Designing a good NA intake manifold?

[spetz]

What are some key aspects to a good NA intake manifold?

At this stage, I am thinking slightly bigger runners, about 4-5cm shorter than factory.
Bigger plenum with two throttle bodies on each side of the plenum (48mm each)

What are ram tubes? What do they do exactly?

Anything else to look out for/ask to make?

[chef_32]

yeah runner length is key, but it must be matched to the desired engine rpm, diameter should probably be slightly larger then overal port diameter. Plenum volum is usually meant to be something like 3-5 tims the engine displacement depending on how much damping and response you want.

why do you think you would need 2 throttle bodies??

[fatboyz39]

why don't you just go ITB?

[spetz]

Well it will be run only by a piggyback ECU, so I doubt that would be ok with ITB?

2 TB is better than one
And if I am making a custom plenum may as well go 2 smaller rather than 1 larger

[panda[cRx]]

i really dont think the gains will be worth it man. but props for trying something different.

let us know how it goes when its done

[barefootbonzai]

it's strange that you wanna invest time into making a new intake when you're only willing to run piggy back ecu. Really doesn't make any sense at all.

[saxman]

I wouldnt' worry as much abotu two throttle bodies, as I would about a center mounted throttle body that'll allow symetric flow to all four runners. Proper runner length is key, and a good airhorn design at the plenum. Plenum volume is based more on individual cylinder displacement.


If you're going to be going down the route of multiple throttle bodies, don't stop with two, go with itbs


whatever you do, you're going to want a real ecu set up to tune the motor with.

[spetz]

Unfortunately the ECU is from a couple of years back and at this stage I don't have the money to upgrade it :(
I do plan on getting a full standalone IF I end up doing cams, which I plan to

Does anyone know exactly what ram/velocity tubes are? Apparently they speed up the air and are good for NA's

With a center mounted TB, wouldn't the middle runners get more air than the side ones?

I would go ITB, but I don't think there is any way to tune them with just piggyback is there?
And really I am already stretching the budget quite a bit (engine has been rebuilt, ported heads etc)

[sivic]

With a center mounted TB, wouldn't the middle runners get more air than the side ones?


then wouldnt that be the case with 2 TB on either side of the IM except the outer runners would get more air than the middle ones?
although it is ideal to have each cylinder having equal access to airflow source, such is the point of ITB's, its not a massive issue for engines which are still fairly mild. think about a stock setup and the distances each runner is away from the TB. no real problems

[spetz]

What if then, it uses a single larger TB, and the plenum is design in such a way that at the other side of the TB the plenum is smaller therefore air goes quicker to the end runners, and the side with the TB is larger so it goes slower to the runners. Would this even it out?


Is there, realistically, any benefit of twin over single TB?
My understanding was with 2 smaller TB's the air velocity is kept higher with the same rate of volume goine in which = more power/torque


Anyone can explain ram/velocity tubes?

[saxman]

having the plenum like that is rather typical for that exact reason... it doesn't work as well as a center mounted, symetrical design, however.

With two throttle bodies going into a single plenum, you're going to have MAJOR air turbulence issues.


A velocity stack is basically a the taper into the runner that's designed to increase velocity and prevent turbulence into the intakes. If you're going as far as making your own intake manifold, this is a very important feature to have. The air horn section needs to be properly designed(the specs for this should be readily available) and the runner length needs to be tuned to specific rpm ranges for valve reversion and all that fun jazz.

[2MPRSS]

Unfortunately the ECU is from a couple of years back and at this stage I don't have the money to upgrade it :(


Dont say that,find your self some money and find ur self a new ecu trust me:thumbsup:

[spetz]

No really I just can not afford any more at the moment :(

So much so I owe money to the builder and I have an overmaxed credit card


I just want to design a really good manifold that gains power now and will be good too once cams go in

Maybe a larger single TB mounted in the middle of the plenum is the way?
I don't know if there is space. The engine is also a V6

[saxman]

with a V6, you could probably get a way with running two throttle bodies, on two intake manifolds. You do not want two throttle bodies going into the same plenum... going to cause way too much turbulence.

[BlitZ]

i read an article on hyundai excel tuning ahahahaha

they have like aftermarket performance manifolds with dual throttles on each side.. it supposidly makes power.. but its a hyundai..

[spetz]

Saxman, How would I tune this though with just a piggyback?

At this stage I think I will leave the intake manifold as is due to money constraints (just found out I need to pay for some custom rod bolts). I will run the 5mm oversize TB I already have on it, and at a later stage maybe once I get a better ECU I will upgrade the intake manifold

Assuming I have a full standalone ECU, what kind of gains will a ITB setup give me?

[saxman]

itb set up isn't going to make huge peak hp gains... what you get is huge midrange gains, amazing throttle response, etc... definetely worth it, especially if you have a well flowing head, higher compression, etc



what motor is this work occuring on?

[spetz]

It's on a 6A12 MIVEC from an FTO but in a lancer 2 door body

What will ITB effect though?
MIVEC kick in point? Top end power?
What happens with cams?
How is idle???

[TODA AU]

What are some key aspects to a good NA intake manifold?
At this stage, I am thinking slightly bigger runners, about 4-5cm shorter than factory.
Bigger plenum with two throttle bodies on each side of the plenum (48mm each)

What are ram tubes? What do they do exactly?

Anything else to look out for/ask to make?

There is no "pot of gold" in horsepower here.
Combination is everything.
There can be power to be made with different manifolds but is has to be tuned into it.
If the combination isn't right, you'll just go backwards.

Regarding ram tubes.
In quad throttle arrangements, the ram tube offers two benefits.
A) It's an ideal design that maintains laminar air flow so that the air volume entering is maximised with minimum turbulence.
b) The lengths are important. This is for shock wave tuning.
If you want to know more about this, check out "Helmholtz Resonance".
It's the wave properties of sound in closed & open pipes.
In layman’s terms, the idea is to catch the positive sound wave to stuff more into the cylinder. Further you want that to occur through the rev range. That is you want to catch the 1st, 2nd, 3rd etc harmonic.
Get it right & you get something for nothing. Get in wrong & the engine falls flat. Tuning cars with quads can be creepy. Things such as "stand off" can occur where a cloud of fuel will hover over the trumpet at full noise. Changes in injection timing will see it devoured by the engine. The cloud fuel is held stationary in the air but the sound waves.

As a general rule of thumb,
Short runners are for top end, long runners are for low end.
Plenums also resonate.
Large plenums for low end, small plenums for top end.