F1 Engine Noise?

[DaveKillens]

When an exhaust valve bangs open, exhaust gases begin to flow out. As well, a pressure wave is created that travels down the exhaust. If and when that pressure wave encounters any large change such as a termination, another pressure wave bounces back, towards the exhaust valve. If the length of the exhaust pipe is constructed properly, that reverse pressure wave arrives just as the exhaust valve begins to close, forcing air back intothe cylinder. Sort of like reverse supercharging. This can increase the gas pressure in the combustion chamber. Done properly, it can increase torque and power.
A four into one exhaust (or as it used to be 5 into 1) has the individual exhaust pipes arrainged in a circle, and in a specific order. One valve would open, then the next to open would be next in the circle. So it is designed so that the individual pipes assist scavenge flow to the other pipes, improving overall exhaust scavenging efficiency.

[RH1300S]

Maybe in simple terms - I'll try

An F1 engine makes lots of power, that is a lot of energy each time a piston makes a bang - not all of that energy turns the crank, some has to escape down the exhaust. Each bang makes a big noise. Because it has high revs you get lots of bangs happening in a short space of time (like a room full of people all shouting at once).

There is nothing to silence those bangs because the rules don't demand it - F1 teams don't carry any weight they don't have to and don't want anything restricting the power output.

So all that noise energy just heads for your ears.

Lawnmowers make little phutting sounds because they make little bangs and not very often. Dragsters make enormous bangs

[saam]

does this mean my women needs a mufler??

[engin007]

Nicley explained DaveKillens and RH1300S. In simple terms the F1 boys would not silence their engines unless someone forces them to!

[DaveKillens]

Exactly, and to be honest, a lot of racing fans like the sounds of those engines. Go to a race where they run showroom stock and the sound and ambience is very different.
It's definitely noise pollution, and slowly becoming an issue, witness Monza.

[Ciro Pabón]

If and when that pressure wave encounters any large change such as a termination, another pressure wave bounces back, towards the exhaust valve. If the length of the exhaust pipe is constructed properly, that reverse pressure wave arrives just as the exhaust valve begins to close, forcing air back intothe cylinder.

This was more or less explained in this thread on six-stroke engines, in case you want to see Dave's explanation in pictures. This is the "end" picture of the three I posted:



Expansion chambers are essential for, let's say, "valveless" functioning of two-strokes engines, and it is the first thing you should do to enhance your bike. These are different from mufflers.



I am completely sure that, for example, Ricardo's software (warning! shameless link to my own page ) allows you to optimize the exhaust pipe form to treat the entire column of air as a single aerodynamic flow, from engine inlet to final outlet. Actually, this is what they excel at.



After reading the thread on Monza, I concluded that a racetrack should include, besides the running areas, emergency roads, stands and landscape, a zone for noise buffering, the same way roads have to. This noise buffering zone should be owned by the autodrome, if it wants to live in peace. I wonder if FIA is not working on regulations on this after Monza.

[pyry]

does this mean my women needs a mufler??

like an f1 car, your woman doesnt need any more weight either, so a definate no.

[Ciro Pabón]

does this mean my women needs a mufler??

like an f1 car, your woman doesnt need any more weight either, so a definate no.

Some low weight mufflers have been devised for this cases, for example, diamond necklaces.

[pyry]

far too expensive. the woman knows shes liked because the man keeps her, and thereby aught to shut up when told to. if this doesnt work you have the wrong woman

edited him to her, must pay more attension

[DaveKillens]

because the man keeps him

? OK, I have to admit mylifestyle is quite different than yours.

[Ciro Pabón]

far too expensive. the woman knows shes liked because the man keeps him, and thereby aught to shut up when told to. if this doesnt work you have the wrong woman

Then I live with the most deliciously wrong woman. I forgot to mention another cleverly developed, low weight, less expensive muffler you could get: kiss her.

This intelligent solution to the secondary problem you present has only one defect: it is time intensive. This is why necklaces were invented. But, try it, you won't repent and you could learn something, if you ever can.

[mep]

Does anybody (Ciro Pabón perhaps)
know something about the exhaust pipes on two stoke engines.
Becouse I have to build one for an 2 cylinder boxer two stoke engine
for a model car.
I need some infos about how it has to look like.
Is there any possibility to conect the two cylinders by the pipe
to get some extra power.

[RH1300S]

I would suggest googling for "expansion chamber design"

The expansion chambers on a two stroke are absolutely critical to engine perfromance - the tiniest error can totally screw the system.

An expansion chamber works by varying it's cross section to let the pressure waves use their energy to help fill & evacuate the cylinder.

A pressure wave will reflect some of its strength in the opposite direction to its travel when it encounters a change in section. A high pressure wave encountering an increase in area will reflect back a low pressure wave in the opposite direction and vice versa.

From the port, the first part of the pipe is the header, this usually has a gentle taper - then into the diffuser section where you start to see a typical two stroke expansion chamber shape - there is usually a middle section of constant area - then the tail of the pipe converges to meet the stinger. Then length of each of these sections and how fast they expand/retract in area is the really critical bit. The length of the stinger is also critical.

A longer more gentle expansion chamber shape tends to suggest a more torquey low revving engine. Short "spannies" with abrupt changes in section tend to point to a more peaky motor.

Good luck!

[Ciro Pabón]

Does anybody (Ciro Pabón perhaps)
know something about the exhaust pipes on two stoke engines.
Becouse I have to build one for an 2 cylinder boxer two stoke engine
for a model car.

I have never ever thought of making one for a model engine! I do not understand if you have a model engine that works, like the one they use on radio controlled aircraft, or if you are building a model car and you just want to create a pipe similar to the original. Whatever, this is what I know:

The information I used (with a friend, on his bike) was to build one expansion chamber for his RZ 350. He got an Excel sheet with the diagrams for the cuts and weldings by asking to Rickard Wänqvist, owner of the site where I got the diagrams I posted. His e-mail is rpm@bredband.net. But this is an specific design for this kind of bike and tuning.

You have to google for your particular bike model, or maybe Mr. Wänqvist can guide you. This could be of no use if your engine has not been analyzed previously by some tuning fan. This analysis should include any modifications made to the carburetor or the ports. It is hard to believe the change you get in the engine power.

You can find several software packages, as RH1300S points out, that you can use to fit your particular model of engine. I have read your PC is far from having the power needed for designing an optimal chamber but these packages can be useful in a model car engine.

http://rcboat.com/anteng.htm Old program, developed in 1999, U$100, you can design your button head and optimal diameter and length of exhaust pipe. It is specifically designed for model boat engines. A friend I have who is nuts for model airplanes has a copy and recommended it, but I have never used it. He explained to me that he hasn't heard of expansion chambers, just pipes cut to a certain length and of a certain diameter.

http://www.users.bigpond.net.au/arrowka ... pe_dsn.zipSimple expansion chamber design program, from Ian Williams Tuning. Do not know if you can use it for small engines, but the price is correct: you can download it for free. The complete MOTA software costs AUD$ 250.

I hope you can do something and tell us if you can get any increment in power! Anyway, thanx. I will post these two links in my simulation software page.

[Ciro Pabón]

Sorry to lengthen this even more, but I found this interesting. I downloaded the software from IWT. I tried small port sizes (2 mm). I found that the smallest chamber length the software gives you is around 650 mm, which is well over half a meter.



To my surprise, the chamber length the software delivers doesn't vary with different port sizes, only with changes in the time the exhaust port opens and the rpm. As this length is probably a function of the properties of the column of air, I would conclude there is no way to use expansion chambers in such small engine as yours, because your model car would seem ridiculous with a pipe bigger than the vehicle. On the other hand, this could be a software limitation, because it is clearly designed for bikes.

I wonder if someone with more experience in small engines can gives us a clue. BTW, every link I found refers you to G.P. Blair book on two stroke engines, that you can buy (with software included) at the SAE site.

To give this some resemblance of a thread, I found that MITRE has developed software to simulate engine noise (another link for me! ) based on engine characteristics. Here you have an explanation that makes a beautiful comparison between exhaust pipes and organ pipes.

You could try to tune your model car engine to, let's say, G major, with a little "pizzicato". Then you could say: hey, this engine rocks! From now on I will think I hear some Bach music every time a Ferrari F1 passes...