optimum airbox volume?

29th October 2011, 09:29

does anybody know or can work out the optimum (or min/max) volume of the airbox/piping after the filter to the throttle body. was gonna put this in track section but wasnt sure so plz move if you feel its better there. cheers

29th October 2011, 10:02

if you have the parts, block the holes off and fill with water, then poor in to a measuring jug

29th October 2011, 10:14

i know how to find the volume of something. i wanted to know what size air box would be more benificial performance wise as ive been told the size and shape of the box effects throttle responce and overall power

29th October 2011, 11:25

would like to know the answer to this one as im sure i got better performance from my factory airbox than the induction kit

29th October 2011, 11:57

i wanna know because ive got a design in mind that im going to make but i need some rough volume mesurements that will give me the best power/throttle responce.

29th October 2011, 12:37

Think you would be best off speaking to Adsayer (or Barry whatever he is called on here now lol) - He did a lot of this sort of stuff a while ago with all complex maths and stuff to do with the OE airbox

29th October 2011, 13:00

The perfect intake would be an enormous air box with a proach enormous filter with the lesse restiction as possible, and overall, overall the maximum of air fow immidiatly available.
You have to know that the ideal intake has got a volume of about 10 times more than the cylinders one: it means about 18 liters of contenance for a 1800cc3 engine like the 18C.

Of course this is not all. A good intake has a good internal aerodynamic without any perturbations.

The filter is by définition a restrictive thing because its part is to prevent a direct contact by etablishing a wall of filtration. The more closer it is forme the engine, the less power is loosed. By definition a N/A engine "inhale" itself its air. If the filter is close to TB the engine doesn't have to spend too much energy to obtain the needed air. If the filter is far (as it is the cas for a CAI) from the engine have to make much more efforts to obtain the air. There is a pump effect. The distance is too important. There is a lack during a certain times between the moment where the engine inhales the air and the moment where all the air arrives and it doesn't arrive in enough quantity. To imagine the situation, think to a human being. When you breath you don't have probleme because your nose is short. If you get a mask: no problem fecause the filter is near your nose. The problem appears when you put 2 small pipes in your nose. If the small (in diameter) pipe have 1 meter of longer you will not breath as well as if the cas where the pipe would have 10 cm.
If you breath in a box of 20 cm3 it is much more difficult than if you breath in a box of 1m3.

quote from teg forum

29th October 2011, 13:33

Quote:

Originally Posted by db_sax

The perfect intake would be an enormous air box with a proach enormous filter with the lesse restiction as possible, and overall, overall the maximum of air fow immidiatly available.
You have to know that the ideal intake has got a volume of about 10 times more than the cylinders one: it means about 18 liters of contenance for a 1800cc3 engine like the 18C.

Of course this is not all. A good intake has a good internal aerodynamic without any perturbations.

The filter is by définition a restrictive thing because its part is to prevent a direct contact by etablishing a wall of filtration. The more closer it is forme the engine, the less power is loosed. By definition a N/A engine "inhale" itself its air. If the filter is close to TB the engine doesn't have to spend too much energy to obtain the needed air. If the filter is far (as it is the cas for a CAI) from the engine have to make much more efforts to obtain the air. There is a pump effect. The distance is too important. There is a lack during a certain times between the moment where the engine inhales the air and the moment where all the air arrives and it doesn't arrive in enough quantity. To imagine the situation, think to a human being. When you breath you don't have probleme because your nose is short. If you get a mask: no problem fecause the filter is near your nose. The problem appears when you put 2 small pipes in your nose. If the small (in diameter) pipe have 1 meter of longer you will not breath as well as if the cas where the pipe would have 10 cm.
If you breath in a box of 20 cm3 it is much more difficult than if you breath in a box of 1m3.

quote from teg forum

reads pretty badly and poor spelling

Is the ideal intake really 10 times the cylinder volume !? I find that hard to believe bearing in mind the intakes on the 4.0+ V8 and V10 audi engines ?

I've got a book on intake and exhaust design so will have a little read later on and update here

29th October 2011, 13:36

Quote:

Originally Posted by raunchz

reads pretty badly and poor spelling

Is the ideal intake really 10 times the cylinder volume !? I find that hard to believe bearing in mind the intakes on the 4.0+ V8 and V10 audi engines ?

I've got a book on intake and exhaust design so will have a little read later on and update here

I know, he's foreign lol

29th October 2011, 15:36

Quote:

Originally Posted by raunchz

reads pretty badly and poor spelling

Is the ideal intake really 10 times the cylinder volume !? I find that hard to believe bearing in mind the intakes on the 4.0+ V8 and V10 audi engines ?

I've got a book on intake and exhaust design so will have a little read later on and update here

I heard about the 10x larger than engine capacity for N/A'd cars but it does seem a bit loose and open debate. Is that book by smith and morrison dude?

29th October 2011, 17:51

Surely having the filter further away would be better as you can have a brilliant induction with the air at high velocity but the second it hits the filter it's slowed down. Wudnt it make more sence having it away from the tb so then after the air has been slowed it has the chance to speed up again because of the decreasing diameter of the scoop/pipe. Or am I missing the point? Cheers for all the replies.

29th October 2011, 17:54

Quote:

Originally Posted by Barry123

I heard about the 10x larger than engine capacity for N/A'd cars but it does seem a bit loose and open debate. Is that book by smith and morrison dude?

Yeah thats the book - is a bit old fashioned but a good read. Got it from amazon a little while ago as was looking into inlet and exhaust designs for the 16v engine.

Ran out of time to get measuring and putting an excel workbook together - got halfway there

29th October 2011, 17:54

GMC worked out the perfect length/angle and size between the throttle body and the filter, ask john