gummyAvenger

I understand that fuel gets caught in the chambers, but why does it only happen when the engine is cold? Does the engine idle at lower RPMs when it's cold? If that's the case, why can't you just rev it up a few thousand RPM and turn it off immediately (as opposed to letting it idle for 5 min and then reving it)?

dillsrotary

no, you didn't search

gummyAvenger

Yes I did. I spent over an hour searching. I also used Google to search the site. What search terms would you recommend? I dug through 15 pages of search results looking for a thread that answers my question. I read rotarygod's enormous explanation of why the engine floods in that huge engine flooding thread, along with many other posts, but none of that answered my question.

Do you know or can you recommend some search terms to use?

Thanks!

TomAssBender

sometimes I will type in the exact title of a thread in the search bar, and will find the actual thread I am looking for like 3 pages into my search results. it annoys me

ken-x8

If searching doesn't work, then asking usually does. Unfortunately, there are enough nimnos who ask stuff that's very easy to find that some of the regulars have (understandably) lost patience. On the other hand, if everyone persisted 100% in searching, there would probably be no new posts.

About flooding and cold... It's not just a rotary thing. Fuel needs to be vaporized for it to burn. When the engine and incoming air are hot, it vaporizes easily. When things are cold, fuel will condense.

Liquid vs vapor isn't an on/off deal. Above the triple point and below the boiling point, there will be some combination of liquid and vapor - the hotter it is, the more vapor. When an engine is cold, the cold start mechanism (choke in the old days) makes the mixture richer so that there will be enough vapor to burn.

Revving a cold engine doesn't do anything to affect vapor vs liquid. Letting it warm up all the way does.

Ken

gummyAvenger

Ah, I get it now. Thanks for the explanation, Ken!

rotarygod

The reason why the rotary is easier to flood than a piston engine has everything to do with total chamber surface area and the distance that the fuel needs to travel before it gets ignited. In a rotary, we have an awful lot of surface area that the air and fuel see. In a piston engine, for the most part the air and fuel stay in the same place and just get compressed there. This is minimal surface area and hardly any distance traveled before combustion. Since air and fuel have to travel to the opposite side of the engine in a rotary before it gets ignited, this is a lot of contact with a cold surface. The fuel will stick to the sides easier. It is harder to ignite and there is lots of waste that didn't get completely burned. This is why cars run rich until they are warmed up. They need to in order to get enough fuel into suspension long enough to get burned.

Since we have the possibility of more fuel getting unburned and falling out of suspension, this means that we have seals pulling the fuel along the walls. The shape of the apex seals is rounded slightly. This means that this liquid can get underneath the edges of the apex seal tips. Cold temperatures and slow engine rotation don't help compression at all. Some of this small amount of fuel under the apex seal can cause the seal to move up just slightly. This causes a pressure leak which further reduces compression. It does not take much fluid at all to make this happen. When we don't make compression, the engine doesn't want to start and we keep cranking it. This dumps more fuel into the engine which makes the problem worse and so forth and so on.

Once a rotary gets flooded, it is extremely hard to unflood it. You can not just wait long enough for it to dry out. You'll be waiting a VERY long time. A flooded rotary might not start after months or even years of waiting! You need to get the fuel out. The factory recommendation is to hold your foot to the floor while cranking. This shuts off fuel delivery and allows the fuel to escape through the exhaust. At least it's supposed to. This too is hit or miss as just enough fuel may continuously stay in the engine as opposed to getting out of it and this will keep compression low. You need to get the engine spinning fast enough to overcome the compression loss. You also need to pray that your plugs will still fire as they may be all gummed up and wet. You can pull start any flooded rotary engine and get it to run. If it can't be done with a simple push start and popping the clutch, pull it behind another car. It will start. Depending on the severity of the flooding, it might take a few feet, it might take a few blocks but it will start. Do not take your car to a dealership to fix it. It is easy and you don't need a tow truck.

Hopefully that helps.

SureShot

THAT needs to start off the FAQ section of the forum.
What? there's no FAQ section?

msrecant

Well, it could be made a STICKY in the Flooding sub-forum. Oh ... I forgot, we don't have one of those either.

nycgps

iTrader: (1)

I heard of push start but I dont really get the idea of it. and popping the clutch ?

gummyAvenger

Too much sarcasm around here lately... hard to tell if anyone's being serious or not

rotarygod

Pull it behind another car. You don't need to go very fast. Let out the clutch slowly in 2nd gear only. There is no need to go over 20 mph and typically you'll have it started right after you start moving.

nycgps

iTrader: (1)

So is it like

one stay in the car, one going to push

turn the key to on (dont crank it)

press the clutch

put it in 2nd

Let all the brakes go

The dude in the back PUSH as fast as he can

Let the clutch go slowly and give gas

Is it like that ?

ken-x8

If the dude in the back is on foot, yes - as fast as he can.

If he's using a vehicle, or there is a hill to help out, 10-15 mph will do. As RG says, not more than 20 mph.

Been there, done that - both ways - with conventional cars. Pusher and pushee.

Also solo, with a hill to help out. Tricky part with a hill is timing when you hop in. And making sure the door doesn't sideswipe anything when you're halfway in.

Ken

msrecant

Careful where/how you push on the RX-8. The sheet metal is very thin and easily dents.

DOMINION

One more FYI: Dont rev your 8 then turn it off! Thats a great way to flood your 8.

Shifty Devil

I thought the "official" deflooding procedure included a step to remove as much of the raw gas as possible to prevent it from getting into the CAT where it will burn and destroy it, or shorten its life.