Scooterotica

What makes a real torquey engine and is there any real science in a box type exhaust?

122+ people looked at my post but no answers?

There is some science in a box ex..and they tried to improve them. Any tube on a motor will aid the draw but its the return pulse that is lacking. Some of these box pipes have baffle plates in. Some of this i guess is to quieten stuff down but maybe also to try to aid a return pulse. At the end of the day tho they dont work like an expansion type pipe.
Torque motors. The timings and areas need to be adjusted in a way to produce it, coupled with a designed pipe. Its all to do with that really. But the thats the tip of the iceberg.

Its 137 now.... Low down Torque is usually developed to the cost of revs... Large cc's, long strokes and long rods and sometimes high compression can add to torque but porting configuration & port time areas have to be used to suit...

Big inlet timings usually drop bottom end pull as do tall exhaust ports... these are the two parts of the engine that most people over tune resulting in high reving engines for road... Wire ringed pistons used with low wide exhaust port timings with a relatively high true compression ratio is usually your best starting point...
Lower reving torquey engines" I think" work better with a high primary compression...
Capacity conversions can give an effective increase in power, the reason for this is that you are trying, in a controlled burn to push down on a piston crown in psi... this means that every square inch of piston crown has pressure bearing down on it (on the power stroke) this is the pressure developed in the expansion of the gasses created during a properly controlled burn, these gasses then pushing down on the piston crown... In theory because this area is increased, and if the psi in the chamber is the same as before, then as you have a larger surface area then you effectively increase the overall power proportionally... this type of power increase shows up in the torque figure...
Box exhausts... I have modified a few with supprising results Unfortunately me being "old Skool" very few ended up on a dyno... but they can be made to rev or pull torque to pretty good effect (though not as well as a true expansion chamber) One of my exhausts was on a small block 190 suzuki running through a std standard 22mm, it made good power and had massive over rev for a box exhaust... It was featured in Scooterings "smalblock shootout" a while ago... It was originally a 32mm Sito prior to me modifying it... They work better than some give credit for... but a little thought into cones used, the upipe choice and interior obstuctions are need...That exhaust done, cost £30 ...cheap and reliable... I started this post before tony replied, but hes pretty much summed it up...

tony wrote:There is some science in a box ex..and they tried to improve them. Any tube on a motor will aid the draw but its the return pulse that is lacking. Some of these box pipes have baffle plates in. Some of this i guess is to quieten stuff down but maybe also to try to aid a return pulse. At the end of the day tho they dont work like an expansion type pipe.
Torque motors. The timings and areas need to be adjusted in a way to produce it, coupled with a designed pipe. Its all to do with that really. But the thats the tip of the iceberg.

So, if I do the maths and work out where to fix a reverse cone, a resonable improvment could be made?

Not that I would buy one,but a box exhaust with a VW reverse cone added,do they work?

Any pointers on adjusting ports to produce more torque?