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Old 04-22-2003, 01:33 PM   #1
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Default Nitro % and engine performance?

I am going to be breaking in a new NovaRossi S3 and would like some advice about nitro fuel %.

Which % should I run? I have heard people running anywhere from 20% to 30% nitro.

What performance advnatages are there to using higher %?

What are the disadvantages of running higher or lower %?

I have heard that running higher % causes engine temps to increase, and therefore the carb settings must be richened. This, in turn, reduces the performance and therefore there isn' really any gain. True?
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Old 04-22-2003, 02:30 PM   #2
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The higher the percentage the more power. Thus 30% nitro would make more power then 20% nitro. Also the higher the percentage the cooler the motor runs. Which allows you to lean it out more to make more power.

I have heard several different stories about breaking in your motor though. Most people say break in your motor with the same fuel you are going to race with, while others say to use fuel made especially for breaking in motors. I use the same percentage I am going to race with to break in the motor. If that is correct I don not know. It works for me though.

Later
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Old 04-22-2003, 02:49 PM   #3
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I use lower % of Nitro when breaking in engine, i.e. 10% or 20% of Nitro, once breaking in process is done, I change the conrod and use my normal 30% Nitro to idle about 1-2 tanks, then let it SCREEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEAM...
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Old 04-22-2003, 02:56 PM   #4
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why do you change your conrod?

is there that much of a power gain using 30%?
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Old 04-22-2003, 03:01 PM   #5
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Quote:
Originally posted by chachi
why do you change your conrod?

is there that much of a power gain using 30%?
You don't have to! But, since initially breaking-in, the conrod was working pretty hard to get it going; hence, there's a lot of stress it's gotta take. So, to keep my expensive engine last longer, I decided to change the conrod. Ask those hardcore 1/8th racers, and they'll agree with this.
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Old 04-22-2003, 04:25 PM   #6
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30 % nitro is for the bigger .21 engines. I have heard of running it in a small block but it does require some modifications. A higher nitro % will not make your engine run cooler. A higher % of oil will let your engine run cooler, a higher % of nitro will cause your engine to run hotter. I would at least run a cold glow plug such as the OS R5, if I were to run 30% in that engine. A good rule of thumb is the higher the nitro the cooler the plug, the larger the engine the cooler the plug.
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Old 04-22-2003, 05:00 PM   #7
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Nitro content theory is all BS.

True. on a larger flowing track with lots of top end power required higher Nitro content will give you a power advantage but with the modern Nitro Touring tracks (smaller and twisty) Nitro doesnt even come into the equation.

Proof.

I run on a short twisty track most weekends. Most of the guys run 16% nitro in their engines and they do go quick. I am currently running 5% (only fuel I had available) nitro in my RB X12 3-port Turbo (unmodded) and I still have the fastest car in a straight line.

As for break in, with modern engines it appears that you can just break them in on whatever percentage you are giong to run on. This is to do mainly with the construction and material used for producing the important parts. The theory of breaking in engines with 0% nitro or small nitro content originates back to times when engines where more fragile (for lack of better word) and required a more gentle break in approach. A classic example of a modern engine like this is the JP 12's. Many people complain that they are not worth the money and that they are not powerful. It is all in how it is broke in. Slow and patient - extremely fast and very reliable. Fast and loose - moderately fast and unreliable.

If you want to see a JP that can shift you want to come to our track. A fellow I introduced to Nitro 10yrs ago runs one that is dynamite. He uses my break in method of slow and consistent over a period of maybe a month before really winding the motor up. Another guy at the club has one and it is way down on power (looked like it was a dummy engine). He just sets his engines in the cars, hits the starter, puts the car on the track and goes flat out from the off, screwing the needles like no tomorrow.
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Old 04-22-2003, 05:10 PM   #8
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I dunno, I've seen a performance difference when I use 30% over 20% in a .12.

My engines also run cooler on 30% than 20% as well.

As far as break-in for 1 month!!!!!!! Say what? Man who has the patience to break-in for that long! 5 tanks tries me as it is, can't even imagine a 1 month break-in....i'd go crazy.
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Old 04-22-2003, 05:23 PM   #9
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thanks for all the info. much appreciated.
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Old 04-22-2003, 05:34 PM   #10
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Quote:
Originally posted by patelladragger
As far as break-in for 1 month!!!!!!! Say what? Man who has the patience to break-in for that long! 5 tanks tries me as it is, can't even imagine a 1 month break-in....i'd go crazy.
Tell me about it. And that is maybe 30mins to 1 hour every night of the week at a carpark across the road from my house.

If I didnt have a race engine for the weekends I would be headbutting padded walls many years ago.

It is even worse when I have a new car as well. After I finish breakin period on the engine I dont put the car on the track until it is running proper. We usually conduct testing runs using tie rods instead of shocks to get the car running straight (adjusting the pivotballs and steering arms to best setting and then adding the shocks (rear ones first) for several runs to get these fine tuned and perfect on both sides. Then we take off the rear shocks and put on the front ones to fine tune them.

This could take maybe 2months from the start to finish before the car is raced in anger. Really requires patience and a calm head to stop you even twitching that throttle the wrong way
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Old 04-22-2003, 07:02 PM   #11
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Quote:
Originally posted by modellor
[BAfter I finish breakin period on the engine I dont put the car on the track until it is running proper. We usually conduct testing runs using tie rods instead of shocks to get the car running straight (adjusting the pivotballs and steering arms to best setting and then adding the shocks (rear ones first) for several runs to get these fine tuned and perfect on both sides. Then we take off the rear shocks and put on the front ones to fine tune them.

This could take maybe 2months from the start to finish before the car is raced in anger. Really requires patience and a calm head to stop you even twitching that throttle the wrong way [/B]

Man that is awesome! Great tip. I've never heard of that technique before but I for sure will try it!!
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Old 04-22-2003, 07:15 PM   #12
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Quote:
Originally posted by modellor
Slow and patient - extremely fast and very reliable. Fast and loose - moderately fast and unreliable.
Now this is interesting. Does this apply to all ABC engines, or just the JP in particular? Let me share my experiences...when I bought my first ABC race .12 (HPI .12R, basically nothing but a rebadged Novarossi), I broke it in slowly at a slobbering rich setting. It couldn't have hit more than 175F. Sure, it lasted a looooong time, but was slower than a turtle running uphill. Fast foreward to now...I break in engines by idling a single tank through them at factory default needle settings, ensuring that the temperatures are around 220F. Then I proceed to run them under load, gradually leaning them out over the next few succesive tanks. I have treated all of my new and rebuilt engines like this and they are by far the quickest I have owned. This includes my 7-port Ofna/Picco, MT-12's, and a Ritchey RTO, as well as a couple of RB .21's.

They are quite reliable, as well.

I guess that everyone has a different take on engine break-in. Go with what works best for each individual.
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Old 04-22-2003, 07:32 PM   #13
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Quote:
Originally posted by Old Skool
Now this is interesting. Does this apply to all ABC engines, or just the JP in particular? Let me share my experiences...when I bought my first ABC race .12 (HPI .12R, basically nothing but a rebadged Novarossi), I broke it in slowly at a slobbering rich setting. It couldn't have hit more than 175F. Sure, it lasted a looooong time, but was slower than a turtle running uphill. Fast foreward to now...I break in engines by idling a single tank through them at factory default needle settings, ensuring that the temperatures are around 220F. Then I proceed to run them under load, gradually leaning them out over the next few succesive tanks. I have treated all of my new and rebuilt engines like this and they are by far the quickest I have owned. This includes my 7-port Ofna/Picco, MT-12's, and a Ritchey RTO, as well as a couple of RB .21's.

They are quite reliable, as well.

I guess that everyone has a different take on engine break-in. Go with what works best for each individual.
I agree. It is what works best for each person. Another factor to take into consideration is the air temperature, etc for your area at the time of break-in. I read a lot of posts about people waiting until the temp reaches a certain range. Here we are lucky to reach these temps in the summer months let alone the early months of the year. I normally break-in my engines come February when we have a whopping 5 or 6 degree Celsius at best.
Makes me wish I was in Cali or Texas at times.
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Old 04-22-2003, 07:38 PM   #14
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Quote:
Originally posted by patelladragger
Man that is awesome! Great tip. I've never heard of that technique before but I for sure will try it!!
Its just something my dad learned from his years of racing when the AMPS Rapier (first nitro car with fully independent suspension) came on the scene. I have never seen or heard of anyone else using this technique especially around here and nobody knew until now that we did this as we always test in private.

It really helps with set up as you can work on each aspect of the car one step at a time to make sure everything is set up properly. It really works wonders as I can break hard with a one-way while in the corner without the rear end snapping out.
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Old 04-22-2003, 10:29 PM   #15
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Quote:
Originally posted by Old Skool
I break in engines by idling a single tank through them at factory default needle settings, ensuring that the temperatures are around 220F. Then I proceed to run them under load, gradually leaning them out over the next few succesive tanks. I have treated all of my new and rebuilt engines like this and they are by far the quickest I have owned. This includes my 7-port Ofna/Picco, MT-12's, and a Ritchey RTO, as well as a couple of RB .21's.

They are quite reliable, as well.
This is exactly the way I break mine in too. I don't really feel that Fuel % plays that much importance during break-in, but REALLY makes a difference in race conditions.

10%: Good for 1/10th Off-Road in loose conditions and Warm weather, terrible in cold weather.

20%: Great all around, On or Off-Road. Use a High oil content for playing and in Heavy Trucks.

30%: This is what I use in my .12 Sedan Engines. If you don't use 30% then you get mowed down by the Guys that do.

40%: In some bigger races, Guys are using 40% Nitro where the percentage is not limited by rules.

Oil percentage also has a large impact on performance and tuning.
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