inlet plenum designs

[tsoob]

Man there is a lot to it haha

Has anyone used bellmouth's inside the plenum> they are supposed to help suck air into the runner

Runner size, i know that for my car we want a shorter runner, but what about the diameter? the big port head has huge ports, but if you go to big in the runner diameter won't that slow down the velocity of the air?

for a 1600 you want about 2.4l (from all the sites i have visited most say capacity x1.5)

what else do i need to consider?

[RomanV]

For single throttle I'm guessing?

Turbo or NA?

[cat007]

Inlet manifold design for a force induction engine isn't as mission critical as if it were for an N/A.....

[frost]

tell that to top secret japan,
i remember they spent over 60 hours on a 6 cylinder manifold, making 12% more power then before, i must find that article again,

i planned on using trumpets on the 3sgte but settled on radius ed runner intakes,

[cat007]

tell that to top secret japan,
i remember they spent over 60 hours on a 6 cylinder manifold, making 12% more power then before, i must find that article again,

i planned on using trumpets on the 3sgte but settled on radius ed runner intakes,

over 60 hours and only 12%? stink!

[matt dunn]

We made trumpets inside my plenium on my race car,
and we have also made them for inside the one on the MRS.

On my car they are in the plenium but before the ITB's as it's multi throttle,

and on the MRS they are inside the plenium after the throttle, as it is single throttle.

[gasman]

60 hours for 12%. i would be happy with that.

[cat007]

We made trumpets inside my plenium on my race car,
and we have also made them for inside the one on the MRS.

On my car they are in the plenium but before the ITB's as it's multi throttle,

and on the MRS they are inside the plenium after the throttle, as it is single throttle.

Cool. Have you got before and after dyno graphs?

[matt dunn]

Cool. Have you got before and after dyno graphs?

No, so no proof that they work or dont,

But the question was is anyone using them and the answer is yes.

[frost]

tell that to top secret japan,
i remember they spent over 60 hours on a 6 cylinder manifold, making 12% more power then before, i must find that article again,

i planned on using trumpets on the 3sgte but settled on radius ed runner intakes,

over 60 hours and only 12%? stink!

12% of 500hp is 60hp = 560hp.
also there was a 12% rise in torque through out,
that's what differs Japanese tuners from others, they push the envelope from what they have/make not just turn up the boost.

[4agtepwr]

Thats a fairly rash statment, seems to me that the jap's can build them but it takes the Americans, Puerto Rican's, Aussies and even little old NZ to develop them to there potenial, Only really have to look for the worlds fastest sport compact cars to realise whos ahead when it comes to engine development.
My plenum has about a 15mm radius entry, I think a full radius is indeed better but the likes of the greddy GTR and 2JZ plenums are just a radius entry and not a full radius trumpet and they seem to work really well

[Mr Revhead]

Inlet manifold design for a force induction engine isn't as mission critical as if it were for an N/A.....

Or could it be that in a turbo there are other facters adding more power to disguise the loss/lack of gain from an average manifold as oppsoed to an optimised manifold?

[matt dunn]

Inlet manifold design for a force induction engine isn't as mission critical as if it were for an N/A.....

Or could it be that in a turbo there are other facters adding more power to disguise the loss/lack of gain from an average manifold as oppsoed to an optimised manifold?

or is it that a 5hp gain on an NA car is a big deal,
where a 5hp gain on a turbo motor is considered bugger all.

[Looonie]

My plenum has about a 15mm radius entry, I think a full radius is indeed better but the likes of the greddy GTR and 2JZ plenums are just a radius entry and not a full radius trumpet and they seem to work really well

Its a bit late at night for me to get my head around this... any pictures to help clarify for us lesser intellectuals please?

[4agtepwr]

I dont have a pic of the entry, sorry but that plate is 20mm thick and it has a 15mm radius on the entry, the runners are 100mm long from memory and 50mm diamter and then tappers down to the smallport flange. I cant really tell you how big the plenum is but id say it would be at least two and a half litres, maybe bigger. Seems to do the job, but its only part of the puzzle i guess

[tsoob]

the biggest challenge i can see is being a big port the size of the runner is going to be a challenge. How long are your runners 4agte?

[tsoob]

we just did some calculations now.

engine displacement 98 cubic inches (whoo baby)
Peak torque 5000rpm
Optimum intake runner area 1.38 SQin (8.9cm2)
Runner length 9.4cm long 6cm round (volume of tube 8.9cm2

[RomanV]

Regarding runner diameter.

Think about this for a second.

The idea of an intake runner is to accellerate 'still' air (or there abouts) at the far end, to the maximum velocity at the other end (at the port)

So. Work out the cross sectional area of the entrance of the port.
(I sketch it into Autocad, then list properties to find area of shape...)

Now work out the diameter of a circle with this much cross sectional area.

If the diameter of your runners is less than the size of this circle, although it will have a higher velocity inside the runner, the air is going to be slowing down towards the port. Which is where it matters.

So it seems like a bit of a misnomer to say that smaller runners get better velocity, if you have small runners and large ports, you're most likely going to get less velocity at the port entrance than if you had a runner size which maintains the cross sectional area.

Small ports and small runners may very well work better than large ports and large runners, but if you've got big ports, to me it makes sense to have the runners the appropriate size to suit that.

[tsoob]

ok, what i was thinking was 60mm across at the start of the bellmouth (which is the same size as the port (but the port is oblong shaped)

And shape it to the shape of the ports at the other end (head end)

So it would look like an upside down pyrmid of sorts..

will that be right?

[RomanV]

Cant say, without knowing what the cross sectional area at the port entrance is.