Question about exhaust popping!

zrk

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The pops and bangs are generally normal for high-performance vehicles, but there are factors that can moderate or exacerbate their presence.

First and foremost, let's talk about the origin of a pop:

The engine's computer is constantly blending an optimal mixture of air and fuel to achieve the right ratio for however hard you're pushing the engine. For example, idle and cruising is often 14.7 parts air to 1 part fuel, also known as a 14.7:1 ratio. Cars going to full throttle usually like to be between 11.5:1 to 12.2:1. The higher the first number, air volume is increasing relative to fuel volume. The lower the first number, fuel volume is increasing relative to air volume. You'll notice that the car moving into full throttle increases fuel relative to air intake (the ratio gets smaller), because a heavier supply of fuel is required to move the engine (naturally) but also because fuel has cooling properties that can keep the engine block cooler under heavy load.

So, now we know the engine increases fuel by a lot under hard throttle. We also know the computer is constantly seeking the best ratio for what's happening with the gas pedal.

Free Range, Organic, Non-GMO Pops: When you suddenly cut throttle on decel, it's easy to encounter a scenario where the car was dumping fuel for high engine load and was gulping down air from the intake to mix and burn that fuel... but that's not what the combustion chambers need anymore. Now there's way too much fuel relative to the air coming in. In such cases, the excess fuel escapes the cylinders through the engine block exhaust ports and detonates somewhere in the exhaust system because the exhaust is hot enough to ignite the fuel. Is this damaging? No. Not really. There's a very small quantity of fuel producing this combustion, and your exhaust is nothing if not a big echo chamber. We'll call this the "natural" way of producing pops and bangs, and their quantity+decibels can increase with wider exhaust diameters and fewer restrictions like resonators and catalytic converters.

The Splenda of Pops: The _other_ source of pop is an artificial one, sometimes called "fuel dump and timing retard." Engines operate in four strokes: suck, squeeze, bang, blow. Suction takes in air + fuel to the cylinder, squeeze compressed the air/fuel mix at the top of the cylinder under incredible pressures, bang is the spark plug detonating the compressed air/fuel mixture, and blow is the engine opening valves to evict the gases from compression into your exhaust. In fuel dump and timing retard, the car's computer is deliberately programmed to add extra fuel during suck and to delay ("retard") the timing of the sparkplug during bang so the blow stroke deliberately has unburned fuel and/or the air-fuel mix is still combusting as it leaves the valves. It's the same effect as the natural pops and bangs: unburnt fuel is detonating in the exhaust system. But this time, the engine has been deliberately programmed to trigger this condition when the user lifts off the throttle. The strength of the bang just depends on how aggressively this function was tuned, and how much throttle you're coming off of. Since the user is already coming off the throttle, the performance loss of firing the sparkplug late doesn't really matter.

The Supra has both of these. A high-flowing 3.5-4.0" catless exhaust will absolutely have its own pops and bangs. But the burble you hear on an OEM car is almost entirely artificial. That's neither bad or good, it just is and everyone has their own opinion on it.
A+ Post. Would Read Again.. A++++
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On the topic of popping , is there anyway to remove the popping when it shifts? My Supra is MHD stage 1 tuned with burbles off (I have it on soft setting with every slider at 0) but the thing still pops aggressively when I’m upshifting at times (sometimes it doesn’t and it sounds much better).
 

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On the topic of popping , is there anyway to remove the popping when it shifts? My Supra is MHD stage 1 tuned with burbles off (I have it on soft setting with every slider at 0) but the thing still pops aggressively when I’m upshifting at times (sometimes it doesn’t and it sounds much better).
You can't get rid of upshift farts, only burbles.




UNLESS someone knows something that i don't.
 

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The pops are normal... matter of fact, the hotter the car gets, the louder the burbles get, i was racing at buttonwillow raceway, i know my car's normal burble sounds and how loud they can get... but in the middle of racing, i noticed in hard braking and downshifting, the pops would be EXTRA loud.
 

AustinGRSupra

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The pops and bangs are generally normal for high-performance vehicles, but there are factors that can moderate or exacerbate their presence.

First and foremost, let's talk about the origin of a pop:

The engine's computer is constantly blending an optimal mixture of air and fuel to achieve the right ratio for however hard you're pushing the engine. For example, idle and cruising is often 14.7 parts air to 1 part fuel, also known as a 14.7:1 ratio. Cars going to full throttle usually like to be between 11.5:1 to 12.2:1. The higher the first number, air volume is increasing relative to fuel volume. The lower the first number, fuel volume is increasing relative to air volume. You'll notice that the car moving into full throttle increases fuel relative to air intake (the ratio gets smaller), because a heavier supply of fuel is required to move the engine (naturally) but also because fuel has cooling properties that can keep the engine block cooler under heavy load.

So, now we know the engine increases fuel by a lot under hard throttle. We also know the computer is constantly seeking the best ratio for what's happening with the gas pedal.

Free Range, Organic, Non-GMO Pops: When you suddenly cut throttle on decel, it's easy to encounter a scenario where the car was dumping fuel for high engine load and was gulping down air from the intake to mix and burn that fuel... but that's not what the combustion chambers need anymore. Now there's way too much fuel relative to the air coming in. In such cases, the excess fuel escapes the cylinders through the engine block exhaust ports and detonates somewhere in the exhaust system because the exhaust is hot enough to ignite the fuel. Is this damaging? No. Not really. There's a very small quantity of fuel producing this combustion, and your exhaust is nothing if not a big echo chamber. We'll call this the "natural" way of producing pops and bangs, and their quantity+decibels can increase with wider exhaust diameters and fewer restrictions like resonators and catalytic converters.

The Splenda of Pops: The _other_ source of pop is an artificial one, sometimes called "fuel dump and timing retard." Engines operate in four strokes: suck, squeeze, bang, blow. Suction takes in air + fuel to the cylinder, squeeze compressed the air/fuel mix at the top of the cylinder under incredible pressures, bang is the spark plug detonating the compressed air/fuel mixture, and blow is the engine opening valves to evict the gases from compression into your exhaust. In fuel dump and timing retard, the car's computer is deliberately programmed to add extra fuel during suck and to delay ("retard") the timing of the sparkplug during bang so the blow stroke deliberately has unburned fuel and/or the air-fuel mix is still combusting as it leaves the valves. It's the same effect as the natural pops and bangs: unburnt fuel is detonating in the exhaust system. But this time, the engine has been deliberately programmed to trigger this condition when the user lifts off the throttle. The strength of the bang just depends on how aggressively this function was tuned, and how much throttle you're coming off of. Since the user is already coming off the throttle, the performance loss of firing the sparkplug late doesn't really matter.

The Supra has both of these. A high-flowing 3.5-4.0" catless exhaust will absolutely have its own pops and bangs. But the burble you hear on an OEM car is almost entirely artificial. That's neither bad or good, it just is and everyone has their own opinion on it.
My candidate for Best Post of 2021.

I have a question: what are the long term effects of popping? Specifically, the effect on the turbo. The explosion or detonation that occurs in the exhaust system makes a wonderful noise coming out the back of the car, but wouldn’t the concussive waves of air (which the human ear detects as pops and gun shots) also be traveling toward the turbo? Over time, and let’s say you only drive in sport and are prone to letting off the throttle just because your car sounds badass, would this hurt the turbo? Or you have a tune such as Ecutek and can dial the sound up?

Thank you in advance for answering.
 

Thraxbert

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My candidate for Best Post of 2021.

I have a question: what are the long term effects of popping? Specifically, the effect on the turbo. The explosion or detonation that occurs in the exhaust system makes a wonderful noise coming out the back of the car, but wouldn’t the concussive waves of air (which the human ear detects as pops and gun shots) also be traveling toward the turbo? Over time, and let’s say you only drive in sport and are prone to letting off the throttle just because your car sounds badass, would this hurt the turbo? Or you have a tune such as Ecutek and can dial the sound up?

Thank you in advance for answering.
This is a very nuanced question for which no data exists. Can these pops and bangs hurt the turbo? In theory, yes. But there's no data to say "not really at X intensity, but somewhat quickly at Y intensity" such that we could make a safe and objective choice. All high-performance vehicles are gonna have some pop at decel, as we've discussed, but the artificial ones do come at some small and cumulative unknown cost.

We can also include there's some amount of design tolerance for pops and bangs, because it's in the factory tune for loads of cars. Shrewdly, we could say the manufacturer allows the tune because the damage might become prohibitive outside of warranty and their concern. But we could just as easily conclude that the impact is so minimal that it's beneath their concern. We just don't know.

I personally like a little pop and bang, but the more aggressive you make it, the closer it comes to a crackle tune, the closer it also comes to a rolling anti-lag solution and that DOES eat turbos for breakfast.

The only way to truly win is to turn the tune-derived pops off. Otherwise, OEM burble is probably fine longterm. More aggression is just betting against time, and it's any man's guess as to how big the bet is.
 

zrk

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This is a very nuanced question for which no data exists. Can these pops and bangs hurt the turbo? In theory, yes. But there's no data to say "not really at X intensity, but somewhat quickly at Y intensity" such that we could make a safe and objective choice. All high-performance vehicles are gonna have some pop at decel, as we've discussed, but the artificial ones do come at some small and cumulative unknown cost.

We can also include there's some amount of design tolerance for pops and bangs, because it's in the factory tune for loads of cars. Shrewdly, we could say the manufacturer allows the tune because the damage might become prohibitive outside of warranty and their concern. But we could just as easily conclude that the impact is so minimal that it's beneath their concern. We just don't know.

I personally like a little pop and bang, but the more aggressive you make it, the closer it comes to a crackle tune, the closer it also comes to a rolling anti-lag solution and that DOES eat turbos for breakfast.

The only way to truly win is to turn the tune-derived pops off. Otherwise, OEM burble is probably fine longterm. More aggression is just betting against time, and it's any man's guess as to how big the bet is.
My pops and bangs expert said turn it down - so turn it down :p
 

FuzzyRev85

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My candidate for Best Post of 2021.

I have a question: what are the long term effects of popping? Specifically, the effect on the turbo. The explosion or detonation that occurs in the exhaust system makes a wonderful noise coming out the back of the car, but wouldn’t the concussive waves of air (which the human ear detects as pops and gun shots) also be traveling toward the turbo? Over time, and let’s say you only drive in sport and are prone to letting off the throttle just because your car sounds badass, would this hurt the turbo? Or you have a tune such as Ecutek and can dial the sound up?

Thank you in advance for answering.
No, in stock form there is no significant risk of damage to the turbo. The turbine wheel doesn't care if a few extra hot puffs of exhaust air pass by it, especially when the throttle is closed on deceleration. A decade of lift-off pops isn't as taxing on the turbo as a couple months of spirited driving. The popping sound waves are generated by the collision of fast & slow moving gasses inside the exhaust pipe, often occurring well behind the turbocharger itself, and essentially travel in only one direction.
 

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A+ Post. Would Read Again.. A++++
While I can appreciate the originality and clever wording of the post, there's some critical phrasing errors that simply cannot be ignored.

Examples include stoichiometric instead of 14.7:1 ratio , and igniting instead of detonating.

B- at best ;)
 

SD_MK

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Doesn't Supras run leaner than normal cars? I know the DI system plays a role on why Supras can run leaner... of course 14.7 stoich at idle but on WOT, i think Supras run leaner than 12.2...
 

Thraxbert

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As I indicated in my post, well-tuned DI turbo cars can often run ~11.5 at WOT. Some even ride the hairy edge at 11.2 right before the top end of the RPM band. It's just a general post and cannot accommodate all scenarios. The actual AFRs are mostly immaterial to the discussion of pops and bangs, be it stoich, WOT, or otherwise.

//edit: and if we're gonna be nitpick ;) these WOT AFRs only make sense for 93 pump gas. EMix is quite different, and you'd want to enrich the mix a touch for 91.
 

JoshuaQ

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The harder you push it, the more and louder it will pop. I have a piggy back tune and catless dp. If I hit redline in 1st or 2nd and let off, it sounds like gun fire. Same behavior pre aftermarket, but just stock pops and bangs, not gunfire loud.

But it's totally normal for it to pop, bang, burble, and brap if you're pushing it, even a little.
Auto mode auto downshifts for you, so when you hit the breaks it will probably instantly downshift, causing the pops and bangs. It also should happen when letting off the gas, period.
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