Full exhaust for MPG gain?

[BennyLava]

How restrictive is the factory yaris exhaust? In comparison to a good aftermarket unit, that is. Whats the diameter... 1.5 inches? Perhaps the aftermarket exhaust would be a 2" diameter to allow for better flow?

Also to be clear, I'm talking about a whole system. From the header, all the way to the tailpipe. If you replaced that with high end tubing, does anyone know what the MPG gains tend to be? Surely someone on this site has done this.

[malibuguy]

Leave it alone. Stock is 1.75". Reaches peak velocity at a lower rpm to improve low end torque scavenging. In all my variants of exhausts i consistantly average 1-2mpg less with similar driving...and obviously more when i listen to it.

Stock is also lightest as its all 18g 409ss material. Anything aftermarket is typically 16g...and local shitty muffler shops use 14g since they can only press bend the tubing

[BennyLava]

Thanks for the reply. So even just replacing the manifold with a high performance header wouldn't help? As for the tubing, I certainly wouldn't want to downgrade. What if 18ga Stainless could be had, in an aftermarket exhaust kit that didn't have cats? And what about the size increase to 2"? Anything to be had there?

Also have you seen those flowmaster hushpower mufflers? They claim straight pipe performance, with factory muffler sound. So they claim.

But if there really is nothing to gain, if the exhaust really is that efficient, then I have no problem just leaving it alone. What else could help me pick up some fuel mileage? A good tune, like they're always doing to Ford F-150's? People will gain 40+hp and 2 or 3 mpg on those trucks just with a good tune. Is there anything like that for the Yaris?

[malibuguy]

Ive heard some people picking up a smidge in mpg with a tune...but i have no first hand experience.

I picked up no mpg with my Weapon*R header before and after i port matched it. My current exhaust is a 100cell race cat going into a '14 Scion TC resonator 2" 409ss mandrelbent piping to the rear axle into a 2.5" 304ss axle-back using a large Borla muffler from a WRX exhaust and twin 2"tailpipes.

Goes like stink and is quiet...however i am still down about 3-4mpg then when i ran a full stock exhaust. These cars love an exhaust...just the mileage doesnt follow suit

Id look into the Tooter manifold spacer...it really shifts the torque peak lower so you can keep the car in a higher gear to help save mpgs. Im happy with my spacer even tho it costed me 2-3whp at top end the low to mid range grunt gains are worth it on the street

[BennyLava]

So to clarify... what you are saying is that the OEM exhaust is not restrictive? As I'm sure you already know, a lot of vehicles benefit greatly from a full aftermarket exhaust system. From the headers to the tips. Bigger pipe, better flowing mufflers and cats, and an a quality aftermarket header/s. Its a little odd that the yaris wouldn't pick at least a couple mpg with no exhaust restriction.

And if not, then what can be done to increase MPG? In terms of aftermarket parts and such. I noticed you mentioned a tune. Usually a tune helps most once you've done a fair bit of work to the engine. What about porting and polishing the head? Just not changing the cam/s

[Jcp123]

Start with the basics. Air up tires, grille block in winter, a light foot and some sort of OBD instrumentation...Torque, UltraGauge, ScanGauge or the like.

[BennyLava]

What do you guys do about toyota's overly sensitive tire pressure sensors? Hell I'd run mine at 50 PSI if I could. When do they come on? I'm told that they come on if you go too high with the inflation, as well.