787B Exhaust Pitch
I've wondered about this for a while now...
What makes the 787B racecar's exhaust note so high pitched? Is it the exhaust construction? Maybe the number of rotors? Port style? Special header? Any info would be helpful! |
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lmao, i'd say the same thing, the 787B is like a flat plane crank v8, 90 degree firing intervals, but with no adjacent cylinders like an american V8.
for some reason you can hear the difference between 180 degree firings (4 cyl/2 rotor), 120/60 degree (6/12 cylinder) and 90, v8. the american v8s have two cylinders that are next to each other physically and in the firing order, so we hear these cylinders as one big one, in an irregular interval, which is why they sound like they do. the 787B exhaust really is normal, its just a 4-1 header into a straight thru muffler. header looks to be in the 30" range, pipes look fairly big, but they are probably around 2" OD, my fist doesn't quite fit in the tailpipe, so ~80mm pipe. |
That's actually really interesting to me.
1. Do you think if most American V8's were 90 degree cranks, they'd have a smoother operation? Less mass/TDC/cylinder= more balance at higher RPM? 2. I'm completely smitten with the high pitched sound... is there any way of replicating or creating a similar pitch with a stock 13B with or without custom piping? 3. A long shot... since the 13B reaches its TDC at 270, 810, etc degrees (making it 1.5x longer than a traditional piston engine) is there any functional way of tuning that down to 90 degrees? 4. These questions are all theory so the more info the better! :) I'm working on a sort of "dissertation" on the rotary engine by itself and I've become completely obsessed lol. |
Originally Posted by BloodbathRX7
(Post 11639576)
That's actually really interesting to me.
1. Do you think if most American V8's were 90 degree cranks, they'd have a smoother operation? Less mass/TDC/cylinder= more balance at higher RPM? 2. I'm completely smitten with the high pitched sound... is there any way of replicating or creating a similar pitch with a stock 13B with or without custom piping? as an aside a 13B at full tilt makes a happy noise 3. A long shot... since the 13B reaches its TDC at 270, 810, etc degrees (making it 1.5x longer than a traditional piston engine) is there any functional way of tuning that down to 90 degrees? 4. These questions are all theory so the more info the better! :) I'm working on a sort of "dissertation" on the rotary engine by itself and I've become completely obsessed lol. |
Excellent. Yeah I've printed off 8 or so service manuals for the rew, the msp, and the first gen modification manual. Great stuff! Thank you for the answers, I'm sure I'll have more soon.
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Originally Posted by BloodbathRX7
(Post 11639576)
That's actually really interesting to me.
1. Do you think if most American V8's were 90 degree cranks, they'd have a smoother operation? Less mass/TDC/cylinder= more balance at higher RPM? 2. I'm completely smitten with the high pitched sound... is there any way of replicating or creating a similar pitch with a stock 13B with or without custom piping? 3. A long shot... since the 13B reaches its TDC at 270, 810, etc degrees (making it 1.5x longer than a traditional piston engine) is there any functional way of tuning that down to 90 degrees? 4. These questions are all theory so the more info the better! :) I'm working on a sort of "dissertation" on the rotary engine by itself and I've become completely obsessed lol. |
Mmm Italians :P
Since I can't afford a Ferrari I'll stick with my Mazdas lol. Although, the Mondial goes for about $20g nowadays. Anyway, how much power loss would one experience if they installed smaller diameter exhaust pipes? Significant? Mediocre? Minimal? Somewhere in between? |
Originally Posted by BloodbathRX7
(Post 11642194)
Mmm Italians :P
Since I can't afford a Ferrari I'll stick with my Mazdas lol. Although, the Mondial goes for about $20g nowadays. Anyway, how much power loss would one experience if they installed smaller diameter exhaust pipes? Significant? Mediocre? Minimal? Somewhere in between? after the collector, depending on power level we'll collect into a pipe that is anything from 2" OD to 3" OD. my car is collected into a 3" pipe, and it lets a lot of low frequencies out, kind of boomy, just to drive it around i have a resonated exhaust tip i put on it, and its maybe 2x 1.25"? this tip kills all the low frequency noises. the primary effect is that it seems quieter, but its mostly through a change in pitch. its not in ferrari territory though… |
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