howardsmed
Ragged trousered Philanthropist
Good morning to you all
I have previously posted the dyno results from our rephased 880cc engine we built for sidecar road racing. The engine design and build has been undertaken as a collaboration between Howard ( ex Smedspeed) Steve Mann and Rick Forte. To date we have achieved 90hp rear wheel at 7500rpm, and a torque spread of over 65lbs/ft from 3500-7500rpm, all the dyno work we have needed done is performed on the same dyno by veteran racer and tuner Ricard Albans at TTS in Northampton. There is as you can imagine a lot of development and updated design work required to squeeze 90hp out of a 50 year old design, but I have a long history of motorcycle parts design so that part fell to me. Steve Mann did all the machining and design for the "raised port" heads, and indeed all the engine build work, I did the crank rephase and machining work on the crank cases.
When the bike was run on the dyno some six months ago, we must have asked Richard not to rev it too hard, which he duly did.. ..the 90hp whilst a superb achievement is actually still well below the accepted maximum accepted piston speed for even a street engine, this would occur ( assuming 4000ft/minute is used) at just over 8200rpm, with this in mind we are returning to the dyno and will use the 8238rpm x 1.05 giving us 8650rpm. It is common practice when engines are developed and tested to use a "test rpm" figure, this is for most engines, (and this depends on the manufacturer) 1.10 x the stock redline.
The dyno sheet we have currently, do not show the power or torque "nosing over" which is where the engine runs out of breath. We believe/hope that the engine will create torque and thus hp to a higher figure than 7500rpm. At present the many calculations and simulations suggest that we will obtain 94hp at 8200rpm.
Despite having such a good power output, this engine is still not a race engine, its max rpm is at the stock point, it runs on good fuel ( which in the UK is 99 octane ) and it doesn't require mach pre race attention other than checking tappets and plugs. it is essentially still just a VERY fast street engine.
So this winter we are fitting larger 45mm diameter 7mm stem valves, this will require new collets and top collars and guides to suit. I have sourced some required parts from a well known American manufacturer to save us making them ourselves. Most parts will be designed by and made here in the UK, all this with slightly higher compression and some revised port work and a higher redline we hope to achieve somewhere 100hp rear wheel.
I hear all the nay-sayers chime in with negativity, BUT how can you do it ? when Yamaha could not.
Well "back in the day" there were no £85,000 valve seat cutting machines, no programable CDi ignitions , no hot plateau honing, these days all the modern machinery and simulation programmes that allow manufacturers and skilled individuals alike to achieve outputs that 50 years ago were unheard of.
Ask yourself how much has your phone advanced in just the last 20 years ???
We will keep you informed
Howard
I have previously posted the dyno results from our rephased 880cc engine we built for sidecar road racing. The engine design and build has been undertaken as a collaboration between Howard ( ex Smedspeed) Steve Mann and Rick Forte. To date we have achieved 90hp rear wheel at 7500rpm, and a torque spread of over 65lbs/ft from 3500-7500rpm, all the dyno work we have needed done is performed on the same dyno by veteran racer and tuner Ricard Albans at TTS in Northampton. There is as you can imagine a lot of development and updated design work required to squeeze 90hp out of a 50 year old design, but I have a long history of motorcycle parts design so that part fell to me. Steve Mann did all the machining and design for the "raised port" heads, and indeed all the engine build work, I did the crank rephase and machining work on the crank cases.
When the bike was run on the dyno some six months ago, we must have asked Richard not to rev it too hard, which he duly did.. ..the 90hp whilst a superb achievement is actually still well below the accepted maximum accepted piston speed for even a street engine, this would occur ( assuming 4000ft/minute is used) at just over 8200rpm, with this in mind we are returning to the dyno and will use the 8238rpm x 1.05 giving us 8650rpm. It is common practice when engines are developed and tested to use a "test rpm" figure, this is for most engines, (and this depends on the manufacturer) 1.10 x the stock redline.
The dyno sheet we have currently, do not show the power or torque "nosing over" which is where the engine runs out of breath. We believe/hope that the engine will create torque and thus hp to a higher figure than 7500rpm. At present the many calculations and simulations suggest that we will obtain 94hp at 8200rpm.
Despite having such a good power output, this engine is still not a race engine, its max rpm is at the stock point, it runs on good fuel ( which in the UK is 99 octane ) and it doesn't require mach pre race attention other than checking tappets and plugs. it is essentially still just a VERY fast street engine.
So this winter we are fitting larger 45mm diameter 7mm stem valves, this will require new collets and top collars and guides to suit. I have sourced some required parts from a well known American manufacturer to save us making them ourselves. Most parts will be designed by and made here in the UK, all this with slightly higher compression and some revised port work and a higher redline we hope to achieve somewhere 100hp rear wheel.
I hear all the nay-sayers chime in with negativity, BUT how can you do it ? when Yamaha could not.
Well "back in the day" there were no £85,000 valve seat cutting machines, no programable CDi ignitions , no hot plateau honing, these days all the modern machinery and simulation programmes that allow manufacturers and skilled individuals alike to achieve outputs that 50 years ago were unheard of.
Ask yourself how much has your phone advanced in just the last 20 years ???
We will keep you informed
Howard