exhaust question

[CoreLEx]

here's a very trivial question:

A few days ago I crashed my hyper7 and got a very nasty dent in my OS exhaust pipe. I tried running the buggy yesterday and it would bog down almost every time I hit half throttle. So my question is: How does an exhaust pipe affect an engine's performance and what would happen if an engine ran without an exhaust pipe?

sorry, but I really want to figure this out. :violin:

 

[Nitroaddict]

the shape of the exhaust pipe is "tuned" for maximum performance. that is why they call it a tuned pipe. when u alter the original shape - u alter its tuning characteristics. by running without the pipe, u will not only remove the pressure from the gas tank, causing air pockets, which will extremely lean your engine, but u have no back pressure for the actual cylinder and this creates performance problems too. it is not advised to fo this ever. u can fix the dent in your pipe quite easily. remove the pipe from the car, then fill the pipe with warm water, and cover the openings with tape. place in the freezer over night, and the expanding water will return the pipe to its original shape.

 

[Error401]

If the dent is extreme, then the tuning is probably screwed up. By this I mean that the pipe is screwed up and is not functioning properly. Tunes pipes are not just mufflers. If you wan, I could dig up an old post that has a detailed explination of how a pipe works.

As for running without a pipe, forget it. You'd have to retune your needles, and when you were done, it would be ear shatteringly loud, plus you would end up with less power than if you ran a pipe.

 

[CoreLEx]

I've actually followed your advice nitroaddict and will check back on it tomorrow morning. I took the pipe to a garage this morning and they said they couldn't fix the dent 'cos the whole thing is made of cast iron. I'm assuming they meant that the material is too tough to easily reshape.

error401, I'd appreciate it if you could post that article on pipes.

thanks for the replies guys.

 

[nitro dave]

I would check this article out and see if it helps

http://www.rcnitro.com/rn/articles/tuned.asp

dave

 

[Error401]

I had to do some digging, but I found my original post on the subject of those dual exhaust things sold on ebay, and it was on another forum, but here's what I wrote:

Ok, I used to fly alot, and most of my planes had pipes. I wondered how they worked, so I did some reasearch on the subject. I can't find my book, but I'm pretty sure it was Clarence Lee's nitro engine book put out by RCM. This guy has been into nitro engines for ever and knows his stuff about them.
Anyway, the reason they're called tuned pipes is that (on aircraft) you have to tune them to the engine. This involves putting the thing on, taching the highend, and cutting off about 1/4 inch from the header side of the pipe and putting it back on. This will result in an increase in performance, up to a point. You keep trimming off the header side until you see a drop in RPM and you stop. The system is now tuned. Since planes are basically long, pipes and their headers have all the room they need to take. Nitro cars don't, so I guess the headers are the length they need to be and the pipe geometry is varied to get the proper tuning.
Take a look at an aircraft pipe, and look at a car pipe. Both are essentially a long cone joined to a short cone. It's not gas flow that matters, it's the shockwave. The shockwave slows down as it enters the pipe (due to an increase in the diameter of the cone), then it gets reflected by the short cone and heads back toward the header. As the diameter decreases, the velocity of the shockwave increases and causes a ramming effect that is greater than the exhaust/fuel air mix comming the other way. This shoves the FA mix and a bit of exhaust to be shove back in and increases the compression ratio, and thus increases HP.

Now to the point. The plumbers pipe dreams are complete BS because there is no tuning or thought to the physics of exhaust systems, even the one with the chamber. That POS should be used only to capture spent oil in case someone wants to use it later to mix their own *beep*. Also, those "pipes" will be ear shatteringly loud. Loud is cool, but ice picks in my ears are not (ever blow a header gasket and run for a while?).
Someone on this thread made mention of the "home depot" cost of the parts for one of these POS's, probably around $10. The roll bar I welded cost about that for my savage. I might try making one of these wonder pipes and see what it really does, probably not much but WTF. Another stupid mod I tried was a silencer for the savage. Worked really well, but screwed up the tuning. Pix comming soon.

yadda yadda whatever, thanks for reading.
Whitt.


here's the link to the thread that this came from incase you want to get it in context.

http://forums.rcinfo.co.uk/viewtopi...order=asc&highlight=savage+tuned+pipe&start=0

hope this helps.

 

[CoreLEx]

thanks.. I appreciate the links :thumbsup:

 

[RaCinJason399]

Heres something to try.. you fill the pipe up with water.. and plug the holes.. and put it in the freezer. When water freezes it expands so it should push it back to normal.. try it.

 

[Error401]

Originally posted by Nitroaddict
u can fix the dent in your pipe quite easily. remove the pipe from the car, then fill the pipe with warm water, and cover the openings with tape. place in the freezer over night, and the expanding water will return the pipe to its original shape.

?

 

[RaCinJason399]

ahh i dindt read them all well oh well atleast i tried to help the guy out..

but tape wont work so well

little rupper fitings would work better

 

[elburro]

If you crashed hard enough to actually pop a dent in the tuned pipe, then I would check to make sure the engine didn't move. A bad gear mesh can ruin your day.

 

[impulseracer]

Do what RacinJason said. But put a wine bottle cork on the bigger hole and those tips from your fuel bottle to cover the stinger.

 

[Nitroaddict]

Originally posted by RaCinJason399
Heres something to try.. you fill the pipe up with water.. and plug the holes.. and put it in the freezer. When water freezes it expands so it should push it back to normal.. try it.

Below is a photo if the kitten u just killed. murderer, lol.

 

[CoreLEx]

Ok, here's the best I could do with the exhaust pipe:

The dent was much worse after the crash (I could fit my thumb in it!). I've gone through a whole tank so far and the engine only occasionally bogged down and died at WOT, so I'll drive it around some more tomorrow and try best to avoid cashing in $100 for a new one :nope:

thanks for the help! :redbuggy:

 

[Nitroaddict]

did most of the dent come out due to the freezer trick?

 

[CoreLEx]

took it to a friend's garage and we managed to fix most of the dent. I tried the freezer trick you suggested and didn't really notice any improvement this morning, probably because the bloody tape was crap and kept coming off, so I'll give it another go tonight using stronger tape or rubber fittings.

 

[Nitroaddict]

try the rubber fittings that someone else suggested - i imagine that would work much better - i just wasn't sure if u hade somethign like that handy

 

[CoreLEx]

the freezer trick definitely works nitroaddict. I noticed an improvement in the pipe's shape this morning when I took it out. Unfortunately, my rubber fittings trurned out to be as useless as my tape and one of them ended up coming off...

but anyway I'm happy with the result!

tc