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[Novakitcar]

Hello,

Is there anybody that know Alfaboxer exhaust very well?

I will have to build a new exhaust system for my Alfasud engine and have some questions.

Det original system have different pipe lengths for the different cylinders, is this something critcal or could they be buildt with the same length?

Could I use 38 mm pipe instead of 35 mm?

Is it critical how long the singel pipes are before they join together, or could I join them after 20 cm?

The engine is installed in a kitcar so it is installed the wrong way. The exhaust manifold have to make a 180 degree turn after 20 cm and the silencers will be installed when you reach the first cylinder on the way back again. The radius of the turn should be approx. 25 cm. Is that any problem?

The system will be made of stainless pipe.

[johnboy]

Hi there

What size engine is it? the 1.7 engine has a bigger bore than 1.5 ,so i would say yes you can go for 38mm. on the equal length front yes again,as there are manifolds out there with equal lengths,which are serposed to give more power,they are called crossover manifolds as they link different banks together.i think 1-3 2-4 but not sure on which ones.
hope this helps?

regards john
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[LDA]

4 into 1 is better than 4-2-1 but i cant remember the reasons why. its something to do with the pulses.

a larger exhaust will allow the engine to shift more gas at higher rpm with less back pressure. the problem is that you lose low down torque and even high up torque if the back pressure is dropped too much.
NA engines need much more carfully thought out exhausts than turbo cars. too big and you will lose out. too small and you will strangle the engine.
to do it properly you need to work out the cfm of each cylinder at max rpm then you need to know how much back pressure is enough for torque and then there is the magic bit i dont understand, the pulses.

the less bends you have in the exhaust the better. 180* turns are not a good thing and best avoided if possible. the straighter the better. but if you must bend it to fit it to the car then make sure you use mandrel bends of the largest radius possible in the space.

your best bet is to speak to a local engine tuner or exhaust fabricator.
good luck!

L.
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