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Old 04-30-2009, 12:15 PM   #16
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what should i be running i have a b3 pro an moded p7r and a sportwerks 21 v2 right now im running 20 im a missing anything from not using 30
yeaklet4, since you are running one of our engines let me take a stab at answering your question. For most drivers that can get around a track fairly well the difference in performance between 20% and 30% (on a properly tuned engine) should be noticeable. What you will see is a reduction in bottom end (punch), basically you will notice less initial acceleration or punch out of corners especially evident when launching for jumps with short run ups etc. It will not affect the top end performance or maximum rpm of an engine (other than obviously taking a bit longer to get there because of the reduced acceleration).

Most European .21+ sized engines are shimmed out of the box for 25%, our engines as we design them for the US where 30% is most common are set up out of the box for 30%. Shimming comes into play when you are trying to get the maximum amount of performance out of your engines by optimizing the compressions ratio and squish band. Adjusting this will affect the compression ration and again the amount of torque that an engine produces. Because purchasers of engine encompass shall we say "a wide range of tuning skills" and the dramatic variations in the ability of certain brands of fuel to avoid pre-detonation, most manufacturers have a tendency to err on the side of caution when setting deck heights at the factory. Meaning they are usually set higher than what would be optimum to avoid people destroying their engine by pre-detonation. So having said this when you reduce the nitro content even further you are reducing the maximum power output of an engine even more. For some users this may not be a factor, for some it might. It all depends on your requirements and the level of competition that you run with.

Now after reading all of that you are probably saying ok, so what does that mean for me. In a nutshell it means that by running 20% fuel instead of 30% you are going to see a reduction in torque unless you optimize the set up of your engine. This optimization will be done by adjusting/optimizing the deck height which frankly requires work/testing and is a story in it's self to explain how to do. (Suffice to say that if this is done wrong you will destroy your engine so if you do not know how to do this, don't mess with it.)

You will however see an increase in run time probably to the tune of 20 of so seconds. Your engine will run hotter, so you will have to run your needle settings richer than you would if you were running 30% (so anyone that is currently running 30% and going to switch to 20% please make sure that you ritchen your needles a couple of hours BEFORE firing it up with the new fuel for the first time and then tune from there). You will also probably save a couple of dollars when you buy fuel. Old beliefs were that you should run a hotter plug with 20% than with 30% (to advance the ignition timing) but since the current trend in off-road seems to be running hot or extra hot plugs with 30% nowadays (for ease of tuning, improved idle performance and better initial on power response even though there is a loss in maximum hp) this is kinda thrown out the door.

People claim that their engines last way longer with 20% etc. From all of the testing that I have done any increase in engine longevity (with the current high build quality of engines) from using 20% is marginal at best. Frankly most will see a significantly larger increase in engine life by taking the time to do three things. A) Learn how to properly tuner an engine. B) Run a high quality air filter set up and properly maintain it as dust intake (even in minute amounts) is the single biggest contributor of wear is buggy engines in the first place. C) Use a high quality fuel combined with after run oil at the end of the day.

My personal opinion on the 20% versus 30% question is that if you are doing any kind of racing and are running any type of performance oriented engine (which you are paying a premium for) it does not make any sense to save the couple of dollars you do by buying a lower nitro content fuel which does not let your engine perform to it's maximum potential. Food for thought isn't it.... Let me know if you have any questions!

Regards,

Ron Hopkins
Werks Racing
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Old 04-30-2009, 12:38 PM   #17
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the main reason i run 20% in my .21 is because i also run gas truck (.12) and its a pain in the but to carry 2 different fuels.. Myself, i have had no issues with 20% so i never went to 30%, i have not felt underpowered to other dirvers at my level of competition.
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Old 04-30-2009, 02:34 PM   #18
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go with 25% trinity fuel or byrons fuel thats what i run u really not need to go higher then that and 25 % makes the engine run good and it makes plenty of power i do remmond change to a cooler plug when its really hot outside trust me i ran a hot plug with smoke coming out of the pipe and it was 300 degress in a .15 engine
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Old 04-30-2009, 03:32 PM   #19
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I would listen to Ron..who is an employee of Werks, and probably knows what he is talking about
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Old 04-30-2009, 05:00 PM   #20
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While on this subject. Is it true that it is best to use 20% for break and then switch to 30% after break in.

What about going from 20% to 30% on an older engine. Any quams or procedures?
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Old 04-30-2009, 05:05 PM   #21
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While on this subject. Is it true that it is best to use 20% for break and then switch to 30% after break in.

What about going from 20% to 30% on an older engine. Any quams or procedures?

You shouldnt just switch after break in. you can, but it doesnt matter.

you just need to retune, a little bit richer
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Old 04-30-2009, 05:11 PM   #22
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Retuning all depends on the fuel you use. It is not always richer! You need to tune according to fuel
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Old 04-30-2009, 05:15 PM   #23
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nobody uses 25% nitro i break it in with it too i would try it if your hobby store sells it
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Old 04-30-2009, 05:23 PM   #24
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I would listen to Ron..who is an employee of Werks, and probably knows what he is talking about
Lol I'm actually the owner but what do I know

dishoap, it really does not make a difference however in my opinion it's best to break in the engine with whatever fuel (nitro %) that you plan on running. What is the point of breaking in an engine which you should be doing under load (driving). So by default you are running each tank leaner, making adjustments to the needle as you are progressing through the break in etc. basically you are tuning the engine. Once you go through all of that what is the point of having to in a nutshell start tuning from scratch again because you switching nitro percentages???

As far as going from 20% to 30% in an older engine those statements floating around the internet about "you have to break your engine in again if you change nitro percentages or fuels" is nonsense. I don't know about you but I have never seen a piece of metal that has a memory, so how would your engine know what is being run through it? Simply put the fuel in it and re-tune!

Pinky2252s, it's actually the other way around. You will need to re-tune the engine, a little bit leaner. When you switch from a lower nitro content fuel to a higher your engine will go rich so you will have to lean the needles.
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Old 04-30-2009, 05:41 PM   #25
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I like 20% its 2 bucks cheaper at my hobby shop
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Old 04-30-2009, 05:45 PM   #26
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i run 20, it makes your engine last longer
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Old 04-30-2009, 05:56 PM   #27
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Not that Iswitch back and forth with nitro content, but I always thought if you switch from 20 to 30, your engine will run faster, harder, therefore requiring a richer needle setting So I was wrong ???
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Old 04-30-2009, 06:13 PM   #28
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20% byrons race, RIPS!!
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Old 04-30-2009, 06:16 PM   #29
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jud u ever triend trinity 25% or byrons 25% i did think that if u which to a higher nitro u have to make it a little richer
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Old 04-30-2009, 06:27 PM   #30
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Thats what I use now. Byrons 25%. When i first got into rc I used 20%. When I started racing 5 years ago I started using 30%.
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