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20% vs 30%

Old 08-18-2007, 02:41 AM
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Buzz1
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Default 20% vs 30%

I've heard and read a fair bit about how once you run your engine on 30% nitro, you can't go back to running 20%. But I can't figure out how or why.

O.K., if you have to add some head gasket to lower compression to keep it from detonating on 30%, I can see why you would have to take the extra gasket out to run 20% again, but that's it. What's left of my braincells can't wrap themselves around any other reason for this theory. Nitro percentage can't affect any physical changes to an engine other than increased wear from making more power, can it?

Or does nitro possess some magical powers that change molecular properties of metal I am unaware of?

Because unless I hear some good reason (engine life of my TRX isn't a good enough reason for me) I think I'm going to go 30% in a good quality brand fuel.


On another note..... any ideas how to use an almost full gallon of Top Fuel for something besides making my truck run like crap?
Old 08-18-2007, 02:52 AM
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Default RE: 20% vs 30%

I'm not surprised you can't figure out why, as it's total rubbish. Add a shim, run 30%, remove the shim, run 20%, it will be fine. The other really funny one that people say is to reperform break in when switching fuel percentage. lol! Like suddenly the engine regains its pinch magically just cos you change fuels. Retuning is all it needs.
Old 08-20-2007, 12:16 PM
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revocat
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Default RE: 20% vs 30%

switching fuel whether % nitro or brands should be no big deal (shim change if needed) and a little retuning is all that is required.
Old 08-20-2007, 12:35 PM
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Default RE: 20% vs 30%

You don't have to always add a shim. Run it and see, some times just going to a colder plug will stop PD.
Old 08-20-2007, 12:37 PM
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Default RE: 20% vs 30%

i have a 3.3 engine...been runnin 20% moved to 33% a few days ago. i kept everything the same and havent had any problems yet...im runnin rich btw
Old 08-20-2007, 12:38 PM
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Default RE: 20% vs 30%

On another note..... any ideas how to use an almost full gallon of Top Fuel for something besides making my truck run like crap?
use it to clean your air filters out
Old 08-20-2007, 12:43 PM
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Default RE: 20% vs 30%


ORIGINAL: gamesbeer1

On another note..... any ideas how to use an almost full gallon of Top Fuel for something besides making my truck run like crap?
use it to clean your air filters out

+1, old nitro makes an awesome filter cleaner.
Old 08-20-2007, 04:42 PM
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Default RE: 20% vs 30%

I agree with revocat. I've talked to shop owners and they say if you do normal bashing, use 20%. If you wanna race with a bunch of people and want a little more ooomph switch to 30% and when you're done go back to 20%.
Old 08-20-2007, 05:19 PM
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Default RE: 20% vs 30%

i would run 33% in my revo but i cant really afford it.
Old 08-20-2007, 09:23 PM
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Default RE: 20% vs 30%

Cool, thanx guys. That's about what I thought. I thought and did. I bought a jug of 30% this weekend, threw another .010 under the head and the truck run's like a champ. Think I'll go back to stock shim though, cause the truck ran fine on my buddies Blue Thunder 30% set-up like that. Something to experiment with, anyways.....

The thing ran so good, it spit out a friction pad on the slipper, so I bought a rebuild kit and dropped 2 teeth on the spur gear, to compensate for the slightly smaller Badlands I put on it, and it still rips harder than it ever did before.

I bought SideWinder fuel, because it only has 10% oil, all the other fuel my LHS carries had 23-28% !?!?! oil at 30% nitro. And that's the car fuel. The Heli juice has up to 35% oil! Jebus. Talk about a rich mixture. The truck runs great, and slobbers way less than it did on any other fuel, even tuned to the rich side. The only thing I don't like about it is the statement in bold on the label. Don't use after run oil. I don't care what additives it's got in it, I feel that's a pretty broad statement for them to make.

I should also maybe toss some credit to the fact I added a small filter to the pressure line (pulsation damper effect, is my guess) and a big one to the fuel line, mounted above the carb as mentioned in the half-tank-lean fix I read someplace here. Everything all combined has increased my run time significantly. I didn't actually time a tank, but it seems twice as long as before. Probably only about 50% as long, but still way better. I was always the first to drain my tank when I bashed with my buddies before. Granted, I tune rich and have a heavy throttle finger, but I haven't changed how I drive the thing. If anything, I'm on the jam harder now.

All in all, a good weekend.
Old 08-21-2007, 03:39 AM
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Default RE: 20% vs 30%

thats odd, when using 30% you use more fuel because you have more nitro so more oxygen in the cylinder, maybe you are running less on the the throttle then you think, or it just seems like longer.
Old 08-21-2007, 11:31 AM
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Default RE: 20% vs 30%

ok im confused...i just switched from 20% to 33% in my trx 3.3. i didnt add or take out any shims and its runnin fine, but im not done tuning yet. should i add a shim?
Old 08-21-2007, 02:37 PM
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rawiswar
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Default RE: 20% vs 30%

only if it does not seem to perform ok

and add shims higher nitro take out for lower

also i hear you can run a cooler plug which could help with out adding a shim as well

as with with a higher nitro your ment to run a cooler plug
Old 08-21-2007, 04:40 PM
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Default RE: 20% vs 30%

I use Traxxas 33% with McCoy MC9 cold plugs and have no problems. I've never added any shims either.
Old 08-21-2007, 10:44 PM
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Default RE: 20% vs 30%

ORIGINAL: ttoks
thats odd, when using 30% you use more fuel because you have more nitro so more oxygen in the cylinder.....
True, but this new fuel has almost half the amount of oil in it. Less oil leaves more volume for power-producing fuel, since oil isn't a fuel, less of it means more power capacity per unit of measure......? maybe...?




.......maybe you are running less on the the throttle then you think, or it just seems like longer.
Either scenario is possible, but if I had to guess, I would guess I must be easier on the loud handle..... I need to time it, but I am fairly sure that I am running significantly longer than before......
Old 08-22-2007, 06:01 PM
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Default RE: 20% vs 30%


ORIGINAL: Buzz1

On another note..... any ideas how to use an almost full gallon of Top Fuel for something besides making my truck run like crap?
Use it in your weed eater.
Old 08-22-2007, 07:03 PM
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Default RE: 20% vs 30%


ORIGINAL: Compstall


ORIGINAL: Buzz1

On another note..... any ideas how to use an almost full gallon of Top Fuel for something besides making my truck run like crap?
Use it in your weed eater.
lol

use it in your grill
Old 08-23-2007, 12:48 AM
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Buzz1
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Default RE: 20% vs 30%


ORIGINAL: Compstall


ORIGINAL: Buzz1

On another note..... any ideas how to use an almost full gallon of Top Fuel for something besides making my truck run like crap?
Use it in your weed eater.
Lol. I actually ran a tank through an old lawnmower. Ran like crappolla. Serious re-jetting of the carb on that old Briggs-n-Strapon makes that uneconomical.

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