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Air Box Info......

WOT - Wide Open Throttle.

I.E. the part of your engines operating regime, it probably spends least time at - even on a track day.
 
Yes it is as simple as that until you start trying to pressurise things.
I was trying to think of a simple analogy(first mistake) that those without a grasp of physics could understand and I should have said if you pass water through a funnel, I tend to use funnels to flow liquid (oil especially) and had not even concieved you'd think I was talking about air as I can't say I have ever used one for that! (air trumpets on webbers and Dellorto's perhaps being the very lose exception)
Of course what you are saying is right, when talking of air and the creation of venturi effect when the bottom of the funnel is in an area of depression or lower pressure than the top. But I don't remember saying anything about forcing air through my funnel or pressure differentials! I was trying to keep it VERY simple.
For the pedantic consider a Bucket filled with WATER with a small hole in the bottom, the water will empty (flow) out a lot quicker if you make the hole a lot larger. if you make the bucket bigger ie more fuel and air in (remember it's just an analogy,please) but the hole stays the same size the flow or emptying will stay the same (assuming no change in pressure!) or to put it another way remove the restrictions to flow within the exhaust system (without losing all back pressure before some bright spark pipes up) and you can flow more fuel and air into and out of the combustion chamber which in turn will create more power.
As for how much difference the hot air makes I don't know but I can say that a few articles that I have read state that the air box mod on it's own makes little or no difference and can infact lose power. See Adrian Palmers (ex RS reg sec) piece in long ago PP for more detail.
 
Laurence please accept my appology as I'm sorry if you think I'm being Pedantic. I'm just having a discussion with you and who ever else joins in.

I thought about air and not water / fluid seeing as we were talking about air.
I thought about it being sucked through the funnel / trumpet / inlet manifold seeing as we were talking about engines.

I was just applying the principles of air being sucket by an engine through the funnel you described. Again I agree with your description of what happens with a bucket with a hole in it full of water allowing it flow out of the bucket due to nothing else but gravity.

My only original point was that I couldn't see how allowing the engine to suck more air would reduce power. Based on the 2 pictures I've posted if you go from standard to the mod shown and do nothing else then you are right in that it may not produce more power, but I fail to see how it would lose power. I've called Adrian and left a message and I'll let you know what he says. The way I see it the mod just removes one of the many potential restrictions of allowing the engine to suck in the required amount of air. I guess the next restriction on the way to the engine is the throttle body and after that the science of a correctly designed manifold to achieve the optimum air velocity is key. If you flow more air / fuel to produce more power without modifying the exhaust then I guess you will build a higher pressure in the exhaust system. I admit I have no idea what effect this will have. I still say its not as simple as that, just my opinion.
 
I know I did'nt explain or perhaps make it clear enough what I was trying to put accross which is why you thought of air rather than fluid (if I had chosen the bucket in the first place you would not have wanted to put it in an engine and pressurise it[:D])(stop right there anyone thinking of a dry sump[:D]). I was trying to put accross that if you do alter one element but do nothing to improve the other elements there will little and sometimes no gain.
I don't think your type of filter would lose any power but the type that are just placed directly in front of where the old filter was "might" and the same can be said of a drilled air box . I will do a seach of some threads that I remember reading on the subject.
 
Just to get a bit more technical, as this subject intrigues me, the power must also be related to the way the air flows. The intake consists of a number of pulses of air being sucked in by each cyclinder, so there is a lot of stop/start air flow. It would seem to be a good idea to reduce the stop/start, ideally to make it continuous. Air has inertia, so takes time (and energy, as supplied by the pistons sucking it in) to get up to speed, and the fuel injectors/air intake must work best at an optimium air flow.

So, opening up the air intake may make the pulses more stop/start, so less power ??

My supercharger puts the air through the same size plumbing as normal, but, because it is being pushed, there is less air inertia to be overcome ? Also, of course, more air in general, so the flow must be smothed out.
 
Interesting. I thought the reason for more power with a supercharger / turbo was because you have compressed the air to make it more dense and hence get more air in to each cycle. I hadn't considered that the smoothing of the stop start affect would also help, if indeed it does.

If opening it up makes the pulses more stop start and as suggested less power I'm not sure why the setup attached works. You don't get more OPEN than this. This is Adrian Palmers induction system. Good for 400bhp normally aspirated and having driven it can say it sounds awesome, and goes a bit too.

Coming back to the original idea that you must do something to the exhaust if you open up the air filter restriction I'm willing to bet that if you bolt this lot onto a standard car accompanied with a remapped ecu you would still get great results without touching the exhaust.

Stop messing around Yoda, dont delay and order it today.

5DAFA1B9005C45BAB9A8A8D2F4E10937.jpg
 
While Laurence is right in theory, that there is only so much air you can out in without modifying the outlet side, I can see no evidenvce that these cars could get anywhere near that limit based on the mods discussed.

This is about a very simple process. For power, you want as much air as you can get into an engine mixed with the right amount of fuel. You then need to get the waste "air" out efficiently. So long as you don't exceed the limit of the exhaust system, you will keep getting power gains so long as you get more air/fuel mix into the engine. As you aproach the maximum capacity for the exhaust system, the gains reduce, to the point you cannot see any gains at all. This is due to the gain from the larger "explosion" being offset by the effort needed to pump the air through the restricted exhaust. I have seen this point reached on turbo engines and what normally happens is that you stop seeing power increases and start seeing heat build up.

So the only question is, are we near that limit with the standard exhaust. My research suggests we must be a fair way off. If you can bolt on a supercharger to a standard engine with standard exhaust and gain as much power as I have seen claimed, I can see no way you could get anywhere near the same amount of air into the engine through non forced induction means, other than dramatic changes to cam profile etc. We are not talking about that so, for the given amount of time that the inlet is open, I am very confident that on standard cams there is no way you could reach the limit of the exhaust system.
 
Well, the replacement air box cover has arrived so I think it will be out with a saw tonight. I may try and copy the Fabspeed design so as to leave a lip over the top to prevent water dripping in - other than that, its all coming off.

Interesting debate, would love to think there are some power gains but happy to settle for some induction roar.

Cheers for the input - if anyone ever wants to try it out (especially on a dyno), feel free to come and try mine as it only takes a minute to swap.
 
Supercharging and indeed turbocharging present a completely different set of circumstances when regarding exhaust flow. The delicate balance of tuning exhaust for maximum scavenge and extraction (most tuned exhausts do not flow exhaust gases they "suck" them out) becomes less of an issue to an engine that is being force fed and literally blows the mixture in, so to speak.
However we are talking about a normally aspirated engine and the given characteristics of exhaust flow when applied to said engine. If your theory for normally aspirated exhausts actually held true Porsche would not have spent considerable time and effort modifying said exhaust for the cup car or indeed redesigning it for the 993. Porsche's admittedly conservative figures for the cup car added a scant 5hp to the 260 of the standard RS. Likewise Adrian Palmer could have saved himself an awful lot of money if the standard exhaust could work as well normally aspirated as it does when supercharging.
"explosions" in a combustion chamber are very much not wanted. Far better for the fuel to ignite and burn rapidly.
 
Laurence

I can see that I am going to have to be very careful with my wording in future. I used the word explosion in inverted commas to show that is not the right use of the word. However, back to the matter at hand.

I think you are talking cross purposes when you say that if my theory is true, why did Porsche spend the money and time building better exhausts. They are 2 totally different matters. Just because an exhaust isn't up to its "capacity" doesn't mean it cannot be improved on. If that was so, it would not be worth doing any mods without replacing the exhaust system to begin with. ASAIK, it is possible to gain more power from a standard set up without changing the exhaust at all.

I probably shouldn't have made any comment about turbos as they are a completely different ballgame. However, suoerchargers aren't. I note the claims of Ninemeister that you can just bolt on their supercharger and with no other changes get 350 bhp and 330lbs/ft of torque. That is on a standard exhaust. I am sure that by using a better exhaust even more power would be unleashed, but that is not the point. The exhaust obviously has the ability to handle the amount of exhaust gasses produced at that power. Therefore it is safe to assume that on a car producing less power, the exhaust might limit gains but it won't stop gains altogether. There is definately spare "capacity" in the exhaust system.

Good luck Yoda. Hope it gives you pleasing results.
 
as supplied by the pistons sucking it in
Click to expand...

Common misnomer.

Piston's don't "suck". When moving down in the bore they create a depression. Atmospheric pressure seeks to remove this depression by flowing air.
 
Well, enough of all this theory, schmeary. Got the airbox cover in the post yesterday and proceeded to dismantle it. Took about half an hour to remove the funnel and cut away the centre and then file everything down to a neat finish. A couple of minutes to put on and it looks quite good, could easily pass for factory finish.

End result - sounds bloody good under load and easy to refit original if required. I guess as I drive it a little more I'll get a feel for any increase/decrease in performance but to be honest if we are talking up to 5bhp I will probably struggle to tell the difference.
 
Common misnomer.

Piston's don't "suck". When moving down in the bore they create a depression. Atmospheric pressure seeks to remove this depression by flowing air.
Click to expand...

Thank you for the physics lesson - I was just trying to economise on words. And the pistons create a partial vacuum, not a depression.

Humph !

Disgruntled of Hammersmith.
 
If opening it up makes the pulses more stop start and as suggested less power I'm not sure why the setup attached works. You don't get more OPEN than this.
Click to expand...

The secret here is that they don't all use the same inlet pipe, so they don't share the stop/start pulses, which is where the problem comes in.

Also, I didn't mean to imply that the supercharger worked by smothing out the pulses, just that this is a by product of it's action.
 

Seems like we've come full circle. I have never said that you cannot make more power by altering both the fuel and air into the engine and I have no doubt that it can be done. What I did say was that modyfying the airbox alone (no other mods) makes very little difference and does not produce much more power and sometimes can produce no gain. Doing the mods in a more balanced way DOES make a difference. I also have no doubt that the standard exhaust has spare capacity but to get the best out of the mods U do, parts of the exhaust that hinder flow are best replaced to free up and make best use of the new mixture.
Proof positive comes from the results of dyno tests. Last year at JZ machtech the RS register had a dyno day. From memory the best 964RS made 281 HP this car had both modified air box cup pipe and remapped chip. Do you believe the car would have made the same figures on the standard exhaust. Mels car makes in excess of 310hp (hope i got that right) his car features a freshly rebuilt engine mass air flow set up modified air box and cup exhaust (although I believe he's reverted to the final silencer for noise reasons) again do you believe the car would have made that power with the standard exhaust . Your theory suggests that the standard exhaust is good for 350hp so it should have the spare capacity right?
All those wishing to ditch there cup pipes cat bypasses and g-pipes please forward them to me I will give them a good home [:)]
 

ORIGINAL: John Bellringer

Common misnomer.

Piston's don't "suck". When moving down in the bore they create a depression. Atmospheric pressure seeks to remove this depression by flowing air.
Click to expand...

Thank you for the physics lesson - I was just trying to economise on words. And the pistons create a partial vacuum, not a depression.

Humph !

Disgruntled of Hammersmith.
Click to expand...
Let's get really pedantic!! I thought depressions were found in conversations about weather systems, rather than fuel injection systems :D I think we should be talking about low pressure areas.
 

Actually I can't see a problem with "suck" at least not the dictionary definition anyway which states "drawn in" and just in case I looked up draw too and that says "move in a direction" so in effect to suck the air in I guess really what is being said is "that air is being moved in the direction of the pistons" not exactly wide of the mark[:D][:D]
Sorry could not resist.[8D]
 
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