Read above for uunetbill's How Stuff Works. It may not be the technically correct term (although it *seems* correct, given the above article), but I've experienced this fascinating phenomenon.

Hey, rather than calling me out on my jargon, why not try it? :impatient I'll let you call it whatever you want. You can even call it "the poached egg effect", if that makes you feel good.

 

http://autorepair.about.com/library/.../bldef-044.htm

Backpressure exists because exhaust gasses flowing out of the engine run into existing exhaust gas in the exhaust system - thus the pistons are pushing to get the gas out of the cylinder. Those gases are all flowing OUT of the exhaust system at the back (unless there is a leak and they flow out sooner.) At no time is there NEGATIVE pressure (i.e. sucking in at the exhaust.)
Try this experiment - take an empty bag (preferably heavy duty paper) put it over the exhaust at idle. Does the bag get filled up, or sucked empty?

 

Well, I tried it. I pressed onto one exhaust tip. Once I overcame the blowing pressure, sure enough, to my amazement, I could feel something of a light inward suction.

I tried to see if I could get a piece of paper to suck against the tip, but it won't.

I figured there must be something of a loop effect happening between the two exhaust tips--block one and the gasses all channel out the other, then causing a syphon effect against the other tube.

Or another theory could be that blocking the exhaust at the tip causes the gasses to escape from around the decorative exhaust tip where it bolts up to the true exhaust pipe, and the diverted air flow creates a vortex...

Or, it could be magic, pure and evil.

BTW, I have the JCW dual exhaust cans with individual pipes and exhaust tips...

 

ROFL!!

You know, I realized a little while ago that I had only tried one tip on a Milltek exhaust. Perhaps this is a one-in, one-out kind of thing, but even so, it would certainly back up my original purpose for mentioning it: submerging your exhaust at idle speed is bad bad bad.

 

The gasses will take the path of least resistance. Sure, if you only cover one tip, it will eventually 'siphon' the paper or bag in - as the gasses are flowing out the other tip, and flow is slightly sucked through the covered tip. It however, will not suck water up to the engine.


The ONLY time I have heard of anything able to be sucked up an exhaust TO the engine, is on a true dual exhaust V8, where the timing of the pulses is acutually right that there IS one pulse of suction in the stroke. I remember a caller/writter into Car Talk, where someone had a car idling, and either had his or his son's shirt sucked up real quick while standing at the rear - I think they were changing a tire or something, I don't remember.

In anycase, a single exhaust 4 cylinder car will NOT suck ANYTHING to the engine, even if fully submerged in water - for that matter neither does a single exhaust V6. I know this from first hand experience, understanding of the engine stroke pattern and COMMON SENSE.

 

Sooooo...

I take it that if one needs a gas bag, just look for kaelaria?

 

Yeah I got some hot gass forya...oohhhhh....yeah, that ones gunna stink!

 

It is interesting to know that there might be some sort of issue with the MINI sucking in water. I used to drive a Jeep and liked to zip through the water in four wheel drive during heavy rains. However this was only water that had just fallen on flat roads and was probably only an inch or so deep and the Jeep was pretty high up. I would expect the MINI to be pretty good in these "normal" rain conditions.

Where my mother lives in the desert of southern California they have these washes and when it rains they have moving water that can be much deeper than it looks. People plow in to them and get stuck all the time and have to be rescued. It happens year after year during the rainy season and she tells me that people are always surprised that they get stuck, even driving their big SUV shopping carts.

I am going to pay attention to what happens with the MINI the next time I drive in the rain. Being as it is so low I think I would go pretty slow in heavy water and I sure would stay out of the washes when they are flooded. I can see how water could get in if you have it splashing over the hood, but I would wonder if anything else is going on, like some kind of wave coming off the air dam or up the wheel wells. Maybe some one needs to do a water tunnel test like they do with boats.

 

Straight outta the AZ Natl Weather Service:

[font=Arial, Helvetica, sans-serif, Geneva, SunSans-Regular][size=-1] With an average of 12 inches of rainfall and 86 percent sunshine. Tucson receives more than 50% of its annual rainfall during the months of July, August, and September.

I lived in Tucson from '79-'87, in the years before they put actual storm drains under the roads. Yes, they designed the roads back then like skateboard tunnels, and the roads themselves carried the rainwater off. Driving in, or more accurately, on the sides of the road after a rainstorm was a terrifying process. A$$hats galore in their dunebuggy's and jeeps would plow thru the water past you, dousing you totally in water. On more than one occasion I lost my brakes and would have to pull of onto a side street to dry them off. And no, I didn't drive like a jerk. A MINI wouldn't stand a chance on those roads, no way no how.
[/size][/font]

 

I spent three years up in Iceland and most of their interior roads run "through" rivers. Not over, but through. Here's a picture of a typical outing.

There was never a fear of water coming up the exhaust, the only fear was if the river happened to go over the hood and stay for long enough to cut air to the engine off. Nothing like having water over the hood to make you suck up the seat cushion. Bottom line is that the only reason for an engine to hydrolock after going through a small amount of water is poor design.

 

Okay, since we have heavy winter rains and I like to zip through the puddles, I am concerned about what will happen to the MINI.

So I checked it out and I notice that the air intake pipe which takes air in just below the hood angles DOWN on the way to the bottom of the air box. Then the pipe which takes air from the mid-point of the front of the air box angles DOWN to the intake for the Supercharger. Also the mouth of the intake is horizontal and wide and flat, so a large volume of water could roll in and flow down it.

So it looks like that if you go through water that is deep enough to hit bottom of the air dam it could be splashed up over the grill and it would roll DOWN the air intake and fill the air box and then roll DOWN the next intake towards the Supercharger which would suck it up in to the motor. Since the MCS is Supercharged their will be a fair amount of suction.

I checked out my other vehicle and with it the air enters from behind the grill and must go UP to the airbox and through the filter and out the TOP of the airbox and then go UP to the throttle bodies. The opening points straight down and water can not splash in. Totally different design.
I remember splashing through puddles in the Jeep and having water come over the hood and splash all over the windshield and it was not a problem.

Also the owners manual on the other vehicle does not mention driving though water. How many other manuals mention driving through water? I am thinking that if MINI decided to mention this it is because they knew they had a design problem.

So I am thinking that the MINI has a sub-optimal design that aids the flow of water in to the engine. I have not measured the height of the air dam or tested what kind of a wave it would make or measured the angles of the intakes, so this is just a theory. But given the number of cases of hydro lock I think this is worth investigating further. Anyone want to drive their MINI through some water for observation purposes? :smile:

 

Terrible terrible terrible.

 

Back pressure is caused from a catalytic converter or muffler. Back pressure does not mean that the exhaust gets sucked back into the engine and majically disappear. If a car is running water WILL NOT get sucked into an engine. You don't see a Jeep with an intake snorkel have a big exhaust pipe sticking up the back do ya? Also, the bends on the exhaust manifold go down so the water would have to defy gravity to go into a cylinder.

 

Actually, yes, I have seen Jeeps with snorkel exhausts. And it was a group of guys who had just returned from Camp Jeep who informed me of keeping revs high to avoid damage from water in the exhaust. It was part of what they were taught at Camp Jeep, which is run by Jeep gurus. So nyeh nyeh.

 

[font=MiniThesis-Bold][size=2]

from the 2005 Cooper Manual:

Driving

[/size][/font]
[font=MiniThesis-Bold][size=2]

Driving

[/size][/font][font=MiniThesis-Regular][size=1]
[/size][/font]

 

hopefully the salesmen went over this issue upon delivery of the car....

 

2miniacs: I think if that picture were with a mini, you'd be buying a new engine. That's a LOT of water. I'm worried about 3-6 inches of water causing problems - not going through a river.

Based on the number of people posting that they had to buy a new engine here and on mini2, and the dealer's response that a new engine would be required before even looking at it, I think MINI must be well aware of the problem. Note that the poster had an MC, not an MCS - maybe the air intake on the MC is lower?

 

just a thought on why i haven't found any mentions
of mcs's w/ hydrolocked engines

could the mcs be more resistant since it has a lower compression engine??

 

hello guys.around march this year our mini club did a run down to a drive in movie about 2 hours from home.on the way there we had to drive through a huge downpour of rain.the water would have been at least a foot deep in places.there were about 4 cooper s minis there and not one of them had any trouble with water intake.we were only doing about 10 kilometres an hour at the most but the cars never missed a beat.:smile:

 

given the variety of roads downunder, i wouldn't be surprised if an ARB snorkel kit was available for the mini.
(i remember quite a few river crossings at fords)

 

Snorkel EXHAUSTS? I gotta see that one! Any pics??
Likey the reason the Jeepers were taught to keep the revs up would be to keep from stalling the engine when fording creeks. But you never know...

 

I've been trying like mad to find pictures. I wish I had one. The best ones I can find online are those silly Japanese "performance" cars with the vertical pipes. But I also remember the US military tested early Humvees underwater (to the tune of about 30'), and using snorkel intakes and exhausts, which must have looked quite silly.

 

i've done my share of offroading in land rovers, and high revs aren't
really encouraged since that causes the fan to throw water all over
the electrical. a steady pace and bow wave generation were encouraged.

'tread lightly' and heavy use of the loud pedal aren't very compatible.

 

Hey, look over there! Is that Elvis?

Pit pat pit pat pit pat pit pat pit pat ...

 

well you know if you fight it youll prolly win ! and get a new engine


reminds me of a story
a man bought a new winabago (not shure of spelling) and went on vacation while driving he pute the winabago on cruise controll got up to make himself a cup of coffe, the winabago carened of the road fliped over and was a total loss,
the man sued the winabago companie and won, he won several millions and a new winabago, his fight was, noware in the owners manual did it say that you had to be at your seat at all times while the cruise was engaged,

i was like its not auto pilot you moron!!!!

it scares me that their are people driving around like this!!!!!

anyway tru storie it was in a book of outrageouse claims and their outcomes, its really amazing what people get away with !!!!