Dirt bikes and diving? Is it possible?

[lowwall]

Hook the air intake to a regulator and put a check valve on the exhaust.

I thought about that, but let's take a KTM 350. It's a single cylinder 4 stroke. Lets assume an average engine speed of 6,4000 rpm (half the redline), thus 3200 fill strokes per minute and an average air:fuel ratio of 13:1, so about 92% of each fill is air:

.35 x 3200 x .92 = 1034 liters of air per minute

Since we have liters, let's take a Euro-standard 10l 232 bar tank (which is very close in capacity to an AL80) = 2320 liters of air.

So a bit over 2 minutes at half throttle. Don't forget to leave some reserve for the ascent

 

[JohnN]

My wife and I only have two hobbies that we are passionate about, dirt bikes (trail riding our KTM's) and diving. As it sits currently we spend a lot of time in the mountains riding dirt bikes and then spend 1-2 weeks a year somewhere diving. I currently live in Colorado, but there is not a lot of diving here. I've looked at places like Florida, but I don't think there is a hill / trail in the state.

My job allows me to live pretty much anywhere in/around North America. So, the question of the day is, does anyone know where a person could both dive and ride?

British Columbia, either the sunshine coast or Vancouver Island. Real mountains and world class cold-water diving.

 

[apenland01]

I thought about that, but let's take a KTM 350. It's a single cylinder 4 stroke. Lets assume an average engine speed of 6,4000 rpm (half the redline), thus 3200 fill strokes per minute and an average air:fuel ratio of 13:1, so about 92% of each fill is air:

.35 x 3200 x .92 = 1034 liters of air per minute

Since we have liters, let's take a Euro-standard 10l 232 bar tank (which is very close in capacity to an AL80) = 2320 liters of air.

So a bit over 2 minutes at half throttle. Don't forget to leave some reserve for the ascent

You are describing a two stroke if you use 3200. A four stroke would be 1600. Down1 = intake, up1 = compression, down2 = combustion/power, up2 = exhaust. So every 4th rpm would be an inhalation lol.....

 

[lowwall]

You are describing a two stroke if you use 3200. A four stroke would be 1600. Down1 = intake, up1 = compression, down2 = combustion/power, up2 = exhaust. So every 4th rpm would be an inhalation lol.....

The R in RPM is crankshaft revolutions. As you correctly described, an intake stroke occurs on every 2nd turn of the crankshaft.

It's a little unintuitive because it seems like "four strokes" would take 4 revolutions rather than two. But you have to keep in mind that full trip through a piston's range of motion is two strokes (up and down), not one.

In a two-stroke engine, a piston goes through each of its operations with every revolution of the crank.

 

[lowwall]

I just thought of an easier way to estimate air usage. Note all the following numbers are reasonable approximations. 1 gallon of gasoline = 6 lbs. Air in an Al80 = 6 lbs. Normal air:fuel mixture is around 13:1 (they tend to run a little richer than stoichiometric).

So to burn 1 gallon of gas, you'd need to burn 13 cylinders of air. 350cc dirt bikes typically use around 2 gallons of gas per hour of riding. That's 26 tanks per hour, or just over 2 minutes per tank. Which nicely matches our earlier estimate.

Edit: Not corrected to Note at the start of the second sentence. Lol.

 

[OTF]

Will an open tank with a normal valve even drain fully in two minutes? Seems to take longer. And icing is an issue. Might need to port the valve for this. Worth it though for a two minute ride on a 50 horsepower fire-spitting DPV. Wonder what it would sound like.

 

[lowwall]

Will an open tank with a normal valve even drain fully in two minutes? Seems to take longer. And icing is an issue. Might need to port the valve for this. Worth it though for a two minute ride on a 50 horsepower fire-spitting DPV. Wonder what it would sound like.

I wonder what you'd have to do to make a gasoline DPV work? You'd have to keep water out of enclosed spaces, keep your electrical paths from shorting, keep the air in the fuel tank pressurized to ambient... We know that they've run submerged engines using snorkels so it's obviously possible.

Once you get this all figured out, the next step is obviously nitrox to increase range.

Edit: Jeep with snorkel. They swapped in a diesel which simplifies the electrical issues. You can skip to 20:00 if you just want to see and hear it drive around under 12' of water.

 

[D_Fresh]

British Columbia, either the sunshine coast or Vancouver Island. Real mountains and world class cold-water diving.

This is a great suggestion. Cold-water diving year round, plus riding in the summer and skiing in the winter....

 

[Mrs. B]

My wife and I only have two hobbies that we are passionate about, dirt bikes (trail riding our KTM's) and diving. As it sits currently we spend a lot of time in the mountains riding dirt bikes and then spend 1-2 weeks a year somewhere diving. I currently live in Colorado, but there is not a lot of diving here. I've looked at places like Florida, but I don't think there is a hill / trail in the state.

My job allows me to live pretty much anywhere in/around North America. So, the question of the day is, does anyone know where a person could both dive and ride?

Some crystal clear lakes in Westalpen? (at altitude, etc)

A guide to scuba diving in our local lakes - The Leipzig Glocal

 

[Mrs. B]

Arizona would have you flipped. Your trail riding is minutes away and your diving is 2 hours away for freshwater lakes and your ocean diving is in San Carlos MX about 6 hours away...

Edit: Just realized if you were in Phoenix, you would have close options for both...

Lake Mohave?