TOPIC:

I was rumaging about in some old manuals I had & stumbled across a couple of interesting bits of paper & thought someone else out there might be interested

Some of you have probably already seen pics in my gallery of a 1/5th scale HPI Baja lookalike car I scratch-built using bits of Shengqi Hummer & fabricated the rest.
The old version Hummer used a copy of the Zenoah G230RC 23cc 2-stroke petrol engine (2.15hp @ 14000rpm), & having tuned lots of 2-stroke bikes in my dubious past, I thought I'd have a crack at making the Shengqi lump silly-quick (Which I achieved to the point it was unusable due to continuous shredding of transmission components...).

So, below are scans of the data printouts from my 2-stroke expansion chamber (Zorst pipe) design software.
The design for 4hp is complete with my scribblings of the actual final dimensions & timing of my lump after some aggressive machining, port-matching & port re-timing. This definately works!
The other datasheet is for 5hp, based on the same engine mods. I haven't tried it (Only cos there wasn't room on the car for the longer pipe) but I can't see any reason why it wouldn't work.
For reference, I read that these lumps usually blow themselves apart at around 7hp, so 4 or 5 should be safe(ish), & certainly more lively than the standard 2.15hp!