2canSAM

iTrader: (248)

TRX 3.3 Brand New a few weeks ago. Performed the break-in as Traxxas recommends. Ran great, smooth process, never stalled there were no issues at all. Break-in was done around 80 degrees ambient temp. Ran it last weekend and it ran perfect. Plenty of smoke. No stalling, gobs of power, snappy low and, idled well. Outside temp around 65. Tried to run it this past weekend and started stalling while accelerating, bogging down then cutting out. Still plenty of smoke and nice power down low. Temps at the plug were 220 give or take 10 degrees but the block was only reading around 120 to 150. I richened the HSN a 1/8 turn and not much better. Now after break-in I swapped the standard REX 3.3 head for a Nova race 3.3 head. I liked the looks of it but have since read it may cool too well. Here is the piston after probably 12 -15 tanks. Running Traxxas Top Fuel 20% and have not really tuned it any. Below is a link to video of it running last weekend. Thoughts? All feedback appreciated.



http://youtu.be/YafpZv34wQA

My ST-RR EVO

iTrader: (5)

There's nothing wrong with that piston. The coloring just tells me it's used.

Sideshow Bob

Runs fine in the video. And as mentioned already, that colouring/buildup is normal.

fyrstormer

iTrader: (1)

It started bogging down on acceleration so you *enriched* the fuel mixture? If it was bogging down it was already too rich, and the temperature readings confirmed that. The engine was breaking-in and producing less heat from friction, so the correct tuning step would've been to lean the fuel mixture instead. Aim for 240°F average with a peak of no more than 275°F.

nate johnston

Very well could have been a lean bog on low end needle. Seems like there was no build up as you were putting your body clips on so I would say low end needle slightly lean with high end needle showing the smoke you see

2canSAM

iTrader: (248)

Thanks for all the info. I richened as it was stalling / cutting out and even thought the temps did not reflect it it acted as it was lean. A drop of spit on the head sizzled away almost instantly even though the temp at the plug and crankcase never seemed hot. I have removed the Nova Race head and will be going back to the Stock TRX 3.3 head and setting needles back to factory and start over. Thank you to all for the help.

fyrstormer

iTrader: (1)

Okay, it's very strange for the plug to be colder than the rest of the crankcase, since the plug is constantly exposed to combustion even during the intake phase, when the platinum coil acts as a catalyst to oxidize small amounts of the methanol in the intake charge, the heat from which keeps the glowplug coil glowing the entire time the engine is running. If the "spit test" produced sizzling and your IR thermometer said the plug was cool, then I would suspect your IR thermometer is inaccurate. Get a second one and see if it gives the same readings. If it does, then perhaps the heat-range of the glowplug is too cold, and the engine is getting so hot because the ignition is severely delayed.

I use medium glowplugs in all situations unless it's obvious I need something else. I only have two engines that need hot plugs, one is a very small engine and the other is intended for running in cold weather. I have none that use cold or medium-cold plugs.

My ST-RR EVO

iTrader: (5)

A picture of the plug might be more telling. ..

shanef

iTrader: (38)

Hard to tell from a video how it's tuned but it appears the top end is too lean. Also you should have a look at the throttle linkage, it sounds as though the carby is opening with no throttle applied, the carb should be fully closed (minus the idle gap) at zero throttle input, you shouldn't have to hold the brake to stop the engine running-on.

Correct the throttle linkage, richen the top 1 full turn and go from there.