Revo 3.3 tuning help - HSN 4.5 out and 265F

[miller]

I bought a Revo 3.3 (5309) a month ago today and have been having a lot of fun and frustration with it. This is my first nitro truck after having wanted one for many years and trying to tune it has been really frustrating.

I used the flow chart from this site to getting the truck drivable: no more brake stalling or idle stalling. Now I’m having trouble getting both needles set correctly. I’m at 4.5 turns out on the HSN and was running at 250-265F after a mid-tank WOT passes (ambient 77F). There is a faint trail of blue smoke and when returning the throttle to neutral the idle stays high (hangs?) for a few seconds. The idle sounds high to me, but I’m a newb, and it’s not trying to creep although with the wheels of the ground [read: upside down after a cartwheel :thumbup:] they do spin. The idle is set at 1mm and the pinch test is about 4 seconds with the engine reving up then dying.

Is it uncommon to have to run richer than break-in settings? Should I keep going richer on the HSN until the temps are down and I see more smoke? The truck flies and I don’t need it to be going any faster, I just want to have a reasonable tune that I can take it out and have fun bashing around rather than driving 2 tanks through it and trying to tune and getting frustrated.

Thanks.

 

[Punisher]

Break in tune is just a guide.

I was 3.5 out on the HSN with the standard pipe, then fitted a THS pipe and in cool weather conditions my HSN went from 3.5 to 4.5 turns.

If you havent already, might pay to seal your back plate and carb to ensure you havent got an air leak.

Dont tune by temp - use temp as a guide - if your revs are hanging on after a WOT pass it is an indication that you are lean on the high speed - give it what she wants - richen your HSN a little more and see if the temp comes down.

If the performance is there, and you have smoke, and the engine isnt melting, I would ignore what the book says (about being 4 turns out) and tune for performance.


Happy tuning . . . .

 

[2revo1maxx]

Yup^. I would richen it up until you know it's too rich, then gradually lean it back in.
A well tuned engine will seem rich for the first couple minutes until it warms up.

 

[Macguyver]

both my 3.3 engines run with the HSN at 4.5 to 5 turns out ..runs great like that ..plenty of power and temps are around 270 ....

like the others said ...let the engine tell you what it wants ...if it wants more fuel , give it to him ...lol

 

[Zdragon71]

What % fuel your running makes a difference too. I run byrons 33% and with my 2.5R my hsn is 5 1/2 out and about 2 1/2 on lsn. My temps still hit 285 on a hot day with a medium plug. And the engine runs at its peak performance with those temps.

 

[miller]

Thanks everyone that really helps. I thought 4 turns was rich (the way I read the manual) and I should be leaning from there and couldn't figure out what my problem was.

I'm using Sidewinder backyard basher fuel, 20% nitro and 16% oil, btw.

 

[Zdragon71]

Thats a good fuel with plenty oil so dont worry about 265. Thats actually still within a good range. I wouldnt worry about it unless you start seeing temps up over 290-300. Then i would start looking for air leaks somewhere.

 

[hamz9561]

I used that fuel in my 3.3 and ran between 260° and 280° with no problems on 100°+ days.

 

[2revo1maxx]

The biggest difference in fuel will be in regards to oil percentage. Less oil content will run cooler and better.

 

[miller]

The biggest difference in fuel will be in regards to oil percentage. Less oil content will run cooler and better.

Thanks. I went with that fuel after reading this on my LHS's website:

20-16 fuel contains 20% nitro and 16% oil. This fuel with its generous oil content, is typical of the fuel generally recommended by an engine manufacturer's instructions. Beginners should probably use a fuel with this amount of oil to protect their first engines from excessive temperature/wear while they learn to deal with proper carburetor needle valve settings.

20-12 fuel contains 20% nitro and 12% oil. A fuel with slightly less oil can offer a better idle and quicker acceleration - but not without some risk of overheating and/or additional wear. That said, this fuel, with its intermediate level of oil, offers some protection for the driver wanting to learn the leaner needle valve settings of competitive racing.

 

[2revo1maxx]

20-12 or 30-11 is a good choice, but like they say, it doesn't offer quite as much of a cushion.

 

[Bkyd Basher]

What % fuel your running makes a difference too. I run byrons 33% and with my 2.5R my hsn is 5 1/2 out and about 2 1/2 on lsn. My temps still hit 285 on a hot day with a medium plug. And the engine runs at its peak performance with those temps.

Wow!!! My truck would not even run at all at those settings. I'm alot alot closer to 1.5 and 3on the hsn. Temps run about 260-280. Also really depends on how u run it though.On our track its kinda small so I'm only in the throttle fully for about3-4 second bursts then just kinda workin it around the turns.

 

[2revo1maxx]

At those temps with not much full throttle? Sounds to me like it's either too lean or you have a hsn that's boogered up.

 

[Bkyd Basher]

Correct me if I'm wrong though, The running lean is bad because it will make the motor run to hot which is not good obviously. So why would it be bad that my settings are a little lean as long as i dont run wide open enough to make it get to hot?Do u know what I'm saying?

 

[2revo1maxx]

Because lean means more friction, it's not all about temps.

In cold weather people will run their engines super lean without even knowing it, and because the temps are cool they think it's ok. I have no way of knowing if your engine is lean or not, but I always run mine as rich as possible without sacrificing performance.

 

[Bkyd Basher]

gotcha,i understand what ur saying. i just figured if u were running lean it would show up on the temp gun. But i guess ambient would have an affect also.Tough thing to master. I seam to have the most problem getting these trucks to idle descent at all.

 

[2revo1maxx]

Idle tuning is tough. I try to set mine for a nice clean idle, not that low 4-cycle idle. Most engines will tell you they're too lean at idle.

 

[Bkyd Basher]

well i might be fighting a winless battle cause whatever took out my bearings made a couple scratches on the side of my piston, so i might be a little low on compression. Runs good though, other than i can't get it to idle for more than 2-3 seconds without stalling. I just loads up and dies, which i would think would be rich. But it idles quite high just as u let off then after a second or so it creeps down then stalls very quick.