Chicken.............

On a serious note will it do the same thing on the hose (trailered)?

Where are all the Holley salesman on here hiding when you need them. http://www.offshoreonly.com/forums/g...-everyone.html

soon as it starts to go rich,,shut it off quick and look up the exhaust pipe and see if its reverting.

If I had to take a stab at it, here would be my guess. Fuel is pooling in the intake after extended idling. You have water going through the intercooler all the time. It's still early in the year and the water is cold. I ran one the other day and my intake air temps in boost (7 psi) were 25 C (under 80 F). Once you start advancing the throttle, the increase in air movement is pushing that puddled fuel into the head. That is about the only thing that will cause a temporary rich condition when the injector pulse width isn't increasing.
Have you ever had the chance to look into a Whipple intake, under the intercooler, shortly after the engine has been run? It's incredible how much fuel will puddle in it. I'm talking about a couple of ounces of fuel in some cases. The bigger the intercooler, the more fuel it can hold. This can also be an issue when the engine is shut off. The intercooler holds quite a bit of fuel and that fuel will drip out of the intercooler and into the intake once the engine is shut off. If it's left for a little while, the fuel will evaporate. If it's only for a few minutes, then there isn't enough time for that much fuel to drip out. It seems to be in the 10-15 min area that can be an issue. We've found that going to the MOAC intercooler, since it is quite a bit thicker, made the problem worse. We've had some issues with starters because the engine is full of fuel and trying to start immediately upon hitting the key. The starter doesn't have enough of a run to spin the engine. If it kicks back, it will kill the teeth on the flywheel and/or starter. We went to high torque gear reduction starters on anything that gets a MOAC. They have enough balls to push right through and spin the engine. With a bunch of fuel and a super hot ignition system (DIS) it wants to crank immediately.

A combo of cool air and lake temps are causing the fuel to puddle in the intake. The block doesn't have any temp, the incoming air is cool and the intercooler is cold because it's getting cool lake water all the time. That is my guess. That is also the main reason that we never run water through them at idle. We just force feed them with a separate pickup.
What plugs are you running? What are your IAT's at idle and while running?
Eddie

Thanks Eddie,
That's pretty much been my thoughts all along but wanted to get some educated 2nd opinions.

Bob

Bob,

Just another thought, you stated that the idle AFR remains relatively unchanged. If indeed fuel was pooling inside the blower/intercooler area, which I too would suspect, then over time that fuel was NOT getting consumed in the combustion process. IF that was the case then the idle AFRs should slowly lean out over the 2 minute idle period.

Since the idle AFR remains relatively constant, then where is this 'extra' fuel coming from? Perhaps it is leaning out a bit but not perceptibly so via wideband. I don't know, just food for thought.

You have to keep in mind that a wideband will not show a rich condition if there is a big excess of fuel. The O2 sensor has no way to read liquid fuel, or any form of fuel for that matter. Actually, an overly rich condition can show up as the engine being lean on a wideband. Once that overly rich mixture starts to take out the plugs, they can not effectively burn off all of the oxygen. Now, you end up with a surplus of unburned oxygen in the exhaust pipes. The O2 sensors interprets that as a lean condition, when in fact, the engine is rich.
Eddie

^^^^^^Exactly why I get nervous when some people put too much dependency on the widebands. Especially with autotune featured ECU's. It's (Wideband) a great tool, but not an end all.

Are you reading the A/F on the dashboard, when this is occurring? If this is happening change your parameters for closed-loop learn. You can also look at you coolant temperature enrichment parameters, the engine may also be dropping below your set, parameter after idling. Haxby, is going to be the EXPERT on this. I have only been using the Holley for a year at this point. I know, for a fact the smallest amount of moisture, hitting the wide band will send it to a dead rich condition !!!!! Its more prone to happen, if there is a full swim platform at water level, until the boat is on plane.

You really have to ask in a marine app how dependent you can rely on wideband readings. Yes they are good to have but so many variables comes into play with o2 sensors in a marine exhaust system.

Mounting is one of the most important things and in marine engine you have to question this.

Thermo shock

The o2 sensor - its really only a representative reading figure of a mixed exhaust stream average of all cylinders - not just one cylinder. Not a full proof reading because its an overall average reading.

Exhaust wall has water vapor even if it a dry wall (no water) until the tails

plus there is no exhaust flow layer right up against the wall of the exhaust

proper depth of the o2 sensor install in really important - very critical

you should never mount any o2 sensor in any form of down hill streams as all water and condensation flows down hill even after shut down.

also EGT temp of 1700 degrees and above is a sure fire way of ruining the lambda sensor ( thru that in for SB)

water kills the O2 sensor in short order and or very poor readings beforehand.

O2 sensor can never read unburned fuel or water or air.