Flashed CB1100 Review

[Greg_imp]

Here is are dyno charts from a stock CB1100, mileage 3400. There are 3 runs: 1/4 throttle, 1/2 throttle and wide open throttle (WOT). I believe he had it in 4th gear for the WOT run.

He also did an idle chart that is not shown here. The AFR was in the range of 17:1

They do run lean out of the box!!

For those who are following along merely out of curiosity, CIP is referring to the bottom section of the graphs labeled "Air/Fuel Ratio". Lower numbers are richer, higher numbers are leaner. The red dotted line at 13 is roughly the ideal air/fuel ratio for a happy engine; 13 parts of air to 1 part of fuel, written 13:1.

So-called perfect combustion, where all the air and all the fuel is consumed, occurs at 14.7:1. Emission standards require that air/fuel ratios be at least 14.7:1 for almost all of the time the engine is running, and the CB1100 only dips below that at wide open throttle and near the top of the RPM range. Practically speaking, most owners will rarely or never operate in that range, so their bikes are running lean all of the time.

One of the great things about our bikes is that they are engineered to be smooth, powerful (enough for most), quiet, relatively clean running and fuel efficient all at the same time. Since optimum tuning for any one of those variables compromises the others, the designers have done a great job of balancing contradictory parameters and making it all invisible to us.
Somewhat related to CIP's thread is air intake.

I calculate the air inflow at 7k RPM at around 141 cubic feet per minute. To feel what this is like, turn on your shop vac and hold your hand near the open hose. A typical large shop vac pulls in about the same amount of air and the vac's hose is about the same diameter as the inside of the air filter on your bike.