I have drilled my airbox.
- Thread starter PJS917
- Start date
Uncanny - I did something nearly identical about three years ago, like this:
Yours looks a bit more smart tho', with the mesh in the holes.
Did it make any difference? I suspect not. It made it noisier, yes, but I think it make the throttle response flatter and may have cost a bit of low-down torque. The design of the airbox as it was from the factory is clearly carefully thought out, with the duct in the side (clearly removed on mine) designed to promote a certain flow pattern.
Would I recommend it? Probably not. But I wouldn't dissuade someone from having a go either.
Oli.
Yours looks a bit more smart tho', with the mesh in the holes.
Did it make any difference? I suspect not. It made it noisier, yes, but I think it make the throttle response flatter and may have cost a bit of low-down torque. The design of the airbox as it was from the factory is clearly carefully thought out, with the duct in the side (clearly removed on mine) designed to promote a certain flow pattern.
Would I recommend it? Probably not. But I wouldn't dissuade someone from having a go either.
Oli.
Ive often wondered about that, why put the airbox in there with such a little hole when the hole could face forwards and gather up huge amounts of air. Isn't there the "ram air" effect as well? IIRC it only makes a difference above 100mph as the air is forced into the intake... Or am I imagining things again?
bennyboy
New member
I think I am in the early stages of this very contageous disease. Yesterday afternoon my brother asked if I was addicted to this forum - I couldn't really say no! But the problem is, whilst I'm sat here clicking I'm constantly thinking about little things I could be doing to my car, that don't cost anything - like drilling airboxes[
]! (and removing foglamp units?!)Big Dave - you seen my email?
sawood12
New member
Unfortunately Porsche have alot of considerations to take into account which is why they don't build the car with ultimate performance in mind. They have to keep an eye on emissions, fuel economy, noise, longevity etc. For example, the air filter is made of paper so they can't have direct airflow exposed directly onto the filter as it will go all mushy when it rains and road debris like stones can puncture through the paper filter and be ingested into the engine. This seems to be quite a common mod on 911's mainly to improve induction noise.
Scott,
Quite agree with the comment about the compromises Porsche (and anyone else) need to make when building cars. As 'enthusiasts', we are willing to sacrifice certain things in order to gain more of other things, and thus make the cars less compromised, hence doing things like drilling airboxes, changing suspension, removing excess weight and sunrooves etc etc etc. I'm still not 100% sold on whether drilling airboxes offers a good improvement tho'.
The point about the air filter being exposed from in front is also a good one, but in practice it would be very unlikely to suffer damage from stones, due to the alignment of the air box with the gap in the front bumper. It was a concern of mine, and when I first did the mod I considered building some kind of baffle to protect the air filter, but if you look through the bumper you can't actually see the holes or the filter as the alignment isn't as close as may first appear. On that basis, I think the risk of damage such as you describe is pretty much nil. I also ran a paper filter with the holes for around 20k miles (OK, two paper filters as I changed them at least once) and they never suffered any damage at all. I now have a K&N in there, which is slightly tougher, but the same applies.
The point about things getting soggy; given the stock design with the air intake on the side, it would get pretty damp in heavy rain. Adding holes won't make things any much worse.
Oli.
Quite agree with the comment about the compromises Porsche (and anyone else) need to make when building cars. As 'enthusiasts', we are willing to sacrifice certain things in order to gain more of other things, and thus make the cars less compromised, hence doing things like drilling airboxes, changing suspension, removing excess weight and sunrooves etc etc etc. I'm still not 100% sold on whether drilling airboxes offers a good improvement tho'.
The point about the air filter being exposed from in front is also a good one, but in practice it would be very unlikely to suffer damage from stones, due to the alignment of the air box with the gap in the front bumper. It was a concern of mine, and when I first did the mod I considered building some kind of baffle to protect the air filter, but if you look through the bumper you can't actually see the holes or the filter as the alignment isn't as close as may first appear. On that basis, I think the risk of damage such as you describe is pretty much nil. I also ran a paper filter with the holes for around 20k miles (OK, two paper filters as I changed them at least once) and they never suffered any damage at all. I now have a K&N in there, which is slightly tougher, but the same applies.
The point about things getting soggy; given the stock design with the air intake on the side, it would get pretty damp in heavy rain. Adding holes won't make things any much worse.
Oli.
edh
New member
good point Thom
I experimented with various airbox setups in my V6 Sierra track car, including piping air from the front bumper - it worked best just with the lid off (and the filter taped in) - the car was able to rev higher and sounded glorious! (you might think a pushrod Cologne V6 is a bit antiquated, but this one just sang [] - until we turbocharged it & blew a hole in a piston [] )
I experimented with various airbox setups in my V6 Sierra track car, including piping air from the front bumper - it worked best just with the lid off (and the filter taped in) - the car was able to rev higher and sounded glorious! (you might think a pushrod Cologne V6 is a bit antiquated, but this one just sang [
] - until we turbocharged it & blew a hole in a piston [] )It's all down to the design of the airbox, and the airflow around and through it. And difficult things like resonance and pressure zones and gas speed and whatnot. (You can tell I failed an engineering degree, can't you!)
On a Mk1 Golf GTi, cutting the bottom off the airbox entirely (air flowed into an intake in the front wing, along a pipe, into the bottom of the airbox and through the filter) improved throttle response massively, gave more mid-range torque, made a glorious noise and improved MPG slightly. Everyone was a winner ... which is why I tried what I did on the S2.
You may be able to get more improvement with the airbox removed entirely, but would need something to hold the filter in place. Cutting the front off the airbox entirely would be a good way to achieve this, but would be a bit irreversible.
Oli.
On a Mk1 Golf GTi, cutting the bottom off the airbox entirely (air flowed into an intake in the front wing, along a pipe, into the bottom of the airbox and through the filter) improved throttle response massively, gave more mid-range torque, made a glorious noise and improved MPG slightly. Everyone was a winner ... which is why I tried what I did on the S2.
You may be able to get more improvement with the airbox removed entirely, but would need something to hold the filter in place. Cutting the front off the airbox entirely would be a good way to achieve this, but would be a bit irreversible.
Oli.
Wigeon Incognito
New member
When I bought my S2 it just had a whacking great cone filter stuffed in where the air box should be so achieved a similar effect without irreversible mods.
I wasn't keen (I'm a bit of an originality nut) so put it back to standard and whilst it doesn't sound quite as good I could swear it feels a little more refined in terms of power delivery - I may just be imagining that though!
The other problem with that particular cone setup was that the filter was so big it had pressed against the inside of my badge panel causing an upward dent! Of course more money was required to sort that out too.
ORIGINAL: edh
good point Thom
I experimented with various airbox setups in my V6 Sierra track car, including piping air from the front bumper - it worked best just with the lid off (and the filter taped in) - the car was able to rev higher and sounded glorious! (you might think a pushrod Cologne V6 is a bit antiquated, but this one just sang [
I put a Turbo Technics kit on my 2.8 capri 20 years ago, it ran great, you must have been running a fairly high boost to melt a piston [
].
It's heat that ultimately holes pistons, that could be caused by a lean mixture, to much ignition advance or a combination of the two relative to the boost, I would think a lean mixture at only 7 psi would be unlikely on a K-jet engine, the only mod my old 2.8 had was a ignition retard module and that ran 8psi on the standard comp ratio without issues, 11 psi was a different matter though and you could easily hear the detonation then.
TTM
Well-known member
Inaudible knock (caused by excessive detonation) can be lethal as well.
Since I have been using a knock detector I regularly notice signficant variations in fuel quality depending on where I fill in.
In the best case I would run 1.3 bar with no knock whatsoever (e.g. last winter), in other cases there would be severe knock at anything above 1.1 bar.
Since I have been using a knock detector I regularly notice signficant variations in fuel quality depending on where I fill in.
In the best case I would run 1.3 bar with no knock whatsoever (e.g. last winter), in other cases there would be severe knock at anything above 1.1 bar.
Tam Lin
New member
That's the thing about this S2 mod and the "ram effect". I would have thought this would be undesirable, as above 5500 rpm, the AFM is pegged open, and fuelling is according to the load maps, with no compensation for the extra air flowing through extra holes, leaning the mixture. Probably irrelevant in Britain, even on track, but I wouldn't want it on an Autobahn..
I'm no authority on turbo charging, I set that old capri up by gradually increasing the boost up to the point of audible detonation and then backing it off slightly, hot days and a couple of passengers in the car was enough to provoke knock, I was under the impression that even minor prolonged detonation caused the piston rings to "flutter" in their grooves eventually shattering them ?.
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