haha, muff...

tis 24"

Muffler...:bonk:

It is 24 right?

No, no, no......Muff (another name for the female anatomy). Now read my above post...

Oh... I got it!!! Get it, got it...

I guess it really seems to be a waste if you/we eventually cut the cat-back muffler off and replace with stock. I tell you what though, I just heard an 07 Escalade start up, WOW! that sounds mean stock. It sounded better than most stock v8's Ive heard in an SUV. So, I don't think I will be taking my muff off anytime this summer

Guys...

It's been about two month since I installed the Magnaflow. The drone got a little bit bearable. Even at the loudest, it's a bit better than when I first installed it.

What's driving me crazy now is that sometimes it's really quiet, even near the "noisy" 2000 rpm range. It sounds civilized. This usually seems to happen in the mornings. I wish it was like this all the time. I really can't explain why it's doing it.

:awais:

Generally warmer weather will reduce the overal exhaust tone as there is less difference between the outside air density and the exhaust gas density.

Also it could be a function of engine load and absolute throttle useage.

So... By having a CAI like Volant will make the exhaust louder?

Wow. Didn't know that.

Also, the tranny kick-down seems to have changed as well, after the install (both Volant and Magnaflow).

There's a hesitant range while it's coasting at about 35mph, and the rpm about the same range as the drone, where I have to step on the gas forcefully to get significant acceleration/kick-down. It almost feels like the drone = blockage. Am I going crazy, because this wasn't a problem before the install... I think.

Yes the exhaust should become slightly louder as intake pumping losses should be reduced thus allowing the engine to breath slightly easier creating more exhaust flow....and hence slightly louder or differring engine note that may sound louder.

As the peak torque and hp rises it may also shift in the powerband and this is why you are seeing changes in the shift patterns of the tranny. The 4runner uses a logic program to determine shifts between power required, power requested, power output and a slew of other factors. Due to the fact that you are changing the torque and hp curves and have less back pressure in the exhaust system, which can become too little and you loose exhaust velocity and exhaust gas scavaging, you may need slighly more power to request the tranny to shift down.

I use my right hand instead of my foot if I want a downshift...

LOL... That is exactly what I've been doing recently.

Just wish the shift gate pattern wasn't so messed up. Maybe even a "manumatic" would have been cool. Damn you Toyota!

After much review and many attempts to solve my drone issue I stumbled upon the scientific approach of designing and tubing a Quarterwave resonator. Sounds fancy but it is very simple. All it is is a J-tube of a specific length that targets a specific drone frequency. A single J tube of similar diameter to the collector pipe (eg 2.25 or 2.5in) ahead of the muffler and installed a few inches a head of the muffler. The tube requires a capped end to bounce back a sound wave with a phase offset to counter the wavelength of the resonating sound wave. Do not put an actual resonator or muffler on this branch as it will dampen the amplitude of the bounced back wave and be far less effective.
This quarterwave principle works when an exhaust produces drone only over a narrow frequency band. It seems that right around 2000RPM is the typical engine speed where many 4th gen 4runners with modified exhaust exhibit drone. My drone was limited to about 1800-2200RPM. In the cab the sound frequency was about 130-140Hz and max drone volume was 82-85dB. This frequency is directly related to my V8 engines RPM.
Using quarterwave resonator cals, the predicted J tube length at this frequency is around 30in. After trying different lengths my optimum J tube length to reduce drone is in the range of 28-29in. Any shorter than 27in or longer than 30 in produces noticeably more drone. This J tube drops the inside cab drone level to 69-71dB, which is very tolerable.

NB my exhaust system is totally custom with Doug Thorley headers and my own built 2.25in Y-pipe (all welded using stainless steel straights and elbows) with 2.5in collector feeding a 22in long 3in diameter Magnoflo muffler.

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