Hate my 3" thermal exhaust

[mitchellj22]

Does anyone really think a dual 3" system is going to make their car faster?

Probably not that many people, but most people certainly don’t expect the car to get slower. I had the same issue with an aftermarket Borla exhaust on previous vehicle. It became a powerful slug. My research decided it has to do with back pressure. The only way to benefit from an exhaust install is to additionally get a tune I think.

 

[2PAC]

Quieter mid-muffler might be the fix. I installed a magnaflow 5x8x18. Added a shuttle deeper tone at idle. Back in the day I had a 67 GTO with headers and reverse flow mufflers running through 2" pipes. Back then scavenging effect was important to flow and performance. Turbos may be different. My point is 3" on an engine half the size of a 6.5 ltr would seem to be over kill and potentially have some negative performance aspects. Just my old gear head observation.

Many turbo 6s use 3 inch pipes, the gtr is oem 3 inch piping on a v6.

Negative performance aspects might occur when the car is not designed for the exhaust and is running a stock tune.

I'm not an expert on what system works best for this car but I'm sure it can pull off the 3 inch with a proper tune + supporting mods.

 

[TMac]

Many turbo 6s use 3 inch pipes, the gtr is oem 3 inch piping on a v6.

Negative performance aspects might occur when the car is not designed for the exhaust and is running a stock tune.

I'm not an expert on what system works best for this car but I'm sure it can pull off the 3 inch with a proper tune + supporting mods.

The stock GT-R uses a SINGLE 3" exhaust pipe back to the muffler. The ST uses dual 2.5 (with a smaller 2.25 in one spot). The area of the stock ST exhaust is larger than that of a single 3".

Dual 3" is not only overkill but will affect low end performance. Here are two posts of mine on the subject:

https://www.explorerst.org/threads/...-a-performance-exhaust-system.2775/post-33847
https://www.explorerst.org/threads/...-a-performance-exhaust-system.2775/post-43705

 

[Boss240]

So the 3" probably hurts performance then?

What exhaust do you have TMac?

 

[TMac]

I have the stock exhaust. I could care less about sound so it doesn't make sense to swap unless you want something that sounds better. If I were going to get an exhaust (after upgrading turbos and downpipes), I'd go with a setup similar to this:
https://www.explorerst.org/threads/as1-valvetronic-exhaust-build.4214/post-55254
Read the posts I linked to in post #23 above to see why.

 

[Boss240]

Oh ok gotcha. I like to hear a little something n that's why I bought a used MRT axle back. Just need a little more noise lol

 

[MR COOL]

that's not how physics works.

I cannot change the laws of physics captain.

 

[Lightning Struck]

FWIW, velocity is important in an exhaust system as is heat retention. The larger the cross-sectional area and the higher the surface area the lower the velocity. A dual 3" system may give you the sound you want, but it's not a performance enhancer.
Here are two posts on the subject:
https://www.explorerst.org/threads/...-a-performance-exhaust-system.2775/post-33847
https://www.explorerst.org/threads/...-a-performance-exhaust-system.2775/post-43705

And again, you're wrong.

 

[TMac]

And again, you're wrong.

Thanks for that sparkling well-thought out analysis. The concise way in which you presented your refutation of my comments complete with unassailable proof causes me to rethink everything I've posted!

 

[Lightning Struck]

The proof is in looking at every single high performance turbocharged vehicle, and analyzing their exhaust. Velocity plays ZERO roll in performance after the turbine. Post turbine, every turbocharged vehicle is better off with open exhaust. A simple look at Formula 1 will show you that! The exhaust is large, and about a foot long and uses a low pressure area around the rear wing to pull exhaust. You can try to refute this all you want, but it's been proven countless times in the past 70+ years.

 

[WindyDishes]

I have the stock exhaust. I could care less about sound so it doesn't make sense to swap unless you want something that sounds better. If I were going to get an exhaust (after upgrading turbos and downpipes), I'd go with a setup similar to this:
https://www.explorerst.org/threads/as1-valvetronic-exhaust-build.4214/post-55254
Read the posts I linked to in post #23 above to see why.

Just let me know we can spit another one out!

 

[WindyDishes]

The proof is in looking at every single high performance turbocharged vehicle, and analyzing their exhaust. Velocity plays ZERO roll in performance after the turbine. Post turbine, every turbocharged vehicle is better off with open exhaust. A simple look at Formula 1 will show you that! The exhaust is large, and about a foot long and uses a low pressure area around the rear wing to pull exhaust. You can try to refute this all you want, but it's been proven countless times in the past 70+ years.

Just saying these high performance cars your talking about are running external wastegates most likely. Your compairing $200k+ cars to a $60k Ford with cheap turbos that cant handle overspool (which will make the vehicle sluggish).

 

[Lightning Struck]

Just saying these high performance cars your talking about are running external wastegates most likely. Your compairing $200k+ cars to a $60k Ford with cheap turbos that cant handle overspool (which will make the vehicle sluggish).

Overspool? Is that a ricer word or something? Does it make flames shoot out? Do you know how to read a compressor map?

 

[TMac]

You are arguing apples/oranges and because of it you have made a mistake in your assumption. An F1 car (which by the way is a completely different animal) is not using the wing to "pull exhaust". It is using the exhaust energy to enhance the car's aerodynamics.

You seem to think that the aerodynamics of the underside of the wing having a low pressure area will "pull exhaust". That is wrong, and that is where you make a fail in logic which causes you to believe what you believe. The reality is quite the opposite. They are harnessing the energy of the exhaust to ENHANCE downforce by creating much lower pressure areas than can be achieved by just the speed of the air flowing over the bodywork. An F1 car is far less interested in generating a few more HP, than it is with aerodynamcs, especially downforce.
.
If you did your research, you'd find that in fact the F1 regulating body has all kinds of rules about exactly how they can use the exhaust on bodyparts to achieve downforce. You'll notice they're not running sewer pipes out to the wing because they PURPOSELY are using the velocity of the exhaust gasses to harness energy. You also don't seem to realize that they may be directing the secondaries into a diffuser (which you probably think is a big pipe) to provide a dampening volume for the exhaust pulses and direct that energy over a larger part of the wing. Once again, you are not seeing the entire picture being too fixated on some sort of "extraction" mechanism for the exhaust which has led you to faulty conclusions.

The fact that the secondaries are short is due to the engine mounting location which means less surface area for the exhaust system to lose heat. The smaller the surface area the greater the concentration of heat in the exhaust system; the greater that heat, the more energy is imparted to the exhaust gasses.

Given any amount of mass flow, the speed of that flow is determined by the cross-sectional area of the pipe through which it travels and the amount of heat in that flow. Depending on the amount of mass flow, there exist calculations which also include temperature of the gas to determine the optimum cross-sectional area to maximize velocity while keeping the speed of the exhaust gasses below the point where boundary-layer forces begin to interfere with the flow.

 

[MikeyP]

I'm just a simple, lowly engineer, so maybe I'm wrong, but I know when I'm looking for exhaust design for a road car that revs to 6000rpm and has turbos the size of raisins, I usually don't look to multi-million dollar F1 cars with a turbo the size of a watermelon that revs to 13000rpm. Well, unless anyone plans to add a blown diffuser to an Explorer.

 

[twin001]

I'm only here for the F1 talk......

CARLOS SAINZ 2023 WDC!!!!! 2022 has been a disaster and I don't want to talk about it......

 

[TMac]

Was a big fan of Sainz back in the '90s. WRC at that time. Interesting to see how well he's done in F1 in the past few years as he's no spring chicken anymore!

 

[MikeyP]

I'm only here for the F1 talk......

CARLOS SAINZ 2023 WDC!!!!! 2022 has been a disaster and I don't want to talk about it......

Mercedes fan here, so yes this season has been rough. However, based on the FIA's treatment of Red Bull's "minor overspend" in 2021, Ferrari and Mercedes should just throw 300 mil at the cars for 2023.

 

[twin001]

Was a big fan of Sainz back in the '90s. WRC at that time. Interesting to see how well he's done in F1 in the past few years as he's no spring chicken anymore!

Sainz Jr in F1. His dad is still racing though! Extreme-E and he did Paris-Dakkar this past year.

MikeyP, agreed, and Toto has already said he will blow through the cap next year because the penalties are negligible.

 

[mcglsr2]

Not sure what the OP is talking about regarding it being slower - but I can say that on a TURBO vehicle, the larger the exhaust (especially starting at the turbo), the better. This talk of a dual 3" exhaust making the vehicle slower is silly. If one wants to argue that it's not any faster, then okay, I'd potentially agree to that. But to say it's slower...no. This is not a naturally aspirated engine where exhaust scavenging is a thing. Turbos love big open exhausts. Full stop.

Backpressure, scavenging, pipe diameter and velocity - all that stuff matters...on a N/A engine. Once a turbo is added to the mix, all that other stuff ceases to be a thing. Because the exhaust is no longer necessary to help suck fumes out of the cylinders. We have good 'ol forced induction pushing it out for us. And the turbo turbine, in order to spool free and happy, wants as little restriction as possible after the turbine housing.

Now. Assuming the OP is correct in that his vehicle is actually slower - if that's the case, then the situation is more likely that the factory tune is getting readings from sensors that it doesn't expect. Maybe the turbos will spool a little better, or maybe the O2 readings are a little off now due to the larger pipe size...I dunno. But what I do know, is that a dual 3" exhaust, or a quad 3" exhaust, or no exhaust at all, is a-okay and your turbos won't mind one little bit.

Does the stock exhaust flow good enough? Perhaps. I'm willing to bet it's a little restrictive because Ford has to deal with the EPA. But I don't have any facts or specs to back that up, so it's just me talking. Will a 2.5" dual exhaust or a 3" be better? Maybe. If you only ever stay at stock power levels, then arguably they are wasted money (unless you are doing it for the sound). If you ever plan on getting a tune, then no, the stock exhaust most certainly is not just as good nor is it better.