Turbo Charge it?

it has been argued many many many times. yes they have showed results where the supercharger made more power. but it does so by leaning the engine really bad. Which will wear out your engine a lot faster. It would be easier, and cheaper in the long run to just put that money toward a bigger more powerful engine.

I ran into a guy who had a super charger on his revo and he said it was really hard to keep tuned and he was looking to sell it because it was more trouble than it was worth. he also said he couldnt keep the little beltdrive from breaking. it looked cool as heck though.

I was thinking it was just a looks thing compared to something that was actually practical

no1 its a supercharger, not a turbocharger. i suggest if you dont know the diff stay away from them.

It's for looks and bragging rights. Pure junk.

AGAIN ill post what happened to me. last summer i spent 4 weeks trying to one to work. there are a number of reasons why the one you are looking at wont work. 1. its porely made. 2. it is NOT a bolt on, ie you have to mod allmost everything 3. it is not big enough to push enough air. 4. the nature if a 2 stroke makes it very hard if not imposable to get a supercharger/ turbocharger to work.

I modded a F4.1 and it spanked three 4.6's with superchargers all day long running 220-240. The 4.6's couldn't touch it no matter how much they leaned out their engines lol. A mod job is cheaper and runs with no tuning issues, that junk is just that..... JUNK.

The actual chemistry is wrong for a nitro application. A Turbo/Super is great for engines running at 8K RPM on almost any fuel, but these little hobby motors are idling at 8K RPM. The intake ports are not open long enough to stuff in extra O2... thats why these run on nitro-methane. There is oxygen in the fuel base, therefore there is a reduced need for atmospheric O2 to achieve Stoichiometric Efficiency ( http://en.wikipedia.org/wiki/Stoichiometry ) That is how these engines can make 35-40K RPM. This is the same reason why Nitrous Oxide will not benefit either. Nitrous is vehicle for extra oxygen and cooling effect. We don't really need a cooling effect or more oxygen for nitro-methane 2 strokes. As stated previously, stick with porting and polishing for the best results.

Traijin

well well well Traijin said it much better than i could. what he posted got me to thinking. way back in the dark ages when building a race engine we would calculate how much cfm a engine needed. i have been in rc for one year and have not seen any thing like that. heres a Q. if you know the cfm at a given rpm, and the Stoichiometric Efficiency couldnt you calculate how many ccs of fuel per minute you need? then flow a carb to that many ccs of fuel? and get to run good? but i know i couldnt do it, my math is just isnt good enough.

If I knew the proper formulas and had the right data, I could probably figure it ot. My problem isn't that though, it's that I don't know what Soichiometric Effeciency is

There's a link to stoichiometry in my previous post. It is the principle behind how we set air to fuel ratio. For gasoline I believe the perfect ration is 13.5:1 air to fuel. That is how my math was based back when I was building AMA Superbikes. The fuel we used for the bike has a 5% oxygen component (Nutech) which always threw off the math. In this world it will be even more difficult to figure the equation. What is the percentage of the Nitro? How fresh is it? What is the oil percentage (oil does not partake in combustion, therefore more oil = less fuel... ergo leaner mixture <Most people get that part wrong>) What is the relative humidity in the atmosphere? What is the temperature? How much volume does you pipe reflect or scavenge? Unfortunately all those variables have to be satisfied to achieve an accurate equation. This never proved to be anything more than a base guideline and a conversation point amongst the pit crews. In the end I did final tune based on the dyno read out at the track. Here we listen and eyeball it.

It could be put to use to match a rough CFM carb volume to engine air needs... I see this is not an issue widely considered in RC. The capability of the carb is mostly controlled by the HSN. On a Holly Dominator, its like putting in bigger or smaller sized venturis. So as long as the carb can pass the theoretical maximum air needed, the rest is academic.

Simply put... test and tune for best results.

Traijin

Traijin said:

There's a link to stoichiometry in my previous post. It is the principle behind how we set air to fuel ratio. For gasoline I believe the perfect ration is 13.5:1 air to fuel. That is how my math was based back when I was building AMA Superbikes. The fuel we used for the bike has a 5% oxygen component (Nutech) which always threw off the math. In this world it will be even more difficult to figure the equation. What is the percentage of the Nitro? How fresh is it? What is the oil percentage (oil does not partake in combustion, therefore more oil = less fuel... ergo leaner mixture <Most people get that part wrong>) What is the relative humidity in the atmosphere? What is the temperature? How much volume does you pipe reflect or scavenge? Unfortunately all those variables have to be satisfied to achieve an accurate equation. This never proved to be anything more than a base guideline and a conversation point amongst the pit crews. In the end I did final tune based on the dyno read out at the track. Here we listen and eyeball it.

It could be put to use to match a rough CFM carb volume to engine air needs... I see this is not an issue widely considered in RC. The capability of the carb is mostly controlled by the HSN. On a Holly Dominator, its like putting in bigger or smaller sized venturis. So as long as the carb can pass the theoretical maximum air needed, the rest is academic.

Simply put... test and tune for best results.

Traijin

Click to expand...

Perfect AFR is 14.7:1 in N/A & CARB legal cars/trucks.

You also have to consider that cars have O2 sensors and AFR sensors on them, to adjust the air/fuel content to get the closest to 14.7:1. Where as on a RC model you do not have the AFR/O2 sensors to adjust the AFR..... Traijin has (pretty much) spot on reasoning on this one.

Perfect AFR is 14.7:1 in N/A & CARB legal cars/trucks.

You also have to consider that cars have O2 sensors and AFR sensors on them, to adjust the air/fuel content to get the closest to 14.7:1. Where as on a RC model you do not have the AFR/O2 sensors to adjust the AFR..... Traijin has (pretty much) spot on reasoning on this one.

Click to expand...

This is precisely why it is academic, our race bikes (which were tuned port injected) did not comply CARB restrictions and using 5% oxygenated fuel were WAY too lean anywhere above 14:1. The extra oxygen in the fuel resulted in the ability to burn more fuel per cfm of atmospheric air. Hence our magic number was richer, ie 13.5:1. Nitro-methane has even more oxygen to contend with.

Academic for sure.

Traijin

Here is a link with some good reading.

http://www.turbofast.com.au/racefuel.html

well well well its clear to me . that all that math is something i can't do. ill let the younger dudes do that.

Stoichiometric ratio for gasoline is 14.7 to 1, methanol is eather 6 to 1 or 8 to 1. nitromethane is 1.5 to 1. that is an engine running on 100% nitro burns 1.5 lbs of air to 1 lb of fuel. the top fuel cars run so rich that sometimes they hydraulic lock. hydrogen has the widest range of air/fuel that will burn. from 4% to 400%

Good numbers, but those are also the theoretical s or rather the ratios at idle. All of the aforementioned ratios have to be adjusted when the engine is under load. Gasoline engines for example, the ratio changes by almost .8 when under load. For tuning, it is important.

like you said those are theoratical numbers, i like to say those numbers are for ideal combustion, ie burning all the fuel. racing gasoline is most of the time ran about 12:1 for best power. the reason street cars/ truck run at 14.7:1 is so the catalytic converter can burn the fuel that didnt burn in the engine. if you run raw fuel through a catalytic converter it can over heat and melt down.

Blah, Blah, Blahh, Blahhhh!