Airbox hiclone, inlet size, engine inlet air flow speeds, pipe sizes/restriction

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Mar 3, 2004
Please check and tell me if I am correct. I may have mucked up as it seems to fast
Forgetting about the turbo requirement which obviously requires more air, lets talk about a naturally aspirated engine. Petrol or diesel, doesn't matter.

4200 cc / 2 (4 stroke) x 4000 RPM / 60 (secs)
=140000 cc of air per second.
If the air inlet to the engine was 10 cm x 10 cm = 100cm sqd, then 140,000 / 100 = 1400cm or 14 metres per second flow requirement. 14 metres per second is the equivalent of 50.4 km/h.

As the air inlet for a LC 100 1HD-FTE, through the inbuilt Toyota hiclone device in the entry to the airbox has only a square area of 36.32 cm sqd, then the speed of the air must be a lot faster to get the same amount of air into the engine.
100 cm sqd / 36.32 = 2.75
2.75 x 50.4 km/h = 138 km/h
This is very fast so by increasing the piping to the air box would slow this down and create less restriction.

Tehnical views appreciated as well as any corrections.
The only thing you forgot is volumetric efficiency. For naturally aspirated it could be 0.75 -0.85. Nothing fancy like exhaust gas tunning and such.

140 Km/h (40 m/s) is not that fast for air. I't only mach 0.11. Compressibility effects starts at 0.5.
Besides SPELLING, any othe info on the original post!
tech content: what is your point, what are you asking, and what exactly are you trying to do? :)
Does the intake air need a high velocity to spin the dust out of the air thru that turbulator (a Caterpillar/Donaldson term) device?

Your maths is probably right - 1 underground mine I worked at had the air requirements for each bit of gear stencilled on it, and IIRC, a 1HZ was over 8000l/min.
Something like that anyway - it was a long time ogo.

I dont know which to use.
This..... :rolleyes:
or this.... meh


You have spelt Warn incorrectly.

apart from my Warn typo in my sig, what's your f#cking point? MacQuarie 4x4 work on Toyota engines all the time and my suggestion was to phone them given their expertise.
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Unlike your local Toyota dealer?

4wd Advert Magazine....:rolleyes: + meh


my local Toyota dealer
1) said that getting massive dust in the l/h back of the LC100 was normal, despite none on the r/h side and none of my friends LC100s have any dust issues
2) couldn't fix my aircon and sent it out to a third party
3) f#cked up an accessory install, i got it fixed elsewhere.

Advert? nope...the company in question is on the DVDs a lot, been mentioned on 4WD TV a lot.....(through their custom trucks section)

so thanks for the spell check.
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