As for your brake difficulties, the first thing we would do is delete the factory combination valve that reduces the pressure back to the rear brakes. This valve was designed to reduce the pressure to the rear drum brakes because drum brakes require less line pressure than disc brakes. It's possible this may be the cause of the reduced pressure, making it difficult to create enough pressure to fully eliminate all the air in the system. Replace the factory combination valve with an adjustable proportioning valve from Wilwood or Stainless Steel Brakes and use maximum rear line pressure to bleed any remaining air from the hydraulic system. After the brakes are bled, carefully calibrate the rear pressure for your particular application. What you want in an emergency-stop situation is for the front brakes to lock up before the rear brakes do. Remember, the shortest stopping distance is achieved at the point of impending lockup. The only way to determine this setting is to do some safe, impending-lockup brake testing to ensure the rear brakes do not lock up first. Do this testing in a safe location, away from traffic or objects like trees or telephone poles. They generally don't move when you hit them.
We don't want to offend you, Carlson, but we occasionally see rear disc-brake conversions where the adapter plates are swapped side-to-side and the calipers are installed upside-down with the bleeder screw on the bottom. All disc-brake calipers must mount the bleeder screw at the top, where all the air can escape when bled. If the bleeder screw is not at the very top of the caliper cylinder, air will be trapped in the top of the cylinder and not be able to escape. This may sound simple enough, but we see this mistake made from time to time.
More InfoStainless Steel Brakes; Clarence, NY; 800/448-7722;
stainlesssteelbrakes.com
Wilwood; Camarillo, CA; 805/388-1188;
wilwood.com
Electronic fuel injectors must be sized properly to flow the roughly 30 percent more fuel required when running E85 compared with gasoline. Most modern injectors are also designed to work with E85.
Alcohol And HP
Steve Telkes, Saddle Brook, NJ; My question is about E85 fuel. What would you have to do to a car equipped with a 14.7:1 narrow-band O2 sensor when E85's stoichiometric air/fuel ratio is 9.7:1? Does Bosch or NTK make a 9.7 sensor? I was told by my corner gas station that New Jersey is now using a 10 percent blend of ethanol in all grades of gas. How will this affect my tune-up? I run an Edelbrock
PN 3500 Pro-Flo EFI with a custom prom that can run closed-loop idle with the narrow-band 14.7 sensor that comes with the system. I was running open-loop on a fuel map I created, but pump price made the decision to turn closed-loop "On" and let the ECM handle the fueling chores. At least WOT is still under "manual" map program control.
Jeff Smith: Let's start by bringing everyone up to speed on oxygen sensors. The early EFI systems used narrow-band oxygen sensors that were only really accurate around the stoichiometric air/fuel ratio of 14.7:1. This is the air/fuel ratio for gasoline, where the three critical emissions components (HC, CO, and NOx) are their combined lowest. This is where the factory EFI systems are designed to maintain the engine's air/fuel ratio during part-throttle operation. This also creates a relatively lean air/fuel ratio, which helps gas mileage.
Bosch was the original designer of the oxygen sensor, first used in a production vehicle in the '76 Volvo 240/260 sedans. While in the U.S. we refer to the output of these sensors in air/fuel ratio terms, the Europeans prefer to work in lambda, which is why these sensors are sometimes referred to as lambda sensors. Using this reference version, the stoichiometrically correct air/fuel ratio lambda number for gasoline is a reference number of 1.0. Numbers higher than 1.0, e.g., 1.07 or 1.15, are leaner than 14.7:1, while numbers lower than 1.0 are richer than stoichiometric. As an example, it is generally considered that 0.85 lambda is a good air/fuel ratio for best power on gasoline. We can easily relate lambda to air/fuel ratio for gasoline by multiplying the lambda number by that fuel's stoichiometric number. For gasoline, that means multiplying lambda by 14.7. So, if we have a lambda number of 0.85 x 14.7 = 12.49 or roughly 12.5:1 air/fuel ratio.