When your overland vehicle is your daily driver

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Lanlubber

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My TJR used to average 17mpg, 14 towing. I bought new tires 7.50R16s. Now I get 22mpg, 18 towing. Plus I need to use the brakes at a red light. With 33x10.50s, I could coast to a stop.

I'm never going back to "big" tires.
View attachment 117227

And I just ordered 2 more rims so I can mount 7.50R16s on the trailer too.
What engine do you have in the jeep ? Yes, it's like you said in another post, skinny tires, less road resistance, better digging quality in mud- snow and now better gas mileage. I'm not surprised. These tires you bought really do look good on your rig too.
 

Lanlubber

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You're mixing units of measurement. Air-fuel ratio refers to weight, not volume. To burn 1 gram of fuel, you need 14.7 grams or the equivalent of 3 gallons of air at stoichiometric. 1 gallon of fuel weighs 3404 grams, so to burn a gallon of fuel you need 50,000 grams of air, or about 10,200 gallons.
A 4 liter, 4 stroke engine uses 1 gallon of air in two revolutions. An engine running at 2000 rpm uses 1000 gallons of air per minute. Travelling at 60mph, that's 1000 gallons of air consumed per mile.
The compression ratio of a 4L jeep is 8.8:1, so at the top of that compression stroke of a single cylinder [(4l/6 cyl.=0.67L)/8.8] is 0.076L in capacity, so a little more than 2.5 oz of water in the cylinder is enough to hydrolock the engine.
Damn good research info. I'm not smart enough to figure it all out but I understand the results of a hydrolocked engine. Thanks for this post !
 

Charles M

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You're mixing units of measurement. Air-fuel ratio refers to weight, not volume. To burn 1 gram of fuel, you need 14.7 grams or the equivalent of 3 gallons of air at stoichiometric. 1 gallon of fuel weighs 3404 grams, so to burn a gallon of fuel you need 50,000 grams of air, or about 10,200 gallons.
A 4 liter, 4 stroke engine uses 1 gallon of air in two revolutions. An engine running at 2000 rpm uses 1000 gallons of air per minute. Travelling at 60mph, that's 1000 gallons of air consumed per mile.
The compression ratio of a 4L jeep is 8.8:1, so at the top of that compression stroke of a single cylinder [(4l/6 cyl.=0.67L)/8.8] is 0.076L in capacity, so a little more than 2.5 oz of water in the cylinder is enough to hydrolock the engine.
I guess I learned something new Thank you... My understanding of what measurement is used was certainly off...
 
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Lanlubber

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I guess I learned something new Thank you... My understanding of what measurement is used was certainly off...
The good thing. We have people in OB that are our assets to information. No not everyone needs it or wants it, but for those of us who are curious enough to want to know, it is there if we ask the right questions. If you had not tried to explain your understanding of the subject, it might never have come to light. So cudoo's to you as well.
 

MidOH

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Want to really melt you mind? If you jeep is crossing a river in 4L at 2000 rpm, how much water can be poured down the intake before hitting that 2.5 oz amount in the cylinder?

It's alot. I used to shock little Perkins engines with water. Get them red hot then turn on a garden hose in the intake at full throttle.
 

Lanlubber

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Want to really melt you mind? If you jeep is crossing a river in 4L at 2000 rpm, how much water can be poured down the intake before hitting that 2.5 oz amount in the cylinder?

It's alot. I used to shock little Perkins engines with water. Get them red hot then turn on a garden hose in the intake at full throttle.
Well what happened ?
 

MazeVX

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Water came out the exhaust.

Nothing. We used this technique to get carbon off the intake valves.
That's quite a rough way... But yes I can see this. It has a lot to do with the compression ratio of the engine and rmp its running.
To really hydrolock a engine it needs a lot of effort masses of water needs to be soaked in in a very short time.
The thing looks different with a turbo diesel...
 

twinight

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That's quite a rough way... But yes I can see this. It has a lot to do with the compression ratio of the engine and rmp its running.
To really hydrolock a engine it needs a lot of effort masses of water needs to be soaked in in a very short time.
The thing looks different with a turbo diesel...
The intake tract needs to be completely submerged to actually suck up the amount of water to hydrolock an engine. Even then, the engine may stall due to lack of air before the water reaches the cylinder.
The amount of air going through would atomize any standing water in the airbox and suck it up in small enough quantity to just turn to steam in the cylinder.
Unless the water is enough to block any air from getting through, or is feed into the cylinder by gravity, hydrolocking won't happen.
 
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Charles M

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Lanlubber said:
The good thing. We have people in OB that are our assets to information. No not everyone needs it or wants it, but for those of us who are curious enough to want to know, it is there if we ask the right questions. If you had not tried to explain your understanding of the subject, it might never have come to light. So cudoo's to you as well.
It is interesting I worked with fuel ratios when dyno tuning for 5 years I always assumed it was a volumetric ratio not weight. Everything was in volumetric tables and we would look at the volumetric efficiency of a motor and use that information when tuning.
I think a lot of us have a great deal to contribute to this forum in a lot of areas. I have a lot of professional experience and skills in many fields. I have enjoyed working in many industries over my 50 years and look forward to more things in the future... lol

Do they obviously run better afterward. How would you know when to do that sort of thing.
Does the water kill the engine under those circumstances ?
I was taught this back in auto mechanics class in HS and have done it more times than I can remember. If you have a motor that is over running or doing a lot of knocking it was normally caused by too much carbon in the combustion chamber. We did this to remove excessive carbon build up. I would get the motor hot and start by pouring about 12 ounces of water into the carb. Just rev the motor a little and start pouring it in. If it stalled no big deal just re start it.

I guess with fuel injection and engine management controls it is a lost art and only the old timers would know about it.

I might not argue it only takes a few ounces of water to lock up a motor but, to get that much water into the motor it would have to swallow a heck of a lot more.
 

Lanlubber

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Influencer I

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It is interesting I worked with fuel ratios when dyno tuning for 5 years I always assumed it was a volumetric ratio not weight. Everything was in volumetric tables and we would look at the volumetric efficiency of a motor and use that information when tuning.
I think a lot of us have a great deal to contribute to this forum in a lot of areas. I have a lot of professional experience and skills in many fields. I have enjoyed working in many industries over my 50 years and look forward to more things in the future... lol



I was taught this back in auto mechanics class in HS and have done it more times than I can remember. If you have a motor that is over running or doing a lot of knocking it was normally caused by too much carbon in the combustion chamber. We did this to remove excessive carbon build up. I would get the motor hot and start by pouring about 12 ounces of water into the carb. Just rev the motor a little and start pouring it in. If it stalled no big deal just re start it.

I guess with fuel injection and engine management controls it is a lost art and only the old timers would know about it.

I might not argue it only takes a few ounces of water to lock up a motor but, to get that much water into the motor it would have to swallow a heck of a lot more.
Very interesting, I have never heard of doing that but it makes sense.
 

MidOH

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Do they obviously run better afterward. How would you know when to do that sort of thing.
Does the water kill the engine under those circumstances ?

Yep. Pretty obvious torque loss.

Metal reclaiming plant. Pretty much gritty dirt. Those engines had ring issues and extra oil getting into the cylinder. I did about 40 air filter changes every monday. That's with the stupid snorkel bowls being dumped daily. Really doesn't apply to us. But when I see a powerboat stall during a race due to crossing someones roost, I have to wonder.......
 
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RichieFromBoston

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Snorkle tubes on the fender and your air box both have holes in them to drain water so they aren't sealed. You'll still fill the engine with water. Maybe just a little slower.

If you watch the Aussies much, they use a technique called a bow wave which means controlling your speed so the pressure wave your vehicle creates in the water with its movement keeps a void behind your bumper to keep the water level low in the engine compartment. That helps as well but you can still drown them out if you stop and the snorkle tube fills through the drain holes.
thats true, some of have sealed those holes up especially in northeast water gets deep.