INTAKE MANIFOLD ( Modification / Design / Fabrication )

[A20A1]

Intake Runner Length (L)
Knowing that the pressure waves (positive or negative) must travel 4 times back and forth from the time that the intake valves closes to the time when it opens and the speed of the pressure waves, we can now figure out the optimum intake runner length for a given rpm and tube diameter. We must take into account the intake duration, but you want the pressure waves to arrive before the valve closes and after it opens (air wont pass though a closed valve). To do this you must subtract some duration, typically you take off 20-30° from the advertised duration. 30° works well for most higher rpm solid cammed drag motors. So the Formula to figure effective cam duration (ECD) will be:
ECD = 720 - (Adv. duration - 30)
For a race cam with 305° of intake duration it will look like this:
ECD = 720 - (305 - 30)
The ECD of that cam would be 445
The formula for optimum intake runner length (L) is:
L = ((ECD × 0.25 × V × 2) ÷ (rpm × RV)) - ½D
Where:
ECD = Effective Cam Duration
RV = Reflective Value
D = Runner Diameter
If our engine with the 305 race cam needed to be tuned to 7000 rpm using the second set of pressure waves (RV = 2) and had a 1.5" diameter intake runner the optimum runner length formula would look like this:
L = ((445 × 0.25 × 1300 × 2)÷ (7000 × 2)) - 0.75
So 19.91 inches would be the optimum runner length.

ECD = 720 - (Adv. duration - 30)
ECD = 720 - (288 - 30)
ECD = 720 - 258
ECD = 462
The ECD of that cam would be 462
__________
The formula for optimum intake runner length (L) is:
L = ((ECD × 0.25 × V × 2) ÷ (rpm × RV)) - ½D
V = ???
ECD = Effective Cam Duration
RV = Reflective Value (why does it = 2?)
D = Runner Diameter (Inner diameter)
If our engine with the 288 race cam needed to be tuned to 7500 rpm using the second set of pressure waves (RV = 2) and had a 1.50" diameter intake runner the optimum runner length formula would look like this:
L = ((462 × 0.25 × 1300 × 2)÷ (7500 × 2)) - 0.75
L = ((300,000)÷ (7500 × 2)) - 0.75
L = (300,300 ÷ (15000)) - 0.75
L = (300,300 ÷ 15000) - 0.75
L = (20.02) - 0.75
L = 20.02 - 0.75
L = 19.27
__________
Well out comes the firewall.
I want to know what the v stands for... if the value is wrong so is my calculations.
the formula I got is from browsing the net.

[fromerly89Exi]

Has anyone attempted this. I have all the resources to do this, I just dont know where exactly to start. Longer runners or shorter, etc..... It would made completely out of stainless steel.

[AccordEpicenter]

longer runners will give you more peak torque but short runners give you high hp on the top end. Ive never seen anybody attempt making a custom intake for an a20.

[fromerly89Exi]

i work at a stainless steel tubing manufacturer. i have access to everything except a lathe and a milling machine.

[Mike's89AccordLX]

I have a short ram intake and I'm putting a hoodscoop right above the filter.

[PhydeauX]

Idealy you want trumpet shaped runners with flairs on the ends.

http://www.sdsefi.com/techinta.htm
Some nice pictures on how to do it, look at the toyota 22R manifold near the bottom.

http://www.billzilla.org/inlet.gif
A chart for calculating inlet length. The total length from the valve to the end of the trumpet is calculated so you need to subtrace the length of the port to get the runner length.

Remember that b16a, b18a, and b18c5 manifolds can be easily adapted to fit on our motors. So make sure you do your homework and come up with a good design, because you can easily enough pick up an ITR manifold off ebay for a few hundred, drill a few holes in it, and your good to go.

andy

[Mike's89AccordLX]

Ahh crap we're talking about intake "manifolds." I'm interested in getting a custom manifold.

[AccordEpicenter]

yeah also you need to have it taper in and then flare the ends, it in creases velocity and thats how the honda and most other manufacturers design it

[1989lxicoupe]

the intake manifold fomr bseries fits our cars , do the ports line up i know te bolt holes dont?

[bobafett]

1/2 the bolts do!

[1989lxicoupe]

i would like to know why this is a performance mod, the civic intake is for a small displacement engine, also the bolts arnt a proplem its the ports do the ports line up, im am not nocking the idea but just questin it, has anyone seen or notecd and gains in this i would like some solind info
thanks,
Kevin

[fromerly89Exi]

and what about port-matching? if there is the slightest difference it will produce a bad swirl

[fromerly89Exi]

i'm also working on a CAI with a velocity stack(reducer) from 3" to 2.5" just before the throttle body. Anyone else try this?

[IWLSF]

Damn, intake runners for a 22R? That's tje same motor in my pickup...

[b20a86lude]

i work at a stainless steel tubing manufacturer. i have access to everything except a lathe and a milling machine.

hey see if u can make an itb for me for the a20a3 ill pay whats reasonable thnx

[A20A1]

Look for the B16A or B18C5 manifolds

they have the same ports as us just slightly different mounting stud positions which is fairly easy to fix.
REDLINE WEBER ITB
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[Sabz5150]

Individual Throttle Bodies.

That is all.

[Accordtheory]

I think the LS integra manifold would be the best option for a street driven car. It has a large plenum, and long big runners, and its engine has the most similar powerband to the A20 of the b series. (Except the b20, but that manifold is huge, it sticks up like a tunnel ram). I have the aebs typhoon manifold for the B16/B18C5, but the reason I chose that is that of the aftermarket b series manifolds, it is the only one I could find that showed good gains all over the powerband, unlike the edelbrock unit, and I believe it also has a larger plenum than the skunk2, which I was previously considering.

Also, I have this theory about how forced induction moves the volumetric efficiency curve of an intake manifold upward in the rpm range, so this may make the LS manifold an even better choice for those who want to go with forced induction..

As far as designing and building a completely custom manifold from scratch, that would be ill to the fullest, and I was actually considering doing that at one point. (I still have the flange) The reason I didnt is if you don't know the formulas for plenum volume, runnner length, runner taper, etc, etc, (I admit I don't) you are going to be building and dyno testing a lot of manifolds before you get one that delivers what you want. I would recommend starting out by at least trying to copy one that is a known quantity, and then going from there.

[smufguy]

Alright, after a long research it is common sense that the B series intake manifolds modded to fit the A20 motors are the best to use for Turbo application. Then comes the question of what kind of design should the intake manifold carry to utelize the maximum flow of pressure with minimal restriction. Larger and streamlined plenum with short runners are the best for the application despite the engine rpm since its forced induction. Instead of slapping on widley used or recommended intake manifolds, i would like to list pretty much all the good quality manifolds available off the shelf for good companison and pick out the best at hand. The following images/products are the manifolds i want to choose from and recommend it to people who are along the lines of turboing their car since the quality of these are superior and reliability is great. So here are the following.

BBK (around $120)



Edlebrock ViictorX ($220 to $350)



Venom ($500 to $600)



JG Engine Dynamics {Endyne} ($ unknown)



AIR Endyne ($400 - $500)



NOTE: The reason for the comparisons is purely based on performance on these manifolds and valid technical responses only. All the bullshit and offtopic posts will be deleted by a mod upon my request to keep this thread clean and specific.

PS: Price is not an issue so do not use it as a reason. If price was a reason for me, i wont be undertaking the turbo project and neither would have many who are under way. I have a pick in my mind with reasoning behind it based on my engineering. Aside from that, i would like to hear what people think would be good based on their experience either personally or thru their friends. Thanks fellas.

[AccordEpicenter]

you forgot the AEBS intake mani

[smufguy]

you forgot the AEBS intake mani

like i mentioned above these are my selections. I did look over it and i disregarded it for the same reason i omitted skunk2. They have much longer runners than the AIR Endyne (longest runner of the pack). and their plenum design and volume is not what i desire.

[AccordEpicenter]

the skunk 2 isnt that much better than the the stock B16/B18C5 intake mani, but the AEBS is one of the best ones for the money ~$150 ish

[NXRacer]

i'm assuming that the BBK will accept aftermarket fuel rails like AEM etc. Thats a pretty nice price for an IM. Its hard to find good stock B series IM's for that cheap.

this has got me thinking. . . . . .

[smufguy]

no fellas, im not talking about the price at all. or what it would accept. Im asking which one will flow good cause all these flow differently and neither of you so far replied to what i asked for.

[AccordEpicenter]

as for flow it probably goes like this...

Victor X>BBK>Venom>JG, Endyn>AEBS>Skunk2>Stock B16/B18C5