How to fabricate an intake manifold and fuel rail

[jeremiahnz]

Hi Guys,

Found this site a while ago and thought it may be of some use to people here looking to fabricate their own EFI setups.

How to fabricate an intake manifold
http://sdsefi.com/techinta.htm" onclick="window.open(this.href);return false;

How to make a fuel rail
http://sdsefi.com/techrail.htm" onclick="window.open(this.href);return false;

[dirtyleppa]

thats real cool man, thanx

[jeremiahnz]

Yeah, it's a good site. Glad you're not to upset that the example is for an RX7

[dirtyleppa]

who cares really, if you have the skill and know how to make shit like that. wish i did

[jeremiahnz]

I'm going the whole trial and error route - have to learn somehow. Went to North Shore Steel and bought what I believe will be everything for the job for $50. Check my build thread for the list if interested but that should do from the intake flanges, right back through the intake manifold and the fuel rail. Doesn't include fittings for fuel input or vacuum lines.

[Bartman]

I know the rotary sample manifold is made from steel, but I think that 6mm for the engine flanges is too thin. (IMO) The example shown was TIG welded, but 6mm leaves little room for error/correction in the event that some flange distortion was to occour during welding.
Good article though. Somewhere I have a notebook with the formula to extrapolate the desired runner length for a given peak power RPM range, with numbers for 1st, 2nd, 3rd, 4th, and 5th harmonics. (Each harmonic is for a shorter legnth where there isn't space for longer ones) However where forced induction is being implemented, the effect of the positve manifold pressure overides the "ramcharger" (Or hermoltz) effect.

[dirtyleppa]

Good article though. Somewhere I have a notebook with the formula to extrapolate the desired runner length for a given peak power RPM range, with numbers for 1st, 2nd, 3rd, 4th, and 5th harmonics. (Each harmonic is for a shorter legnth where there isn't space for longer ones) However where forced induction is being implemented, the effect of the positve manifold pressure overides the "ramcharger" (Or hermoltz) effect.

what he said

[Bartman]

long story short, the airflow inside a manifold doesn't run like a river, it fluctuates in pulses. If a pulse runs down the runner and the valve is shut, it bounces back, and then rebounds to the valve. When the pulse hits the valve while it is wide open, the intake is at max effeciencey. For each time the pulse rebounds before hitting the valve while open, the strength of the pulse weakens. Hence 1st, 2nd, 3rd harmonic etc. The longer the runnner, the lower in the rpm range this sweet spot will be acheived. And also the fewer times it will bounce before it is reached. the hemholz equation relates to the speed of sound in a vacuum, which is how fast these pulses are bouncing in the manifold. (Bare in mind that the speed of sound is something like 330 m/s)
During R&D jaguar were able to acheive volumetric effeciency exceeding 100% (thats like having boost!) at one given specific rpm by using runers that were extreemely long. (Possiblely even too long to sit inside the engine bay of a car?)

Now consider having a purpose built race engine where, Your exhaust header primary length, intake runner length, camshaft profile (and timing) and cylinder head flow numbers, all hit their sweet spot at the same rpm. The engine would have an insane torque peak!
Now imagine all the R&D and time/money required to build an engine that had all these things factored in. OUCH!

[dirtyleppa]

now throw all that out the window, and just screw some more boost into it

[Bartman]

Still, compare the manifold that Jeremy is gonna build to a factory a series one. Which do you think is going to run harder?
Hmm, Low performance antique, or better thought out custom jobbie?