TWOCANE
RCTalk Addict
I went from 30% to 20% and had to retune like crazy but she is running with no problems. I've pnly ran 1 and a half tanks of 20%,. Is it ok to change since she is running fine or should I go back to 30%?? Thanks
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jetmechG550
RCTalk VIP
Going from 20 to 30 is not a big deal but going 30 to 20 can sometimes lead to problems. Some leading from compression and shimming the head or "squish" and con rod stretch.
TWOCANE
RCTalk Addict
- Thread starter
- #3
I have heard that the other way around though. Then I wa told to retune and it should be fine, so far mine is fine. Thanks for the info I will look into that.
jetmechG550
RCTalk VIP
Who ever told you the other way told you wrong. Going up in percentage is fine, you just need to retune for the increase in nitro, which causes the engine to run cooler because of the higher nitro content. Going down = not such a good thing, you won't see it right away but you will, trust me, I've been doing this long enough.
helotaxi
RCTalk Basher
Last I knew you typically added head shims when going to up in nitro percentage to reduce compression and prevent detonation. Going down in nitro content should have no ill effects other than a slight loss in power.
jetmechG550
RCTalk VIP
I know there's a couple of threads where this was discussed already. I know from experience that going down is not a good idea. You'll find certain break in procedures that say the same thing. Also just about every mill I have ever run larger than an .18 has come setup (shimmed) to run on 30% (or 25 if it's italian, still no need to reshim to run 30) it's when you get one and start out to run on 20% you need to shim it properly.
How much 30% did you run before changing? If you've ran a lot of it dropping will be more of a problem, if the engine is fairly new it shouldn't be a big deal after retuning.
Don't want to start a big debate but, More nitro will not be cooler if you are using the same standards of tuning.
Don't want to start a big debate but, More nitro will not be cooler if you are using the same standards of tuning.
frickenjoey
Official RCNT Cyber-Bully
Supporter
Active Military
I had overheating problems even if I re-tuned trying to go back down in nitro content. I ran out of 30% so I said hey I have plenty of 20% so go play right....yeah nevemind of to the store I was after a few stupid hot runs....it was either overheating or spitting rich....
jetmechG550
RCTalk VIP
No need to debate, more nitro runs cooler, think about it and get back to me.
hint,if you go from 20 to 30 you will need to lean it out.
TWOCANE
RCTalk Addict
- Thread starter
- #10
I allways heard more nitro more heat. But any how I am on my third tank and man she screams. How will I no if its going to hurt in the long run jetmethg550?
jetmechG550
RCTalk VIP
where did my reply go?
You probably hit 'back' instead of 'submit'. I've done that twice today.
jetmechG550
RCTalk VIP
I was on my iPhone, back is only there if you have the upper portion of the page displayed. This is the thread though that I posted I was having problems replying to.
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.
jetmechG550
RCTalk VIP
Gotcha bro!
TalonOne
Hardcore RCTalk User
I learned something today from Rolex......and it did not involve him telling me he was not wearing underpants....or describing some part that was dangling...
THANKS ROLEX!!!!!!
:surrender
Never end a sentence with a dangling participle. If you're not wearing pants, nothing will get your attention faster than spilling 30% nitro on your participle.
TWOCANE
RCTalk Addict
- Thread starter
- #18
good answer, rolex! I talked to a tech at traxxas and he said RETUNE when you change and that would be it. Called back different guy, said the same.
I've never used anything but 20% in anything I have that stays on the ground. However, from what I've read, you should do a tank or two as a mini break in while you tune for the different percentage. The piston and sleeve need a chance to re-adjust to the different expansion caused by different percentages of nitro.
There are plenty of opinions out there, but I would go this route just to be on the safe side.
There are plenty of opinions out there, but I would go this route just to be on the safe side.
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.
