What have your experiences been with going with the 2.5" exhaust? Did the low end torque disappear like everyone says it will? How did it affect the powerband? I'd love to have more torque in the upper 2k rpms range. I don't spend much time around 2k rprms unless off-road (thanks to the auto ). Any input is appreciated. Also if you have any significant engine mods (headers, cam, port and polish, etc), please throw that in there too.


Thanks

 

i bought my truck with a 2.5 and magnaflow not madnrel bent... i dont cant comprare it to b4 and after. but to other yotas iv wheeled.. at above 2.1 or 2.2+ rpm it works out fyne.. lower than that i can feel that it doesnt hand with other yotas.. but above it it deffinetly makes an imporvement i think (againt not comparing to b4 and after, but to other yotas (never the same model 4runner) i would deffinetly side with not getting a high flow cat with a 2.5.. maybe jsut having your cat cleaned, or replace with an OEM cat...

deffinetly go with mandrel bent with whatever you choose... and get a custom mandrel bent intake while your at the pipe shop...

 

when I replaced my catback 2.25" pipe and 3A Racing turbo muffler with a high flow cat and 2.5" catback dynomax superturbo, I may have noticed a slight low end loss... but it was so little I'm not even sure there was any. now in the higher rpm range I have a lot more power, and it actually keeps giving power all the way to redline instead of feeling like there is none after 5k.

the only thing I'm unhappy with is the dynomax isn't quite loud enough at certain rpm's for me =p

 

You just need to move more air. After my rebuild my 2.5" dynomax ultra flo is a bit too loud now.

Im pretty happy with my 2.5" system but Im running headers and tons of other work so its probably not a very good indicator for you

 

well my previous muffler was a lot louder, the exhaust went straight through and there were little spirals to catch some of it. at start up it'd sound like a beast, but with dynomax it's hardly half as loud.
the dynomax actually has the deepest loudest sound at lower rpms, but the cool part is at high rpm's it sounds almost like a straight pipe. definitely not near as loud as something like a flowmaster 40

 

I experienced a very noticable loss in low end power when I went to 2.5". So much so, I decided to go back to 2.25" from the muff back (cat is still 2.5"). All the power was restored. When running the 2.5" I didn't notice anything special on the high end (rpm).

For your 3.0 to benefit from 2.5" exhaust, you'd have to be running a turbo or SC. Without one of those two, it just doesn't move enough air.

Edit: I had headers at the time. So the increased air flow from the headers played a part in the loss of back pressure, resulting in the significant loss of low end power.

 

GOOD POST! Answered some questions I've had for quite some time now. I just used a stock system from 1sttoyotaparts.com, it was cheap, even with all the gaskets, hangers, rubber, and bolts it was under 2 bills and took only 1 hour to install in my tiny gravel driveway w/new aftermarket cat. I liked that the stock system had smooth bends (compared to the Walker brand Advanced sells.) and was all welded up and fit perfect.
I figured without some nearly impossible tuning that my 3.0 auto 4runner would be a dog no matter what, and I might as go with the stock setup, which is VERY well built compared to all the aftermarket ˟˟˟˟˟ I looked at.

 

If you havent read it already, heres a quote from NWOF:

"FACT! Before purchasing an oversize 2-1/2" exhaust system give it a little thought! The problem with 2-1/2" exhaust tubing (a common size mistake) is that the velocity in the system decreases with larger diameter tubing. This reduction of velocity is caused by the exhaust expanding in the larger tubing. This actually produces more back-pressure by slowing the flow. The result of this is a significant decrease in low end (2000-4500 rpm) performance of your Toyota's engine."

I also did a lot of research on this subject and i decided to go with headers, high flow cat, and 2.25" pipe. Theres too many people dont recommend 2.5" on the 3.0 motor.

 

Very good info rocket.

Backpressure does NOT increase low end torque. This is a common misconception. In general you want as little backpressure as possible. The reason that smaller diameter pipes can sometimes provide more torque in specific RPM ranges is due to a "tuned" resonance effect. This is called exhaust scavenging, basically the back end of pressure wave from one exhaust port helps pull the gasses out of the next, quite the opposite of backpressure really. But people noticed that the smaller headers made more torque down low and assumed it was "backpressure".

 

great info.. thanks a lot

 

I have a sorta related question about my exhaust set up.

I will be installing the "190 HP" 3VZE Hi-Pro Engine into my truck.

I will also be putting on the 2.5" Thorley Headers and y-pipe, a 2.5" flowmaster high flow catalytic converter, and a 2.5" borla muffler.

What can I do, with what I have, to retain that low end power?

Can I connect everything with 2.25" tubing? 2" tubing?!
Or can I have a complete 2.5" setup because of the extra HP the engine will have?

Let me know what you think

Thanks dudes