Quote:
Originally Posted by Jason.MZW20
Ah, the turbo 1MZ sounds ridiculously good.
Exhaust length doesn't affect sound much (other than being louder since there's no room for resonators), but rather power delivery. I didn't expound on that. Longer exhaust systems tend to have increased low-mid range performance, while shorter systems tend to be suited for upper mid-high range performance. That's usually why you see race cars in stock bodies using side exit exhausts just after the front wheel well, since the engine will mostly be operating at high RPMs most of the time on track.
Unfortunately, the stock 1MZ cams don't allow that to be shown as the cams themselves are suited to low-mid range RPM performance anyway. Normally aspirated race engines tend to have a large amount of valve overlap, cam duration, and valve lift, which make them more sensitive to exhaust length and routing.
The stock 1MZFE and 2JZGE use 6 degrees of valve overlap without VVT-i, while some race engines use around 50-70 degrees of valve overlap, high duration, and very high lift cams.
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I am apeaking of exhaust manifold runner length and timed pulses, not exhaust system length...!
On the side note, exhaust system length rarely has anything to do with top-end or low-end power on NA cars if the header was properly designed for the motor. When we speak of race cars, I assume there is enough R&D and making decent power. Near-OEM engine race cars simply run side exits due to weight savings and simplicity. An exhaust turn down is done sometimes due to noise regulations. I have tuned some of these cars, both sponsored racers and hobbyists alike
It's all about exhaust scavenging and exhaust velocity during overlap cycle. Where the best power is made vs RPM, is when peak VE occurs due to scavenging based on the header design. Race cars (circuit or drag) rarely have any exhaust piping after the header collector. The exhaust pipe length is really only 6.0 - 12.0" of piping aka "megaphone".
More about megaphone:
http://wikiscootia.wikidot.com/expansion-chamber
Whether it is side exit at the fender, or a straight downwards dump under the shifter console, solely depends on the header length/design. Short stroke/long rod engines will prefer headers with long primaries, stepped up diameter and into long secondaries, then into a long collector due to its slower exhaust pulses. Long stroke/short rod motors will like long primaries/short secondaries and collector, due to faster pulses. Both, can be tuned for the same type of intended RPM usage with cams/heads to match. The differences in motor design, will have different header requirements.
It's a major misconception that people think "short exhaust system" is for high RPM. It's always the header itself. You can have a lengthly 12-ft exhaust system with a nice properly designed header, and you can still make power up to 10000RPM. As long as the exhaust system isn't a physical flow restriction, the pipe length after the header is negligable for scavenging. For example, a 3.0" exhaust system in a 180 WHP 1.6L NA motor (approx 130 BHP/L) using 12.50mm lift / 300+ deg duration cams, can easily still make power up to 10K RPM regardless of exhaust system length.
The above example is actually a typical Honda Civic B16A with Skunk2 Pro2 cams and a nice HyTech/SMSP Tri-Y header + 3.0" exhaust system, mildly built. This is also a car that you will notice no power gains or shift in RPM band if you went with an open-header or a short exhaust setup.
But anyway...
Exhaust runner length among cylinders, and how their pulses are grouped at the last "merge point" is really all there is when speaking of different exhaust notes among cars with the same cylinder count. Besides firing order, this is what separates from a typical even-fire V6 with unequal headers and Y-pipes (raspy 1MZ/3VZ, or Honda J30/J32/J35), to a Nissan VQ35 G35 or 350Z (longitudinal RWD layout, symmetrical Y-pipes) in which we are all familiar with their nice exhaust note.
Which is why I linked my video up here to show everyone why my Camry sounded like an R35 GTR/350Z alike. I have stock cams, stock bore/stroke, stock valve angles and such.
I have close to equal length side-winder exhaust manifolds, close to equal length merge pipes (before the turbo), single exhaust.
Why a Subaru boxer engine sounds the way it does, it also due to the same principle. Put equal length exhaust manifolds on a Subaru boxer motor to replace its stock "very-unequal length" header, and you will notice that the Subaru now sounds pretty much like any 4-cyl.
Subaru, equal vs unequal length header:
As another example, here's my Camry with....
Twin turbo setup, true split dual exhaust with unequal length downpipes:
Current close-to-equal-length manifold/pipes/single turbo:
Besides the useless torque from my previous twin turbo setup, the boring exhaust note is also what lead me to scrapping the TT setup within a few weeks...LOL But that's another story for another time...
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