I was just wondering; since Nissan spent a lot of time getting optimal airflow under the car, isnt' changing to one of the aftermarket exhaust systems going to have some detrimental effect? The stock exhaust cannister has that fairing welded on that I haven't seen present on any of the aftermarket units. Won't that change the center of pressure and the high speed handling traits of the car? Won't it also increase drag and hurt gas mileage? Look at the Injen exhaust, there is a big *** hole left behind with it's two seperate canisters.

 

C'mon, Steve. Don't go and burst everyone's bubble. I asked this SAME EXACT QUESTION when the first Stillen exhaust went on one of the cars here a couple of months back and NO ONE would address the concern.

I'm with you. I think it would negatively affect high-speed underbody flow.

 

Well, if you really are interested in that high speed control and the like, you can always find some way to fabricate some items for the underbody to maintain that optimal flow.

 

Can you think of a way to test this ?

 

Didnt make a diffenrce at Daytona for us. We have been running a dual exhaust for a long time now. We pinned up the part of the rear bumper that sticks down between where the old tips went.

 

So you did fill in the void? Do you guys run the Injen exhaust??

 

We are running Nismo headers,not cats and a straight dual exhaust all the way back....no mufflers. I believe our exhaust is 2"
or 2 1/4".
We are getting the latest/ updated Nismo headers this week which is improved over our current header.
Our sway bar is madde for dual exhaust!
You ll see the pictures soon.

 

I agree with you Steve, with all the different exhausts coming out now you would think someone would have caught this. Who is up to the task to make a difusser to the big *** hole left by after market exhaust.

 

It makes a great location for 16 row diff cooler and a 16 row tranny cooler!

 

I am just surprised the aftermarket does not account for it on any of the designs I have seen. Yeah, I have heard a few times that because of lack of airflow around the rear end, a cooler is necessary for heavy track use.

So it looks like big gains are there by losing the cats, running some O2 simulators, and running a pretty open dual exhaust all the way back.

 

I had the shield cut off of my old muffler and welded to my flowmaster.

 

as long as your new exhaust bottom is fairly smooth, and the rear bumper area still has about a < 4 degree up diffuser, similar to the stock setup. there will be no adverse drag effects.

nissan did ALOT of air tunnel testing for the undercarrage to get Zero Lift, and alot of it has to do with the rear section under neath the car..i.e. spare wheel well and the exhaust can surface..

if you have smooth airflow under the nose, the rear as to follow up as well. but you went with the borla exhaust, right? shouldnt be too much big "air pockets" after you remove the stock exhaust...

 

I was surprised when I looked under my car to see that I was missing an aluminum plate which I saw in an article in a magazine review of the Z. The picture showed an additional plate near the pre-silencer. I asked the dealer but they said they need to see the car.

Also doesn't the air flow under the car change when using the Nismo front and rear spoiler like downshift's race car?

 

jack,

If that was the Sport Compact Car article, they were using a pre-prod car. That piece doesn't exist on the production cars.

dwnshift,

If I understand you correctly, your feeling is that the high speed stability was not adversely affected by changing out to an exhaust that doesn't mimic the stock configuration?

JD

 

Well, changing the suspension and ride height will also effect the characteristics at high speeds, so it's more then just replacing the exhaust. The compairison is not quite apples to apples.

 

articfury: Thanks. It was the SCC article.

 

Very true, but a lower ride height should also help decrease lift by itself. I am looking into copying the stock piece onto an aftermarket piece now.

 

Check this out

I only scanned this website. Thought you guy might want to read it.

Aerodynamics is a very interesting field of study--based on my limited knowledge. Fluid behavior over complex geometries is diffucult to predict. Hence trial and error (especially for people that don't have access to a CFD program or a wind tunnel.)

 

So do you know where we can get some O2 sims?

 

What do you do if the "Check Eng." comes out for having no cats in the car?