flows where we needed <0.1μm filtration, high fluid flow and minimal filter changeovers. Random layers of fibres were dismal in comparison to regular, ordered structures. For some reason, it's not really developed in automotive use (I don't count those AliExpress gimmicks).
Something approaching a scientific investigation was done on this. I might be able to link it back again if you don't find it in a search. In this test, panel filters had a barely significant increase in air throughput compared to paper ones and, given that faffing around with washing and reapplying some expensive proprietary oil doesn't appeal half as much as chucking some dirty folded paper away (when Greta's not looking), I have stayed with paper. Cone filters, as you and Pugh have already noted, require a cold intake, but they did, when tested, have a significantly higher throughput (K+N was disappointingly poor - they might be the best known, but not the best if high throughput is your top criterion).

The problem is, with cotton or whatever, is that higher air throughput simply means more particles getting through (and this was measured to be the case). It's a simple trade off and there's no getting away from it when paper, fibre, foam or other random stuff is used as the filtering medium. The best way to achieve high throughput (until it blocks up) while maintaining particle retention is to have regular, precise holes. I found this in the lab with high-pressure liquid flows where we needed <0.1μm filtration, high fluid flow and minimal filter changeovers. Random layers of fibres were dismal in comparison to regular, ordered structures. For some reason, it's not really developed in automotive use (I don't count those AliExpress gimmicks).
So what would you recomend?
And what do you think about pipercross viper induction?
 

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What would I recommend? Well, I'm not qualified as a mechanic or engineer nor someone with hands-on experience of performance modifications (except intercooling my diesel turbo); I'm a scientist. It depends on how much initial work, regular maintenance, cost and possible filtration compromise is acceptable.

I did find the article which looked at flow restriction:

It's 7 years old now, so I expect manufacturers have improved their products, but it shows that cone filters restrict less than panel filters (but you pay by more particulates passing through). There is not much data on their filtering abilities so it depends how much that is important to you. I drive across Europe and don't want to be stranded, so I use standard paper filters which I replace inside 10,000km.

I haven't seen the Viper before and I haven't seen any data (I am always sceptical of "designed to increase..." labels, as this guarantees nothing). For >€200, I know I wouldn't. For that money, it appears to source cooler, and therefore denser, air using something I would call "a long piece of tubing" and talks about a Ram Pipe that sounds a bit Supercharger (which, if it were any good, would heat the air up and benefit from an aftercooler) but is probably just a bit of rifling that achieves modest benefits or even just a wider bore into a narrower bore.

I sound very cynical, but I am no more than sceptical; especially when I see claims not backed up independently with data.
 

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One thing, though. The C's standard airbox for the filter does look really badly designed and causes the majority of the filtration to take place over a very small area. A disposable filter is thrown away with only a portion of it really clogged. If I wanted to get more air in at no cost and no compromise to the filtration, I would cut away that plastic tube shape inside before spending money. It might not be any improvement but I can't see what harm would be done either and it might make better use of a panel filter's less restrictive throughput.
 

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People used to drill holes (not close to the engine side) in the bottom half of the air box


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The filter element is usually the least restrictive part of an OEM induction system which is why changing them tends to make no noticeable difference. Open cone filters can give very little restriction and the 'heat soak' problem from having them in the engine bay tends not to be a problem at all. A few years ago I did a test on my astra and whilst stood in traffic on a warm day the inlet temperature went up, but once the traffic cleared and by the time I was in second gear the temperatures were almost back to those of the OEM system.
Anything that implies it has a ram air effect is lying.
 

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EDIT: My mistake - I looked at your opening post and you have the CDTi - I don't know if this would even fit but you could look up the 57i and check.

Mauro, just to counter all my negativity, here's a little help:

I don't know exactly why (the starting price is very reasonable), but I have seen this listed on ebay several times without ever attracting a bid. The seller says collection only and might not be very keen to post internationally (Croatia, judging by your flag under the forum name?) but he might be getting fed up of it sitting unsold and respond to an enquiry. It could be a way to experiment without spending a lot of money.
 

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Discussion Starter #12
One thing, though. The C's standard airbox for the filter does look really badly designed and causes the majority of the filtration to take place over a very small area. A disposable filter is thrown away with only a portion of it really clogged. If I wanted to get more air in at no cost and no compromise to the filtration, I would cut away that plastic tube shape inside before spending money. It might not be any improvement but I can't see what harm would be done either and it might make better use of a panel filter's less restrictive throughput.
Thanks.
I removed that plastic that you said and I feel like its pulling a little better.
 

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People used to drill holes (not close to the engine side) in the bottom half of the air box


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I've done this on all of the Vectras I had. Drilled holes in the side furthest from the engine and the bottom of the air box, you can also remove the trumpet part from inside the air box at the inlet.

I've got a cone filter with a metal Heatshield fitted and holes drilled in the side with the original ducting to direct the cold air straight to it.

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