Increased Gas Mileage with Performance Muffler or Cat Back Discussion

So I got my 2015 Tacoma TRD Sport this past August, drove it for 3 months stock and then I installed a Borla ProXS muffler and so far am seeing a very noticeable and number/math verified increase in gas mileage.

First I'll say that I drive it exactly the same as I did before. I keep the RPMs at or under 2k on the highway, which keeps me at right around 65 mph. So that is about 35 miles total to work and back every day, 5 days a week of highway driving and an additional 5 to 10 or so miles of around town driving every day during the week. On the weekends Ill drive a bit around town as well but nothing too substantial.

Before I installed the Borla my average mpg was 18.03, and on the schedule I detailed above, a full tank would last me roughly a week and 4 days.

After installing the Borla muffler, and driving with it installed for about a month, my average is around 19.4 mpg and a full tank will last me a good two or three days over 2 weeks now. I swear im driving the same exact amount.

To me this seems like a pretty substantial increase in efficiency. Have been thinking of installing one of those afe Pro Dry air intake filters to see if i can squeeze any more mileage out of it by increasing flow more.

The reason I installed just a muffler instead of a full cat back system was because I was dead set on doing a Borla exhaust, and the system they offered for the 2015 Tacoma had the same pipe diameter as stock, of 2.25 in. To me it seemed like the better, straight through pipe design of the muffler, would be most important if I was going to see any increase in efficiency. I didnt think Borlas pipe, same width as stock, would make any difference, it just didnt make sense to replace the existing pipe with shinier pipe and spend an extra $500.

Has anyone else ever done anything like this or noticed mileage increase by installing a muffler or cat back exhaust, or any other exhaust part like headers etc?

 

If a $50 part, less the cost of the OE unit, gave a 1+ mpg boost, why would Toyota not have done it?

MPG is an expensive goal all OEs chase.

 

Because its loud as hell lol and most people dont like that, I think would probably be the answer.

 

And it was probably a little more expensive than the OE muffler. I paid $120 for the Borla

 

There are so many things all manufacturers could do but they are either too dumb or too cheap to do so.

 

Seems plausible to me. Oem exhaust systems will be designed to be quiet and cheap. Aftermarket exhausts tend to be neither. I've never put an aftermarket exhaust on a car though so I can't say from my own experience if it's true. Been eye balling the Jones turbine exhaust myself though.

 

It is normal! I have a Flowmaster delta series 50 and yes, I've seen the impact of the muffler over the mpg. But in the other hand, I have 5 inch lift and 285s tires, so, the good mpg went to hell long time ago. Hey, it's all about the Vrooooommm Vroooommm

 

Doesn't mean it's not a $50 part.

I mean Toyota would get a discount if they bought enough for all their trucks, don't you suppose?

And raise their fleet average at the same time? What a deal.

Care to share a list? You might get hired into a corporate R&D role if the right folks read the forum!

Please make 2 lists. One for the 'too dumb' grouping, and one for the 'too cheap' grouping.

On the 2nd one, please include your estimated ROI numbers. Cost benefit is a critical factor in being 'too cheap' or not.

 

Riigghhtttt

 

OEM manufacturers need to adhere to strict federal EPA noise standards (in addition to a host of other parameters). It's not that Toyota is too "dumb" LOL, it's that they've got to pass those standards and still make a cost effective and profitable product.

 

Basic examples:

Why are the fog lights just big unearodynamic holes?

Why is there no smooth aerodynamic underbody cover?

Makes no sense.

 

Because both of those examples will not:

1). Increase profitability of the company
2). Increase safety of the overall product (the truck)
3). Increase perceived value
4). Increase perceived reliability
5). Increase fuel efficiency enough to justify the added cost

 

All comes down to cost my man. We could have all that, but it would just increase the cost of our trucks.

 

That makes no sense... the underbody aerodynamic cover alone would greatly increase efficiency. When you learn about aerodynamics and automotive tech school that's one of the first things that they mention is that that's where all the waste is.

And from a manufacturing perspective a big plastic sheet manufactured an extremely high volumes for the truck would basically cost nothing. Yet it would surely add a few mpg's.

There have been many many many people who have done crazy aerodynamic mods to cars and have achieved insane fuel economys sometimes for less than a thousand bucks. no I'm not saying that manufacturers need to do all of that super crazy stuff, but at the bare minimum at least make the bottom of the vehicle aerodynamic.

There are a few, few, vehicles that do utilize an areodynamic underbody cover which is how some of them achieve ridiculous fuel economies.

Now the fog lights? There's no reason it couldn't have been designed to be flush with the body or they could have just put some kind of a clear lense over it. That's another item that again at extremely high production levels would have basically cost nothing.

Look I'm not saying Toyota alone extremely dumb or anything, but every car manufacturer could definitely do a lot better than they are currently in the logic department.


Here's another one although unrelated to fuel economy, why in the hell are there solid axles that have shock brackets that are lower than the axle itself? And I'm specifically talking about trucks that are sold as offroad trucks... Thankfully the Tacoma doesn't really have this issue at least not on the 2nd gen.

But I've seen some Ford and Chevy 4 x 4 off-road trucks that the lowest part of the undercarriage is the damn shock mount. I mean what the hell? Why does it need to stick out so far below the axle? That's the first thing that's going to get hit if you go Offroad.

 

That is just what our trucks need. An undercarriage cover that will reduce height, increase corrosion and cost and make it a pain in the ass to do any maintence. Do you even know if it will reduce drag? Did you do the math and engineering?
My neighbors 911 doesnt even have a full carriage cover, but I guess porsche engineers are a bunch of dummies.

FYI: Trucks arent designed first and foremost for offroad use. 99% of people dont ttake their trucks offroad. So who really cares about your lame shock bracket arguement.

 

I'm not saying Toyota engineering is perfect anymore either (aside from 70 series Land Cruisers). But most of the decisions you see on your Tacoma were due to a bureaucratic compromise between engineers, bean counters, and regulatory agencies. Could you or me build a better truck? For our uses, the answer is most definitely! But more than likely, it wouldn't be globally profitable or pass ANY EPA regulations (haha!). Not everyone wants/needs a loud, lifted truck.

Toyota has developed a formula that works for them (otherwise they wouldn't be around to build cars and trucks in the first place) and the various items that you see bolted to your truck are there because of very deliberate corporate decision making. You want any thing more or less? Thankfully the aftermarket will take care of you. Tacoma's are definitely not perfect (There are at least a dozen things I would re-engineer if I could on my new 2nd gen) but they still are a decent platform to build a capable, reliable truck that holds its value well over time.

 

A simple plastic underbody in full scale produce would probably cost Toyota less than $100.

So again, my point is about the whole $50 part thing because that was the original point above.

But let's say it cost a lot more than that and they add $1,000 to the cost of the truck... But let's also say it gets 2-5 mpg better (or more, need testing). Is that a selling point?

 

Yeah don't get me wrong I'm sure the engineers are on the right track but everyone else is getting in their way as that seems to be the way every industry works nowadays... but again back to the original point I'm just saying that it's not impossible for a $50 part to greatly enhance the truck.


Also side note, I don't want to loud raspy truck either haha

 

I don't know what kind of undercarriage cover you're thinking about but it would not change the clearance any amount that would matter. And yes... It would decrease drag... if you do your research like I said or go to automotive tech school the first thing you learn about aerodynamics is that the underside of the car is a total wash in terms of aero efficiency.
Oh no I lost 1/5 of an inch!

A smooth level surface vs a bunch of different surfaces that are uneven with different parts and other random things are other places for air to crash into... Yeah...wouldn't help.

And the fact that they even make a sports car/supercar/whatever without an aerodynamic underbody cover is just pathetic. The whole point of spending all that money is maximum performance, then guess what... Aerodynamic efficiency effects performance.

Also... how on Earth does it increase corrosion? If anything it would decrease the chance of it because water and crap splashing up with hit the plastic and not be allowed to hit the metal.

So...to recap

Pros:
-Increased fuel economy
-Reduced chance of rust or corrosion of frame/body
-Added protection from smaller road debris, even if minor...

Cons:
-It's slightly more difficult to work on the vehicle.
-It may cost slightly more.

So yeah I'll definitely take the underbody cover. This shouldn't even be an argument.

 

The longer the shock is, the longer the stroke/range of movement. The axle can droop more