Tubular exhaust manifold, pairings of primaries.

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paulmanta
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Tubular exhaust manifold, pairings of primaries.

Post by paulmanta » Sat Jan 28, 2012 9:05 pm

I am fabricating my own exhaust manifolds, I am intending to make a system with 1 5/8 primaries, going 4 into 2 at two collectors, at the merge into 2 pipes the pipe will change into 2 inch pipe, then go past the bellhousing and then into a 2 into 1 merge, this merge will also go up to a 2 1/4 inch pipe for the rest of the system.

After the last set of merges the 2 1/4 pipes will meet at a X pipe somewhere under the transmission and then go back out to a pair of pipes to the back of the car.

The engine is only a 3.5 but i intend to fit a larger capacity Rover V8 in the future so am keen to build the system I need for the bigger engine rather than re-do all this again.

Obviously there will be two manifolds, a left and a right, the firing order is 1-8-4-3-6-5-7-2, is there a tried and tested pattern for pairing the merges ?



Pitschi
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Post by Pitschi » Sun Jan 29, 2012 5:21 pm

http://www.the289register.com/phpBB3/vi ... &start=105

and scroll down and go to page 9 too

Cheers
Pitschi

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kiwicar
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Post by kiwicar » Sun Jan 29, 2012 7:00 pm

Hi
The ideal pairings are with cylinders fireing 360 degrees apart, then joining these pairs with pairs firing 180 apart, this ends up having to match pairs across banks (like a dual plane inlet manifold). The pairings are 1&6, 8&5, 4&7, 3&2 as you can see this is not easy on anything but a mid/ rear engined car.
Next best thing for the rover is 1&5, 3&7 off one bank and 8&2, 4&6. This is assuming long ish secondarys (around the same length as the primaries).
In current nascar practice you would join 1&3, 5&7 and 8&4, 6&2 with a much longer secondary than primary before joining the sided pairs. However I dont think you would ever ger the rover in a state of tune to take advantage of this set up.
Best regards
Mike
poppet valves rule!

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ChrisJC
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Post by ChrisJC » Sun Jan 29, 2012 8:02 pm

The Range Rover EFi manifolds (the ones with twin outlets) seem to have the following pairings:
1&5
3&7

2&4
6&8

Chris.
--
Series IIA 4.6 V8
R/R P38 4.6 V8

paulmanta
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Post by paulmanta » Tue Jan 31, 2012 6:46 pm

Many thanks for the advice, I will probably go with the 15 37 28 46 configuration.

I am undecided about primary lengths at the moment, I understand the fag packet rule of longer primaries give more torque so if this is true and not an old garage myth I want the make soemthing to get the best of both worlds.

Probably 12 inch primaries, around 14 to 18 for the secondaries depending on space.

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