[DGthe3]

Originally Posted by Richard0nee

Yeah not sure NPP really gained any additional hp/torqe.. I wondered what competitive mode yields vs track/sport.

On an unrelated topic, If the peak of HP if before 6k rpm and peak torqe is at 5200 rpm wouldn't it make sense to shift at 5200-5500 rpms? Why waste time hitting redline if after 6k the power especially torque will drop?

Just one of the things I wondered.

Power accelerates, not torque. Torque determines how much power you make at a particular rpm.

For fastest acceleration, you want to make the most average power.

[Richard0nee]

Originally Posted by DGthe3

Power accelerates, not torque. Torque determines how much power you make at a particular rpm.

For fastest acceleration, you want to make the most average power.

Hmm.. so then on his graph, the most average power would be at 5200 rpm? HP peaks at 5900 rpm.. so shifting at 5900 rpm would be ideal I'm assuming.

I have drove a lot of cars fast but never really tried to based it off the powerband :/

[DGthe3]

Originally Posted by Richard0nee

Hmm.. so then on his graph, the most average power would be at 5200 rpm? HP peaks at 5900 rpm.. so shifting at 5900 rpm would be ideal I'm assuming.

I have drove a lot of cars fast but never really tried to based it off the powerband :/

It depends on how much the rpms dropoff each shift, but its probably going to be at or near redline.

For the sake of argument, lets say it drops by 1500 rpm every single time.

Shifting at 5900, based on the above dyno, you'd go from about 380 hp down to about 330 hp @ 4400. The curve is skewed slightly to the top end, so the overall average is going to be something like 360 to 365 hp.

Now, if you wait and shifted at 6250 rpm it would be going from about 355 hp to pretty much the same 355 hp at 4750. The kinda flat power peak is going to be in the middle of that, so I'd estimate the average to be around 370-375. Just slightly more than shifting at peak power. Not enough to make a big difference, but more power is more power.

I drew some lines on the dyno chart from above to help illustrate my point. The horizontal line is the approximate average power being made between the vertical lines (the rpm you shift at & what the engine goes down to)

[Richard0nee]

Originally Posted by DGthe3

It depends on how much the rpms dropoff each shift, but its probably going to be at or near redline.

For the sake of argument, lets say it drops by 1500 rpm every single time.

Shifting at 5900, based on the above dyno, you'd go from about 380 hp down to about 330 hp @ 4400. The curve is skewed slightly to the top end, so the overall average is going to be something like 360 to 365 hp.

Now, if you wait and shifted at 6250 rpm it would be going from about 355 hp to pretty much the same 355 hp at 4750. The kinda flat power peak is going to be in the middle of that, so I'd estimate the average to be around 370-375. Just slightly more than shifting at peak power. Not enough to make a big difference, but more power is more power.

I drew some lines on the dyno chart from above to help illustrate my point. The horizontal line is the approximate average power being made between the vertical lines (the rpm you shift at & what the engine goes down to)

Thanks man! Using a 1500 rpm drop off shifting at redline I will be more into the powerband vs shifting before redline after each shift.

Makes sense.. trying to stay at the high powerband level is a critical factor.. I see why tuners alter shift points, etc.

[crankaholic]

DGthe3 is correct. It's all about area under the power curve - the rev range with the largest area will yield the fastest acceleration... doesn't matter that torque, or even power, started to drop off - if the area of that range is larger, you'll accelerate faster.

OP, I'm pretty sure NPP opens the flaps after a certain RPM in all modes. Unless you disconnect the valve servos in the closed position, there's really no way to test this.

[bluerayone]

Parish8 thanks for posting your dyno results. One question though, what was the difference between open runs 1 and 3 (in other words, why the third pull, what were you testing there or trying to bring out).

I am surprised it was not more restrictive with the cutouts closed. In my other post in the camaro5 forum (link to that post in the beginning of this tread) I posted a cutout of Gen 6 NPP muffler

If I were to guess how an NPP muffler was designed I would have thought the inlet would have emptied into the muffler with equal access to both pipes exiting the muffler. Instead the gen 6 NPP cutout diagram reveals the inlet empties directly into the cutout pipe and bypass only occurs only when valve is closed and exhaust is forced through perforations in cut out pipe to reach the inner pipe.

I would have thought that design would be inherently restrictive,however, given your dyno results, guess its not. Apparently engineers have included enough perforations in the cut out pipe to feed the exhaust capacity of 2 1/2 in inner pipe without restricting too much.

All posters on this thread predicting a marginal HP difference (if any) were right. Apparently NPP is more of a noise maker (that I appreciate once in awhile), giving a panacea effect of more power akin to sticking a card in the spokes of your bicycle when you were a kid.

Good to know. Thank you for your post.

[parish8]

I got 3 runs for $75 so I made 3 runs. it is a good thing I did or we might have attributed the loss in hp to the cut out being closed on the 2nd run. the runs were only about 5-10minutes apart and I believe it lost power due to heat soak but I am not 100% sure of anything on this car yet.

someone mentioned above they think the cut out opens at wot even in stealth mode. I don't think it does but I am not 100% sure of that. my a/f ratio also got leaner each run. not sure why and if that may have been the cause of the hp loss. there are still too many unknowns to be sure the cut out doesn't add any power but we have a little more info than before.

[Deadi9mm]

Parish8 how many miles on your 2017

[parish8]

400, the car is just 1 week old.

and it has its first door ding. sometimes I hate people...

[bluerayone]

Parish, that is why I asked about your 3rd pull, I noticed your HP/ TQ fell off with each successive run suggesting other factors may have contributed to the power loss and if true then its quite possible there is no power difference between open and closed.

I have a 2015 2SS/RS 6M. Most of the time i run closed (though I must admit open is growing on me, it's just very loud at start up, and until engine warms up). I clamp the actuators. and can easily reach down and slide the clamps off without looking under the car, putting clamps back on takes less than a minute. Of course I realize there are more elegant solutions for gen 5 owner like 3-way switches to control the valves from the seat (not the street..LOL), and you can always alter the wiring much cheaper then a 3-way switch as suggested by a poster in this thread. There is also the very convenient Palmer Engineering's Dashlogic than can close the flaps using the cruise control buttona, but I worry about battery drain with that setup as dashlogic connect to the ODBC II and I believe that connector is alway hot (though I'm sure stand by power is minimal, and my concern unwarranted, just don't like the thought of any battery drain, especially since I historically run closed most of the time, though I becoming more intrigue with stock operation lately which is open 75 percent of the time)

On your point about your flaps possibly being opened at WOT in stealth node, not sure however I have read the 2016 owners manual and there is brief mention not to run in stealth if you're tracking the car so I wonder why chevy would be concerned if WOT overrode stealth flap setting, it would suggest to me that it may not.

[enzia35]

Why we gotta know calculus for this stuff...I had enough of that in collage.

[bluerayone]

crankaholic , about your remark on no way of testing the flaps at WOT , there are youtube videos posted of Gen 6 owners running test runs of different modes with camera / and mic mounted on the rear of the car aimed at the exhaust. Thats a lot of trouble to go through but certainly one way of testing your theory (and of course on a Dyno it would be easy, just set a stationary camera aimed at the exhaust as you going through the run to see whats going on ..)

[Deadi9mm]

Parish8 your Dyno numbers should go up when you get a few thousand miles on your car hopefully a little over 400

[irmb]

Originally Posted by bluerayone

I have a thread in the Gen 5 forum http://www.camaro5.com/forums/showthread.php?t=463992
thought I check with here with you Gen 6 owners too.. granted we don't have same type of NPP system, however its a similar design and your cars have the built in capability to easily toggle between exhausts modes so you may have more insight in what I am looking for: the perceive power difference (or better yet, dyno pull results to track time sheets) running between stealth and track. Is there a great power difference between the two or is it just a noise maker as some suggest and perceived power increase is a panacea effect from the louder more powerful sounding exhaust

If there is any power is waking up and pissing off the neighbors - then NPP makes lots of it!