Anyone tested the Drag caused by swapping exhaust?

robones · 04-10-2012, 08:24 AM

Notice how the Z's exhaust is designed, it's engineered so that the air passing underneath the car curves through the bends of the exhaust through the rear diffuser in a smooth way. This causes less drag at high speed.

By changing the exhaust to a two piece set up, i.e: Fast Intentions, Berk, etc. you are are creating essentially a parachute on the rear of the car. I would think drag is significantly increased by this design.

When you remove the CAN design, the rear bumper gets exposed and creates a huge gap which traps air underneath the car just as its exiting through the rear.

The better designs would be exhausts similar to the stock setup and/or the nismo setup. Stillen, Greddy have similar designs which leave less of a gap in the rear bumper.

Your thoughts?

osbornsm · 04-10-2012, 08:42 AM

You are absolutely correct... much like the square back of a VW golf creates a vacuum. However unless you are looking for absolute top speed of the vehicle, this may be just an academic observation.

LakeShow · 04-10-2012, 08:59 AM

Interesting point, never really thought of that. Significant to affect necessary performance, not really.

robones · 04-10-2012, 09:07 AM

Well just imagine how much drag you are creating at higher speeds? The higher the MPH the higher the drag your car is creating. I would think that any significant HP gain from these two piece setups systems would be offset by the increase in drag they create?

I know the two piece setup sound nice and looks cool from the back but not much engineering thought is put into these systems IMHO.

wheee! · 04-10-2012, 09:08 AM

But the car goes much faster while standing still with the HKS style exhaust setup

robones · 04-10-2012, 09:13 AM

Quote:

Originally Posted by wheee!

But the car goes much faster while standing still with the HKS style exhaust setup

DarkJak · 04-10-2012, 09:32 AM

I've noticed that too. It's such a huge gap, and the back is mostly solid. There are several aftermarket exhausts that still use a setup similar to OEM though, like Invidia, Akrapovic, Ark DTS Type 1 (did that ever go into production?), and probably a couple more I can't recall.

One could probably just put a flat piece over the entire area to cover it up if the drag really is significant.

wheee! · 04-10-2012, 09:34 AM

I haven't noticed any issues at speeds around 240km/h....

TerribleONE · 04-10-2012, 09:35 AM

I see the difference being extremely minimal..

Nick911sc · 04-10-2012, 09:59 AM

I'm going to sell my exhaust now and revert to stock. I need to make sure I'm as aerodynamic as possible.

TerribleONE · 04-10-2012, 10:02 AM

Quote:

Originally Posted by Nick911sc

I'm going to sell my exhaust now and revert to stock. I need to make sure I'm as aerodynamic as possible.

robones · 04-10-2012, 10:31 AM

Quote:

Originally Posted by Nick911sc

I'm going to sell my exhaust now and revert to stock. I need to make sure I'm as aerodynamic as possible.

LOL funny but hypocritical and sarcastic at the same time! lol think about it aerodynamics and drag coefficient should be equally considered and are equally as important as HP gains, back pressure, etc when considering an exhaust setup! Otherwise, why get one at all!

my2004Z · 04-10-2012, 10:31 AM

Sounds like an opportunity for someone to develop a fireproof foam insert to fill the gap. Only way to find out is to line up a stock Z and a Z with upgraded exhaust and wind sail for a 1 mile race.

TerribleONE · 04-10-2012, 10:35 AM

Blocking it with something would just make things worse IMO... At least the canisters are round and they are pretty slick.. A straight wall would make it even harder for the air to go around

mantella87 · 04-10-2012, 10:35 AM

Quote:

Originally Posted by robones

LOL funny but hypocritical and sarcastic at the same time! lol think about it aerodynamics and drag coefficient should be equally considered and are equally as important as HP gains, back pressure, etc when considering an exhaust setup! Otherwise, why get one at all!

The large majority of people who buy an aftermarket exhaust system are more concerned with sound and looks.

04-10-2012, 08:24 AM	#1 (permalink)
robones Enthusiast Member Join Date: Mar 2011 Location: Miami Posts: 357 Drives: 2011 - Nissan 370 M6 Rep Power: 14	Anyone tested the Drag caused by swapping exhaust? Notice how the Z's exhaust is designed, it's engineered so that the air passing underneath the car curves through the bends of the exhaust through the rear diffuser in a smooth way. This causes less drag at high speed. By changing the exhaust to a two piece set up, i.e: Fast Intentions, Berk, etc. you are are creating essentially a parachute on the rear of the car. I would think drag is significantly increased by this design. When you remove the CAN design, the rear bumper gets exposed and creates a huge gap which traps air underneath the car just as its exiting through the rear. The better designs would be exhausts similar to the stock setup and/or the nismo setup. Stillen, Greddy have similar designs which leave less of a gap in the rear bumper. Your thoughts?

04-10-2012, 08:42 AM	#2 (permalink)
osbornsm A True Z Fanatic Join Date: Jun 2011 Location: WHAT Posts: 2,551 Drives: 2018 Camaro SS 1LE Rep Power: 423	You are absolutely correct... much like the square back of a VW golf creates a vacuum. However unless you are looking for absolute top speed of the vehicle, this may be just an academic observation. __________________ 2018 Camaro SS 1LE (455hp) - 2011 Nissan 370z (333hp) - 2004 VW R32 (240hp) - 2000 Civic Si (160hp)

04-10-2012, 08:59 AM	#3 (permalink)
LakeShow A True Z Fanatic Join Date: Dec 2010 Location: L.I., NY Posts: 5,307 Drives: Everything Rep Power: 25	Interesting point, never really thought of that. Significant to affect necessary performance, not really. __________________ \|2013 Audi S4\|Ibis White/Black\|S-Tronic P+\| \|2013 370z\|PearlWhite/Persimmon\|Touring/Sport/Nav\|F.I. CBE 18" CF\| \|Sold\|2011 370z\|Gun Metallic\|Touring/Sport/Nav\|

04-10-2012, 09:08 AM	#5 (permalink)
wheee! A True Z Fanatic Join Date: Sep 2009 Location: Mod Capital of Canada Age: 57 Posts: 7,354 Drives: cars. lots of cars. Rep Power: 40181	But the car goes much faster while standing still with the HKS style exhaust setup __________________ H&R / Stillen / Berk / HKS / Swift / Michelin / UpRev / SPC / Amuse Rep / Seibon / Fringe XVO / TWM / more... My Journal

04-10-2012, 09:34 AM	#8 (permalink)
wheee! A True Z Fanatic Join Date: Sep 2009 Location: Mod Capital of Canada Age: 57 Posts: 7,354 Drives: cars. lots of cars. Rep Power: 40181	I haven't noticed any issues at speeds around 240km/h.... __________________ H&R / Stillen / Berk / HKS / Swift / Michelin / UpRev / SPC / Amuse Rep / Seibon / Fringe XVO / TWM / more... My Journal

04-10-2012, 09:07 AM	#4 (permalink)
robones Enthusiast Member Join Date: Mar 2011 Location: Miami Posts: 357 Drives: 2011 - Nissan 370 M6 Rep Power: 14	Well just imagine how much drag you are creating at higher speeds? The higher the MPH the higher the drag your car is creating. I would think that any significant HP gain from these two piece setups systems would be offset by the increase in drag they create? I know the two piece setup sound nice and looks cool from the back but not much engineering thought is put into these systems IMHO.

04-10-2012, 09:32 AM	#7 (permalink)
DarkJak A True Z Fanatic Join Date: Jun 2011 Location: Madison, WI Posts: 1,390 Drives: 2009 370Z Rep Power: 13448	I've noticed that too. It's such a huge gap, and the back is mostly solid. There are several aftermarket exhausts that still use a setup similar to OEM though, like Invidia, Akrapovic, Ark DTS Type 1 (did that ever go into production?), and probably a couple more I can't recall. One could probably just put a flat piece over the entire area to cover it up if the drag really is significant.

04-10-2012, 09:35 AM	#9 (permalink)
TerribleONE A True Z Fanatic Join Date: Jan 2009 Location: Socal Posts: 10,203 Drives: WOT Rep Power: 5850	I see the difference being extremely minimal.. __________________ 638WHP 541WTQ @ 13.5PSI Build thread

04-10-2012, 09:59 AM	#10 (permalink)
Nick911sc A True Z Fanatic Join Date: Feb 2009 Location: Long Island, New York Posts: 1,698 Drives: 2010 Nissan GT-R Rep Power: 20	I'm going to sell my exhaust now and revert to stock. I need to make sure I'm as aerodynamic as possible.

04-10-2012, 10:31 AM	#13 (permalink)
my2004Z Enthusiast Member Join Date: Apr 2009 Location: New Mexico, USA Posts: 285 Drives: 09' 370Z w/Sport 7AT Rep Power: 37	Sounds like an opportunity for someone to develop a fireproof foam insert to fill the gap. Only way to find out is to line up a stock Z and a Z with upgraded exhaust and wind sail for a 1 mile race.

04-10-2012, 10:35 AM	#14 (permalink)
TerribleONE A True Z Fanatic Join Date: Jan 2009 Location: Socal Posts: 10,203 Drives: WOT Rep Power: 5850	Blocking it with something would just make things worse IMO... At least the canisters are round and they are pretty slick.. A straight wall would make it even harder for the air to go around __________________ 638WHP 541WTQ @ 13.5PSI Build thread

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