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In the Sept 2010 edition of "Car Craft" under "whats your problem" they document a problem I've noticed for several years. A cammed engine will throw a wideband oxygen sensor off since the overlap can pass unburned fuel into the exhaust. I started out with a LM1 the LM2 and now run a Autometer wideband O2 sensor in my car. At idle it shows 16:1 (top of the scale) but the instant I touch the accelerator it jumps to 14:1. What this means is that any EFI that goes closed loop at idle is going to be riching the mixture to overcome this seemingly lean condition. This is why all EFI systems come with a preloaded map to get you started. My question on the EZ EFI or any other "learning" system, whats it gonna do at idle.
Lean at idle is generally a lack of back pressure, or it might be the sensor placement too close and not seeing all the exhaust in the collector, or lastly, raw fuel actually getting on the sensor and cooling it, being too rich. The plugs will tell you which way it actually is.
That's why I like the carbs with screw in air bleeds, you can tune the idle mixture to near perfection with them and it doesn't effect anything else.
The efi should have a smoother idle just based on the better metering of the fuel, but if it doesn't and it surges, the IAC, the throttle blades, and the threshold values can be used to sort that out. Typically in that order, so the engine doesn't surge, and it remains nice and steady. That's where, if you have a nasty cam, you might get to where you need timing control as well and step up to full efi. The learning efi will try to adjust itself with the above mentioned IAC, but it still may need some manual intervention.
The cam in my Cuda would not be runable on the street with a carb or ez-efi....It does in fact run super well with the Classic FAST that I use, but it wasn't easy to set-up initially. The learning efi is waaay worth the $$$ for some of us. I am not worried about the payback on it, nor the fuel mileage. Keeping the engine alive & happy and drivable was my goal.
Last edited by Dragula; 07/20/10 09:56 AM.
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