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Inlet runner lengths
adrianreeve - 1/2/09 at 08:06 PM

Now I've got my throttle bodies, thoughts are turning to a manifold. The bodies can only be split into pairs, so I think rather than re-spacing them, I'm going to leave alone, and build a manifold to suit them. This means that the two outer runners will be longer than the inner two, and at a more extreme angle. I know ultimate performance will be slightly down, but I'm happy to live with that for the moment. I was thinking of buying a laser cut flange from Short track, and then using mils steel tubing to make the rest. Does anyone have any photos / ideas from building their own? I was also wondering whether there is an ideal length for the inlet runners to be? Might as well make it as good as I can. It's a 2l Zetec silvertop BTW.

Thanks for any help, Adrian

[Edited on 1/2/09 by adrianreeve]


blakep82 - 1/2/09 at 08:13 PM

here's mine. they don't need to be anything too technical. just some straight tubes to connect everything up. i need to do mine again though. the angles were all wrong...

have a look in jackos photos too

as for runner lengths, i don't know they affect where in the rev range your peak power is, but i don't really know how it all works. i know i've got to do mine again though

[Edited on 1/2/09 by blakep82]

oh yeah, forgot my photo


[Edited on 1/2/09 by blakep82]


jacko - 1/2/09 at 08:15 PM

Is this what you want?
have a look in my photos under zx9r & manifold lots of photos in there
Jacko
top view painted manifold
top view painted manifold


tul214 - 1/2/09 at 08:21 PM

I have a flange for my 4A-GE from Short Track and it looks the Bo11ox.

I have used 40mm steel pipe for the runners and cut them at 15degrees along the length and rotated the 2 pieces 180degrees so I now have a 30 degree angle.

Because the inlets are oval I have squashed the ends in a vice until the pipe is the same shape.

It just needs welding up now.

And I have re-spaced the carbs...its not that hard. Have a look at this ;
http://www.dwjenkins.plus.com/carb-details.htm


will121 - 1/2/09 at 09:28 PM

im in the process of making mine, started with a shorttrack blank plate. im cutting a 'V' in my tubes and then bending it to close it back together before welding, it seemed easier than lots of individual tubes as it stays together rather than trying to align bits, ive respaced mine so bit easier as only need bend in one plane but cant see why technique cant work on more complex bends






zetec - 1/2/09 at 10:03 PM

The zetec works best with a long inlet. with the bodies near the head with long trumpets..looking at a length of 250mm for good results (head to trumpet end), space is normally the limiting factor.


hughpinder - 2/2/09 at 08:34 AM

If I remember correctly there is useful information on the jenvey site, I think for an 9000 rpm max engine speed you need 200mm butterfly to centre of valve, lower max revs=longer tubes. There is also an optimum inlet trumpet to valve centre distance, which is about the same length I think

Regards
Hugh