2.7L exhaust system

I was looking online for exhaust for my 2.7L regular cab. I have noticed that the Jardine exhaust is 2.25" inches in diameter as well as the collector on Doug Thorley's header. Since I cut off part of my exhaust few days ago and had the size in my mind, I had thought it is really close, if not exactly 2.25". So I went outside and measured the piece of exhaust I cut. I was NOT surprised when I measured exactly 2.25" in diameter.

There could be more power obtained from the 2.7L by having custom header made with larger collector and custom exhaust with larger piping made, however that system would loose low end torque and only gain horsepower on the top end around 4.5k rpm. Since this is a truck and it needs low end torque, system like that would be waste of money. I think that's the reason why aftermarket header & exhaust retain the stock piping diameter size.

My conclusion that the exhaust is waste of money since it doesn't change the diameter of the exhaust piping. The only thing which is different on the Jardine exhaust is the muffler. You are much better off, getting a muffler of choice welded in the exhaust system, which should run around $100.

Now where I think the real gains can be made is getting rid of the two catalytic converters which are located on the pipe which is located before the exhaust. Have those cats cut off and replaced with straight pipe. To get rid of the CEL light, space the 2nd o2 sensor with two spark plug anti foulers, which can be found at local autozone. **DISCLAIMER** Cutting out the cats will make your truck fail emissions, if your emission station does sniffer test (hooking up pipe to your exhaust). Here in AZ, they just hook up to your OBD-II port and if your vehicle doesn't have CEL, you will pass. My previous car passed emissions here with no catalytic converters.

This all can be done for less than $200, if you can weld maybe even less than $100 and it should yield the same amount of horsepower as getting a Header for $450 & exhaust for $280 new.

Looking on the stock exhaust manifold, I don't think replacing it with aftermarket header will yield much horsepower anyways, maybe 3-4whp, since the stock exhaust manifold doesn't have a catalytic converter like the 4.0L does. The Doug Thorley header has 2.25" collector, which I believe is the same as on the stock exhaust manifold... The only difference is the design, where the Thorley's header has longer runners before the collector and that is the only benefit of the header.

 

Thats true to a point, however pipe diameter is not the only factor that affects flow. The smoothness of transitions makes a difference. Longer runners and smoother collectors do yield gains. Triple-y headers result in better performance than common collectors.

But you are right, the gains are minimal, hard to justify the cost versus the gains. A muffler is a much better investment.

Eliminating the 2 converters will net you as much as 5 whp, but at the cost of low end torque and fuel economy. The cats help with the scavenging process at low RPM, and without them, more spent exhaust is left in the cylinders. Leave the converters alone. Toyotas are know for being obscenely sensitive about converters, and messing with them is likely to result in a constance CEL. The non-fouler doesn't work because the Toyotas use a more complex catalyst monitoring algorithm based upon both waveform and voltage. Running without cats causes a drop in the rear sensor voltage, which the computer will interpret as a non-functioning converter. The non-fouler approach only work on vehicles that use a waveform monitoring system that ignores voltage.

 

That is good to know!

Very good info about the Toyota 2nd o2 sensor

The 2nd o2 sensor is placed behind the 1st cat, so in theory eliminating 2nd cat shouldn't trigger CEL and could result in horsepower gain.

In conclusion the best route would be;

1, replacing stock muffler with your muffler of choice

2, eliminating 2nd cat with straight pipe.

That shouldn't cost more than $100-$140 including parts & labor and should result in 3-6whp, which is not bad on naturally aspirated motor for $100 - $140...

 

today i just had arrow muffler in south jersey pin up a center outlet exhaust for me. the exhaust is all stock he just used my tip and replaced the factory muffler with a flowmaster 40 series. its deeper sounding than i thought it was going to be but its pretty loudin a good way i guess. i really like it alot and the guys at arrow did a great job. let me know what you think.

 

throw some tint on that bitch! hha

 

i cut out my muffler and installed a flow master muffler and upgraded to 2.5 inch piping after the 02 sensor and i regret it i lost ALOT of bottom and all the power went so high that i can even really drive in 5th gear on the highway anymore.

 

i tinted the back windows myself lol they turned out great. but when i tried to do the sides it was a fucking hot mess haha i need professional help with them. but my wife said that if i spend one more penny on the truck she will cut my dong off while i sleep lol. i have in transit black magic lights grill crafts top and bottom, undercover se and bed rug and digital floor mats and window visors. haha i spent like almost 2000 in like one night not to mention the bhlm and the other odds and ends. lol but i plan on sneaking in wetokole seat covers in black. haha its a good thing i like my new truck because i might soon be living in it lol.

 

I have the same setup goin on in my mind. (I also have a 2.7) Cut out cat and replace with straight pipe, then throw in a flowmaster super 44 maybe. I'm not sure on the muffler yet. Have you done this to your truck yet? If so, post a vid!

 

Not yet. Saving money for FatBob's lift kit

I don't even know where to start when picking a muffler... *sigh*