Yes it can, the the place who did it could have used a smaller diameter piping.

 

True, that would be the stupidest thing ever, but I would not put it past some exhaust shops to weld a piece if 2.25" pipe on there instead of the stock 2.5" pipe.

 

I did the delete myself. Used a piece of 3" stainless cause 2.5 was too small and didn't have 2.75". This is just temporary to make sure I liked it. I plan on getting a piece of 2.75" and using a tranistion to step to 4" for the tip. Maybe I'll just by some stainless bends and make a 3" catback without a muffler to support future mods! I'm just gonna put it on the dyno next week and use the LNF tuning guide to get started and fine tune from there

 

Goog thing you don't sound like you have much personal experience! All us DUMB ASSES don't have much to worry about then! Lol! I'd like to know how cutting the muffler off can royally **** your car up in the long run?

 

Found this info:

"successful muffler does two important things: It allows sufficient unimpeded airflow, and it reflects pressure waves. If you build an engine that only runs in the top quarter of its rpm range, like a road racing engine, an open megaphone is still hard to beat. However, useful power through the middle half of your engine's rpm range requires a muffler design that delivers "back pressure."



I've never been fond of the term "back pressure" as it implies pressure in the muffler and isn't entirely accurate. What you do want is a strong positive pressure wave sent back up the exhaust pipe to reduce air/fuel mixture losses from the combustion chamber. When the engine is running slower than is optimum for the cam design, incoming air/fuel mixtures tend to continue to flow across the combustion chamber and out the exhaust port. A timely pressure wave slows this loss and the engine makes more power at that rpm.



When properly implemented, a muffler with back pressure does not limit cylinder fill at high rpm because the pressure wave arrives at the exhaust port after it closes. This is why baffles, which reflect such pressure waves, are located at the rear of the muffler"

 

It's kind of hard to take you as an experienced tech when you just cut off your muffler and claim that your car is now running poorly.

Here's a suggestion: PUT THE MUFFLER BACK ON.

 

I'll just tune it and be done with it. Just kinda curious why cutting the muffler off would yield this result. I don't want the car quiet...that's why I cut the muffler off! I've never heard of a car acting different after opening the exhaust. That's why I made a post, just didn't appreciate being called a dumb ass for doing so. Everyone puts aftermarket exhausts on them, which essentially does the same thing and they aren't called dumb asses! I was referring to his experience because his maturity showed his lack of. I've built many 1,000hp+ street cars and 2,500hp+ race cars all with turbos. All of them have little to no exhaust and few had mufflers. So unless the lnf is unlike every other engine on the planet...I shouldn't have noticed any power decrease with opening the exhaust.

 

It probably only feels slower because you shifted your powerband when you change exhaust components around like that.

 

I don't see how opening up anything post cat would really make any difference at all ..... OP still has the stock downpipe so anything behind that isn't going to "open up the exhaust " .... Removing the stock muffler isn't going to do much more than change the exhaust note.

Could you imagine all the power SS/TC would lose going to a catless downpipe if this backpressure theory held true .... now that's a restriction.

I'm betting your car is picking up on a change in the weather .... humidity is a big one . Or it's on the rag .... I've had days where my car felt like crap for no reason....felt like it was down 20-30 hp only to hop in it later that night and be fine . Did you get any gas lately ? Anything like that? Pull the battery cable and let it relearn ... then see how it is.

 

I will say that it doesn't pull as hard up top but it sure does spool up much faster. Before I had to really get into the guys to make boost...now just a light tip in and it starts making boost. I did have the battery ground off while I welded on the exhaust. I thought was part of the change but it's been long enough for it to re-learn. I guess it just moved the power around in the powerband. Ohh well, tuning will make it feel a whole lot better anyways!

 

Anyone that tells you that you want back pressure on a FI car, especially a turbocharged car, isn't too bright on the subject at hand and is just continuing the terrible trend of spreading mis-information.

Turbo cars HATE any and all back pressure (This is why DP's and to some extent, much larger exhaust diameters, pending the displacement of the motor/setup, help so much). Supercharged cars, be it top mounted roots/twinscrew or a centrifugal, also are not too fond of back pressure and will definitely benefit from little to none.

NA setups are a bit different as was already pointed out, some back pressure can be beneficial in helping to scavange in the lower revs and helping to increase torque production, which is great for daily driving. However, this is not going to carry throughout the power band. An NA setup/car that is looking for as much power as possible is also going to want little to no back pressure.

I'm going to go ahead and agree with some of those who pointed out that the car, on the stock tune, will always correct itself, be it up or down, to achieve the targeted air load for 260hp. It's in your head.

 

You sound full of ****, dude.

 

/Thread

 

Yup...I am. I don't do that **** for a living...I made that up to impress **** like you on a cobalt forum. Whatever dude, go stick your head in someone elses thread. I hope this forum doesn't turn out to be one of those forums that people come in your threads and start **** and call you stupid.

 

You're the one that started the name-calling. I figured someone that could build 2500+ horsepower cars would know that cutting a muffler off a car doesn't affect anything but sound, but your 2500+ horsepower-butt-dyno is clearly in need of calibrating.

 

Good luck with that one.
But on the other hand I had the muffler delete done on my car as well and have not felt a loss of power.

 

I normally stay out of this ****.... But I am curious..

1# if youve built so many ultra high hp cars how cant you figure out this issue on your own?
2# if youve built so many ultra high hp cars why are you driving a cobalt?
3# if youve built so many ultra high hp cars why did you have to go to a buddies shop to do the delete?
4# if youve built so many ultra high hp cars how is it you dont clearly know the technical side of how exhausts work?

 

I didn't start any name calling....I believe it was you with the "*******" comment. I've never had a car that felt different after cutting off a muffler or changing a cat-back for that matter. That's why I was baffled. But I'm telling you. The car does not pull the same as it did before. Again, was jbust trying to figure out why? My butt dyno is not in need of calibrating. If it wasn't a huge waste of time to put the muffler back on and strap it on the dyno...i'd prove it. Not trying to prove anything to anyone on here...just asking questions to get answers. That's what these forums are for!

And for the record... I only mentioned the fact that I've built plenty of high hp turbo cars to let people know that i'm not some young punk kid who doesn't know what he's talking about. Cause that's sure how most of the replies were implying.

Again, not here to prove anything. Just don't like smartass or negative post in a thread that someone started for answers. Not trying to start **** and sorry about the *** comment ;-)

 

1. I was just curious on why/how this could be a result of a muffler delete. Never had a cobalt, never messed with one before. Just seeing if anyone else had this issue.

2. I bought a cobalt because I drive 75 miles a day rd trip work, gas is expensive and my truck doesn't 't get great gas mileage. My ws6 is not a daily driver. I think the cobalt ss is a sweet car.

3. I went to a buddies shop that I used to work at to use the lift and welder. Unless you know of another way to remove the muffler and add a piece of pipe...without rigging it with exhaust clamps!

4. I fully understand how exhausts work...kinda why I was stumped on how taking a muffler off could change anything.

Man I must've offened the wrong person on here! Feel like the new guy at school gettin picked on by the cool kids! Really didn't think my post was that stupid. Maybe I shoulda titled it "muffler delete, could it, in any way have resulted in a change in low end torque"?

Got flamed like a ****...**** set a blaze is more like it!

 

I agree...... People went the tar and feathers route with you ....... uncalled for . There has to be more to it because it makes ZERO sense that you lost any power to a muffler delete . It just shouldn't happen .

Have you done anything else to the car in the past week.... before doing the delete? Maybe got some bad gas right after the delete .... or the weather got hot and humid ....anything like that ?

 

Data log the ECU in a third gear run. Otherwise this is all just speculation.

 

No, weather has been about the same, just got gas yesterday. Honestly, everyone is saying the muffler delete won't change anything. But the fact is, the car is making 2# less boost. Boost is a measurement of restriction, the muffler had to be a little bit restrictive. Now the turbo spools much faster and I see 5# w/ just a light tip in. So it changed something. Like I said it titled this thread wrong. My thought is, the muffler is a bit restrictive....it' a oem muffler, they usually are. Once it was opened up, the loss of backpressure let the turbo breathe easier. That explains the faster spool time. I would guess that with having the back pressure, it was choked up a bit, more boost, usually means more torque. Or at least a flatter torque curve, maybe why it doesn't feel like it pulls as hard up top. I think it just changed the curve around a bit. Maybe it's the learn down pulling boost to keep the same hp/torque levels as stock. Again, the muffler delete is the cause of that.

Honestly, I just made the post because I didn't believe removing it could change anything! I was expecting to have say, ohh yea that happens. You just gotta get it tuned or just do this. I'm a totally newbie with these cars. They may only be cobalts, but they really are a pretty advanced car. Especially with pcm control and turbo/boost control. All the wastegates I've ever used/messed with have a damn spring in them! Lol.

Again, didn't mean to offend anyone by the comments I made earlier. I was just a little thrown back by the responses I was getting and kinda got a little pissed. No hard feelings! ;-)

 

It just goes against what most people see . When i removed the dual cat converters and went to a catless downpipe I didn't see must boost lose at all ... maybe a PSI but the car pulled harder .

The downpipe is the biggest restriction in the whole exhaust.... the car is so much louder with them removed and i left the stock catback alone. The car is almost too loud so the muffler and resonator on mine don't muffle much at all .

 

You need to see what the VE airflow is doing compared to what it was with the muffler on to really know.
As the flow increases, the turbo may have a harder time holding pressure depending on where you are running on the curve but more power should be made as the flow increases as was posted above. The 60-100 mph ricer runs in third are good for doing comparisons when logging.

I really doubt you lost power, I just think your butt dyno stinks!

 

Been in Puerto Rico, no internet so sorry for the late reply...

Negative, let me explain...
I have experience with diesel trucks and turbo cars that don't like having the exhaust chopped apart... That being said the truck in my sig has a 3 inch downpipe stepped to a 4 inch pipe with no soot trap or muffler. It depends on the turbo. In this case the turbo has been allowed to spin more freely which is fine but the turbo on these cars, from all accounts i have read on here and from personaly experience, aren't the best upper RPM performers. You moved the power into an RPM range not widely useable on the street, well unless you are going stoplight to stoplight against someone. The people that have cutouts in the DP open them up for strip or track use, unless I'm mistaken. And that use is pretty much WOT or on the brakes. And WOT is when you want the engine to preform in the top 20% of the RPM range.

Too bad no one read it. Your info was spot on Dr. Watson.

On a side note... the catalytic converter doesn't cause as much backpressure as people think... The old cats in the 70's-early90's hell yes... But now they are alot better. Arguably the turbo causes more backpressure while under load due to the heat and impeding the velocity of expanding gasses... Which incidently is exaclty what it is supposed to do.