Intake Interest

veecee · Post by **veecee** » Wed Jun 13, 2007 8:26 am

now gary,

take vlades picture of the venturi's inside the plenum.

if you had to turn them to face the butterfly, the leading edge would go down toward the base of the plenum, but the trailing edge would have to go up toward the top of the plenum.

so the first venturi would be raised at the back, and this would then be "in the way" or would "shroud" or would "shadow" or "block" the airflow to the lowered leading edge of the 2nd venturi.

and the 2nd venturi would shroud the 3rd, etc, etc.

does that clear it up?
calibrator, is this what you meant?

Gary57 · Post by **Gary57** » Wed Jun 13, 2007 8:30 am

Yeah VC I get that but the air is flowing through the length of the plenum and then has to change direction to enter the runners which are 90 degrees to the plemun. This change in flow direction is turbulant and disruptive.

veecee · Post by **veecee** » Wed Jun 13, 2007 8:42 am

Gary57 wrote:Yeah VC I get that but the air is flowing through the length of the plenum and then has to change direction to enter the runners which are 90 degrees to the plemun. This change in flow direction is turbulant and disruptive.

on an N/A engine the cylinders suck in the required quantity of air, and in a boosted engine the air is waiting at the gates (valves) ready to be forced in.

i think you're over-analysing this whole thing. the plenum is just a feeder tank for the intake runners, i dont think that turbulence has as big a detrimental effect as you're making it out to be. on most setups the venturi's and runners sort out turbulence before the air gets to the valves, so no big deal.

but like vlade said - i'm no expert on this, and my thoughts are merely intuitive!

Gary57 · Post by **Gary57** » Wed Jun 13, 2007 8:46 am

I was just wanting to see if there was anything "wrong" with my idea, seems not so I am happy. As I said the costs involved in building a manifold like this will out wiegh the power gains.

veecee · Post by **veecee** » Wed Jun 13, 2007 8:52 am

Gary57 wrote:I was just wanting to see if there was anything "wrong" with my idea, seems not so I am happy.

but a few people have given you things "wrong" with your idea. so it seems so, not so?

Gary57 · Post by **Gary57** » Wed Jun 13, 2007 9:06 am

but a few people have given you things "wrong" with your idea. so it seems so, not so?

Nothing to re-think the principle.

veecee · Post by **veecee** » Wed Jun 13, 2007 10:01 am

Gary57 wrote:
but a few people have given you things "wrong" with your idea. so it seems so, not so?
Nothing to re-think the principle.

ok i concede!

veecee · Post by **veecee** » Thu Jun 21, 2007 4:41 pm

you know whats really funny???

i just recieved the new product brochure for the latest M3 to be launched in SA in September.

its the full brochure with the engine specs, car options, colours, etc... and there is a lovely picture of the new v8's intakes that lie under the plenum.

remember the v8 has individual throttles, and it has venturi-type collectors that are turned towards the air intake hole. fancy that???

The Calibrator · Post by **The Calibrator** » Thu Jun 21, 2007 5:41 pm

Because it has a huge plenum chamber with a hight problem and you will find that they dont point exactly at the entrance.

veecee · Post by **veecee** » Fri Jun 22, 2007 9:41 am

nah but they close, its about a 45 degree angle. the plenum covers almost both of the heads though, so it is huge.

but looking at the picture, it seems the front ones might starve the rear ones of air - although i'm sure that tons of research went into this, because the car retails without options at 650 000. quite pricey i reckon!!!

i'll get that pic, and post it soon!

veecee · Post by **veecee** » Fri Jun 22, 2007 9:59 am

The Calibrator · Post by **The Calibrator** » Fri Jun 22, 2007 10:24 am

That looks pretty good and there are about 20 reasons why that was done like that and much time was spent on development.

Vlade · Post by **Vlade** » Fri Jun 22, 2007 10:34 am

2 things to keep in mind here guys...

1 Air is not forced in its sucked in... since its N/A
2 Each runner has its own butterfly...

the only way not to shaddow the venturies is to mount them in V pattern (speaking of the pic above) but then the length of the runners wont be the same...

I'd say the current way with the venturi pointing forward and the sloping of the plunem is the best way, that or a side induction like the old RB motors...

veecee · Post by **veecee** » Fri Jun 22, 2007 10:45 am

speaking of those RB motors.

the RB25det in its natural form has a intake that comes over the tappet covers.

and if you look closely the runners are all different lengths.

so the design from the factory has been tried and tested and it works right?

but there are people who do the swop into their s13's, and then move the throttle butterfly from the middle of the plenum to the side that faces the radiator. i know its easier and cheaper than lowering the engine to make it fit, or than buying a Greddy manifold for instance, but does it have a detrimental affect on the engine breathing???

are there some cylinders that might get more air than others???

here's pics, first of an original, and second of the mod i am talking about.

over the tappet covers:

new intake position:

Vlade · Post by **Vlade** » Fri Jun 22, 2007 10:51 am

The second car is Rezlo's