Quote:
Originally Posted by Ecky
Also, as was mentioned before, take a look at Mazda's design. They were advertising that a carefully designed header was crucial in letting them use extremely high compression.
|
Had a bit of a look at it (see
autozine.org article)... basically the upshot seems to be that better scavenging allows higher compression ratios without knocking (very useful info!
). As I'm planning a mini-me head swap soon with the option of a mild compression ratio increase, this is very good to know, this might persuade me to actually build a header
The header geometry itself seems to be a standard 4-2-1 design, but the innovation seems to be that they've coiled the tube around the cat to warm it up faster, and also allow the longer length to fit in the engine bay given an exhaust-ports-at-the-back layout.
Now I'm dubious about the "warms the cat up quicker" claim, it seems to me that the amount of radiation / convection heating at startup would be tiny compared to direct exhaust flow, but maybe that extra few percent gets them over some EPA-mandated "is your cat this fast to warm up" line
. In any case, I reckon just having a ceramic-coated SS manifold should be sufficient to do the same trick.