Airbox construction

[Mr Ed]

So if I understand this correctly, If you run a 50mm TB fed by 50mm tubing, building a big arse airbox is a waste of time. The only reason a big air box could be justified would be if the tubing increased from tb to box. Big Funnel. For the amount of time and effort I'd doubt you'd se much increase besides in intake noise.

A big filter flows more air than a small filter, so any decent intake will have an increase in size between the throttle and the intake opening.

Yes, filterless ITBs dont require an airbox at all. We've already covered this.

Trying to prove Quality over Quantity arguement

Yeah stay away from those low quality Chinese oxygen molecules. Proper american oxygen molecules are the only ones worth burning.

[Mr Ed]

Well the N54 is a nasty piece of work for that... one inlet into one turbo goes at the front of the engine, the other goes round the back for the rear facing turbo...

The airbox inlet is OTR style...

See that flat tapered POS pipe below?

And?

I imagine the engineers would have had to compromise their design to fit within the engine bay.

[takai]

Yep, probably done for packaging reasons. There are a few exceptions to these rules. The Audi or BMW race cars way way back used a tiny inlet into the bellmouthed area.





See here:
http://www.bufkinengineering.com/intake%20manifolds.htm


Besides the original question is all about airboxes for quad throttle setups, which in effect is really a plenum anyway.

[chartreusehj]

Yeah stay away from those low quality Chinese oxygen molecules. Proper american oxygen molecules are the only ones worth burning.

Ever had the opportunity to breathe chinese air?

id wager there is indeed a difference between the oxygen PERCENTAGE in the atmosphere in downtown shanghai versus say, the daintree rainforest, or what our two headed friends down south have available in the low lying areas.

trouble is, there aint many racetracks to test that theory, but there are in the states and an unusual amount of records get broken at certain racetracks due to factors not related at all to the track, rather its location.

the most oxygen anyone gets to burn in an ICE in ideal conditions aint even 33% of the total volume of air ingested and even thats with the adding of a chemical blend, not natural.

so yeah, theres a difference...

A friend of mine likens inlet airflow to a b double truck, needs a nice turning radius and not too many stop/starts or shit goes bad...

Im going to call the above, Rule2 which covers the design parameters of any inlet tract and any part of it.

[Mr Ed]

So im guessing you missed the point of why I mentioned 'Chinese' air then?

[chartreusehj]

So a shitload of dirty china spec air is better than 20% less cold clean air?

No, because your cold clean air is likely denser for the same volume, means more oxygen in the same size space so less volume at a much lower temperature is always a winner.

Otherwise the innercoolah industry has pulled the wool over many an eye.

Ill always take the increased density of cold air, as long as the volume of it is still sufficient, and efficiently moved from A to B

combine Sufficient and Efficient and its happy days!

dunno, im confused now...

[ahk068]

My basic point is rather than fuck about build a wiz bang big arse air box, just get the one you've got to work more betterer.

[chartreusehj]

I cant remember the original point of the thread, so im out lol.

[Russell]

No, because your cold clean air is likely denser for the same volume, means more oxygen in the same size space so less volume at a much lower temperature is always a winner.

Otherwise the innercoolah industry has pulled the wool over many an eye.

Ill always take the increased density of cold air, as long as the volume of it is still sufficient, and efficiently moved from A to B

combine Sufficient and Efficient and its happy days!

dunno, im confused now...

Best way to put it.

[GTSBoy]

Now that's an interesting design. You can see how it is intended to work. The slot is going to shoot the air across the plenum "floor" and then the air will up and over and down into the trumpets.

The only problem is that in order to make the air distribute evenly through the slot, the slot will want to be narrow enough to make a decent pressure drop - ie it has to work like a nozzle. If the slot is wide enough that it doesn't make a restriction, then it is not going to do ANYTHING to distribute the air evenly. You are still relying on somehow making the entry conditions to the slot nice enough that the air is presented to the slot evenly.

id wager there is indeed a difference between the oxygen PERCENTAGE in the atmosphere in downtown shanghai versus say, the daintree rainforest, or what our two headed friends down south have available in the low lying areas.

trouble is, there aint many racetracks to test that theory, but there are in the states and an unusual amount of records get broken at certain racetracks due to factors not related at all to the track, rather its location.

the most oxygen anyone gets to burn in an ICE in ideal conditions aint even 33% of the total volume of air ingested and even thats with the adding of a chemical blend, not natural.

so yeah, theres a difference...

I think you'd lose your money. The actual variation of O2% in the atmosphere does not vary very far from 20.9% anywhere. Cities are little places compared to the atmosphere. Even rainforests are little places compared to the atmosphere.

Even allowing for the local displacement of O2 in the air by combustion products from cars and industry etc, the maximum variation in dry O2 percentage would only be in the order of 0.1 to 0.2%. That's far less than changes due to humidity.

The differences seen between racetracks are NOT due to changing oxygen %. They may be due to changes in pressure (ie one being higher than another) or perhaps humidity - but not oxy%.

cheers

[takai]

Now that's an interesting design. You can see how it is intended to work. The slot is going to shoot the air across the plenum "floor" and then the air will up and over and down into the trumpets.

The only problem is that in order to make the air distribute evenly through the slot, the slot will want to be narrow enough to make a decent pressure drop - ie it has to work like a nozzle. If the slot is wide enough that it doesn't make a restriction, then it is not going to do ANYTHING to distribute the air evenly. You are still relying on somehow making the entry conditions to the slot nice enough that the air is presented to the slot evenly.

That one pictured is a replica of the Audi factory ones from the 80s, which tended to work DAMN well. See the photos just above the cutaway.

[chartreusehj]

I think you'd lose your money.

cheers

duly noted, i dont have much anyway...

[GTSBoy]

That one pictured is a replica of the Audi factory ones from the 80s, which tended to work DAMN well. See the photos just above the cutaway.

Yeah, I can see it's the same layout, if not the same workmanship!!

The Audi one pictured has a nice taper on the entry part of the plenum, same as anyone smart would do on any plenum. I guess the slot makes sure that the incoming air doesn't flow straight over the tops of any of the trumpets. All the air gets to the trumpets from below them - which can only help. Even if the slot doesn't flow evenly over its whole length (say it flows more at the far end like you'd suspect it would), I guess it will still have a decent effect on the way the air gets to all the trumpets.

[Ben Wilson]

Yeah, I can see it's the same layout, if not the same workmanship!!

The Audi one pictured has a nice taper on the entry part of the plenum, same as anyone smart would do on any plenum. I guess the slot makes sure that the incoming air doesn't flow straight over the tops of any of the trumpets. All the air gets to the trumpets from below them - which can only help. Even if the slot doesn't flow evenly over its whole length (say it flows more at the far end like you'd suspect it would), I guess it will still have a decent effect on the way the air gets to all the trumpets.

Someone did a hell of a lot of work developing one here