[ChrisSabo]

If I remember correctly, doesn't the EPA regulate noise emissions too? That being the case, I would say that Honda engineers were also calculating that into the mix when they designed the stock muffler. Kinda like my CBR1000, there's a whole little system operating a flapper in the intake system to meet noise requirements at certain rpm to sell the bike in the states. As a higher flowing can from a quality manufacturer, I would say it would have to impact efficiency positively. But as others have said, it would be negligible and you may or may not like the sound results long term. When I put them on my Camaro years back, I did not notice any gains or losses. But I can tell you that after a few years, we drove my girlfriend's Celica around a lot more often because I really kinda got sick of the droning exhaust... all the time. I'd hang on to your stock mufflers just in case

 

[r_vest]

Installing a CAI and exhaust will help, slightly. An engine is basically an air pump; the easier the air can get into the engine and out of the engine without restrictions the more power it will create. That said, the engine puts out 250 hp on an engine stand without any restrictions installed which are there now, at the end user. These restrictions are air filter, silencer prior to the throttle body, and exhaust, minus headers. In the current form; installed in the vehicle, the engine puts out approximately 170 whp. Installing the K&N air intake, according to dyno results, will increase to 180 whp. http://www.knfilters.com/dynocharts/57-3515_dyno.pdf Not substantial but worth mentioning.

Installing a new exhaust, if possible depending upon where you live, CA I would not do this but I no longer live there, take the J-Pipe off and have a muffler shop or yourself, if you are so inclined and have the tools, redesign as RV6 performance has designed for other Honda models. The factory J-Pipe is very restrictive. I would imagine that you would pick up maybe another 10 or 20 tops whp by removing that, along with the rest of the exhaust, and installing a free-flowing exhaust. It would also be lighter.

The ECU from the factory is tuned for "all" people because they cannot know how an individual person will operate the vehicle. That said, the RL computer is of a solid state design and does not allow for a "piggy back" chip to be installed as on older computer designs. Your ECU would greatly benefit by remapping from a reliable dyno person. These are sometimes expensive ~$400 or more. What they do is they remap the fuel so that excess fuel is not dumped into the cylinders. Richer burns means less likely-hood that an engine will burn up from a lean mixture. Of course the dyno operator will need to know how you drive, typically, what your intended purpose is, and what modifications you have. This is where you will see the most improvement in HP as this will increase the stock 250 hp. I have seen somewhere, cannot find it right now, but they lean out the fuel but still in a safe level so you won't burn up the engine. This is where you will see large increases, maybe as much as, they claim 50 hp. One guy here on the RL forum did this and had dyno numbers to show that as well. Of course that was with the CAI and exhaust. Mileage will increase but I would only guess around 2 mpg, maybe 4 with everything. In the long run, if you keep your truck, worth it at least in my opinion. I am doing my exhaust by the end of this year and then the computer next year as I don't have tons of extra money to throw at my RL. It works superbly but I always want more.

 

[rollinhonda]

Throwing money at a car so you will spend less on gas could cancel itself out pretty quick, I reckon.

 

[r_vest]

That it can, you, sir, are correct! So in the end, if you want a little better mileage, better sound then ok, otherwise it works as advertised. I'm a tinkerer so I always want more of, well everything. That is why small steps. The payoff will probably take, if you put everything on and gained 3 mpg and drove 20,000 per year, like I do, then it would take about 2.5 yrs to pay for itself. After that you would save about $478 per year in fuel, @$3.40 per gallon. (K&N 225, Exhaust 450, CPU 450) If you get a stainless exhaust by borola or magnaflow then that is an additional 650-800 so you would need to add another year) Not exactly an immediate ROI.

 

[Timberdog]

I'm not sure about exhaust but when I installed my tonneau cover I seem to be getting better mileage, I would say up to 2 mpg. I'm going to stick with OEM as anytime you tinker with exhaust, intakes, etc. you need to know if your O2 sensor has been affected or if your FI mapping needs to be adjusted.