Thread: Exhaust system....I need your ideas?

Ive seen cars of 300whp gain whp by just switching from a 2.5" out back to a 3" cutout just after the flexible

I did mean to say liquid, I dunno what the hell I said fluid....

Water is a fluid, the Co2 coming out your exhaust is not. I am now confused, Ben.

Fluids will flow differently depending on the viscosity, right? Does maple syrup flow the same at 40* compared to water at 40*? Both are fluids but flow differently.

Most "flow" depends on pressure and temperature. Sorry, guys.

I can't comment on much in here but I can agree that that front bumper side exit exhaust is really loud. I have a 3.5" one (thats what piping we had lying around) and it is VERY loud. I like it though, however it can be annoying. I went this route because even with 3" pipe my downpipe would scrape on speed bumps and was starting to fray at the woven flex piece...

RedDragun, how long did you have the system on your car? And was it stainless steel or aluminum?

That side exhaust looks pretty interesting.. I have never seen a car with a side exhaust before. But it sure looks really cool..

Yes it is.

fluid (countable and uncountable; plural fluids)

1. Any state of matter which can flow with relative ease, tends to assume the shape of its container, and obeys Bernoulli's principle; a liquid, gas or plasma

They all obey the same freakin' laws of fluid dynamics.

Test your own theory here: Air flow calculation

Set it to calculate flow rate (not pressure drop). Calculate with a low temperature, then a high temperature and watch the mass flow rate results.

(Hint, you'll find that you are backwards about the temperature part. The colder gas flows more.)

We've already had this discussion a ton of times including here: http://www.sr20-forum.com/general-sr20/17191-heat-wrapping-vs-ceramic-coating-header.html

The velocities changed but the flow rates did not.

One was moving something faster but the volume cannot change. That was dependent on the diameter.

I tried changing the pressure and the flow rates were once again, constant, the only thing that changed was the velocity again. The warmer one flowed at a higher velocity according to this calc.

I am assuming I did this correctly, I only changed the temperature to F (used 40 and 60 degrees as my variables. Then changed pressure from 6 bar to 3 bar.

"Air pressure drop" is that the right calculator? Now I gotta go to work again and I cant sit here and fart around more. Dammit.

Yes "air pressure drop" is the right calculator.
Then you want to change the radio button on the right to have the calculator calculate for "flow rate" not pressure drop.

Then I picked 800 degrees F as the exhaust temperature and 3 bar as the initial pressure. You can pick whatever pressure drop across the pipe you want but I chose 0.1 bar. It won't matter as long as you keep it the same between calculations.

We can then calculate the flow rate in volume and in mass and they will display on the left. Mass is more important, but volume follows suit quite nicely.


Then I changed the temperature of the gas down from 800 to 700 degrees F and ran the calculation again (so we're assuming the same initial pressure and the same pipe size, just a lower temperature gas) and clearly we get a higher rate of flow through the pipe. 340 kg/h at 700 degrees versus 324 at 800 degrees.



You can try it with any temperatures you want. And any pressures and whatever. Just make sure when you change the temps between calculations that the other variables stay the same so it's a valid result. You'll notice that the colder gasses flow more. Always.

The problem is you guys are not understanding what turbines actually do. There are 2 different types:
Turbine - Wikipedia, the free encyclopedia
Impulse and Reaction are the two types of turbines.
Automotive turbines are definitely NOT impulse because the DON'T use nozzles to speed up the exhaust gasses, so that only leaves Reaction. Since an automotive turbo is definitely a Reaction type of turbo it is safe to say a delta-p or a delta-m is really how the turbine is driven, not based on gas velocity. How to you maximize delta-p (p2-p1) in ALL conditions? By setting p1 = p atm, or open air. That is your ideal condition. How do you maximize your delta-m? By setting your m1 = 0, or open air. Ben is correct. All other 'factors' ultimately do not effect the turbo.

Hey Nate would you call the Shelby Dodge CSX turbos incorrectly named? They are called "Variable Nozzle Turbine" or VNT turbos. =D