I cut a hole in my cheap exhaust

[Teejay112]

So I cut a 1cm square in my exhaust and managed to move the engines powerband down so I have increased mid and top end power I didnt think it would work but it did
The reason for doing it is I bought a dbxl ql racing pipe and it had the same performance in bottom end and mid as a sto I can exhaust power band was late so I made it early lol bit louder but not too much plus I didnt reach my max rpm due to not enough road but the rovan is only meant to run 14500 mine does 17600 on a good long run or with a dominator pipe so question is if I make the hole slightly bigger will I get a bit more bottom to mid range power instead of mid to top? I know one of you guys will know

 

[Z.hb71]

So I cut a 1cm square in my exhaust and managed to move the engines powerband down so I have increased mid and top end power I didnt think it would work but it did
The reason for doing it is I bought a dbxl ql racing pipe and it had the same performance in bottom end and mid as a sto I can exhaust power band was late so I made it early lol bit louder but not too much plus I didnt reach my max rpm due to not enough road but the rovan is only meant to run 14500 mine does 17600 on a good long run or with a dominator pipe so question is if I make the hole slightly bigger will I get a bit more bottom to mid range power instead of mid to top? I know one of you guys will know

i don't know how that would help but OK. i couldnt make it bigger cuz then you might be creating a big ass exhaust leak and then you loose back pressure (i think, im kinda talking out my ass right now LOL)

 

[Milo]

Mate I think you are in unknown territory. You need to look up 2 stroke exhaust design. Without using a dyno, I don’t see how you can determine results. It’s pure suck it and see. Speaking to people in the know, they tell me it’s about the volume and length of pipe that affects the engine characteristics. Either way I’m very interested in your experiments.

Anyhow I’m about next week if you fancy meeting for a run? I hope to finish the back end of my rig so should be good to go.

 

[Teejay112]

i don't know how that would help but OK. i couldnt make it bigger cuz then you might be creating a big ass exhaust leak and then you loose back pressure (i think, im kinda talking out my ass right now LOL)

Your half right I thought that's what was going to happen when I cut the hole I was like oh poop time for another exhaust then I tested it and was like yeah baby lol the reason why I got a noticable increase is if you look at the exit pipe at and how small the cone shrinks around it you would assume that the air is directed straight out of the pipe but upon cutting a hole in it I saw the pipe is also a little way inside the cone that would mean alot of the pressure was sent straight back so basically I had too much back pressure that was keeping my engine from reaching its powerband peaking early like it did with the dominator if you get me? But now I have better all round power it's now good enough for a good drag race again to think I was gonna fork out another £120 on a dominator clone when all I needed was a dremel this thing is a beast I also found a supplier for the rovan f5 that sells alloy parts and the high end shocks that have the reservoir and adjustable pressure for under £60 so I will be slowly upgrading the chasis might even machine one out of 4mm carbon fibre and have a carbon and alloy mcd

 

[Milo]

The volume and length create different resonances and back pressures and it’s that what affects the power band.

 

[Z.hb71]

oh so your saying u had too much back pressure and so u cut a hole to relieve sum? if thats correct couldnt you just have cut the stinger off? very interesting to me as i don't know anything about exhuast sizes and stuff lol.

 

[Teejay112]

Mate I think you are in unknown territory. You need to look up 2 stroke exhaust design. Without using a dyno, I don’t see how you can determine results. It’s pure suck it and see. Speaking to people in the know, they tell me it’s about the volume and length of pipe that affects the engine characteristics. Either way I’m very interested in your experiments.

Anyhow I’m about next week if you fancy meeting for a run? I hope to finish the back end of my rig so should be good to go.

It is volume and length but this pipe is small and was restrictive for the 45cc so once I cut it I relieved some of that pressure I can see the improvement in performance I'm getting more in mid range and seems better in top too I'm running out of road space now while the car is still accelerating and it's getting off the line quicker spinning the wheels like it did with the losi dominator pipe I don't have anymore but this engine should only rev to 14500 I get more and with authority it pulls hard I'm almost having to get used to it again anyway where you based then?

 

[Milo]

It is volume and length but this pipe is small and was restrictive for the 45cc so once I cut it I relieved some of that pressure I can see the improvement in performance I'm getting more in mid range and seems better in top too I'm running out of road space now while the car is still accelerating and it's getting off the line quicker spinning the wheels like it did with the losi dominator pipe I don't have anymore but this engine should only rev to 14500 I get more and with authority it pulls hard I'm almost having to get used to it again anyway where you based then?

Tooting

 

[Teejay112]

oh so your saying u had too much back pressure and so u cut a hole to relieve sum? if thats correct couldnt you just have cut the stinger off? very interesting to me as i don't know anything about exhuast sizes and stuff lol.

The stinger goes about 2cm into the cone so air is bouncing back from around the stinger where as with the hole most bounces back and some exits = less going back to the cylinder more escaping the pipe is for up to 32cc so it was simply holding the 45cc back until it reached high revs

 

[Z.hb71]

The stinger goes about 2cm into the cone so air is bouncing back from around the stinger where as with the hole most bounces back and some exits = less going back to the cylinder more escaping the pipe is for up to 32cc so it was simply holding the 45cc back until it reached high revs

Ohh i get it now

 

[Teejay112]

Tooting

Say whaat not far at all lol yeah I'm good for a meet what rc you got btw

 

[Milo]

Say whaat not far at all lol yeah I'm good for a meet what rc you got btw

Check the kraken thread in the HPI section.

 

[Thrasher]

Get hold of one of the 2 stroke design software and see if they allow for such creativity. Without math there is no way of knowing and its the hairy kind of math thats nice to have a program do for you.

 

[DougStar]

Your half right I thought that's what was going to happen when I cut the hole I was like oh poop time for another exhaust then I tested it and was like yeah baby lol the reason why I got a noticable increase is if you look at the exit pipe at and how small the cone shrinks around it you would assume that the air is directed straight out of the pipe but upon cutting a hole in it I saw the pipe is also a little way inside the cone that would mean alot of the pressure was sent straight back so basically I had too much back pressure that was keeping my engine from reaching its powerband peaking early like it did with the dominator if you get me? But now I have better all round power it's now good enough for a good drag race again to think I was gonna fork out another £120 on a dominator clone when all I needed was a dremel this thing is a beast I also found a supplier for the rovan f5 that sells alloy parts and the high end shocks that have the reservoir and adjustable pressure for under £60 so I will be slowly upgrading the chasis might even machine one out of 4mm carbon fibre and have a carbon and alloy mcd

hey maybe i should kept my bart pipe like this

sure it would have added 2hp .......NOT!
good luck with the chop job M8

 

[Teejay112]

Well not really on here to argue with know it all clowns anymore I experiment I know what I did and it did the job your using a high end pipe me a poop quality ql pipe that the engine even managed to rattle the weld on the mount and break it if I had a decent pipe which I'm gonna get next week I wouldnt tamper with it so your stupid opinion is really worthless to me about as interesting or useful as water is for my air cooled engine I mean before I messed with the pipe 15600 or so rpm now take a look that's while the car was on the ground at the aerodrome

 

[Z.hb71]

Glad it works for you!!

 

[Thrasher]

... your stupid opinion is really worthless to me

Have you considered starting a blog? Since you apparently know everything already whats the point being part of a conversation forum. There are a lot of people who love to hear themselves talk uninterrupted and you would feel right at home in the blogosphere.

 

[Z.hb71]

So was his comment I'm just more direct .I mean I cut a hole I tested it it was the same effect as cutting a hole into a stock can muffler it was a tiny exhaust that was that it's not a bartelone or boosterpipe it was a small ql dbxl pipe restricting too much flow I don't need to tell lies about something so little if I hurt the performance I would have said I did it really was simple as that then old man had to come at me with some dumb shite there was really no need for that it's not banter its straight up asking for a negative response and he got one

im not saying hes correct or your lieing, his comment wasn't cool either, but cmon that's not cool to come at his mom and poop.