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Air intake pipe sizes
flak monkey - 28/12/09 at 07:02 PM

So... been thinking about what sized tubes I should run from the supercharger to the intercooler and intercooler to plenum.

The oulet of the supercharger is 2" and the inlet and outlet of the intercooler are the same. Not sure what the plenum is yet as its not arrived.

I often see systems with massive (3" or larger) pipes running from the turbo/supercharger to the intercooler and to the plenum, even though the outlet on the turbo/sc is much smaller so there are all manner of adaptor hoses fitted.

Is there any advantage in doing this? As surely it just leaves you with a larger volume of air in the system which you need to get moving, hence more lag?

My current plan is to run the whole system in 2" pipe.

Anyway....discuss...I would like to hear your thoughts.

David

tomgregory2000 - 28/12/09 at 07:14 PM

mine is:

turbo inlet 63mm

turbo outlet 51mm to 63mm silicone reducing elbow

turbo to intercooler 63mm pipe

intercooler to throttle 63mm with a reducer on the throttle to go from 63mm to 76mm

plantman - 28/12/09 at 08:17 PM

I've used 50mm all the way would have used bigger but a bit if a squash under the bonnet
I guess you know the more air in the system the more chance of lag and be less driveable but produce a bit more power, you being supercharged it should not be a problem.

Raw engineering look like they use 50mm all the way on their supercharged toyota engine.

Chippy - 29/12/09 at 12:33 AM

Keep the pipework at 2", as thats the size of the existing items, if you fit bigger between them I think you increase the lag, although with a supercharger thats going to be pretty minimal anyway. Cheers Ray

Ivan - 29/12/09 at 07:17 AM

I seem to remember reading somewhere that you should keep the air velocity in pipes to manifold below 200 MPH - so simple calc should give you some idea of size.

I could well have the figure wrong - perhaps you could google it somewhere.

Anyway a simple calc (that I am sure you are well up to) given air speed, temp and density and pipe size should give you the pressure loss over the length of pipes, then you can make decision on size.

t16turbotone - 29/12/09 at 08:11 AM

yep...i used 50mm all the way too, if thats of any help

BenB - 29/12/09 at 08:29 AM

I guess it depends how long the runs are as well. I'm sure Corky Bell has an opinion on this but I can't remember for my life what his recommendation on pipe sizing is!

I guess one way of checking would be to keep it in 2" but add some manometer take-offs. Then when the cars up and running attach a manometer to the take-offs and see if there's an obvious differential between the outlet of the blower and the I/C intake and also between the I/C outlet and the engine intake. Adjust accourdingly

MakeEverything - 29/12/09 at 10:11 AM

quote:
Originally posted by Chippy
Keep the pipework at 2", as thats the size of the existing items, if you fit bigger between them I think you increase the lag, although with a supercharger thats going to be pretty minimal anyway. Cheers Ray


^^ what he said.

Theres no advantage to reducing it if you need to increase it to 2" again.

If you go too big, youll end up with a 1000 RPM power band, and nothing low down. (extreme Lag).

Keep it 2" all the way through the intercoolers (there will be two on mine), and try and get the plenum to accept 2".

I suppose it would help to try and get the plenum as small as possible to avoid it having to 'fill up' before pressurising??

Just my two bobs worth.

In the future, im planning to re-make a fibreglass planum for mine to eliminate the big heavy monster of an inlet manifold, and this will be almost direct to each cylinder from a smaller plenum in an attempt to eliminate lag completely.

Incidentally, mine is all 50mm.