intake and muffler worth the mpgs??

[mgwalker]

i have an 05 aveo ls... just wondering if getting these parts would be worth it. i figure its prolly around 250 dollars to get both w mufffler install. but what kind of numbers to you get from adding these? i have a 5spd and just recently taught my g/f how to drive it and hoping she starts driving to and from work as opposed to her gas guzzling honda passport. will i get a cpl mpgs gain??

[thehunterooo]

not really, you will have more noise though

what are your mpg's looking like right now?

[petrified.rabbit]

more air = more fuel. opening up the intake and exhaust will result in more fuel being used.

[mgwalker]

right now im getting around 30mpg .. i live in southern ohio so its all curvy hills and city driving.... hwy before was worse but i was driving 70 and aveos dont seem to enjoy being that speed for effiency..

i thought if ur motor is more efficient it would enhance gas mileage. idk i had a lt1 camaro before so im new to the mpg scene. lol thanks guys

[thehunterooo]

30mpg is very good, if you keep it at 55mph on the highway, you will see the best numbers.

You can get a scangauge for $120 or so and use it to find ways to improve as well, it would be more useful than bolt ons.
But yeah, anything more than a couple of mpg's is an improvement

[mgwalker]

i was just looking for a few more mpgs. greedy i kno lol. 30mpg was good considering the way.i drove and roads around here i think

[northguest47]

both the intake and the exhaust are over-restricted in the stock motor. if one changes the stock motor by reducing the friction losses in both the intake and exhaust more mechanical horsepower at a given rpm will be generated (if one compared the stock dyno curve to the post-mod dyno curve), the catch for improved mileage is to ease off on the gas pedal while accelerating and cruising. if one were to keep the gas pedal at the same spot post-mods, more gasoline will be consumed (and more acceleration/power/noise).

[Daox]

When you're just cruising (low engine load) there really is no restriction since you are using such a small percentage of the power the engine is capable of providing. During acceleration (high engine load) is actually where your engine is being used most efficiently. Google brake specific fuel consumption for more info.

Bottom line is, intake and exhaust will do absolutely nothing to improve your mileage. It'll actually probably hurt it.

[northguest47]

Bottom line is, intake and exhaust will do absolutely nothing to improve your mileage. It'll actually probably hurt it.

Thanks for the BSFC info Daox, and, I respectfully disagree with the above statement. If one makes the airflow into and out of the motor more laminar then the motor would be more efficient making more horsepower at the same rpm, wouldn't this mean the car would accelerate to target speed using less fuel if it were compared to the same acceleration curve with a stock car? The cruising part makes sense for sure but what about during acceleration, and city driving having a lot of it?

Right off wikepedias entry on BSFC, "a reciprocating engine achieves maximum efficiency when the intake air is un-throttled", and it is proportional to fuel consumption rate, r

A corollary statement could be if you made the intake and exhaust smaller, say 1" or 1/2" are you saying that this won't affect mileage whatsoever? Thats really what I am interested in, because was thinking that some of the horsepower of the motor has to be used just to overcome friction losses in the system, so then it wouldn't be going to the axle, and it seems there is an efficiency loss there.

[Daox]

The wiki is mostly right. Below is a BSFC map. You'll see that there is a peak area where the engine is operating at maximum efficiency. However, if you continue increasing the load on the engine there is a drop off before peak torque is achieved. The drop off is due to two different reasons. The first is switching from closed loop to open loop mode which decreases the air fuel ratio and richens the mixture. The second is retarding the timing to avoid preignition. On this engine the effect isn't that bad, on others the drop off is much more pronounced. For example, turboed engines need to go into open loop a lot more often than naturally aspirated engines to keep the charge cool enough to avoid preignition.

Factory engines are tuned to the intake and exhaust they come with. A new intake and exhaust may very well give you more power. However, that power may cause your engine to retard timing and/or go into open loop more often during hard acceleration. It might even have to retard timing in closed loop mode.