Quote:
Originally Posted by Chris Canning
That made me smile the R1200s sold in such numbers take your shoes and socks off you probably count all the sales  ,infact is was so good they stopped production in under 2 years you get a hand full of RT people turn up on here and that's it,there maybe somewhere to market a few to the RT people who may even be remotely interested in extra performance but it ain't here, |
First you did not consider models other than the R1100S, now you want to limit the discussion to R1200S and possibly the RT.
Many bikes are commonly discussed here including plenty of non BMW models. Why should a discussion about Lennies sprockets, which fit the vast majority on boxer bikes, not include ALL relevant models?
Quote:
Originally Posted by Chris Canning
but as I said in the post if you get out there and look you can get the same result with a Rexxer map that also advances the iginition hence why you can't have sprockets and a map,it's been tried!!!
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Really, I've be using altered fuel and ignition maps with the sprockets for years, works great.
Your understanding of how internal combustion engines operate seems to be rather lacking. Valve timing is a dominant factor in how an engine draws in air at any particular rpm, and therefor has a very significant effect on volumetric efficiency and effective compression ratio.
Most modern car engine designs employ variable valve timing to give a broad spread of torque and maximum efficiency. The cams are advanced at lower rpm for improved low end torque and retarded at high rpm to give good top end power.
Without variable valve timing systems the designer has to make a choice, either maximum low end torque, maximum top end power or something in between, they cant have a cam setup that does everything.
BMW in their wisdom went with a setup that slightly favors top end power over low end torque, that may be the best compromise for people traveling at 140mph on an autobahn and give the highest HP numbers to put in the product advertising, but for most of us its less than ideal. The sprockets re tune the engine for better low down performance more suitable to normal use.
The 9 degree cam advance allows the engine to draw in more air from 1000 to about 6000rpm than is possible with standard timing and therefore allow more power to be produced in that range. No ECU remap or fuel tweaking device can do that.
All a Rexxer map can do is fine tune fuel/air ratios and ignition timing. Fuel/air ratios have to be a long way off to significantly affect power. Slightly lean normally provides the most power, but most people tend to prefer slightly rich as it gives a smoother running engine that feels better to use. The difference in power is tiny either way.
Ignition timing is important for performance and throttle response. Luckily the BMW ECU uses knock sensors and adaptable ignition advance. The default advance curves can be a little conservative when good fuel is available, but luckily we can force more advance and more fuel with a simple air temperature spoofing device (a resistor attached to the intake air temperature port of the ECU). This simple and very cheap mod adds enough fuel to get away from the lean standard mapping and gives us a smoother more response bike. The extra advance gets automatically trimmed to the ideal by the knock sensor feed back system.
So we can get 90% of the advantages of a Rexxer remap for $10, the other 10% I could not care less about.
I strongly suggest people installing the sprockets also add a temperature spoofer, either home made or purchased from one of the various vendors. The combined effect of both is very impressive and well worth having IMHO, especially for the tiny cost.
I can provide resistor values for anyone that is interested.