Mitch, I am not trying to pick a fight, but 'supersonic' is pretty fast. Do you have anything to back up the claim that an exhaust pulse goes supersonic? Or even transonic? Thanx,
I think the shriek actually comes from the crossover in the bypass - you get both banks with perfectly even alternating pulses (due to the flat plane crank) in the same exhaust path which doesn't occur when not bypassed. Hence it sounds like it's revving twice as high as a 'normal' motor which has the pulses coming through two separate paths and not perfectly spaced without the flat plane crank. This is also why some 355 exhausts have a higher pitch than others, it's how that secondary bypass path is handled in the muffler. The Capristo, for example, has a much higher pitch than the stock muffler on bypass and I think it's due to them keeping that bypass path completely separate from the primary, where the stock exhaust mixes them (the bypass just skips part of the muffler). If it were the header design, all of the 355 exhausts would have that same high pitch shriek when used with the stock headers, which they don't. Most of them mix the secondary bypass back in with the primary at some point in the muffler which seems to dull it. As the 348 doesn't have any direct crossover, it doesn't have that same pitch to it unless an aftermarket setup adds it in. In that case, you still wouldn't get the dual nature of the 355 where it sounds more 'normal' at lower revs and then explodes when it gets on bypass.
A 348 sings like a 348. The reason a 355 sounds the way it does is two fold. 1) A 355 has 1000rpm more revs than a 348. 2) The design of the 355 Exhaust system. This clip is of the Dyson Racing, Spice chassis race car powered by none other than a 348 engine. The engine revs to 9500-9800rpm, and makes over 500+hp. Oh and, it did it on the STOCK 75mm 348 crank. Does it sing? Ppfffftttttt ......it SCREAMS!!!!!! [ame=http://www.youtube.com/watch?v=MNkpFGKziqY&feature=youtube_gdata_player]Spice Ferrari 348 Super Loud REVS - YouTube[/ame] They finally stopped racing with the 348 engine because they couldn't keep up with the cars running the Aurora V8s on the short tracks, they made too much torque. But on the longer, higher speed tracks the car could do okay. That and the Spice chassis couldn't handle worth a crap. Hear is one more clip of a Reynard chassis power by, could it be.......a 348 engine. Me thinks it is. [ame=http://www.youtube.com/watch?v=_UvTJHJY_ZU&feature=youtube_gdata_player]Reynard F2 with Ferrari V8 - YouTube[/ame] Long live The 348 Brotherhood.
A rifle shot or any gunfire is supersonic. That's where the boom come from. With exhaust it's oscillation and resonance. Cinquevalvole is part of it but planar crank is more. The stroke timing, rpm and pipe/resonator design effect the pitch and tone.
I have extensive CFD (computational Fluid Dynamics) simulations of F355 engine airflow. With the narrow headers in the F355, the exhaust gasses are above 1150 fps from about 100mm through about 700mm from the back side of the exhaust valve. The simulator indicates that in this area there is a very high frequency sound component that goes away when the gasses cool and drop below the speed of sound.
Im currently designing an exhaust for the 348 that targets producing the F1 scream....the prototype will be finished this weekend....and I will put up some videos...I am OBSESSED with the higher octave produced by pulse doubling and the exhaust im building will expose the most F1 scream possible from a 348 through acoustic tuning.
We already have a screaming exhaust for the 348 - it's made by goth. But knock yourself out, more is always better, for those who want to try it. So, Mitch, the 355 header has a muzzle velocity of a 9mm pistol round? Hmm, no wonder it blasts through the tubing.
I have seen a few designs..... Kreisseig, Nouvalari, Larini, Capristo, Tubi, that are generating the higher octave.....but I am also testing a slightly different design that I think will clean up some the "extra" sound that these systems are letting through....Ill share my results after its on and tested.
Here's a teaser of the completed protype: Ferrari 348 custom exhaust - YouTube this was taken in the shop on the lift so theres an echo...(like a tunnel or parking garage) but after the car is back together and on the road Ill shoot more audio clips...
Mitch sounds like he knows. I agree because there's a YouTube video of an F355 with no cats and no muffler. The 2nd harmonic is there straight out of the headers. That's why I think the sound can be aped on a 348 with a clever header design. You still have a lower redline, which is not a big deal if the harmonic and the volume are there.
This is a custom setup Sound is amazing sounds like a CS Ferrari 348 Tunnel Run With Custom Exhaust - YouTube https://www.ferrarichat.com/forum/348-355-sponsored-bradan/414581-my-custom-348-exhaust-vids-inside.html
Heres a new setup I have on my spider.... http://www.ferrarichat.com/forum/348-355-sponsored-bradan/466447-new-348-exhaust-f1-sound.html#post143493784
