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Discussion Starter #1
Well I deleted my mufflers a while ago, and it sounds perfect but the other day my little brother and I raced our cars. He has a 370z both cars are automatic. Standing start I always pull ahead and beat him but when we're rolling we're about even, I have the RT base with the skinny tires lol. Now my question is could the muffler delete have caused power loss? Sometimes it feels like I should be able to kill his car, the other thing is can I buy the Challenger wide tires and put them on a 7.5 in wide base wheel? His tires are like 9.5 inch wide so he has a ton of grip.
 

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Well I deleted my mufflers a while ago, and it sounds perfect but the other day my little brother and I raced our cars. He has a 370z both cars are automatic. Standing start I always pull ahead and beat him but when we're rolling we're about even, I have the RT base with the skinny tires lol. Now my question is could the muffler delete have caused power loss? Sometimes it feels like I should be able to kill his car, the other thing is can I buy the Challenger wide tires and put them on a 7.5 in wide base wheel? His tires are like 9.5 inch wide so he has a ton of grip.
If your running straight pipes your losing power and you probably didn't use a tuner to let your computer know you changed everything, now your computer thinks something is wrong and is trying to deal with it, which is costing you torque and hp, Run some good mufflers and 2 1/2 pipes with no resonators and get a tuner to dial it in and that 350Z will be reading your rear licence plate instead of the front.
 

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You are more likely to notice a difference in power due to ambient temps than you are from removing the mufflers. With the stock tune, our cars HATE warm weather. By warm I'm saying anything above 75F or so. The PCM will start to pull quite a bit of timing and on really warm days your car could feel like it's lost 100HP.

I don't know where you live or what the weather has been when you've been playing with your brother, but running in 60F weather vs 80F weather will make your car feel completely different and, possibly, downright embarrassing in hot weather. :)

You have the base, so 18x7.5 and running 235/55R18 tires? You could run a 245/55R18 or 255/55R18 on an 18x7.5 wheel, but those are going to be taller and hurt acceleration, IMO.

FWIW, a 235/55R18 is about 9.7 inches wide and a base 370Z is running a 245/45R18 in the rear and that's going to be pretty dang close to what you have.

Lots of variables... :)
 

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If your running straight pipes your losing power and you probably didn't use a tuner to let your computer know you changed everything, now your computer thinks something is wrong and is trying to deal with it, which is costing you torque and hp, Run some good mufflers and 2 1/2 pipes with no resonators and get a tuner to dial it in and that 350Z will be reading your rear licence plate instead of the front.
The PCM doesn't think something is wrong, it will adapt. If the exhaust resulted in more flow and the O2s reading lean as a result then the PCM will adjust with more fuel to keep the AFR within range. You don't need to use a tuner when doing simple muffler or cat-back changes.

A tuner with a custom tune will help regardless of exhaust changes.
 

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Discussion Starter #5
If your running straight pipes your losing power and you probably didn't use a tuner to let your computer know you changed everything, now your computer thinks something is wrong and is trying to deal with it, which is costing you torque and hp, Run some good mufflers and 2 1/2 pipes with no resonators and get a tuner to dial it in and that 350Z will be reading your rear licence plate instead of the front.
Wouldn't that also cause power loss? Removing the resonators?
 

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Discussion Starter #6
Yeah, I just need some wide tires! Cause I hate how skinny the stock ones look. I live in Sacramento, it's getting hot as of late lol. When we raced it was about 70 degrees. The 370z he has is a 7speed auto and when I drive the damn slip light comes on at least 4 times, I think if he gets more traction he would kill me. I actually have a picture lol. By the way I noticed you have a GWE, I would kill for that color. I attached a picture of the 370z that my little brother drives, the dog on the side is my German Shepherd Fox, and the middle car belongs to my wife.



You are more likely to notice a difference in power due to ambient temps than you are from removing the mufflers. With the stock tune, our cars HATE warm weather. By warm I'm saying anything above 75F or so. The PCM will start to pull quite a bit of timing and on really warm days your car could feel like it's lost 100HP.

I don't know where you live or what the weather has been when you've been playing with your brother, but running in 60F weather vs 80F weather will make your car feel completely different and, possibly, downright embarrassing in hot weather. :)

You have the base, so 18x7.5 and running 235/55R18 tires? You could run a 245/55R18 or 255/55R18 on an 18x7.5 wheel, but those are going to be taller and hurt acceleration, IMO.

FWIW, a 235/55R18 is about 9.7 inches wide and a base 370Z is running a 245/45R18 in the rear and that's going to be pretty dang close to what you have.

Lots of variables... :)
 

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These cars require back pressure thats why you are feeling the loss in the bottom end.
 

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Wouldn't that also cause power loss? Removing the resonators?
No, there's quite a bit of confusion and misinformation out there about exhaust. The biggest "myth" is related to "backpressure."

Not to over-simplify, but the best exhaust is one that has as few bends as possible, nothing that restricts flow, and is the correct size to promote scavenging. Whenever the flow has to change direction it causes a restriction and a disruption to the exhaust pulse flow, this can cause exhaust gasses to stack up and the engine has to work to push the exhaust out.

You also don't want an exhaust pipe that is too large, otherwise the gas velocity slows down, the exhaust gas pulses stack up, and you lose scavenging. Scavenging is the effect of exhaust pulses "drafting" the pulse in front, being pulled along, and this effect will help pull exhaust gasses out of the combustion chamber. Any power that the engine doesn't have to spend pushing exhaust gasses out of the cylinder is power that can be sent to the wheels.

The "bigger, straight mufflers cause power loss" myth essentially started with the ricer crowd installing massive exhausts on their tiny 4-cylinder engines and blaming the free-flowing nature of the exhaust and not having "needed backpressure" on the power loss when the problem was using an exhaust that was too large for what the engine was producing.

An exhaust with straight-through mufflers that is the correct size is going to yield the best results, IMO.
 

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Here is a great explanation on the myth of backpressure and what makes a good exhaust, in case anyone was wanting an outside reference to what I said.

exhaustbackpressure
 

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Here is a great explanation on the myth of backpressure and what makes a good exhaust, in case anyone was wanting an outside reference to what I said.

exhaustbackpressure
This is good info but the op says he removed the mufflers assuming he means the resonators that will cause loss in the bottom end. I did not see anything on wider pipes or aftermarket exhaust.
 

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Discussion Starter #11
I removed the mufflers lol. The ones directly under the car, not the resonator's in the rear. I actually want to run a straight pipe in the rear also but probably would suffer a CEL or loss of power I assume.
 

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This is good info but the op says he removed the mufflers assuming he means the resonators that will cause loss in the bottom end. I did not see anything on wider pipes or aftermarket exhaust.
It's all tied together, man. It comes down to flow and velocity, removing chambered resonators will improve flow, the size of the pipe staying the same maintains velocity and scavenging. There should be no loss, I'd be willing to bet the "problem" is what I said before; Warmer weather. Happens every year when the weather warms up and people get caught off-guard. If there is loss at the bottom end it's minimal and you'll accelerate out of it rather quickly, then the RPMs will be kept up and it's no longer an issue.

These aren't little 4-cylinder cars where a couple HP or lb-ft can make a huge difference. :)
 

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If your running straight pipes your losing power and you probably didn't use a tuner to let your computer know you changed everything, now your computer thinks something is wrong and is trying to deal with it, which is costing you torque and hp, Run some good mufflers and 2 1/2 pipes with no resonators and get a tuner to dial it in and that 350Z will be reading your rear licence plate instead of the front.
Something I never thought of till I read this...Do I need a tune if I only have a resonator delete? I cut those tumors off at 500 miles, so can't say I can feel as power difference.

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Something I never thought of till I read this...Do I need a tune if I only have a resonator delete? I cut those tumors off at 500 miles, so can't say I can feel as power difference.

Sent from AutoGuide.com Free App
Nope! No tune needed for simple cat-back or CAI/air filter mods however a custom tune will help performance in general regardless of mods.
 

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Thanks. That's what I thought but then I started to freak that my baby was missing something. Lol

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