Lot's of tinkering with u-bends, silencers etc. Lots of exhausts being cut open and looked at.
Basic engine spec is 225 RT kit, 70mm piston, 58mm alpha crank. Carb is a 28mm VHST which is a new-ish Dellorto flatslide we are trying after seeing some good results on some autos.
Solid red line is horsepower with devtour pipe.
Dotted red line is horsepower with modified clubman.
Solid green line is torque with devtour pipe.
Dotted green line is torque with modified clubman.
As you can see the clubman is slightly up on power and torque up to about 5000-5500 rpm, the devtour takes over after that.
Both exhausts hit peak power at about 6500 rpm.
In real terms using SX200 gearing 15/46 this would equate (on the road) to being sat in 4th and just winding the engine on in 4th from about 40-45mph to about 65mph. Both engines would over-run to 70-75mph (we find that once the engine hits peak power on the dyno any power after peak would be only be seen on the road downhill or with a tailwind). The devtour with the better torque would have a nice powerband kicking in at 50mph or so. Of course there is plenty of torque to pull higher gearing.
The clubman would be better for round town up to 50mph - the devtour would pull better after 50mph so better for overtaking lorries without dropping down a gear etc.
To me the interesting thing is that both curves are so broadly similar which makes you wonder if we all really need expansions on touring type engines.
