blis

Yes, this is due to excessive air, this could be caused by an air leak, so it's always wise to check bearings, carby, carby boots, exhaust manifolds etc for leaks. The FAUX idle is evident when you have cleared the block and crank of excess fuel, specially after a long straight.

Lean the LSN 1/4 turn and see if the idle rises or behaves more consistently, but also consider the engine should be at operating temperature before you attempt a fine tune.

Add to it the fact that your engine uses the methanol to cool and it's best in a state of richness off power and at low idle, this won't harm the rod, crank and bearings as much as a rich top HSN. So in my experience, it's very difficult to get a perfect LOW/IDLE tune and it's safer is it richens and stalls than it is with a LEAN IDLE as it might overheat under racing conditions.

It's really up to you and your observation, every engine tunes differently, operates at different temperatures and many will do it by feel, sound and smell.

PS: Weird or erratic shifting is often caused by a dirty or slipping ONE way bearing.
Clean it with a clean cloth, add one drop of ONE WAY LUBE (it's a thin not so oily lube) or just lube the lay shaft and work in the oil by putting the one way on the shaft to distribute it evenly.

snuvet75

iTrader: (16)

I learned that I should lean LSN too.
Regarding inconsistent shifting I still need to find the answer. U may be right about one way but I cleaned thar bearing many times and lubed it properly. It doesn't seem broken either. It's better nowdays but still.does that. It shifts especially if I gun it after letting the car cruise for a brief moment when,at that speed, it should be the first gear that engages.

blis

Alas, perhaps you leaned the bottom too much, if the engine starves as it peaks revs before shifting it may need a little more fuel OR you are still very fat/rich on the bottom and you observed that your shift occurs after clearing the bottom end.. 2 Speed setups are for me the most painful experience in RC. It can take me hours to find the sweet spot and symmetry of the shoe to shift. You do need a consistent engine tune, relatively similar tyre diameters. You could use rubber EP tyres to make for large consistent diameters. This would then create a good reference point for you to know whether you need to tighten or loosen the shoes. It takes no more than 1/8th - 1/4 turn of the tension screws to make a difference once it's right. Finding that spot is the hard part! Better tight than loose, so start with a tighter shoe and take it off the car and set it up first.

Remove the shoe, loosen the screws (DONT COUNT TURNS), loosen it until you can open the shoe with your hands and look at the gap, make them equal.

Then begin to count turns from that point and tighten it until you can barely open the shoe with your hands and check the small gap is the same. At this point put another 1/2 turn in each screw to be sure you are in first gear. Then work backwards with the shoe on the car.

Also, check...

• Your two speed shoe is the correct way around, if it is asymmetrical then the trailing edge of the shoe should have more mass. (NOTE: Some cars are backwards to my method *eek*)
  
• Also check your two speed shoe is symmetrical with spring tension, if one side is tighter than the other side, the shoe wont expand correctly
  
• Check you havent oiled the bearing and the oil has dispersed into the drum. I didnt believe it would behave like it does, but it's true, it wont shift and slips.. Usually a lot of residue on the shoes.
  
• Check the gap between the shoes and the drum are correct, there should not be a large gap there.
  
• It's always safer to tighten loosen your 2 speed to ensure it's in first gear than it is to be shifting too early
  
• Ensure your engine is tuned and warmed up before you test any of this
  
• Ensure your tyres are not too large, this changes the shift.
  
• Always consider the SPEED of the 2 SPEED DRUM, not the engine speed, so any 1st speed gearing changes will afffect shifts
  
• If your car's clutch is not failing, or slipping, this could impact shifting too

AND MOST OF ALL....

Realise what an achievement it is to get all this to work correctly, don't look at it as too much trouble, once you master a Nitro car, you have won the biggest trophy of all!!

To finish first, first you must start!

greg.dawn

and when you get it to change right leave the thing alone we have changed baileys 2 speed /2/when we changed shoes/and when I starter to use it ///see I donot go fast enough for it to work right we always take at least 3 laps to get mtx5 to change right the car has many laps/and titles on it now
greg

snuvet75

iTrader: (16)

Well it's been a while since you answered but I taught myself a lot since then I got it all figured out. The 2 speed shoes were fine. It's hard to say what was the problem since I re tuned the engine and rebuilt the drive train but I'm pretty sure it was the lean bottom as you mentioned. I learned to tune engine better and everything got much better. I always like to come here to either learn something or confirm what I did or learned was the right thing. Thanks,

blis

Happy to hear you are feeling comfortable with tuning, it is daunting to begin with but once you get the science down pat and get a feel for it, it becomes second nature.

snuvet75

iTrader: (16)

Zakariah

and just when i thought i was getting comfortable with tuning.. lol

i could use a few tips apparently

i have a .21 nova on my cobra gt, just got it broken in a week or so ago, and im having a little trouble getting it dialed in. idles pretty good, takes off without sputtering so much, and has pretty decent top end, for like a lap or two. i also notice for the first lap or two, it shifts well. after it warms up, it feels as though i lose top end. i have a cheap duratrax temp gun, so im not 100% sure how accurate it is, but its ready 200-220 at idle (which is ideal i believe) but after just 2 or 3 WOT passes the temp skyrockets to 270-310. (body off!!)

plenty of blue smoke from the pipe, and the temp drops back off relatively quick when i bring the car back to idle.

where would an expert engine tuner begin with this problem?

is it a problem? would high temps after speed passes be normal engine behavior?

also.. where should i check the engine temp? ive been told to check directly on top of the cooling head, but i get a higher reading at the bottom of the head just above the manifold on the side of the block. i figured the highest reading i could get would be the temp to go by?

i really don't want to ruin this brand new nova.. thanks for any and all help guys

dan_vector

iTrader: (27)

Check the temp consistently at the glow plug as that is the 'standard' place to do so. The temps will climb rapidly if your just doing speed runs however if the engine is dropping off after a few laps then that's symptomatic of being too lean on the top. Richen the engine up an 1/8th of a turn and run again. What's the temp at the glow plug?

Serpent-Dan

iTrader: (18)

What percentage fuel are running?

Zakariah

using the flashpoint on the top of the head, right above the plug stays around 220-240. but im not sure how accurate that reading is because its not consistent.
i'll take it out again tomorrow if it doesnt rain and get some current glow plug temps. i should probably invest in a better temp gun soon..

too rich on the top wouldnt cause overheating would it?

offroad racer

what is the best tuned pipe for the losi 8ight 3.0?

blis

Check tank, carby, fuel lines and gaskets for leaks.

qstorm777

iTrader: (2)

I'm new to nitro. I've read all kinds of things on nitro tuning. I still don't have a clear cut answer as to how to tune an engine. Are the pinch test still valid for today's engines. If so, I can successfully perform the idle gap pinch test. However, when doing the 7 second pinch test, where do you pinch the fuel line? How do I know when to stop leaning the hsn? Thanks for any help. If the lsn is too lean, the car will run with a high idle after a high speed pass for a little while. Is that correct? I'm running everything very rich right now until I understand this.

alport78

HI,
I've a tuning issue. My engine revs very high between high throtle inputs. Its' idle is normal but when I go trough some curves without any throttle and brake with the cars own speed it's rpm is very high (sometimes like a machine gun ) Is it lean on LSN or HSN or some other problem to look for ?