Expansion Crossbox Kit

Following graphs show very well the engine power versus backpressure of the exhaust system. Please read: Back Pressure

Why we propose a DIY expansion crossbox kit for uprated 2CV engine!

Graphs are from Mr. Chance, custom 720 cubic engine destined to the 5.000,00 Kilometres Rally in Tunisian Sahara.

Graphs with the friendly approbation of Mr. Chance.

Type : Citroen 2CV

Gearbox : 2CV long ratio, tyre 135mm

Engine : 720 cubic, 8:1 compression ratio, 7,5 mm/288° camshaft, manifold with Weber carb and air filter coming from Visa engine. Custom flywheel with high inertia and low weight. No indication about connected sand filter.

Engine kilometres : ca. 1.000,00 miles

Exhaust system :

  1. Standard exhaust system (Curve is not shown, read at bottom),
  2. Emptied standard exhaust cross box with big diameter dogleg pipe to "torpedo" silencer and big final exhaust pipe (AK type),
  3. Big expansion chamber crossbox with big diameter dogleg pipe to "torpedo" silencer and big final exhaust pipe (AK type).

Date of Dyno run : 15-09-2003

Black curve is the final power curve with the expansion chamber.
Red curve show the power curve with emptied standard Walker crossbox.

Power curve in comparison
Power curve

Torque curve in comparison
Torque curve

Comments :

With standard exhaust system the engine will not rev up 5.000 RPM, acceleration was very lazy, engine hesitating during acceleration with floored accelerator in second gear!

  1. With emptied standard exhaust system (read above exhaust system description) the acceleration in second gear would be better, 5.500 RPM where reached at top speed. Carburetor was rejetted for this setup.
  2. With expansion chamber crossbox etc., now full and strong acceleration in second gear was possible and 6.000 RPM where reached without problems. Carb was rejetted in accordance.

Mr. Chance comments to engine combo :

The exhaust is only a little noisier than the standard and has a metallic ring to it. With the Visa filter and this exhaust the car is quite comfortable.

Clear message :
Been in 4th gear, you must no longer gear down for accelerating ...

[expansion crossbox]

DIY-Expansion crossbox kit for twin exhaust :

DIY-Kit Price: 34,45 €


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