Muffler removal, any power/fuel gains?

Well, if everyone did what you did, we would be all very miserable. Only one Harley bike minus muffler makes me miserable enough, to consider running the bike over. Fortunately, I control my impulses.

Your type is rare on priuschat as most prius drivers are very considerate people.

 

Having done mods on all of the street driven cars that I drag race I can tell you that it all depends on the car itself. My 96 Geo 3 banger lost power and got less mpgs with the stock muffler removed. My 98 and 95 SOHC Neons both gained power and mpg with headers, performance cats, and performance mufflers....but exhaust cut outs made them loose power. All of the turbo cars I ever had ALWAYS got better power and mpg with better flowing systems, the more flow equalled more hp. My 94 Dodge Shadow with the 3.0 V6 Mitsubishi motor went to the track when 2 months old (it was nice to have the dealership be one of my sponsers...but it never broke) and I was equiped with a hack saw and a Super Trapp muffler with 24 discs, double the number it came with. After 2 passes the stock muffler was hacked off. The car sounded GREAT, but ran slower by a full 1/4 second! Putting on the ST with no discs made it quicker, but still slower than stock. It eventually took 18 discs to get it a tiny bit better ET than the stock muffler. Street testing with a variety of the number of discs showed that the 18 discs were the best for mpg too.

I would suspect that the Prius would get worse mpg and power with a different exhaust, but only real world testing would tell for sure....as an aside, the other day I heard and saw a Prius with a FART CAN on it....WAY out of place, especially when he got off the gas and it got quiet! You could hear the gas motor kick on and off as he cruised down the road!!???

 

For improved fuel economy, especially in nonhybrids, I hear more about warm air intakes. Doesn't help power though.

I though this was variable. With the intake stroke volume very crudely 1/3 to 2/3rds less than the exhaust stroke, that really puts the exhaust stroke at 50% to 200% more than the intake.

 

The crossfire if it increased any performance and fuel economy it was due to the o2 sims.You basically turned it into a non adjustable car so it was prob running a little leaner then factory all the time and your lucky you didnt burn a piston doing so.You would have been better just changing the fuel curve and timing.And leaving the o2 sensors.

Contrary to popular belief making less back pressure and making the exhaust flow better has the exact opposite effect on fuel mileage if the same air fuel mix is obtained.

Same engine rpm at the same speed + more air thru engine+ same fuel ratio=more gas burned.

 

Since the RPM, number of cylinders, and compression ratio determines the volume of air/gas mixture through the engine, your analysis is a bit off.

JeffD

 

Larry, just out of curiosity, are you fairly young?

Tom

 

Larry, did you remove the entire exhaust on the Crossfire including the cats or was this a cat-back straight pipe?

Curious because I did a K&N aftermarket induction filter, off-road y-pipe and Z06 exhaust on my C5 and picked up about 3-4mph in the 1/4mile.

 

I think you will find that the engine in a Prius is designed not to breath. The intake valves do not close until the piston is 1/3 of the way to Top Dead Center. (also the crankshaft is offset so it is not centered at TDC)

Strapping different diameter pipes on the outside of the engine will not change that.

This may be the only time in your life you will hear this phrase: "Bolting an Matrix engine on your car in place of the stock engine may add 35 HP."

[ame]http://en.wikipedia.org/wiki/Toyota_ZR_engine[/ame]

Got Hybrid? - Sport - Car and Driver

 

No your analysis is off urs is based upon perfect volume and exhaust.Mines based upon actual volume that is actually taken in and out of the engine.Which is totally different then theoretical.

Any given engine is not perfect on exhaust or intake.So when you free them up you get closer to the perfect volume you are trying to base your formula on.Which once again more air passing thru with the same air fuel ratio 12-1 etc equals more fuel burned.

Which is good for power(most of the time) but not good for gas mileage.

Of course this is all all based upon the engine being able to adjust.When all the way on the throttle in closed loop operation it goes out the window.

By the way lots of tests have been done on exhaust and intake systems and found a decrease fuel mileage when you for instance change ur air filter etc for a more free flowing one.Do some searching and use some physics and you will see what actually happens.

 

Sorry that my last post appeared to have a tone to it to the other poster.I was a hurry to get to work.We could talk abouy backpressure .Pulsing.valve opening and closing events,all kinds of things.Torque vs hp etc. I was just trying to give a simple answer which is that if u make a car. Flow better then add fuel it in fact will get worse fuel economy under normal conditions. Now I believe that this is all a non issue when it comes to the post,Its apparent to me that the original poster is going to do. Free up the exhaust no matter what is discussed or reasons.Then he's going to without scientific data. Feel that he's got more power and more fuel economy both together.Once again without scientific data.I get this impression by the original tone of it works on all my cars attitude. The thread should have been hey guys I'm pulling off all my exhaust no matter what anyone says. What's the best way to do it. So my advice is to get out the saw or cutoff discs and have a good time.Its your car so go have a ball.Of course when ur done. And ur saying its better gas mileage. These people are gonna want hard number and to know all the variables temp wind speed driving condiotion lots and lots of data.This isn't facebook or twitter. There are some very sharp people on here and just spouting that its better isn't gonna go over well.

 

Your neighbors must love you.

 

It still all depends on the car....ALL my car, but one, ran quicker and got better mpg with CAIs added, but the muffler issue was different. The 3 banger Geo ran slower and got worse mpg with a CAI. On the Geo forums lots of posts are there about even a K & N air filter makes them get worsed fuel economy.

When are you going to get the SRT6 Crossfire? I onnly can dream about those. At the 2006 SRT Nationals at Topeka no one was entered in the SRT6 class so the money was just sitting there. A lady showed up with one and we talked her into just entering and driving down the track. Driving IS what she did. She said she had never been on a drag strip before...sat there for ever after the light turned green, then ripped off a 12.9 pass!!!! She got the money for the class win!

 

Therefore the opposite to the OP claim = decreasing the air intake volume and maintaining the exhaust volume (if the ecu didn't adjust), I should expect reduced performance(power) and increased FE???

 

There really are no mods to improve the engine performance of the Prius HSD, I know tuners have been trying since the first ones rolled off the line in '97! There are lots of suspension kits available, and a few cosmetic body kits, but the car is just designed with a far different purpose in mind!

 

IMHO
Muffler removal and or muffler replacement. First off back pressure is back pressure. Go watch the movie "Thunderbolt and Lightfoot" more specific the scene when Jeff Bridges and Clint Eastwood are inside a vehicle that has a cut off tailpipe "not fun to act in i am sure"

More humble minds might go with a performance muffler "all muffler shops" carry for your specific vehicle. The OEM toyota muffler is primarily for sound reduction via baffles. OEM stock muffler weight(lbs.) is more than a more performance muffler. Performance muffler has straight thru design with interior expansion design into product.
Save your time go to a local muffler shop. I guess Nevada does not have "tightly enforced" Emission, Safety, and sound laws

 

first off.. to address an issue i didn't see covered. those lines that run to your first converter are coolant lines that help the engine heat up faster. taking them off may make your engine run colder.. which means less mpg and less power.

modifications HAVE been successfully done with a prius. there has been supercharge and turbo test.

in relation to a post above... increase in hp is going to net more mpg.. and a decrease will decrease your mpg.

increasing the hp is going to make the battery charge easier.. the battery being topped out faster will net you more hp.. it will also want the car to fire up the ICE less since it doesn't like the battery to be full.

when the guy added on the turbo, he mentioned quicker times... but that's because the battery state of charge fell a lot slower.. so. it's not really faster... just has better endurance. (state of charge didn't drop as much going up hills... more jackrabbit starts available.. etc)