Dented exhaust pipe dyno runs

[Varastorm]

I think this may be a repost, but not too sure.

I thought it was really interesting, funny & a must watch for fiddlers

[youtube][/youtube]

[mike.kir]

Saw it but still fixed a dent in front pipe left by some high kerb

[sirch345]

They say seeing is believing, who would have thought that

Chris.

[VTRDark]

That is one nice engine.

[Shauned71]

I wouldn't say no that that... perfect fit for my car too

[Pete.L]

wow!

[AMCQ46]

that just confuses the hell out of me, so what feature of the pipes is helping the breathing? is it all down to the length? why bother with big bore exhaust systems?

[VTRDark]

why bother with big bore exhaust systems?

So you can say that you have one

It don't make sense to me. I'm wondering if they are using some kind of trickery here. When I had a smaller 90 mandrel on the left link it made a difference that showed on the dyno run.

Look at the fuelling

[fabiostar]

from a different angle. when i was racing supermoto we used to buy headers from the states that came from FMF that had the headers squashed by near half the dia by about 4 inchs in length. swan neck or something they were called and they always made more power than the big bore pipes. go figure????

i think length and taper overall have more affects than just a few dents...

[ConTRo13R]

My thoughts are.... Where the pipes are squashed the diameter is smaller. Therefore as exhaust exit it helps to build up speed of the gasses passing, almost like holding the end of a hose pipe.. This also adds more back pressure which helps to recycle wasted fuel in the pipes for a second chance. I may be wrong but that's my observations on this.

I have always found that the vtr works best with baffles/ restricted and long cans.

[mattycoops43]

My thoughts are.... Where the pipes are squashed the diameter is smaller. Therefore as exhaust exit it helps to build up speed of the gasses passing, almost like holding the end of a hose pipe.. This also adds more back pressure which helps to recycle wasted fuel in the pipes for a second chance. I may be wrong but that's my observations on this.

I have always found that the vtr works best with baffles/ restricted and long cans.

THIS

It's all about the velocity. Smaller diameter, higher velocity, more torque. Better scavenging. yadda yadda yadda. I always laugh at the boy racers with 4" systems on the shopping trolleys, I wonder if they know how much power they are losing.

[VTRDark]

Smaller diameter = more velocity yes....venturi effect, but this is not always a good thing and can have a negative effect. It all comes down to timing and things have to arrive at the right time at the cylinder head depending on your engine in particular cam timing and porting. Scavenging only takes place during the overlap so the gases have to arrive at that point for maximum effect otherwise one is still left with some wastage sitting in the exhaust. You cant shove the gases down there as fast as you can and expect them to hang around waiting or they may have even already missed the boat.

[RedStormJ]

This video is total Horse .... No science to it what so ever. Dented pipes dont make the HP the heat does. I bet the engine had not reached full temp on the first run. Also how much pipe is after the header... none. There is a maximum that a header can do and I would be willing to bet that those headers are not well made.... Actually I know this because they are my cheapest go to for annoying clients who do not want to pay for a real system but want the headers. I used them on a ford van. They arent well made. Do that to a nice header and what is more likely is a rich or lean condition in 1 cylinder leading to a burned up piston or a fouled plug. Just leave the science to good header makers and if you got a naty mc nastie living on your pipe try to smooth it back out.
Look at port polishing.... Those small bumps can give 1/2 a hp. so a dent can take 1/2 a hp or more.
Also the chamber conditions were not regulated. Small changes in hp in a big engine are nothing to write home about. From a science perspective this video is a poop stain. ( Ok IMHO not science.)

I get a bit huffy when I see well paid actors doing stupid things claiming to be scientific...... If we do it its fine but they had the money to do multiple runs. and check with another engine. Id test it with a 302 or 305 with a nice set and see what happens... over a week of testing.

[VTRDark]

Your right. I know for a fact that changes in exhaust systems make a huge difference like when I put a smaller diameter elbow on the left header to get that upswept look. The Blue line in my above graph, that's what it caused. There's a good reason why we have exhaust systems and it's not only to reduce noise and pollutants.

[RedStormJ]

There is an ancient article in a book from the 90s about super cars. It featured all of them at the time. There was a land speed car and it featured 3 inch tuned exhausts at 2.5id . The article mentioned long pipes mid pipes and short pipes to balance torque vs h.p. In a car the optimum position is just behind the drivers door. or abouts for most engines. That super car I am mentioning had 3000 h.p. and had to run for a while without blowing up. Torque suffered heavily but in that application it did not matter. Just say no to dynamiter decreases dents and steps . I hohartedly believe that a port should be cone shaped narrowest at the valve and that the pipe should gently increase in ID as it nears the exit unless its a turbo then wide wide wide is the way to go. If you can end the pipe after the down/ up pipe

(A bit of a hijack but I am trying to figure out if I am going to coil the pipe like the rc213v to reduce noise and add tq or just let her exit right at the rear set with a removable baffle. This is bending a titanium exhaust. Anniversary is coming so I cant spend big on the toy as I already got my rr rim and tire.. )