delhi

So it seems like the flooding issue is when the rx8 is started cold and switched off without warming up.
My question is what if you start when it is already warmed up and switch off. Will it flood still?

NgoRX8

iTrader: (1)

no problem

delhi

why is that? I don't see the difference after all both experience short fuel burn rate despite engine temperature.

Jax_RX8

When the engine is cold a lot more fuel is fed to maintain idle - like the old chokes in carbs - but even more so for the rotary.

Thus when the engine is turned off, the combination of the engine being cold (less complete combustion) and more fuel being fed (than when hot) causes excess fuel to be left in the combustion chambers on turn off.

What causes it not to re-start is the excess fuel fouls out the plugs and keep them from firing properly.

To prevent this - don't turn off cold!!

If you have to turn off cold for some reason - rev to 3000rpm for 10 seconds and turn off at that rpm - the engine momentum will burn or flow through most of the excess fuel to keep from fouling the plugs.

Hightshoe

The hot engine temp is key.

MazdaManiac

iTrader: (3)

Though, it is sometimes more difficult to get a hot rotary started than one that has cooled slightly.
Immediate, hot re-starts can take a spin or two more to get going.

Jax_RX8

True - but this is not a flooding issue, but just a heat soak issue like any engine can have.

delhi

thanks Jax. makes perfect sense. If the fuel is controlled by the ecu, then shouldn;t a reprogram of the ecu to put less fuel at start up mitigate flooding?

corners

That's what they did.

Don't forget, rotaries also don't have valves. In a piston car, any fuel left condensed on the intake walls just sits there and puddles in the bottom of the intake. On a rotary, it runs down and floods into the chamber. Once a rotary floods, the apex seals loose their seal and its hard to dry out again.

The only way to actually stop flooding is to go to direct injection.

MazdaManiac

iTrader: (3)

Actually, in the case of the '8, it is a fuel delivery problem.
The start-up mix is so rich that it doesn't light off when the motor is hot.
The newest flash cures that a bit.