Power loss

How big role does the intake manifold play on a N/A application? Would it be possible (with an unskilled designed one) to loose hp. To be more specific, would it be possible to loose in the region of 18hp on a 2l 16v engine :disappoin ?

intake manifold design is VERY important. With a piss poor manifold, yes i think its possibly to lose that much hp. Air velocity, equally length manifold runners, all play an important role.

What an answer. Thank you. I didn't even know of things like "Air velocity, equally length manifold runners....." Would you please be so kind to elaborate a little bit, especially on air velocity and equally length manifold runners. Just a little bit. Where would I be able to find more info?

In a nutshell, the air in an intake manifold has mass. Every time the valves open and close that mass of air has to move and then stop. If they are all not equal length intake runners, their inertias are different and one cylinder will get less air while another will fill more fully. There are manifolds with different length intake runners, but the manufacturer has the benefit of billions of dollars worth of test equipment and computer modelling to make sure that it doesn't cause abnormal flow qualities.

As a general rule, as you lengthen or narrow intake runners, they favor low RPM torque production. As you shorten or widen intake runners they favor higher RPM torque peaks. This effect is less in Multiport EFI because the mass of the air in the runners doesn't carry fuel with it. With a carbureted or Throttle-body injected intake, the gasses moving through the runners is heavier since it carries fuel with it and the affect it has on the physics in the manifold is increased.

Another general rule is that as you increase the size of the Plenum, it favors higher RPM torque peaks, but again, this effect is minimized with MPFI

Thank you again. This information is very informative. Just one quick question. Doesn’t the air get sucked into the engine causing an equal distribution of air into all intakes?

Are you able to post some pictures of your set up?

First of all Im curious, Im always interested in home made custom work, it shows a lot of intiative.
Second of all it will us have a better idea of what it is your doing, and may give us some clues as to whats going wrong.

Are you able to post some pictures of your set up?

First of all Im curious, Im always interested in home made custom work, it shows a lot of intiative.
Second of all it will us have a better idea of what it is your doing, and may give us some clues as to whats going wrong.
Sure thing. Will take a pic in the morning (seeing that it is like 22:06 Monday) and I will then post it during the course of tomorrow. Here is a pic of my project ride. It is a Nissan LDV RWD application with a weight of plus minus 650kg's. Forced induction will follow soon.


http://img.photobucket.com/albums/v451/simonella1/Picture036.jpg

Thank you again. This information is very informative. Just one quick question. Doesn’t the air get sucked into the engine causing an equal distribution of air into all intakes?

i could relate all this to some crap even i wouldnt completely understand to helmholtz's stuff.

but i am too tired.

for a more refined approach, try this, think of a 4cyl engine as 4 individual motors sharing a common crank shaft and air source.

each piston must pull its own air... lets make your lungs piston 1 at TDC right before the intake stroke, go get a smaller straw, bigger than a coffe stirer but larger than thoes fat assed things they use at mickey D's something you can feel resistance to sucking.
suck with all your might untill you cant suck anymore (air that is) now cut the straw in half and repeat... notice a difference? :eek7:

10 / 4

CB has given you the key to the knowledge that you seek; helmholtz's work applies greatly to the design of an intake manifold, and to to exhaust design as well (though i'm still not sure if stock exhaust resonators are intended to attenuate noise or help exhaust flow). research "helmholtz resonator" and after a but of reading curtis' post will make even more sense to you. the major problem with intake and exhaust resonance is that the effect helps only in a narrow region of of the engines rpm. i once found a whitepaper on the design of an "active" helmholtz resonator which used a viberating diapharam in conjunction with a microphone in the resonator chamber, and controlled by an opamp, to cause the chamber to resonate outside of its tuned frequency. it is unfortunate that i lost the url, and i don't know if i downloaded the file; at least i printed a hard copy.

found it! if you don't understand the math don't worry. an engineer i showed this to said the math did not matter so much if you just want the gist of the idea, and it is an interesting alternative to the dual runner design.

http://www.egr.msu.edu/~radcliff/LabWebPages/home/papers/SmartHR.pdf#search='active%20helmholtz%20resonator '

Guys, here are some pics of my intake. Please note that it is a project car and that we are still in the process of making it looking good as well as being strong as well.

http://img.photobucket.com/albums/v451/simonella1/Picture013.jpg
http://img.photobucket.com/albums/v451/simonella1/Picture012.jpg
http://img.photobucket.com/albums/v451/simonella1/Picture011.jpg

Moppie, please be so kind to advise.

Moppie, please be so kind to advise.


Listen to Curtis and the other guys, they are the ones who know what thier talking about :)


From what I can see the manifold looks pretty good.
Possible things I can see causing a problem are:

Inlet running length, they are very short.
Plenum chamber size, is it big enough?
Intake running to Plenum Chamber join, is the angle to sharp? does the air have to make a radical change in direction?

Did you do any resurch into manifold design before building it?
They are an interesting mixture of science and art and require a lot of thought to make them work right.

What did the engine come out of?
If its the one I think it is, then its from the same family of enignes that are in the MX5, Famila/323/Astina/Laser and 626/Telstar.
If so you might find that a Manifold from an MX5 will fit, or may require some small modication to the inlet runners to fit larger ports on the 2.0L head.
Or, it might give you some idea of the design you should be copying, in terms of runner length, plenum size etc.

Plenum to small. Got sorted out. Thanks guys.

it appears that you have great metal fabrication skill, the intake looks good. i went digging through some of the stuff that i found when researching intake manifolds and subwoofer design, you'd be surprised how similar the two subjects are. here is some stuff that is actually usefull.

this one is a good reference:
http://www.grapeaperacing.com/GrapeApeRacing/tech/inductionsystems.pdf

though i don't think you need guidance with the metal work aspect of fabricating a manifold, this site has pictures of the fabrication process. note the use of velocity stacks at the end of the runners.
http://www.themininut.com/inlet.asp

also since you said that you plan to install some type of forced induction device the manifold specifications will be less critical, though a tuned runner length would be beneficial. you would probably have been more pleased with your creation if a turbo charger, i'm asuming, was already in place.

I agree 100% with zagrot, but I wish to add something. The construction of the intake is less critical with forced induction, but only under boost.

For instance, if you construct an engine designed for low-rpm power but use a large, short-runner intake, you'll have sluggish performance. If you add a turbo tuned for high rpm boost, you'll have an engine that is frustratingly sluggish until boost comes in.

Although the intake design has less importance under boost, its still wise to tune a proper intake for times when you're not under boost. I guess what I'm saying is, since intake design has little to do with performance during boost, but a lot to do with performance off boost, design it for the naturally aspirated engine so you have the best of both.

it appears that you have great metal fabrication skill, the intake looks good. i went digging through some of the stuff that i found when researching intake manifolds and subwoofer design, you'd be surprised how similar the two subjects are. here is some stuff that is actually usefull.

this one is a good reference:
http://www.grapeaperacing.com/GrapeApeRacing/tech/inductionsystems.pdf

though i don't think you need guidance with the metal work aspect of fabricating a manifold, this site has pictures of the fabrication process. note the use of velocity stacks at the end of the runners.
http://www.themininut.com/inlet.asp

also since you said that you plan to install some type of forced induction device the manifold specifications will be less critical, though a tuned runner length would be beneficial. you would probably have been more pleased with your creation if a turbo charger, i'm asuming, was already in place.

Thank you very much. Yip, by forced induction I mean the Turbo route, the only route!!!!!!!!!!

I agree 100% with zagrot, but I wish to add something. The construction of the intake is less critical with forced induction, but only under boost.

For instance, if you construct an engine designed for low-rpm power but use a large, short-runner intake, you'll have sluggish performance. If you add a turbo tuned for high rpm boost, you'll have an engine that is frustratingly sluggish until boost comes in.

Although the intake design has less importance under boost, its still wise to tune a proper intake for times when you're not under boost. I guess what I'm saying is, since intake design has little to do with performance during boost, but a lot to do with performance off boost, design it for the naturally aspirated engine so you have the best of both.

You guys are rocking.

one thing i haven't seen mentioned, & it can make quite a bit of difference, is port matching. not just between intake & head or head & exhaust but also port matching your gaskets. ideally, you can get all your ports to equal sizes between cylinders for equal flow, but also, matching the mating surfaces of the intake/head so that the openings are precisely the same shape & alignment, AND trimming the opening part of the gaskets so that the transition from intake, across the gasket, to the head, is a completely smooth one. granted it is a time consuming task, but one that yields an engine that doesn't have as many "quirky" spots across it's rpm range.