FastestBusaAround

Is there any other reason besides noise levels as to why the exhaust flap stays closed under 3500 RPM? Does it have anything to do with low end TQ?

dougatl

The Z is definitely quieter with the flaps closed under 3500 rpms, you'll gain low end torque keeping them open and.or changing out the exhaust.
doug

Pipedreams

I am sure GM wanted the "cool" factor and to also have the car quite for the people that wanted it quite. Those are the only reasons. I have a few videos on my site www.nakidparts.com with exhaust open and close with and without headers

blazeone

The OP's speculation is well founded. It is a fact that higher exhaust back pressure at low rpms builds power and reduces high rpm power.

Same principle as large volume intake runners are good for high rpm power but rob low end power

Many motorcylce exhaust systems use valves and they are not there for sound. Other cars use two set of intake runners and use a valve to direct the intake air depending on rpm.

Now after saying all that, I believe in the case of the vette that it is a sound and wow device.

GMuffley

Torque is slightly higher with the flaps open.

FastestBusaAround

I would have thought TQ would have been lower at lower RPM w/flaps open. I've had several liter bikes and as Blazone said, they weren't there for sound, which is why I asked the question...

I'm not looking to change the exhaust just yet on my 08, as I like the OEM exhaust sound, but wondered if there would be significant loss of TQ at low RPM's. I was considering removing the fuse or installing the remote bypass...but don't want to lose any low end grunt in doing so. All the reading on this has given me mixed results on the TQ question so far.

TAILWAG

take the fuse off....drive it for a while - you WON'T notice the difference as far as "torque" goes...and, who cares what happens below 3,500 rpms anyway? 7,000 is where it's at!

FastestBusaAround

LOL, I'm not doing track days with the Z...it's mostly for when I'm too lazy to get on my ZX14 (Ninja). I just like to whack the throttle often, but I'm used to bikes that 1/4 in the 8's...and though a Z won't quite get the insane feeling of acceleration in comparison, I sure don't want to lose whatever's there now in low end TQ.

GTB/ZR-1

It'll be minimal, if much @ all, really. Nothing you should be able to pick up in the SOTP. I drive my car in both modes & am not able to pick up any noticeable difference.

Enjoy it

Steve R

I pulled my fuse to the flappers today but didn't like the interior resonance around town. So I'll try some B&Bs soon. I couldn't detect any difference in low end torque. I am also used to zx-14s and now have a 08 Busa with full ti system and dyno tuned . I bought the Z06 last weekend and my bikes have been sitting, which speaks volume for this car. I am head over heels with this ride.

Steve R

Oh Yea. Welcome!!

Luweegy

If you didn't like it with the fused pulled.You won't like B&B's for sure.Have fun with your new ride.

Red C6 Z06

I'm not sure that I can agree with you about that. When I pulled my fuse, I was severely disappointed because the drone at some [lower] RPMs was worse than any aftermarket drone I have ever heard. That is what bothered me. I liked the Borla Stingers on my C5 a lot better than the pulled NPP fuse on the C6Z.

FastestBusaAround

Oh man -- not what I wanted to hear...LMFAO -- I live bikes...and the Z was only for the lazy-don't-feel-like-gearing-up-for-a-ride-day. Here we go now -- so, what's faster, the 08 'Busa or the 08 ZX14? LOL -- kidding Steve and thanks for the input...

BTW, I went down one on the front and up 2 on the rear on the ZX, with a full Brock Gen III (flies out, mapped, 6" over, and +4 advance @193 RWHP)....I play with Vettes/Ferraris, etc and eat em up without as much as a single downshift at any speed now, still, the Z06 is a real thrill!

DSOM Z06

This is why I didn't pull my fuse. In 5th and 6th at certain lower RPM's the drone is intolerable with the flaps open.

LT2UnderGlass

Umm....yeah I would hope so...you're driving a 530lb machine with a power to weight ratio of .3058..
Mean bike though!
Cheers.

RWTD

The flaps OPEN definitely improve both horsepower and torque below 3.5k. See the difference in my car here (only look at the pre-3.5k, not the gains above, as that didn't come from the exhaust, but rather from the tuning):

TedG

There you go Steve, a flies out mod for cheap!!

jgaches

Why do you assume the gains down low aren't from the tune? We would need to see a stock to stock to gather any conclusions.

RWTD

Because I tuned the car! I know what it gained and what it didn't. Those ARE the gains down low. There's rarely any changes in power down low from just tuning alone. From a stock longblock comparison, the real gains start above 4k in the tuning process.

Besides, this is OLD news. You must be a late bloomer to this crowd. Tell you what, look below. Are you happy now?

Local friend and customer's 2008 Z06 before and after between the exhaust flaps opened and closed, both with the same tune.