No mufflers

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So, the previous owner of my vehicle cut the mufflers out and welded pipe in place, with some nice exhaust tips. For a 4 banger, it sounds mean. My concern is, I'm sure I'm losing back pressure, which from my current understanding, means that I'm also losing HP.

Question #1 - What long-term effects, on which components, will the lack of back pressure have?

Q #2 - What are some options to add back pressure without putting mufflers back on? I know some fellow bikers I've met have welded bolts, washers, etc. inside their short exhaust to compensate for the loss of back pressure.

Thanks in advance!
 
I would be more concerned with the long term effects on your hearing and getting stopped by police for your excessive noise. Hopefully, a nice officer will convince you to change your thinking.
 
I spent 6 weeks in New Plymouth for a previous employer by the way. You have a very beautiful country! I hope to go back some day!
 
Lol, I'm not going to pay to put mufflers on if I don't have to. Haven't been stopped yet, I'm not obnoxious with it during sensitive hours. To each their own I suppose.
 
i think they make clamp on exhaust tips that have a couple baffles to quiet the exhaust a smidge and maybe add a little bit of backpressure.


if you do end up putting mufflers on, you can get either a turbo muffler or glasspack for not a lot of money.


the glasspack would only tone it down a little bit, but a turbo muffler would dampen it enough to be legal and they do give a nice rumble.


or you could always cut out a section of pipe some where intermediate and put in a section of small diameter pipe so going from stick size to small size back to stock size to add some restriction
 
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Whatever forum you are frequenting that perpetuates the blanket "engines need backpressure" claim is a forum where you want to log off and never return. Engines need proper breathing and an exhaust that's properly tuned and sized, i.e. tube diameter, for the amount of airflow the engine is capable of producing. And depending on the specific engine, that may mean smaller diameter piping for proper scavenging. Put huge pipes on a small engine and the airflow is going to be terrible because the exhaust velocity is going to be slow and the engine is going to have issues, usually being gutless on the bottom end.

My friend had a Dodge Ram a few years back, and towed his 25 ft boat with it. He then went all out and put a beautiful aftermarket full chrome exhaust on it, huge pipes, huge money, sounded absolutely incredible..... and now he couldn't tow his boat, it was like pulling a 30 ft camper with a Prius. He called me and said he thought he screwed something up, could I come look at it, he can barely tow his boat anymore. I took one look at it and thought these pipes belong on a Kenworth semi, not on a pickup. I said "where is your factory exhaust?" He showed it to me, I looked at the pipe size difference, and said "Put your factory exhaust back on". He reluctantly did. Then he was thrilled he did. The torque was back and he could tow again.

You can run lean, run rich, burn valves, run hot, induce detonation, and whole bunch of other undesirable things running an exhaust that is a bad match for the engine and how it is used, what cams it has, how its being fed fuel, what RPM range its running, and lots of other variables. Simply removing mufflers, putting on big pipes, welding in baffles and washers and other things just says that the person doing it doesn't really have a good understanding of exhaust tuning. Plenty of reading to be had on the web about this.
 
If the 4 banger has a catalytic converter it has backpressure. If it's supposed to have a cat but now your running catless then it probably has or should have a tune for the check engine light and performance. What is this 4 banger in any way?
 
Unless you are getting a check engine like for something like lean conditions, you'll be fine. Fiat Abarths come without mufflers too from the factory and they sound terrific.

[Linked Image from fototime.com]
 
Quint nailed it on the head. If your engine has to work to push the exhaust out, like what happened when his friend put a massive pipe on his truck, the engine is now using power to push that exhaust out instead of putting it to the ground.
 
Originally Posted by atikovi
Unless you are getting a check engine like for something like lean conditions, you'll be fine. Fiat Abarths come without mufflers too from the factory and they sound terrific.



Being a Fiat tuner and fan from the 70's and early 80's ( Yugo GV too!)

I'm not a fan of that new abarth sound. , Also that's a turbo - which take a lot of energy from the exhaust.

I wonder if the OP car is a turbo?

If not, I would put a muffler on that pig! You will in time. Its get old fast.

Youth, hormones. Lots of testosterone, the "run through the forest gorilla" attitude dragging a branch making noise to show your station - Its actually in our DNA

To point, 4 strokes don't need "back pressure", they need proper scavenging, which means the " correct" sized pipes for the torque range.

Its resonance tuning - like organ pipes in church or ported subwoofer boxes. and its not just the primary length, the "collector" area air mass and velocity is critical too. Open headers make less power than say a header with a necked down 20" collector extension with a turnout.

The car will have a muffler soon.
 
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Back pressure is a myth. It was most likely started decades ago when people would put bigger exhaust pipes on their car and lose a few hp. They mistakenly thought this meant the engine liked back pressure. In reality, the engine liked the higher exhaust velocity of smaller pipes while not being small enough to cause back pressure. It's a bit of a goldilocks zone.

I am considering no mufflers on my track car because 1) the class I race in doesn't require them, and 2) I have no way to run mufflers right off the headers without hacking at the frame. I would have to add intermediate pipes to extend back with a merge and put mufflers back near the rear axle. That adds weight, and this pig is already heavy enough. So... probably going sans muffler.
 
How much back pressure is there on a V8 dragster running ONLY headers ... not much. And they make HUGE horsepower. At HIGH RPM ...

A cars exhaust system is a compromise between flow and emissions and sound. Back pressure will always reduce absolute horsepower. ALWAYS. Reducing back pressure can push the torque / hp peaks up the rpm range, making the car feel slower at low rpms, but faster at high rpms once the engine starts to push out more exhaust volume, and optimize flow. Likewise, tuning back pressure by pipe size / cat flow and muffler flow can can bring the torque peak down the rpm range, making the car feel FASTER at lower revs, but ultimately SLOWER in absolute terms.

Most street driven NON TURBO cars like some back pressure, because street cars aren't operating high in the rpm range that frequently. They FEEL better when the torque peak is at a lower rpm.

The truck towing example is reflective of the importance of torque curves. The truck was likely FASTER 0 to say 100 mph, a test where the engine is able to use the high rpm power gains. But when towing, you need low rpm torque, not high rpm power, and the truck exhaust was tuned in a way that moved the torque curve UP the rev range. Not ideal, when you need the power just off idle to get the load moving.

Be a respectful neighbour, and put some mufflers on ... your neighbours will thank you, and your car will probably FEEL better to drive, and sound better as well. Uncorked 4 bangers just hurt the ears.
 
Believe or not, but a quiet exhaust can actually make your car, or motorcycle faster. I can redline my Corvette in first gear at 45mph, and no one can hear me. I find the stealth mode of driving without attracting attention to be much more fun. That's the fun zone of driving with technique.
 
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Originally Posted by 2014_K5_Optima
Lol, I'm not going to pay to put mufflers on if I don't have to. Haven't been stopped yet, I'm not obnoxious with it during sensitive hours. To each their own I suppose.


How do you know if a neighbor might be sleeping during the day because they are shift workers?

That's plain rude.
 
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Originally Posted by geeman789


Most street driven NON TURBO cars like some back pressure


It's not the back pressure. It's the exhaust velocity. Back pressure hurts power no matter the rpm. You can run straight pipes off the engine and just change the pipe diameter and see the power peaks move around with no changes in pressure. My old tow rig had longtube headers with an H-pipe and straight-thru style headers for no obstruction. However, it was just 1.5" diameter primaries in the headers to 2.5" collectors that necked down to dual 2" mid-pipes to the mufflers and out the back. It was designed around an ideal velocity at 2000-3000 rpm.

A 300ci engine with (theoretically) move the same volume of air at 6000 rpm as a 400ci engine at 4500 rpm. That doesn't mean you would design the same exhaust around them both. The 300ci engine would want smaller and shorter pipes while the 400ci engine would want larger and longer pipes. The diameter is for the volume per rotation per cylinder and length is determined by time needed to reflect the harmonic wave back to the cylinder at the ideal time for scavenging. Lower rpm needs more time and thus longer pipes.
 
Originally Posted by AC1DD
Originally Posted by 2014_K5_Optima
Lol, I'm not going to pay to put mufflers on if I don't have to. Haven't been stopped yet, I'm not obnoxious with it during sensitive hours. To each their own I suppose.


How do you know if a neighbor might be sleeping during the day because they are shift workers?

That's plain rude.


I used to have a neighbor who was retired. I'd come home at 6am, grab a bite to eat, and try to lay down at 8am... only for him to keep me awake with his lawnmower and weed wacker for the next 3 hours.
 
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