Airbox for Carbs and TB,s

changed my mind,im going it make a grp on


easier, cheaper (can get materials free) only need one mould,


will be able to mould round some type of tubing - of a suiatable diameter to which other after market piping would be attached


i feel a business venture comming on.......


tim

 

get to work!

 

designing it now........

 

I would be interested in giving it a go - but it depends what power its
rated to - 250hp needed - let us know what the flow tests show

I have a 2L 16V Seat Ibiza on 45mm throttle bodies (but they may become
48's this year)

Noise is now a major issue with TB cars - and if you have a powerful one
the induction noise is massively more than tailpipe noise - so much so
that I am not evenb bothering going back to donnington until I get an
airbox fitted

Cheers

Rob

 

oh rite ok, thats interesting to hear,


ill have a think about that,


what would be an approx maxair flow rate for a car on 45's?! -or is that an impossible questions to answer?!





tim

 

i should go dig my airbox out take some pictures and let you see what you think.

 

Assuming 100% efficiency, on a 2L engine at 7000rpm, it'd be around 0.06 m3 / sec.......

I think, off the top of my head ......

 

Whats the airbox total volume in cc?

 

Me old Jetta (memory lane) only ran socks but they quietened things down massively to no socks.. (which did get me pulled off track a few years ago.. Something to do with hearing me go all round the circuit! Woops.. but ACE!)

 

That jetta did sound kool, could hear the colway slick all the way in to Quary, sounded like it had a eaton charger on it.

Size on that airbox did worry me a bit, ideal is 1L of airbox capacity for each 100cc of engine capacity I believe.

 

bump on this thread following trip to autosport international

right - I have finally found an airbox that will fit my ibiza, this one, took loads of measurements off the one on the pipercross stand and have today made an exact dimensional copy in cardboard, and it fits ! finally may get to go to donny again...(looking forward to kicking some golf ass in 2007)

BUT

Is it going to be restrictive ?????? 100mm inlet to the box but is only approx 6.3L in volume.....

if the pipercross guy is on here still, I would love to hear about those flow tests you were going to do and the types of power people have run with these boxes fitted ?????

 

hugely interesting webpage about resonant theory in airbox design:

http://www.calsci.com/motorcycleinfo/Airboxes.html

"A modern engine with valve overlap will naturally have a dip in the torque at about a third to a half the red line rpm. If the air box is tuned to have minimum resistance to air flow at this rpm, the dip in the torque curve will be partially filled in by the ease of pulling air into the engine.

So, your air box is most likely designed to add horsepower in the mid-range. The air box will have little or no effect on peak hp"

pipercross box is approx 6300cc
10cm ducting has intake cross sectional area = 78.55 cm2

resonant frequency of box will be following rpm for (inlet tube length in cm)

7279 (10)
5147 (20)
4202 (30)
3639 (40)
3255 (50)
2971 (60)
2751 (70)
2573 (80)
2426 (90)
2302 (100)
etc

So if you have a dip in your torque curve, perhaps by tuning the intake length it can be improved upon.....

If take 30cm long duct as a point of interest, resonant frequency for a 6300cc box is 4202rpm. If that was an 8000cc box, freq would be 3729 rpm. If it was a 4000cc box, it would be 5274rpm.

Air speed in a 10cm diameter pipe at 8000rpm is 0.49mach (169m/sec) so the pipe may be getting restrictive to flow

Now, if 75mm bore tube is used (cross sectional area 44.18cm2) and assuming our 6300cc box again:

resonant frequency of box will be following rpm for (inlet tube length in cm)

5459 (10)
3859 (20)
2729 (40)
2228 (60)
1929 (80)
1726 (100)

gas speed in a 75mm bore tube at 7000rpm is 300m/s of getting scarily close to speed of sound 340m/s

75mm bore tube is not a good idea

starting to understand why mini miglias have such huge air intake ducting:



so sounds like a short intake pipe is a good idea for beefing up midrange, approx 30cm with 100mm ducting, but this has to be balanced by the need for an effective cold air feed......and it could do with being abit longer to achieve this goal...hmm....

 

interesting link

http://e30m3performance.com/tech_articles/engine-tech/airbox_symposium/index.htm