I changed nitro%!

[Rolex]

article by Don Nix.

A good read. Some interesting info. One more man's opinion.

 

[jetmechG550]

Nothing to think about, one thing I've found(25+ yrs of working on cars and drag racing) is that ANYTHING that increases horsepower increases heat. If you are running cooler you are NOT using the same standards for tuning. More likely the engine is set up to be run on the 30% meaning it wasn't TUNED for the 20%, possibly the compression ratio or wrong glow plug. I would bet more on the glow because it not only ignites the fuel mixture but controls engine timing. Timing can have drastic effects on operating temps.

Here's you another article by Don Nix.

That was the most erratic article I have ever tried to read in my life. The guy can't keep on one topic for longer than one sentence. I stick by what I said from experience, if you try and run say a .21 on 15 or 20% it runs hot and runs like crap. Shim, glow plug whatever, doesn't matter. If you run on 20% and then change to 30% you will be leaning it out.

 

[frickenjoey]

I will have to agree with you Rolex...as you said I had to LEAN my engine to keep my heat UP when I went from 20% to 30%. I like 30% good stuff....I have had jet fuel (Jp-8) on my dangling participle and that was not cool at all.

 

[jetmechG550]

I will have to agree with you Rolex...as you said I had to LEAN my engine to keep my heat UP when I went from 20% to 30%. I like 30% good stuff....I have had jet fuel (Jp-8) on my dangling participle and that was not cool at all.

skydrol is much, much worse! Trust me I've had both!

 

[Rolex]

That was the most erratic article I have ever tried to read in my life.

That's why I said it's "One more man's opinion." Just because he got his opinion in print doesn't mean that HE's the one that's 100% correct. Look around, and you'll find other articles printed that will totally dissagree with his.

For Jetmech and Friggin' Joe WEE, I'd rather spill 20% on my dangling participle than 30%.

 

[helotaxi]

Have you ever noticed how cold your hand gets if you spill nitro on it? That's due to rapid evaporation. Inside the engine, where it's mixing with air it has the same effect. The higher the nitro content, the faster the evaporation, so it tends to cool the engine more.

Actually nitro evaporates slower than alcohol (the filler ingredient in nitro fuel) BUT it takes more heat away when it does evaporate.

After a bit of research real reason: Nitro burns cooler than alcohol. More nitro cooler burn. However, it also burns faster and is more prone to preignition, thus the need for a cooler plug and reduced compression for a higher nitro content. It is more energy dense than alcohol so it gives more power when it burns as well as removing more heat from the intake charge when it evaporates.

 

[frickenjoey]

Hell that sounds good to me helotaxi.....I say sold.

 

[Rolex]

Yup, I'll go along with that.

 

[TWOCANE]

now thats a good little lesson in chemistry.

 

[HeartBreak]

skydrol is much, much worse! Trust me I've had both!

Bro, I don't even want to know what you did to earn that honor....

Kidding aside, I would have to second Jetmechs' wisdom here. I don't have as many years under my belt as he does, but I have seen several engines blow up (broken connecting rods). Of course, the person that owned those engines would just grab any ol' fuel off the shelf, with the explanation that "fuel is fuel is fuel". I think I sold him 5 engines while working in the local hobby shop......

 

[TWOCANE]

Bro, I don't even want to know what you did to earn that honor....

Kidding aside, I would have to second Jetmechs' wisdom here. I don't have as many years under my belt as he does, but I have seen several engines blow up (broken connecting rods). Of course, the person that owned those engines would just grab any ol' fuel off the shelf, with the explanation that "fuel is fuel is fuel". I think I sold him 5 engines while working in the local hobby shop......

So what are you saying? 30% hot or cold? compared to 20%

 

[HeartBreak]

I was refering more to the careless switching of fuel, and not the percentages ran.

If you stick to one percentage, or switch once in a blue moon (not every other tank, as this guy was doing), then you are more than safe (in my opinion).

edit; Now, as for 30% running hotter or colder; I personally have never ran anything but 20%, but everything I've read has stated that 30% will run cooler with more power, because the sleeve will expand more, hence less friction.

Personally, I'm content with 20%, and will probably never run 30%.

 

[TWOCANE]

cool, just wondering

 

[jetmechG550]

For whatever reason, 30% is easier to hold a good tune, it's really evident if you've ever had a traxxas mill like the 2.5r or the 3.3. Some say that running 30% shortens engine life, I've alway had to question anything like that by saying, when have you ever purchased an engine and read on the box or in the manual that an engine is garaunteed to last for 10 gallons? I've never had what I would consider to be premature engine death by running 30%. My last motor that blew had 9+ gallons and it was the bearing that rides on the connecting rod wearing that allowed too much play in the con rod and it hit the case and cracked it.

 

[helotaxi]

but everything I've read has stated that 30% will run cooler with more power, because the sleeve will expand more, hence less friction.

The reason it runs cooler is described above. Nothing to do with friction and why in the world would 30% cause the sleeve to expand more? And how would the sleeve expanding more not lead to a loss of power from reduced compression?

 

[TWOCANE]

The reason it runs cooler is described above. Nothing to do with friction and why in the world would 30% cause the sleeve to expand more? And how would the sleeve expanding more not lead to a loss of power from reduced compression?

I was wondering the same thing.

 

[HeartBreak]

I thought my above post was clear enough. I'm not going to bite into any flamewars; so this will be my last post on this thread.

I stand by what I posted above.

 

[Rolex]

This topic has been discussed before, and just like this thread, it doesn't end. Facts, figures, experience and hearsay, there's no final answer it seems.
Run what you like, and make your own conclusions.

 

[Racer 1966]

Run what you like, and make your own conclusions.

That's definately the best bottom line for this subject!

 

[helotaxi]

I thought my above post was clear enough. I'm not going to bite into any flamewars; so this will be my last post on this thread.

I stand by what I posted above.

No flame intended, sorry if you took it that way. My point was that your post doesn't make sense from a physics/chemistry standpoint.