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Mapp Gas Percentage

Post questions and info about combustion (flammable vapor) powered cannons here. This includes discussion about fuels, ratios, ignition systems, safety, and anything else relevant.
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Mapp Gas Percentage

Unread postAuthor: Pibster » Mon Aug 18, 2008 10:32 am

I currently use propane on my gun and may switch to mapp gas. I use a meter and a fan. Is the Mapp going to have a noticeable difference. 2nd question, the propane is 4%, what is the mapp percentage?

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Unread postAuthor: SpudFarm » Mon Aug 18, 2008 10:36 am

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Unread postAuthor: starman » Mon Aug 18, 2008 10:42 am

Barely noticable. Under ideal conditions, 5 - 10% increase in velocity using a golfball projectile. Shooting a basic spud, not worth the money.
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Unread postAuthor: Pibster » Mon Aug 18, 2008 11:44 am

I also have a golf ball and softball barrell. 10% more might be worth it.
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Unread postAuthor: starman » Mon Aug 18, 2008 3:24 pm

On an HGDT calc I did for a golf ball and using a small burst disk, the performance went from 606 fps using propane to 645 fps using MAPP...only 6% and will be only noticable with a tachometer. When used with a stiffer burst disk the advantage falls even further to 3-4%.

I would focus more energy on gun design to most optimize performance....but that's just me. MAPP is not going to offer you a generational improvement in performance by itself.
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Unread postAuthor: Kennymester » Mon Aug 18, 2008 6:10 pm

With talk of burst disks and stuff is Mapp only used with hybrid or can it replace propane in a normal combustion?
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Unread postAuthor: ralphd » Mon Aug 18, 2008 6:28 pm

I started to use mapp in mine only because I ran out of propane and I was to thrifty(my wife says cheap) to pick up another bottle. It works fine but I don't have a chrony to tell if I really gained anything. As far as burst disks....I was told it only makes a difference in hybrids, with combustions it justs makes it louder. Again, I don't have a chrony to really tell. You can pick up propane for $2 and mapp for $7.
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Unread postAuthor: starman » Mon Aug 18, 2008 7:29 pm

Kennymester wrote:With talk of burst disks and stuff is Mapp only used with hybrid or can it replace propane in a normal combustion?


MAPP can be used in a normal combustion just fine. You can use HGDT to model the real performance gain.

ralphd wrote: As far as burst disks....I was told it only makes a difference in hybrids, with combustions it justs makes it louder.


Nope, performance improvement with regular 1x combustions as well. The sound characteristic is a little different with a burst disk than without not necessarily louder though. Several factors play into the loudness thing.
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Unread postAuthor: SEAKING9006 » Mon Aug 18, 2008 7:54 pm

Also, burst discs are good for combustions, especially if you want to make pre-loaded shells, like for an anti-tank gun. Helps seal better than just the projectile.
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Re: Mapp Gas Percentage

Unread postAuthor: starman » Mon Aug 18, 2008 11:36 pm

Pibster wrote:2nd question, the propane is 4%, what is the mapp percentage?


Oh sorry, didn't answer this one. 5% for MAPP is optimal. So either 25% more pressure in your meter OR 25% more volume, but not both.
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Unread postAuthor: jimmy101 » Tue Aug 19, 2008 10:22 am

MAPP fueling is not as clear cut as is propane fueling. The problem is figuring out exactly what is in a MAPP bottle. "MAPP gas is a proprietary mixture of various hydrocarbons, principally methylacetylene, propadiene and propane." Methylacetylene and propadiene have the same chemical formula so they have the same fueling ratio, 5.24% for additive fueling. But the MAPP cylinder also contains propane, which needs a 4.2% fueling ratio (additive). How much propane is in the bottle? How much other stuff? I've never seen reliable numbers as to exactly how much of each gas is in the bottle.

The best data is probably Latke's. He found 4.6% to 5.1% MAPP give the best performance. Looking at Latke's data, it looks like you probably can't tell the difference between MAPP ratios in the range of about 4% to 5.7%
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