195LikesNovarossi engines thread
04-06-2007, 02:34 PM
#2011
What is the best pipe for a NSR3?
And what are the characteristics that make it the best one for that motor?
Thanks
And what are the characteristics that make it the best one for that motor?
Thanks
04-06-2007, 02:44 PM
#2012
Tech Addict
Originally Posted by Bigbarn
What is the best pipe for a NSR3?
And what are the characteristics that make it the best one for that motor?
Thanks
And what are the characteristics that make it the best one for that motor?
Thanks
04-07-2007, 12:38 AM
#2013
Originally Posted by Nitro-mech
SalvadoriRacing is correct !!
http://www.challengers101.com/IntakeTuning.html
Copied from above: Read last paragraph !
A 2-stroke is different of course since there is only a finite amount of fresh mixture available in the crankcase to be transferred up into the cylinder. In a 2-stroke, we want to maximize the retention of that finite fuel charge. We can't afford to "waste" any of it by having it escape out the exhaust port.. This is not a concern in the 4-stroke because the intake flow of fresh mixture is unlimited, or at least limited only by the duration of the intake valve timing. The closing of the exhaust valve prevents significant escape of the incoming charge.
The exhaust tuning of a 2-stroke is designed to preserve the positive pulse going down the pipe and reflect that positive pulse back up the pipe. A racing engine exhaust system uses an expansion chamber at the end of the pipe which is basically two cones that reverse themselves prior to the end "stinger" where the spent exhaust is allowed to exit the chamber.
That sort of expansion chamber creates a very strong positive wave reflection back up the exhaust pipe, and this positive pulse will reduce the amount of fresh charge escaping out the exhaust port, and in some cases, force back into the cylinder any charge that may have escaped before the positive pulse arrives.
On 2-stroke racing engines, we will see an immense change in power delivered when the exhaust system is tuned for a particular RPM range and the engine revs into that range. It's called "coming on the pipe" and the burst of sound and power that occurs when that happens is easily witnessed.
The length of the exhaust pipe, prior to the muffler, is another important factor due to the speed of the pressure waves mentioned earlier. The length must be such that the exhaust pulse can travel to the end of the cone and be reflected back up the pipe to arrive at the exhaust port just before it closes.
Higher RPM will require a shorter pipe and lower RPM a longer pipe to produce the maximum effect at the RPM we want to use for maximum horsepower. It's not practical to vary the pipe length, so we compromise with some specific length that will deliver the best push at near top RPM.
http://www.challengers101.com/IntakeTuning.html
Copied from above: Read last paragraph !
A 2-stroke is different of course since there is only a finite amount of fresh mixture available in the crankcase to be transferred up into the cylinder. In a 2-stroke, we want to maximize the retention of that finite fuel charge. We can't afford to "waste" any of it by having it escape out the exhaust port.. This is not a concern in the 4-stroke because the intake flow of fresh mixture is unlimited, or at least limited only by the duration of the intake valve timing. The closing of the exhaust valve prevents significant escape of the incoming charge.
The exhaust tuning of a 2-stroke is designed to preserve the positive pulse going down the pipe and reflect that positive pulse back up the pipe. A racing engine exhaust system uses an expansion chamber at the end of the pipe which is basically two cones that reverse themselves prior to the end "stinger" where the spent exhaust is allowed to exit the chamber.
That sort of expansion chamber creates a very strong positive wave reflection back up the exhaust pipe, and this positive pulse will reduce the amount of fresh charge escaping out the exhaust port, and in some cases, force back into the cylinder any charge that may have escaped before the positive pulse arrives.
On 2-stroke racing engines, we will see an immense change in power delivered when the exhaust system is tuned for a particular RPM range and the engine revs into that range. It's called "coming on the pipe" and the burst of sound and power that occurs when that happens is easily witnessed.
The length of the exhaust pipe, prior to the muffler, is another important factor due to the speed of the pressure waves mentioned earlier. The length must be such that the exhaust pulse can travel to the end of the cone and be reflected back up the pipe to arrive at the exhaust port just before it closes.
Higher RPM will require a shorter pipe and lower RPM a longer pipe to produce the maximum effect at the RPM we want to use for maximum horsepower. It's not practical to vary the pipe length, so we compromise with some specific length that will deliver the best push at near top RPM.
Also there is limited space for the exhaust and the cone cannot be the right distance away from the exhaust due to the length of the car. 1/8th cars rev to 45,000 and they have exhausts 1/2 as long again as 1/10th cars If the above is correct, which it is, they should be the same length. If you do a quick calc you will see at 35,000 RPM the pressure wave traveling at the speed of sound has to travel a distance of 300mm. A 1/8th pipe is 150mm from exhaust entry to the end of the chamber making it 300mm from the exhaust entry to the end and back again. A 1/10th pipe is 115mm so the pipe is tuned for 50,000 RPM!!
For the exhaust to work properly it has to be 150mm long, have no internals and the stinger must exit straight out the back.
By selecting a different exhaust and adjusting the length you are just finding the least worst soution.
Cheers
04-07-2007, 05:18 AM
#2014
not exactly, since a .21 engine exhaust pulses mush higher pressure compared to a .12 engine, so the exhaust pipe must have a bigger volume..........
for example >>> the difference of pressure is so noticable that a .21 engine doesn't face vapour lock when it flames out no matter the temp it was running at the track, something very common to .12 engines specially over 130ºC
........
for example >>> the difference of pressure is so noticable that a .21 engine doesn't face vapour lock when it flames out no matter the temp it was running at the track, something very common to .12 engines specially over 130ºC
........
04-07-2007, 09:43 AM
#2015
More info on pipe length
The tuned pipe length is the distance from the exhaust outlet along the centreline of the manifold to the middle of the diverging cone on the end. This distance is calulated by using Lt = (Eo x Vn)/N
Where:
Lt is the Tuned Length in Inches
Eo is the Exhaust Timing in Degress
Vn is the gas velocity (1700 ft/sec)
N is the Crank RPM
So for 152 deg exhaust timing (Is that right?) and RPM of 37,000 (Most .12 engines peak around there) you get a tuned length of 6.9"
I just measured my 2630 pipe and the length is around 5.9 to 6" so the pipe is tuned for just over 43,000 and thats way to high. I need to add an inch of manifold length to bring it to 37,000 rpm!! I'll try it out and see what happens
Cheers
The tuned pipe length is the distance from the exhaust outlet along the centreline of the manifold to the middle of the diverging cone on the end. This distance is calulated by using Lt = (Eo x Vn)/N
Where:
Lt is the Tuned Length in Inches
Eo is the Exhaust Timing in Degress
Vn is the gas velocity (1700 ft/sec)
N is the Crank RPM
So for 152 deg exhaust timing (Is that right?) and RPM of 37,000 (Most .12 engines peak around there) you get a tuned length of 6.9"
I just measured my 2630 pipe and the length is around 5.9 to 6" so the pipe is tuned for just over 43,000 and thats way to high. I need to add an inch of manifold length to bring it to 37,000 rpm!! I'll try it out and see what happens
Cheers
04-08-2007, 03:58 PM
#2016
Originally Posted by ziggy12345
More info on pipe length
The tuned pipe length is the distance from the exhaust outlet along the centreline of the manifold to the middle of the diverging cone on the end. This distance is calulated by using Lt = (Eo x Vn)/N
Where:
Lt is the Tuned Length in Inches
Eo is the Exhaust Timing in Degress
Vn is the gas velocity (1700 ft/sec)
N is the Crank RPM
So for 152 deg exhaust timing (Is that right?) and RPM of 37,000 (Most .12 engines peak around there) you get a tuned length of 6.9"
I just measured my 2630 pipe and the length is around 5.9 to 6" so the pipe is tuned for just over 43,000 and thats way to high. I need to add an inch of manifold length to bring it to 37,000 rpm!! I'll try it out and see what happens
Cheers
The tuned pipe length is the distance from the exhaust outlet along the centreline of the manifold to the middle of the diverging cone on the end. This distance is calulated by using Lt = (Eo x Vn)/N
Where:
Lt is the Tuned Length in Inches
Eo is the Exhaust Timing in Degress
Vn is the gas velocity (1700 ft/sec)
N is the Crank RPM
So for 152 deg exhaust timing (Is that right?) and RPM of 37,000 (Most .12 engines peak around there) you get a tuned length of 6.9"
I just measured my 2630 pipe and the length is around 5.9 to 6" so the pipe is tuned for just over 43,000 and thats way to high. I need to add an inch of manifold length to bring it to 37,000 rpm!! I'll try it out and see what happens
Cheers
if you check the RPM at peak power of any engine the the piston displacement, you can estimate the carburettor venturi..............
I tried the formula and there is a constant K which is supposed to be around 0.8~0.9 according to the author
here follows the formula:
carb diameter = K * SQROOT(piston displacament in liters * rpm at peak power)
try it out for every engine you know and you will conclude 2 things.......
the formula or the K constant are completely wrong for small high performance 2 storke glow engines............or the engines are designed wrognly..........
what I mean is that theories can lead us to very confused thoughts.......
besides pipe lenght, the chamber geometry has a lot to do with engine performance and powerband, so I am sure that the lenght you have calculated is way far from the ideal, not to mention that 1 inch longer than the EFRA 2630 pipe will be more than enough to make impossible turning to the left.........
04-08-2007, 04:06 PM
#2017
Ziggy the author himself says that the 1700 figure is a little high on the gas velocity, and remember that the author is talking about a full sized 2 stroke gasoline engine. Chamber temperatures and therefore exhaust temps are a lot higher in these motors than ours with the lower flashpoint. Lower exhaust temps = slower motion of the wave through the gas. I suspect that the calculation is not far wrong, except that the 1700 is wrong on our motors. Perhaps reverse engineer some calculations based on the dyno results you have available and see if you can find a more realistic constant. I have done just that and arrived at a constant that actually seems to work fairly well.
Also I am sure that you know this, but in 2 chamber pipes the convergent cone is not at the end of the pipe, it is internally and is perforated with holes to allow the gasses into the 2nd chamber and out the stinger. This is somewhat different to a regular motorcycle pipe. You must measure the pipe length from the exhaust port to halfway down the complete convergent cone using the above formula.
Also I am sure that you know this, but in 2 chamber pipes the convergent cone is not at the end of the pipe, it is internally and is perforated with holes to allow the gasses into the 2nd chamber and out the stinger. This is somewhat different to a regular motorcycle pipe. You must measure the pipe length from the exhaust port to halfway down the complete convergent cone using the above formula.
Last edited by AMGRacer; 04-08-2007 at 04:23 PM.
04-11-2007, 08:15 AM
#2018
Tech Adept
Hey guys,
Bought a Nova Plus 12-3c the other day and have read that the microcast pistons dont last as long as they CNC ones.
How much fuel have you guys been getting through the plus 12 engines before its time for a rebuild?
TIA
Bought a Nova Plus 12-3c the other day and have read that the microcast pistons dont last as long as they CNC ones.
How much fuel have you guys been getting through the plus 12 engines before its time for a rebuild?
TIA
04-11-2007, 08:32 AM
#2019
Originally Posted by Delta9
Hey guys,
Bought a Nova Plus 12-3c the other day and have read that the microcast pistons dont last as long as they CNC ones.
TIA
Bought a Nova Plus 12-3c the other day and have read that the microcast pistons dont last as long as they CNC ones.
TIA
my expierence is exactly the opposite!
microcasted pistons are made with less stress to the material than the full cnced brothers.
04-11-2007, 09:03 AM
#2020
Tech Adept
Thanks for the reply Team Novarossi,
Its in this thread, i will find the posts and paste them here.
Edit* here is the link to page 35 on this thread on the microcast pistons it goes onto 36 aswell.
http://www.rctech.net/forum/showthre...&page=35&pp=30
Its in this thread, i will find the posts and paste them here.
Edit* here is the link to page 35 on this thread on the microcast pistons it goes onto 36 aswell.
http://www.rctech.net/forum/showthre...&page=35&pp=30
Last edited by Delta9; 04-11-2007 at 09:15 AM.
04-11-2007, 07:44 PM
#2021
Originally Posted by Delta9
Hey guys,
Bought a Nova Plus 12-3c the other day and have read that the microcast pistons dont last as long as they CNC ones.
How much fuel have you guys been getting through the plus 12 engines before its time for a rebuild?
TIA
Bought a Nova Plus 12-3c the other day and have read that the microcast pistons dont last as long as they CNC ones.
How much fuel have you guys been getting through the plus 12 engines before its time for a rebuild?
TIA
04-11-2007, 10:25 PM
#2022
Tech Adept
Thanks Suntok2, thats is what i was looking for! 
anyone else?
anyone else?
04-11-2007, 11:15 PM
#2023
Originally Posted by Delta9
Thanks for the reply Team Novarossi,
Its in this thread, i will find the posts and paste them here.
Edit* here is the link to page 35 on this thread on the microcast pistons it goes onto 36 aswell.
http://www.rctech.net/forum/showthre...&page=35&pp=30
Its in this thread, i will find the posts and paste them here.
Edit* here is the link to page 35 on this thread on the microcast pistons it goes onto 36 aswell.
http://www.rctech.net/forum/showthre...&page=35&pp=30
I destroyed about 4 evo5 engines with a exploded cnc-ed piston...
04-11-2007, 11:42 PM
#2024
Originally Posted by Delta9
Thanks Suntok2, thats is what i was looking for!
anyone else?
anyone else?
Don"t let it run too cold (idle on the box), but keep it in the 90C range from the get go. The MC piston doesn"t need as much break in as the CNC piston.
04-11-2007, 11:44 PM
#2025
Tech Adept
Originally Posted by team novarossi
that's from 2005... if I remember me correctly that was the time of the NM evo 5 engines (.21) ...those had huge problems with the cnc pistons....they disintegrated or exploded...
I destroyed about 4 evo5 engines with a exploded cnc-ed piston...
I destroyed about 4 evo5 engines with a exploded cnc-ed piston...