Author Topic: Intake manifold for NA (Read 10339 times)

Ivan Petrov · « **on:** April 18, 2009, 07:00:00 PM »

Can anyone help me with tips n tricks for building intake manifold for Natural Aspirated engine

I`m planning to biuild it for single trottle but I can`t find on net know-how for NA intake :confused:

Are these types of manifold siutable for NA engine?
http://www.picvalley.net/u/2690/1592085381574043803.JPG
http://www.picvalley.net/u/2050/14228201831731706904.JPG
http://www.picvalley.net/u/2702/17009939681844704442.JPG

Deftones · « **Reply #1 on:** April 19, 2009, 09:47:16 AM »

these are good for a turbo or supercharged engine, for na is better a set of throttle bodies, you can take them from a M3 or an M5 or if you are quite good in do-it-yourself you can adapt some motorcycle ones (from an R1 or a CBR or a hayabusa should be perfect)
anyway you can put on what manifold you want but the problem remains the MAF...

Ivan Petrov · « **Reply #2 on:** April 19, 2009, 05:47:01 PM »

I will use single trottle, but I want custom manifold

I couldn`t find info about building manifold for NA engine, so i decided to take an idea from the experts... That`s right, I`m talking about M GmbH! I like most the E46 M3 CSL air box and I`m planning to build something similar to it
http://img18.imageshack.us/img18/4605/manifold.jpg

Deftones · « **Reply #3 on:** April 20, 2009, 03:45:43 PM »

i think you wants something like this:

http://cgi.ebay.it/BMW-M3-E30-S14-AIRBOX-CARBONIO-CORPI-FARFALLATI-FLAUTO_W0QQitemZ260393086794QQihZ016QQcategoryZ33613QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

it is a set of throttle bodies from an M3 e30 with a small carbon airbox and with a custom made flange designed with CAD and made by CNC machine... i think you cannot do a better job for an M42, the only problem is that all this is meaningless without head machinery and lots more rpm

xwill112x · « **Reply #4 on:** April 20, 2009, 03:58:23 PM »

Why do people want to do mods that give them no gain?

In actuality, changing the manifold to much with out some sort of tune would probably cause some huge flat spots in the power band.

Ivan Petrov · « **Reply #5 on:** April 20, 2009, 04:05:23 PM »

Good work, but a lil bit difficult for me to build something like this. Maybe I`ll try my luck with something like the CSL airbox with S14 trumpets...

Quote

In actuality, changing the manifold to much with out some sort of tune would probably cause some huge flat spots in the power band.

One of the most important for NA engine is the intake, I`ll try to make it that the air comes more direct to the engine... I expect better response, and I can also tune in what RPM to have peak point of torque

If I keep my OEM manifold I can only polish it...

Bunta · « **Reply #6 on:** April 20, 2009, 08:31:37 PM »

Quote from: Deftones;70440

http://cgi.ebay.it/BMW-M3-E30-S14-AIRBOX-CARBONIO-CORPI-FARFALLATI-FLAUTO_W0QQitemZ260393086794QQihZ016QQcategoryZ33613QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

This is SICK.
What a nice setup I wonder how much it'll go for?

Hunter

Deftones · « **Reply #7 on:** April 22, 2009, 06:02:29 AM »

i don't know how much power he gains, i only know that he sold the whole car for 4000 euro and he used that airbox with an M3 MAF

however, a friend tried to make something similar to his stock 318is e36, using only a fuel pressure regulator and using the M3 TB and airbox and he loses quite all the low torque and gains not so much in high rpm, then he made a smaller airbox and the car runs lot better. in simple words a too much large airbox on a stock engine is worst than a smaller airbox

Ivan Petrov · « **Reply #8 on:** April 22, 2009, 06:08:01 AM »

Thanks for the useful info

:cool: I have doubt about using 2 or 3 mm aluminium profile... 2 mm would be easyer for cutting but I`m not quite sure if it`ll hold on the weight of the trottle :confused:

Deftones · « **Reply #9 on:** April 22, 2009, 02:11:27 PM »

use 2mm for the surfaces and 3mm for the corners and the borders

Ivan Petrov · « **Reply #10 on:** April 23, 2009, 08:47:40 AM »

Ok but in this case it won`t be smooth becouse of the corners in the manifold caused by different aluminium profile

RouteZeroDesign · « **Reply #11 on:** April 26, 2009, 04:28:05 PM »

Emm...
http://img18.imageshack.us/img18/4605/manifold.jpg
^The visible flap on an M3 CSL airbox is for a switchable second entry into the airbox, the m3 csl uses Independent throttle bodies!

By copying the CSL style and only using a single throttle body at the chamber throat, you will be losing allot of torque, and probably horsepower too.

Have a search for Helmholtz frequency/resonance before setting out to build an NA plenum.

NA plenums are allot harder to get right compared to a turbo manifold.

Basically, an NA plenum should promote even distribution of air to each cylinder aswell as increasing the suck effect of the engine.
Where as a turbo manifold has to ensure even distribution of air to each cylinder, and guide the air as smoothly as possible into the engine.
It is allot easier to guide air, than it is to help suck air.

Good luck with making your manifold man, but please read up on what your doing first, they're allot harder to get right than they look..
...ive been designing/prototyping mine for nearly a year now!

Ivan Petrov · « **Reply #12 on:** April 27, 2009, 05:34:02 AM »

I won`t be sure till I don`t try it

Thanks for comments

Ivan Petrov · « **Reply #13 on:** November 21, 2009, 08:45:18 PM »

Ok, I already know the design of the manifold and also the runners lenght but I couldn`t find info about the throttle... I have 65 mm throttle from M30B35, but this week I founded that the M52B20 throttle is about 67 mm wich is not big difference but if I need to replace da trottle it would be more easy to find M52 throttle than M30. I`m worried about something else - bigger diameter of pipe - lower air speed, smaller diameter of pipe - faster air speed but less air! As I mentioned I couldn`t find formula about how big trottle I need... I want better response! How to calculate how big throttle do I need or the bigger is the better

I calculate it like this - 4 cylinders engine and 4 intake valves with diameter 45mm, as you know the engine uses only 90% of the valve so 41mm diameter... This means that r=2.05mm! S=Pi (3,14) x r x r
3.14 x 2.05 x 2.05 = 13.2 ... this is the area of one valve but I have 4 valves so 13.2 x 4 = 52... In other words this is the area from wich the air comes into the cylinders. So I need throttle with area about 52 or little less to have better response and also getting enough air.
We have throttle with 65mm diameter and r=3.25 so 3.25 x 3.25 x 3.14 = 33... smaller than the area of the four valves! That makes me think that something is not as I think.

Any ideas