"too hot for nitro"

[nintendodude]

Hello!

I have a T Maxx with the 3.3. I am running the Traxxas Medium-long plug and Byron's 20% nitro fuel.

I was running the car today and performance was all over the place. I ended up re-tuning to factory specs (HSN all the way in and 4 turns out, LSN flush with 2nd ridge of the "throttle puller") and still, the temp hit 350 at the plug and it was just crazy. Starting was difficult and it would die for no reason.

It was about 90-100 degrees out. I talked to the guy I bought it from (I put a brand new engine in it last week and it's got about a gallon through it, broken in carefully on a cooler day) and he said that it's too hot for nitro, anything over 85 degrees (F) is too hot for nitro and I'd need to use a lower (10%) fuel or a cooler plug.

Is this true? What considerations do I need to make for running when it's very hot outside?

Is my engine shot now that it's hit 350 from one high speed pass? I think the LSN was too lean because it sounded ANGRY at idle.

 

[StevoRevo]

I found that the 3.3's need to be sealed.. if its got a leak it will suck in air causing lean condition.. making it hard to tune/run well had get a little to hot..
As for anything over 85 i think that is wrong.. my Revo 3.3 runs around 250 but i never let it get over 300..
also I'm not to sure if it has destroyed your motor or not.. i wld think that if it was only once there shld not be a problem but I'm sure some1 else on here will b able to give you more info..
good luck mate

 

[Scrogg]

You are correct more than likely. The engine tune was off or there was an issue such as drivetrain "drag" or inadequate engine cooling. Make sure the shift point is not set too late. 2nd gear should kick in around 2 seconds after you nail the throttle. Any later and you need to adjust it to shift sooner so you can run a richer HSN setting.
The weather does increase engine temps but it is not the issue. "Too hot" for nitro....b.s.
The 3.3 will run at 280F all day long without losing compression or damaging itself IF tuned proerly.
I highly doubt your engine is hurt. The glow plug is shot for sure. Install a new one and retune. My 3.3 ran a HSN setting of 4 1/4 turns out. Exhaust, air filters and gearing all play a factor. There is no such thing as a perfect all around tune. You tune the engine to the driving you are doing.

 

[Metalhead Matt]

I'd guess that it's sucking air. High temps and erratic behavior, tune wise, are both sure signs. I've ran my maxx when it's been over 90 degrees outside. Just have to tune to conditions. The guy you bought it from is full of it.

 

[olds97_lss]

I run nitro from 20F to 95F. Anything more or less in either direction and I just don't want to be outside myself, let alone standing around playing with toys. I have noticed that my small blocks run better in the cold, guessing the surface area of a BB allows it to cool too quick.

I've found that high humidity affects nitro engines more than high ambient temps. Kind of turns them into high RPM steam engines and you loose some power while it runs hotter. It has to be sticky humid, but that's what I notice.

 

[nintendodude]

"sucking air"

from the head? It's been on it's back more than once (actually, more than I care to admit...) and I've gone through a few head protectors. should I torque down the head, or is the head possibly damaged?

Thanks for the info, guys. Any need to run anything other than my usual medium/20% for the hotter weather?

 

[Scrogg]

Don't over tighten the head bolts. Just make sure everything is tight. Install a new plug and retune. A fuel with higher nitro and lower oil contents will run cooler and offer more power. If you are running the Byron's 20% with 14% oil, try the race blend. You'll be amazed at the difference.

 

[nintendodude]

I'd rather have longevity than performance - I can't afford a new engine every 5 gallons, and from what I hear from the guys at the hobby shop, i'd be lucky to get that. I did destroy the plug that was on the engine when it hit 350 and i've replaced it a few times (keeping the "bad" one) when troubleshooting - now I know what a bad plug really is

I had a hell of a time starting it too, this morning, lots of resistance when pulling. Turns out the exhaust pipe had about 3 tablespoons of fuel in it - another lesson learned. I assume that this is from running rich and always killing the engine by plugging the pipe?

 

[Metalhead Matt]

Yeah, most likely. I pinch the fuel line to kill my nitros, but honestly, I don't know which is worse. Running it out of fuel is running it out of lube. Never had any problems though. Your carb throat, header, backplate and in some cases, the hsn housing need to be sealed with sensor-safe, high-temp, copper Rtv. I won't start an engine without knowing that it is sealed. And that means doing it yourself.

 

[nintendodude]

I saw a DIY on sealing the engine and didn't think it was necessary - the theory is that it runs extra lean/crappy because it's sucking air from gaps in the engine?

 

[Metalhead Matt]

It's very necessary. The smallest leak will make an erratic tune. Sealing is basically the "trick" to getting a nitro engine to run right.

 

[nintendodude]

Hmm.. Any point in going back and sealing an engine with over a gallon of gas run through it?

 

[Metalhead Matt]

Hell yeah. It's never too late to do it right. You'll be amazed at the difference. It's really quite easy. I use a tooth pick to cover the o-rings with a light coat of the rtv. It doesn't take much. Then put your backplate together, but leave the screws hand tight for about an hour. Then tighten them up. The carb, just coat the o-rings, press the carb in firmly with your thumb and tighen 'er up. Give the header the same treatment as the back plate. Let it set up a bit, then finish tightening. Let the engine sit over night, then fire it up and tune it in.

 

[StevoRevo]

Yes sealing my engines made the world of difference.. its not as hard as you first might think.. once you have done 1 you will be confident enough to do 100.. its easy.. every1 here suggested to me to use High Temp Copper RTV.. Worked well for me

 

[Scrogg]

20% fuel with higher oil content vs. 30% with 10-12% oil is not going to make an engine last longer. It's a myth.
Engine quality, proper tuning and maintennace make them last. Traxxas mills need bearings every gallon IMO if you want to make them last, still they don't last long. The materials used to make the engine are just poor quality.
If you get 3 gallons out of a TRX mill with no maintanence, you got your money's worth.

 

[MotoGod]

Being from the South at the moment....we race even on 100+ degree days down here. I think it's worse for me than it is my Nitro engines! They seem to run pretty decent, even when it's a scorcher outside..me on the other hand...I turn into a sweat monster. hehe

 

[2revo1maxx]

Plugging the stinger floods the engine with nitromethane, Which attracts moisture and makes it hard to start. You should always pinch the fuel line. The engine will burn off excess nitro and you'll have a nice coating of oil left behind. It will also start much easier next time.

 

[Metalhead Matt]

How's it goin' 2revo? Nice seeing ya back. +1. Plugging the stinger can flood the engine as well. Pinch the fuel line and put your piston to bottom dead center pronto.

 

[StevoRevo]

YES YES YES definatly piston at BDC ASAP..
I do mine as soon as i have stopped the engine.. i have the tools very close to me as I'm shutting it down..

 

[2revo1maxx]

How's it goin' 2revo? Nice seeing ya back. +1. Plugging the stinger can flood the engine as well. Pinch the fuel line and put your piston to bottom dead center pronto.

Not bad man, how you been? I've been lost in the 350z forums. I've been trying to put some mods on my full size car before the wedding and/or kids...LOL. I totally forgot the bottom dead center thing that's funny. It's really tough to do much of anything this time of year. It's busy time again at work. I did get my 21 max running strong though!