Newest Project - Lower Intake Manifold for Fabricated S4 Intakes
 

I have been toying around with this project for a while. For a long time I had my thoughts set a full cast part with an upper flange. It wasnt until this weekend that I went back to the drawing board. Spent all weekend testing various angles, and this is the "final" product. Dimensionally it is correct, but will add fillets, webs... etc as necessary as soon as I send models off to my machinist and foundry to see if it is more cost effective to machine or cast the part in the volume I think something like this will support.

First, to answer a question I know I will come up, the flange was taken from a S4 R2 head. I have no intention of doing a S3 or any earlier version. (the S3 and spider manifolds are slick anyway, why bother).

Second, it is designed around the later plastic body injectors. I have inserted the new EV14 injector model, and it fits, as well as Siemens Deka. I do not believe the original fat Bosch injectors will work, but I am making the overreaching assumption that anyone taking on a project like this would use a modern injector.

The upper "flange" is designed around a 2" OD 11g tube. This was selected for its nominal ID and structural support for some projects (like mounting ITB's or heavier plenums. There tube will sit inside the runner, providing a clean transition and collar for welding.

There is a clean and organic transition inside the part from the round tube bore, to the oval S4 port. Care was taken to try and match the entry angle into the S4 head. The injector pintle is shrouded, but can be opened up to expose it to the airflow with a mill. This was left closed to support the newer extended injectors.

You can see in the drawings attached that there is a 22.5degree bent tube in the assembly, but strait tubing could be used for a cross-runner system.

The injector boss is designed to limit the travel of the injector, so a rail without clips can be used. This boss will intentionally be cast tall for cutting down on a mill to support multiple injector dimensions.

I need to add some fuel rail hold-down provisions, which I will do today after considering the most modular approach, and hopefully will send this out tomorrow to find out if its better cast or machined, and then make the necessary final tweaks for the manufacturing method.

Please note, the linked PDF is a 3D file to be used in Acrobat Reader.

https://www.box.com/s/46gn29f56h5khafpm1ax

Thanks,
Hans

Forgot a bottom view....

Very Nice Hans. Much more complex machining than the wedge shape Ben and I worked on.

Nice.

Is the auto shifter project dead?

Interesting.

What's your target price and quantity?
Is the plan to use this with the stock intake gasket?
How much pressure can those 11g 2" OD aluminum pipes hold, with a lot of pressure cycles like in a boosted motor?
How much taper is there in terms of cross-sectional area from the head end to the runner end in this flange?
Is there a individual throttle body model that easily fits this flange?
How much room there is to match the flange if one has ported heads with much larger ports in the intake flange (I don't, just curious)?

Very nice design work Hans.

Since getting my '83S i thought about what 4 DD Webers could do for it's performance.

Has anyone done that?

Hans, this is very cool. Have you done any flow modeling?

...an example of high res intake modeling is here:
http://nsproj.googlecode.com/files/n..._velocity.mpeg

Wow, that a lot of questions.

As it relates to the intake project:

11g tubing will hold up to any conceivable boost you can throw at it. 11g is ~.12" thick or a hair over 3mm.

In my measurements, the stock intake gaskets did not match the head or intake very well. The stock gasket could be used, but this design matches the 2R head I had here, which was significantly different than the intake or gasket. I would provide new silicone gaskets that match this profile.

The taper is not that great. Area at the port of the head (in my drawings) is 1867.8mm^2, area at the port on the proposed intake is less as there is the impediment of the injector bung at 1688.7mm^2, crossectional area of a 2"ID 11g tube is 1569.6mm^2. So the difference between the port at the entry of the runner and exit at the port (in the manifold) is ~119mm^2.

It is the closest match in standard materials that I can find. Additionally the ID of the 11g tube is approximately 44.7mm, and there are several 45mm ITB available.

Ross Machine Racing (over priced items, but convenient) has intake construction extrusions and accessories that would be compatible, including their 2"OD .125" wall thickness strait tubing and velocity stacks.

I have not done any flow testing, as I dont have the FEA software to do this testing. However, I am not sure that I could improve much upon the design. There are certain constraints we are stuck with, like port size, injector placement... etc, plus the finite number of stock tubing dimensions which yielded this particular design.

There is plenty of material here for port matching an enlarged port, but I cant see any reason why someone would want to enlarge the already over-sized 928 port apart from smoothing out casting issues.

Regards,
Hans

Attached are some renderings and a 3D model of the lower intake revised with fuel rail hold down hardware. The standoffs are standard 3/4" round stock, and can either be attached with a stud, or a cap screw below.

Should be able to accommodate almost any fuel rail, including stock with a 1/4" plate bracket. Shown are some simple tabs on 1/4" flat stock.

Thanks
Hans

Great job Hans. Why wouldn't this work with an s3? Aren't the intake ports pretty much the same as an s4?

Keep up the great work,

Now we just need to make enough so that they aren't too costly.

Slick.

Sure wish these were made up when I started my intake manifold project. Building this stuff out of billet aluminum is terribly time consuming.

You're right, the 2" od is so small that 3mm wall will hold most anything. The standard rating formula gave 900 psi. I've been thinking about plenum construction, and there of course the effective OD is much larger and the pressure rating of 3mm wall correspondingly much lower.

Nice. Here's a follow up question. If the intake runners are then rigidly attached to a plenum, will your gaskets have enough give to accommodate the thermal different expansion of the intake and the block? Or should one put another flexible connection between the runner and the plenum? Perhaps I am overthinking it, but I am trying to think about all the potential cycling stresses for a boosted intake.

So if I understand this design correctly, there's going to be a minimum CSA point in the head at about the valve guide. Then, the port will expand to the flange/base, and then contract again upstream as the flange/base is blended into a 2" OD pipe which reduces the CSA again. Since the pipe is round it's optimal for friction is straight sections and maybe the acceleration-deceleration-acceleration pattern doesn't cause an inefficiency.

Still, I am curious why you didn't design this for 2.25" OD 0.125" wall thickness pipe, which would (conveniently from the math point of view) give a 3.14 sq inch or 2026 mm^2 CSA for the runner? Is it your view that the port is so much too large at the flange where the injectors spray that one is better off with a smaller diameter runner despite the non-uniform taper, and thats why you chose the 2" OD pipe for the runner?

Yeah, I get the constraints. Ross Machine Racing has 2.25", 2", and 1.75" OD runner pipe and trumpets. I guess one wants to pick form those.

I tend to agree with you that for most engines being built the port has a large CSA, probably larger than what would produce maximum average power over the used rpm band.

One simple calculator would give the peak torque rpm for 2.25" OD runner (3.14 sqin area) at 7300 rpm for a 5.0L engine and 5600 rpm for a 6.5L engine. For the 2" OD runner (2.43 sqin area), the 5.0L peak is at 5700 rpm and 6.5L peak at 4300 rpm. Since by far the most engines will be 5.0L and redline under 7000 rpm, the calculator agrees with your choice.

Tuomo,

Gaskets could be waterjet cut out of whatever material was necessary for the application. I suspect a standard .125" silicone would be fine for most applications, but its very easy for me to have them made out of a number of materials.

The CSA is greater at the mouth of the port on the head than anywhere else in the intake system proposed. There is a void for the injector and then the complete port profile. On the intake side, the injector boss displaces some of this CSA. I tried to keep the diameter someone constant between the exit port in the lower intake and the intake port of the lower intake. 119mm^2 is about equivalent to the same CSA of a drinking straw. When considering the range of materials and bends available in the 2"-11g format as compared to other tubing diameters, it was a clear choice. I think a 2.25" OD runner would be way to big, and kill any velocity for people interested in using this for single throttle NA applications. I wanted this to be useful for any S4 intake configuration.

I am working on some drawings for you to help illustrate the CSA of the port. Will post that soon.

Thanks
Hans