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Switch from Top Fuel to O'Donnels question

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MrClean

MrClean

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  1. Bashing
I know a re-tune is required when switching fuels even though you stick with the same percentage. Here's my issue. I repaired my front and rear diffs that I tore up being an idiot. When I put the truck on the ground and give it a push (motor not running) it rolls pretty freely.....nothing out of the ordinary. I started it and tooled around about 1/2 throttle to let the motor warm up and then began giving it WOT runs. My temp shot up to around 300 degrees, I shut it down, put the piston at BDC and let it cool. Richened the HSN 1/8 of a turn and ran it again, same deal, temps got up to around 300 again. I didn't see a change in the amount of smoke and it's not shifting into second (I think I might still be too lean). I thought maybe I had something getting into a bind, but I checked everything I can think of and it all seems to move pretty freely....driveshafts, mesh, brakes etc.

Can switching from one brand to another make your tune totally out of whack? Should I reset the needles to factory settings and start my re-tune or continue to richen the HSN until the temp drops?
 
Just continue to do what you are doing until you get the temps down. Odonnel needs to run quite a bit richer than Top Fuel to see the same temps. You're on the right path...
 
Start it, let it warm up, just drive it in slow circles for a while and then check the temp. Not everything can be corrected with the HSN. I would suggest you richen the LSN and idle till you get good take off, shifting, and then adjust the HSN for WOT.
 
I just started using O'Donnel fuel in my 21tm because it was running a little hot with the Traxxas Top Fuel. Plus OS said to stop running it in their engine, "it is horrible on it". I noticed that the O'donnel's fuel runs a little cooler. Plus I got a Trinity Pipe and it lowered the temps even more.
 
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i just whiched from traxxas 20 percent to sidewinder 20 percent and it took me about 15mins. to get it tuned i had to run it richer than the traxxas but other than tht the gas works way better than traxxas my engine idles and runs better and has better temps.
 
Thanks for the advice guys, Saturday will be the day I get to straighten this out. I wanted to make sure I wasn't missing something. I knew Top Fuel had a ton of oil compared to other brands so I assumed I'd have to richen it up some.

Rolex, I will try that, it seemed to have very little power on take-off. It used to pull the front end up like crazy when I hit the throttle. Now it just starts going, not too slow and not too fast.
 
Completely start over on the tune when you switch fuels. You may have to go back to factory settings and start over. Don't try to tune from being lean/hot. it does not work.
 
Today's lesson............. gear mesh.....LOL. I finally started getting the tune dialed in but it wasn't shifting to second gear (still a little rich), so I leaned the hsn an 1/8th of a turn and took it for a run down the street. As soon as it shifted to 2nd gear, it shifted right back to 1st and slowly rolled to a stop. I guess when I was checking the mesh I left it a little too loose and the shift to 2nd did a nice job of grinding down the teeth on the spur. I think I'll buy an extra one when I go the lhs today.
 

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