battyone wrote:
What are we trying to achieve here?
We are trying to reduce the amount of correction to the fuelling to reach taraget AFR. In the CL and CLL areas this is 14.7, as driven by the lambda sensor which acts as a virtual switch. This results in a smoother, more responsive engine and a nicer bike to ride.
battyone wrote:
If looking for max fuel economy then a different powerplant would be better.A big bore 2valver is never going to be very efficient.
Yes. The size of the powerplant is very important. For max efficiency, the throttle should be wide open for max cylinder filling and max compression ratio. This is why diesels are more efficient. Other things come into play, such as design point (valve timing and interation with exhaust/inlet). If we were to compare the efficiency of the 1125 and the 1203, you will see that at motorway speeds the 1203 is nearly 50% more efficient even though the 1125 is 4 valves per cylinder with more advanced port and piston design.
battyone wrote:
As I understand it,all buell ecms seem to be adding fuel in closed loop.This is patently wrong!
ECM adds fuel until lambda sensor reads >0.5V, ECM reduces fuel until lambda sensor reads <0.5V. This is normal operation for controlling a dynamic system.
battyone wrote:
...firstly good quality combustion is always going to be lagging as there will be a few poor -lean cycles - before the ego correction catches up. and secondly-as Willie has already seen-when your O2 sensor goes bad the bike runs dangerously lean.
What is dangerously lean? There are noise abatement systems in the Buell ECMs that pull fuel out, but the time which the fuel is pulled out is not long enough to cause damage.
battyone wrote:
From a tuning point of view,if the closed loop fails the bike-or car- should actually run better.
Really? Only if the fuel map matches the ignition timing.
battyone wrote:
Closed loop should only subtract fuel for better economy, not add to keep it running.Just because manufacturers do the opposite to get thru emmissions,doesn't mean we have to follow the same flawed philosophy.
Tis not a flawed philosophy. I spent some time writing an explanation of this in the tuning guide. For max power you need to run around Lambda 0.9, for max efficiency you need to run at around Lambda 1.1 (or leaner). For Lambda 0.9 you use all the air up (you are always air limited) at the expense of some unburned fuel. For Lambda 1.1 you use all the fuel up. Not that as you run leaner you need to increase the advance otherwise the burn will continue later in the cycle which will result in higher piston crown, valve and exhaust temperatures.
Sure, at cruise, at the same TPS and RPM, if you go from Lambda 1.1 to Lambda 0.9, you may get a 10% increase in power at that point, however the fact that you have your throttle partially open tells you that you want to limit the power of the engine to give a set speed. More fuel, faster, need to close the throttle more, less efficient cos you have unburned fuel and higher pumping losses as a result of the throttle being more closed...
battyone wrote:
Lean burn is fine,in motors designed for it. I'd expect the buell/sportster to be much happier in the 13:1 region than at stoich.
Stoich is only good for tree huggers,not for an old push rod,2valve Vtwin..
Where do you get that figure from? Willy will tell you if my Firebolt is happy at 14.7:1.
battyone wrote:
My carbed bonnie runs mid 12's:1 across most regions and will pull 5th at idle,the wife's efi bonnie will stall when pulling away if you don't give it loads of throttle and stutter when rolling back on the throttle after decelleration.
Nice, but what does that prove other than that the fuelling is poorly set up?
battyone wrote:
Richer mixtures will likely lead to less rider input required to make progress and so assist fuel economy.
How do you work that out?
Don't be offended by my responses...
Register
Login
FAQ
Search
