I also have concerns with this loss of the little winglet. The Amuse exhaust mimics the placement of the stock.

I'm going to make something out of aluminum or plastic that starts right behind the diff and blocks any airflow to above the mufflers or bumper.

On a side note, when I have some more time, I'm going to start smoothing out the bottom of the whole car. Has anyone else seen the bottom of a new C6? They are very flat on the bottom.

 

it seems we think alike

 

i see it more clearly, thanks for the pic

 

the stock piece is metal...probably not worth trying to re-use. i have a fuji ti catback which has a similar style muffler but there is no way to attach the stock diffuser. if somebody created a diffuser, hopefully it would work for both single and stock style mufflers. a full under body diffuser (plastic) would be nice, similar to that in the front area, and covering the mid to rear areas.

 

USafarice Quote:
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"Has anyone else seen the bottom of a new C6? They are very flat on the bottom......"
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I did a little research on the C6, and yes it is flat for the most part......believe it or not the Lexus 430 has a better coefficient of drag than the C6.......due in part to to Lexus's time and attention to underbody airflow.
The rear of the Vette seems absent of ground effects type work...

 

For us Borla owners .... I will see what I can fab up in the next few weeks.

This has always bothered me ... and I though I was the only one ... thanks for the motivation

 

There are subtle differences between the Injen and Greddy, but I imagine some sort of universal "plate" could be made to at least smooth out the back bumper in between the mufflers. A triangular peice would probably make the most sense....or a small winglet like on the stock muffler that directs air down and away from the open gap of the rear bumper.
(BTW- it may be metal, I never really touched it...it's just black, so I assumed it was plastic, but since the muffler gets hot, its probably is metal)

The first person to make something that bolts in there could potentially make some $$ if it looks decent.

Any pics of projects would be appreciated as well....but my skills are weak in metal fabrication techniques.

 

I haven't looked at a Borla too closely, but I think you guys have an advantage since the muffler part takes up a good section of the "pit" (abscess, gaping hole...etc)

You could fab something close to what they use on the stock muffler and probably be pretty confident that it works.

 

yeah this would be a cool thing to have... but how much of a diff will a plate make? i may get one if the price is right

 

I looked into this a Loooooooong time ago when i first got my RSR exhaust-

you lose the stock diffuser on the stock exhaust, it will affect the overall aerodynamics of the car, and no, you dont have to be in the triple digits to feel it.. pretty much anything over 60+mph and you'll get affects from wings and diffusers.

most importantly is where you start the diffuser from. generally you want to start your slope from just before the rear axle and gradually slope up.

from aerodynamics books from Joseph Katz-
Racecar Aerodynamics, it suggests no more than a 6 degree incline from the axle back

http://www.amazon.com/exec/obidos/tg...glance&s=books


from my previous research on the stock muffler it is practically a 6 degree slope,





i even drew it up in some engineering software,



but the problem is not producing this plate, its the mounting of it.

there are four bolts underneed the bumper that hold the heat sheild, unless you produce an Xbrace of some type its not going to be stong enough to hold the diffuser in place at high speed, since you will be effectively producing a suctioning low pressure effect (venturi).

i've thought about putting it next to the rear diff pumpkin like those images before , but again, its trying to make it work, rather where it would be optimal...

i have a cardboard/laminated piece already made for the rear end, but i tossed the idea of ever making it since its too hard to generically make a rear diffuser to fit all the aftermarket exhausts... the RSR is worst since there is a pipe that crosses in the middle RIGHT where i want to put the diffuser... *sigh*

those with the Greddy have a better option (and why i am soon to get that Evo2 exhaust) so that i can actualyl put something there where it will work-

if you know someone that will make this, then i got all the drawings still on my computer that i can forward... this is a good project, but in reality, its not that feesible unless everyone switches to the same exhaust.. its not good to mess with aerodynamics on a car...

to get rid of the 'parachute' effect, cut some vents into the rear bumper.. even if you put a plate to 'seal' it off, you'll still get air that will wrap around the edges....

 

the holes would have to be insanely big to have any effect. I can't quantify the amount of air going under the car but unless you cut most the rear bumper off, holes won't do it.

I'd rather stick a big block of foam to reduce the volume of the "chute". Something very light that won't melt or burn easy should do it... as long as drag is minimal under 90mph it's good enough.

 

here's a link that we discussed this in depth..

https://my350z.com/forum/showthread....=rear+diffuser

 

rear carbon diffuser ... mabey this will help.

 

Cutting holes....now there's an idea. I hadn't thought of that...but once you go down that road, you're stuck.
I imagine a rear mesh peice would look ok, if you could do it right.


Those cad drawings are sweet...that's exactly what I was looking for. Let me know when you get that EVO exhaust (mine is going on today) and I'll help fund your developement by buying one of your creations.

I figure mounting would be a pain...and the styrofoam idea just to stuff something in that space is probably what I'll try and do for now.

 

The only exhaust that I know of that utilizes a rear diffuser is the APS Exhaust.

 

I would not over and not underestimate this piece of metal but I would definitely not call it a "diffuser"!

It was a nice idea for the Nissan engineers to tilt the muffler the way they did and it was consequential to also mount this air guide to the now tilted muffler or it would have become counterproductive.

I hope you are getting my point.

Any muffler that is not tilted will not requiere the air guide! Fighting any "parachute" effect of the rear bumper cover is another story but I wonder how many cars before went away without anything like it...

 

if its not a diffuser than what is it....i couldn't find any reference to it in the manuals...its simply part of the muffler as far as nissan is concerned.

i would like to see if anyone has or could make a rear diffuser for the underside....mainly rear section of the z that would work for the stock style of muffler...or even better a universal one.

 

Since I have the Fujitsubo exhaust and the muffler is very similar in shape and placement, I was thinking of having a muffler shop remove the stock difuser and have them attach/weld it to the Fuji canister.

Any thoughts?

 

That would be a quick easy fix. I'd do it in a heartbeat.

I had my car up on the lift yesterday putting on the Greddy and I was noticing all the air difusers that are under the car...they're everywhere. Nissan payed some attention when doing this, which is why I hate the fact that I lost one.

Side note: There's a heat sheat under the trunk that gets removed when you put the greddy on....I might try and use this aluminum piece to make a new diffuser for the rear bumper. The cutting holes idea is possible too, but scares me.