OEM D-Series Intake Manifolds

[saxophonias]

Here we will see the OEM intake manifolds that D-Series are equipped with and we could use.
The worst manifold ever, is this one, found in d14a3/4/z and d16y7.

Here is the same next to d16z6

Here is the one from d16y8

D15b7

Who is going to add the plastic manifold of d14a8?

And this is for Ilya

The auto y8 manifold has the whole for iacv blocked, as this is on the TB like d14a4. So the auto guys just use their own TB and block the whole that is left if they have bought a manifold from manual transmission which the most likely.

[Law_]

D15B7's looks nice.
D16Z6's and D16Y8's look similar. The volumn of the plenum looks Bigger on Y8 but the Z6s is more beautiful... In terms of performance are they similar? Cheers

[saxophonias]

Which performs better is a big debate There are several dynoplots but i don't think we can say for sure.
First you have to measure their air capacity. In order to get an idea you can do the following experiment. Tap all their holes and fill them with water. Then measure the water they took and you will see which can accept the most capacity.
After that you can measure the size of the runners (length and width). These to get an idea. Joris can do some measures
As far as i know these 2 oem manifolds have some slight differences in mid and high revs. But actually no big deal.

[Law_]

i've read that IM should have:
Large plenum for capacity
Short and fat runners for max. hp
That water thing is great
If someone has these IM's around could do some measures.
Thanks !

[SquirtAndSpark]

short runners gives you power on low rpm. long runners gives power on height rpm.
(search for acoustic supercharging )

IM desing also changes the poweband.

[Law_]

i've encountered this:
Quoting:

"A large plenum has a few draw backs though so it is not the magic bullit either. A large plenum breathing through a single butterfly will have a lag between throttle opening and engine response.

Long thin runners = low end torque
Short fat runners = high RPM power"

What it seems to me, is that design is important but for the shape itself we cannot say if this or the other one are better...

[TassosNitrous]

For a force-fed application, runner design is less of a factor than for a N/A design. Plenum volume is the key---the rule of thumb is plenum volume >= engine volume when force-fed. A large plenum has a few draw backs though so it is not the magic bullit either. A large plenum breathing through a single butterfly will have a lag between throttle opening and engine response.

Basically, there is no easy recipe for intake design. There are some rules of thumb---long thin runners=low end torque, short fat runners=high RPM power plenum volume=engine volume for superchared applications but there is no perfect solution nor is ther an easy formula (helmholtz calculations can get pretty scary when one takes valve timing exhaust pulse velocities, intake pulse velocities exhaust length and desired operating conditions into consideration---even then there are 12937492137 not even accounted for so you are nowhere near optimal).

http://www.physicsforums.com/archive/in ... 80364.html

Being a physicist i can't agree more with the above. Besides, i noticed a tremendous improvement in the high rpm range when i installed the Edelbrock intake manifold in Saxophonias's car.

[Law_]

was my quoting site also

[SquirtAndSpark]

short runners gives you power on low rpm. long runners gives power on height rpm.
(search for acoustic supercharging )

IM desing also changes the poweband.

looks i make a big mistake

please read this page, is very complete

http://www.team-integra.net/sections/ar ... icleID=466

[Law_]

i've read it all and did some calculations...
for me, to have peak torque at 6000rpm and volumetric efficiency of 1 i should have: 35cm in lenght and 4cm in diameter IM. can someone give aprox measurements of D16Y8? B headers fit our engines? Thanks