will I benefit from a collector size change?

Grumpy

The Grumpy Grease Monkey mechanical engineer.
Staff member
Will there be any benefit to increasing the front half of my true dual exhaust from collector flange to a exhaust that routes past the collectors too an X crossover, 2.5" to 3", but only to return/reduce back to 2.5" before the muffler section? This is on a blown lt1 Trans Am, mild street car. Hoping between 550-600 rwhp. Reason I can't go all the way back is clearance won't allow past the hump over the axle

ok, you can ignore facts but as an engineer I suggest that if you ignore facts,
your engine will not benefit from your not understanding the advantage of proper design, potential,
a single 2.5" pipe has just under 5 sq inches of cross sectional area
a single 3" pipe has just under 7 sq inches of cross sectional area
run the two 3" collectors into a 3" x pipe and each cylinder banks 7 sq inches feeds into dual 5 sq inches of cross section,or 10 sq inches
further reducing the INTERMITTENT flow restriction each banks exhaust pulse every 90 degrees of engine rotation produces
exhaust gases lose heat rapidly and contract as they cool, a true 2.5" dual exhaust is likely to be restrictive near 500 hp,
the use of the long 3" dual collectors feeding an (X PIPE) then dual 2.5" is usually able to handle 600 hp rather easily

installxpipe11.jpg


http://garage.grumpysperformance.com/index.php?threads/header-dimension-calculator.15013/

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Devo9er said:
In a way I don't like the idea of the exhaust slowing down in the expansive section just to be necked back down and sped up. There's something to be said for keeping the pulses zooming out.

what part of the individual cylinders mass of exhaust gasses going from 7 sq inches of exhaust area, per exhaust pulse per bank to a dual 5 sq inches totaling 10 sq inches per exhaust pulse, is " necked back down and sped up"
this is by design constantly reducing the flow restriction, and improving cylinder scavenging
 
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