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Lebowski · Guest

I bought a new exhaust today for my 1.5 Sprint engined Clover, and it seems to me to be very poorly designed. I went for the 1.7 exhaust as I've heard this is a worthwhile upgrade, but the primary diameter (straight out of the engine) is only 1.25". This diameter continues for around 3 inches before expanding to 1.5" for the rest of the manifold, including the parts after the primaries and secondaries have joined together.

This to me seems like very poor designing in terms of flow and performance. Unfortunately it looks like I'll be taking a hacksaw to most of it for the rest of the week.

Guest · Posted: Wed Oct 11, 2006 5:00 am Post subject:

Any stock exhaust is a compromise between flow and scavenging effect unfortunately. Sad

I would be interested in seeing pics of your finished product, I'm thinking about modifying the exhaust on my 1.7 at some stage... Smile

Ben_nz · Posted: Wed Oct 11, 2006 8:11 am Post subject:

Do you mean you bought a new Alfa Romeo factory standard exhaust system for a 1.7 boxer engine?
I've heard that the exhaust ports in the head are the same size for the 1.7 engine as for the 1.5, which is why they use the 1.5 mounting plates and weld on a thicker pipe a few inches later!
I've never taken the exhaust manifold off to see.

Guest · Posted: Wed Oct 11, 2006 10:29 am Post subject:

I'll check port size when I get the old exhaust off. To me it seems that using thinner pipe at the start of the exhaust would negate the benefits of having a larger bore further along.

Plus, after the primaries and secondaries meet, the pipe diameter still remains 1.5", which surely must be a restriction.