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Okay. I'd asked this before but since I goofed with my signature the post was deleted.

I have some folks whose engines (Traxxas 3.3) run hot (280 - 310). After richening the mixture, they run hotter.

This goes against everything I know about engines.

Any ideas?

Rob

Argess

Sounds like an airleak that worsenes as the engines warm up. It can also be from using fuel with too much oil in it, like airplane fuel or Backyard Basher fuel (I have a pet peave about that stuff and over-heating!). Also check what plug they are using.

It is probable that the engines are just continuing to heat up even though you richen them. Does the temp go back down as you lean them?

And finally, as the fuel level in the tank drops, the enigne leans out. Pressurizing then fuel tank minimizes this problem. Maybe check the tprssure lines are intact and operational. (Also check the fuel filler cap for a tight seal when closed)

twomanytoys

BTW traxxas dont make a 3.5 engine!

125cchyperman

Sounds like an air leak, but it doesnt really make sence though. But using a fuel that has a high oil conent in the fuel will not cause this type of problem. It causes OWB (One Way Bearing) problems, it causes the OWB to slip and continuely slip. The only way to get rid of this is to get a new OWB and to use a fuel that doesnt have as high of a oil content in them. Also high oil content fuel's can cause people to over compensate with needle setting. Another words to get more performance, they will tend to lean it out and will actually lean it out to much to get the performance they want and or like. So it can actually cause an over compensation of the needles to get the desired performance, but does not cause a heating problem with the engine though when richening it up.

But about the only thing I can think of is an air leak, but it doesnt make sence. Another thing that it may be is maybe the needles are bent, causing the temps to raise when richening it up cause a bent needle will sometimes cause an actuall lean condition at points and will have very eratic tunning. But those are the only two things that I can think of at this point right now.

46u

My Feedback: (3)

Yep high oil content fuel like Traxxas top fuel can create a problem.
Why 8% to 12% Oil

Using high oil content fuels in gas car engines won't provide improved engine life, as some would expect. Through extensive testing we've discovered the point of diminishing return as far as oil content to engine life is actually around 8% for most car engines. In other words any more oil than 8% in the fuel does noting to improve the life of a car engine. In fact the secondary effects of high oil content fuels can actually cause engine damage by encouraging over lean runs. Here's how.

Using high oil content fuel causes a car engine to be unresponsive during acceleration acting as if the engine were running rich. Typically when using high oil content fuel, in order to get crisp acceleration and response, an engine will need to be adjusted overly lean. In addition the high oil content prevents lean bog when an engine is over-leaned thus allowing the engine to run at this lean setting without the customary telltale lean bog warning letting you know the engine is overheating.

In summary, high oil content fuels don't give added protection. The point of diminishing return from a protection standpoint in a gas car application is about 8% oil depending on the oil type and engine. Anymore oil than this doesn't offer added protection and has potential secondary effects that reduce performance and can actually cause you to over lean your engine in an attempt to get crisp throttle response and acceleration.

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3.3 Sorry

Rob

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The issues do not appear to be fuel related (from what I can tell). Each person is using 20% fuel. Traxxas, Blue Thunder and O'Donnell. I do suspect the engines may not have been broken in properly, since the customers are calling about this only a day or two after buying the cars (Trucks, okay).

I'll get in touch on Monday and see if they can try these solutions.

Thanks

Rob

Pacific Rider

I had a big heat on a used 2.5, found after messing w/ fuel tank lines several times. The bearing inside the case was bad. It finaly was running great, then the rod poped where it conects to the wrist pin, broke the piston.
Another one bites the dust..