Individual Throttle Bodies and Improved Airflow

[Dessertrunner]

Hi Adam,
Due to the closeness of the throttle to the head it is changing direction going from a circular to oval to match the head.

Your point about building a mould sounds good but I am not sure I can keep up with all the current projects I have infront of me now. But I would like to understand how I would do it so if you have any suggestions were I go to learn more I would appricate it.

Tony

[Dessertrunner]

Trying to post images

[oab_au]

Originally Posted by Boxersix

What are you factoring in for taper in the throttle bores and the ram pipes(v-stacks)??? I've always calculated in about a 1.5% taper per inch in these type of setups to maintain laminar flow throughout the induction system. Many shrug off taper as being a useless/unnecessary variable in the designs of these "grassroots" setups but it really is not the case.

Just curious.

Also, have you considered composite ram pipes of your configuration? Now that you have a CNC you can mill you own molds and go nuts. It's what I do. Screw sticking to the off-shelf stuff now that you have the equipment

I agree with tapering the tract, to reduce the velocity where it is not needed, and increasing the velocity at the port where it is needed.

The bit that does change things is the amount of taper or belling of the inlet end of the tube. If the ram tube is parallel with only a small flaring at the inlet end, the sound wave will do all the expanding at the end to give a strong but narrow pulse.
if the inlet end has a lot of taper, the wave will start expanding as it travels up the taper, reflecting all the way. This gives a less intense, reflected pressure, that covers a wider rev range. It works the same as a megaphone on the exhaust.

Also if the ram pipes are made out of a flexible material, the sound wave will diminish as it expands and contracts the pipe.

Harvey.

[Dessertrunner]

Originally Posted by oab_au

I agree with tapering the tract, to reduce the velocity where it is not needed, and increasing the velocity at the port where it is needed.

The bit that does change things is the amount of taper or belling of the inlet end of the tube. If the ram tube is parallel with only a small flaring at the inlet end, the sound wave will do all the expanding at the end to give a strong but narrow pulse.
if the inlet end has a lot of taper, the wave will start expanding as it travels up the taper, reflecting all the way. This gives a less intense, reflected pressure, that covers a wider rev range. It works the same as a megaphone on the exhaust.

Also if the ram pipes are made out of a flexible material, the sound wave will diminish as it expands and contracts the pipe.

Harvey.

Interesting Harvey, if the crazy brain I have thinks this through Adams point of a tappered intake makes sense as it enables a constant acceleration of the airflow which inturn means that the amount of force required to suck the air into the intake is the lowest possiable. Okay this means then its a balance of narrow enough to get airflow velocity up high enough to be able to force the air into the cyclinder at the bottom of the piston stroke and large enough to keep friction down low.
So how does length factor in here, my guess its all about the sound wave pulses and there ability to interfear with the airflow between valve openings. At low revs the time between sound pulse is greater so if the pipe is longer it takes that sound wave longer to travel along the pipe before it excapes the opening of the ram pipe, sound wave really are just air shock waves.
Okay so your logic Harvey is that the mouth being larger at the opening is better is right if my tooth fairy logic is right.
As the wave reaches the edge of the ram pipe it will slow down therefor giving the valve more time to open.
If you imagine air inside the Ram pipe going into the engine then valve closes and the sound wave bounces back if it reachs the out let of the pipe before the valve opens it will stuff up the air going into the pipe. My guess is at that Point (harmonics) the engine will run like **** due to the disruption of air flow.
Dumb question but if the sound wave is such a big issue why wouldn't you have the 2 vavles at slightly different opening and closing timing?
Tony

[oab_au]

This will take a bit of answering mate.I'll get back later.

Harvey.

[Dessertrunner]

**** Harvey I though you had the answer on the top of your head, just kidding.
I wonder if anyone in the SVX world has formula for airflow friction inside a small diameter pipe? Would be good to run some numbers over the pipe design. Also tooth fairy tells me if we know the airflow & velocity we might be able to rough calc the pipe as regards harmonics (problem just dreaming here).
Tony

[Dessertrunner]

This is interesting has a airflow simulation as well

http://www.epa.gov/eogapti1/bces/mod...y.htm#animate1

Check the difference duct shape example

Tony

[Dessertrunner]

I finally got the ram pipes from the UK and they look great they will give a intake path length of 350mm and they start wide getting smaller as they go. I am pretty sure they won't meet Adams target tapper but they will be great to get started with. Here is a couple of photos.





Tony

[Boxersix]

Originally Posted by oab_au

Also if the ram pipes are made out of a flexible material, the sound wave will diminish as it expands and contracts the pipe.

Harvey.

Most certainly correct as the flexing of the pipe will alter the resonance of the wave. Composite(carbon) of appropriate weave, layering, and resin ratio will result in a ram pipe lighter and even more rigid than a comparable aluminum counterpart. The benefit of aluminum is off shelf availability as well as low cost. Building them out of composite eliminates any constaints prefab aluminum stacks leave you

Originally Posted by Dessertrunner

Interesting Harvey, if the crazy brain I have thinks this through Adams point of a tappered intake makes sense as it enables a constant acceleration of the airflow which inturn means that the amount of force required to suck the air into the intake is the lowest possiable.

The big thing with taper to remember is that it maintain laminar flow throughout the pipe. Air flowing down a pipe with straight walls creates turbulence in itself along the walls of the pipe due to a breakdown in the laminar flow. Many refer to this as a "boundary layer", which remains much more stationary than the flowing air at the core of the pipe. Air flowing over a layer of air has less friction and less turbulence than air just flowing over a surface

Originally Posted by Dessertrunner

I am pretty sure they won't meet Adams target tapper but they will be great to get started with. Here is a couple of photos.

They've got taper according to that picture, and in this case unknown taper is better than no taper Those look quite nice actually

[oab_au]

There is a fair but of taper on them, so it will spread the resonate peak over a wider rpm range, than all arriving at the same rpm with a BANG.
The overall length at 350mm looks OK also.

Harvey.

[Dessertrunner]

I hope to get the injector ports and mounts sorted this weekend I have it mounted in the vice but I am having trouble with it moving due to the fact that its a fully adjustiable vice. Anyway I will figure a way around the problem.


HAve a good day all.
Tony

[Boxersix]

Mill a jig at the appropriate angle and mount in a single axis machinist vise or bolt directly to machine table with you part attached.. Compound machinist vises never have the rigidity required for this type of work and often require multiple repositions to complete the machining process, which is just a pain in the arse.

[Dessertrunner]

You are right Adam its a pain and slow doing it in the tilt vice. Your idea of makeing a jig to put in the normal vice is smart I didn't think of that. As usal I am in a rush so I managed to get by with the tilt vice for now. Finished the first one and have the injector ports cut out. There is no doubt the 3d cad is the only way to go it makes it easier to do the job right the first time.
Here is a photo of the injectors test mounted.


Next challange is the new mounting plate for the ram pipes I need then to bolt further to the side so I have more meat to drill the bolt into.

Anyway it all foward motion.
Have a great day.
Tony

[Dessertrunner]

Any ideas on how I should build the airbox, I was thinking of Aluminum but it may be a bit hard to make it rigid enough unless its pretty thick. The ideal world would be carbon fibre but I am not sure I can do it without build someform of mould first. Any suggestion greatly appricated.
Tony

[aust92pearl]

Originally Posted by Dessertrunner

Any ideas on how I should build the airbox, I was thinking of Aluminum but it may be a bit hard to make it rigid enough unless its pretty thick. The ideal world would be carbon fibre but I am not sure I can do it without build someform of mould first. Any suggestion greatly appricated.
Tony

mdf or ply ? then fiberglass it nice and thick or use that as the mould and make it out of fiberglass or something like these ?
http://www.summitracing.com/parts/SUM-471500
http://www.summitracing.com/parts/SUM-471500
or maybe fab one simmilar to them but to the size you need