exhaust systems

[tk-421]

Originally Posted by cali yaris

Here is a recent dyno showing that an axle-back can make more power THROUGHOUT the power range, including low end

Were those dyno runs measured on a "bone stock AT Yaris" by any chance?

I've read multiple reports from members complaining about low end power loss after an axleback swap with no other exhaust mods. All I'm saying is that opening up the exhaust on one end without making up for it on the other end is less likely to give worthwhile results.

To the OP: The way I was personally able to avoid losing low end power was to make the car lighter and swapping pulleys first. Only after doing that did I feel comfortable moving on to the exhaust. Personally I had great results starting from the front, so i started with an SRI, then the 1ZZ throttle body, then header, and finally a custom exhaust with 2.25 piping from the resonator back.

Obviously, I'm not saying "don't get an exhaust", just take the time to read some posts about some people's experiences and do it right the first time. Otherwise it's almost not worth it IMHO (althought the looks and deeper sound are very nice extras).

[tooter]

Originally Posted by tk-421

Were those dyno runs measured on a "bone stock AT Yaris" by any chance?

I've read multiple reports from members complaining about low end power loss after an axleback swap with no other exhaust mods. All I'm saying is that opening up the exhaust on one end without making up for it on the other end is less likely to give worthwhile results.

That's an excellent point, tk.

The stock Yaris muffler has a pressure operated valve inside of it which provides more backpressure for better low end torque, and then opens up at higher rpms for better top end horsepower. I really didn't think it would hurt my engine's performance and got curious enough to find out. The dyno told the tale... a definite loss across the board. So my wife will just have to get used to the sound.

While my engine block is totally stock with no tuning and stock ECU, the comparative dyno runs were all done with exactly the same bolt on parts with the axle back exhaust as the only change.

Equipment used in both dyno runs:

BLOX velocity stack air filter with short ram intake tube.
Corolla 55mm 1ZZ throttle body
tooter et aluminum intake manifold
Weapon R 4-2-1 exhaust header