hey fire blade to you mean the new 2.5 motor or the .15 stock motor???? just asking... i just put a mugen .12 in a t maxx and fired it up last night and ran like a champ even running rich as heck... when it's broken in it will be a rocket compared to the new 2.5 motor since the power racting is .83 or .86 hp im not real sure i cant remember right now... compared to the .12 mugen rated at 1.15 hp and others can't duplicate the hp from this small .12 mill......

late teamatlas

ahh ding! sorry, its the 2.5, not 1.5 WHAT IAM I THINKING>??????? lol Yea ever since ive seen your losi, man all iam going with is the mugen. is it a .12?

yes it's a .12 not a .15 bro..... late

Well, no. I think you are misinterpreting what they are saying. Due to the natural design of 2 stroke engines because of lack of intake and exaust valves, at low rpm they tend to build reverse pulse's at low rpm. Depending on the pipe, at low rpm there is not enough negitive pressure in the pipe to pull all the pressure out the exaust on the down stroke so some of the pulse at low rev's "spits" backward out through the carb intake disrupting the natural flow of the engine.

The "boost bottle/chamber" taps into the case below the carb and is supposed to give this backward pulse somewhere else to go besides out the carb throat. Then when the engine rev's up to higher rpm the increased intake vaccume is supposed to bleed that excess in the "bottle/chamber" back into the engine and be used.

Two inherent problems here. First the location of the pressure tap in most engine blocks is in the wrong place. Most all engines have the pressure tap drilled right below the carb inlet. Most carb throats are around 5.5 mm or so and the inlet of the pressure tap is about 1/8th inch. Pressure is going to seek least resistance so when the port in the crankshaft opens to the carb inlet the backpressure will still vent out the carb.
The pressure tap should actually be drilled in the block just below the carb inlet so the crank port opens to the pressure tap first, then open to the carb.
And then the second problem is most all boost bottles/chambers are not nearly large enough to be of any value. The bottle needs to be at least equal to or twice the volume of the entire crankcase volume.

Sorry, long post stating what all of us already know.

That does sound about right. What I heard from a local hobby shop was that it sucks more fuel down to be burned. But then why do I find fuel inside my bottle if its only used for air?

You have to think outside the box here. Each intake stoke draws air and fuel into the bottom end of the engine. On the piston's down stroke pressure builds in the lower end of the engine which drives the fresh mixture up into the combustion chamber, but positive pressure in the bottom end of the engine also tries to push some of the fresh "FUEL/air" mixture back out then carb throat at low rev's because there is no vaccume created in the header from the tuned pipes reverse pulse to help draw the fresh charge into the combustion chamber.

Some of the excess mixture goes into the boost bottle. So you end up with air and fuel in the bottle. Since you can't see air you are only noticing the fuel in the bottle but there is air in there too.

Which btw, if you are finding much fuel in the bottle then you have it mounted wrong. It really should be mounted upright with the outlet pointing down and it should be above crank height.


(p.s. don't talk to "hobbyshop" guys.)

ok. I had it pointed up, that could of been the problem

ok fireblade here is you exp on the boost bottle ... from a experet in the feild ok,,,,First, they are not in any way similar to Nitrous Oxide (NOS) systems on real cars, the hobby versions don't contain any Nitrous Oxide and they don't boost power.

R/C Boost bottles are designed to store a small amount of vacuum to stabilize the pressure inside the engine. Most people report little or no gain in performance. In many cases, you have to drill a hole in the crank case to connect them.

HPI does not make boost bottles for any engines


later dork .....

Never said there was any NOS in them. But it would be cool though hehe
BTW- Whens the next time u are racing.

no little one you said they waste fuel and burn the motor's out right???? and like pinky said you need to mount them up right...

i dont know when the next time i will race who know's im putting my atlas back together for carpet..

ahhh. the come back from the closet.

TPhalen
Sorry to burst your bubble but I have been using 05 motors in my E-Maxx for a while now and this thing really rocks!
I geared down and use P2K motors, no problems yet, even the ESC stays cool.

dang, the p2ks have enough power for a e-maxx? do they get hot at all because of pushing so much weight

Fireblade:
Nope the motors don't get that hot, I have been doing this for quite awile now with no ill effects so far.
My Maxx has alot of aluminum parts on it and it is still really fast just remember to keep a good eye on the comms because if the brushes get short the comm can be burnt.