Money2536's Case Study: Dyno of Connected/Disconnected Exhaust Valves
12-20-2014, 07:00 PM
#76
Rennlist Member
Matt
Well done buddy. First of all, thank you for taking a big one for the team. Really much appreciated.
The results are outstanding and ends the disput regarding the role of the PSE being on or off, and also dispel the theory of higher torque if the valves left connected at lower RPM. This indeed solves a big puzzle and thanks to you.
On the subject of lower overall wheel HP, as you indicated the numbers are only approximation and are only meant for comparison reasons only. As you indicated, the loses to turn the front wheel at the same speed as the back probably costs the GT3 a 15% to 20% total penalty if not more. But people also need to remember this GT3 engine oil, and coolant run pretty hot, and is very sensitive to temperature variations, and I recall when I punctured my radiator and coolant seeped slowely and the coolant temperature climbed slightly above normal levels, My butt dyno told me I lost some engine power, and it felt as if the car was running little richer mixture to reduce power and compensate for the added heat. I also recall when I had the thermostat issue and while it was stuck open and could not get the car to normal operating temperatures, the car again felt it was running in some limp mode and power again is reduced. So the car would not tolerate temperature variations above or below what it views as normal. I know during the test, they were running a fan to simulate air flow against the radiators while testing at these speeds, but unless you have really a fan big enough to produce 35,000 to 40,0000 CFM or higher pointed towards the radiator, the car is probably not getting the cooling it needs, and it is possible it was enriching the mixture or retarding the spark to compensate for the lower air flows passed the radiator.
My point about the above and as Matt indicated, the maximum HP figures are really meaningless and he was only interested in comparing the various runs so we all can gain some knowledge about the mystery of the PSE and the impact of the valves on low end torque & HP, and for that he deserves our gratitude and appreciation. Thank you Matt. Mark
Well done buddy. First of all, thank you for taking a big one for the team. Really much appreciated.
The results are outstanding and ends the disput regarding the role of the PSE being on or off, and also dispel the theory of higher torque if the valves left connected at lower RPM. This indeed solves a big puzzle and thanks to you.
On the subject of lower overall wheel HP, as you indicated the numbers are only approximation and are only meant for comparison reasons only. As you indicated, the loses to turn the front wheel at the same speed as the back probably costs the GT3 a 15% to 20% total penalty if not more. But people also need to remember this GT3 engine oil, and coolant run pretty hot, and is very sensitive to temperature variations, and I recall when I punctured my radiator and coolant seeped slowely and the coolant temperature climbed slightly above normal levels, My butt dyno told me I lost some engine power, and it felt as if the car was running little richer mixture to reduce power and compensate for the added heat. I also recall when I had the thermostat issue and while it was stuck open and could not get the car to normal operating temperatures, the car again felt it was running in some limp mode and power again is reduced. So the car would not tolerate temperature variations above or below what it views as normal. I know during the test, they were running a fan to simulate air flow against the radiators while testing at these speeds, but unless you have really a fan big enough to produce 35,000 to 40,0000 CFM or higher pointed towards the radiator, the car is probably not getting the cooling it needs, and it is possible it was enriching the mixture or retarding the spark to compensate for the lower air flows passed the radiator.
My point about the above and as Matt indicated, the maximum HP figures are really meaningless and he was only interested in comparing the various runs so we all can gain some knowledge about the mystery of the PSE and the impact of the valves on low end torque & HP, and for that he deserves our gratitude and appreciation. Thank you Matt. Mark
Last edited by mqandil; 12-21-2014 at 04:09 AM.
12-20-2014, 07:09 PM
#77
Rennlist Member
On he subject of power, I would have loved to see if these runs were repeated with PDK sport engaged. My understanding that engaging the PDK sport does not affect the HP, but again most of us also did not also expect the PSE to alter power. I would have been curious to verify the impact of engaging the PDK sport button on power. Mark
12-20-2014, 08:22 PM
#78
Three Wheelin'
Frankly, I'm over 800 miles now and am hitting 7k RPM. It sounds great as is so, I'm not even sure I want it much louder.
Dan (enjoyed some weekend driving
)
12-20-2014, 09:26 PM
#79
Three Wheelin'
If I'm right in thinking the valves open a hole in the exhaust between the side mufflers and the centre one then the effect ought to be greater with the stock exhaust.
12-20-2014, 09:34 PM
#80
Rennlist Member
12-20-2014, 10:12 PM
#81
Race Director
Try the mod, it's simple, see if the result is what you're looking for.
12-20-2014, 10:26 PM
#82
RL Community Team
Rennlist Member
Rennlist Member
Yep. The reality is I can install and if contested I'd happily assert Magnuson Moss if any issue arrises. But, I'm genuinely concerned my techs know something I don't. I was told there were some issues with older model GT3s with SW associated with back pressure. Another Rusnak customer had it installed despite recommendations against doing so and I'm waiting to see if any problems come up.
Frankly, I'm over 800 miles now and am hitting 7k RPM. It sounds great as is so, I'm not even sure I want it much louder.
Dan (enjoyed some weekend driving)
Frankly, I'm over 800 miles now and am hitting 7k RPM. It sounds great as is so, I'm not even sure I want it much louder.
Dan (enjoyed some weekend driving
)Interesting.
(FWIW, leaning towards not modding the car mechanically, except for a back-up camera.)
12-20-2014, 11:50 PM
#84
Rennlist Member
Thread Starter
I would guess tire pressure would factor a little in the dyno results. Do we even have to worry about a tire "blowing" with modern rubber technologies. I think it would simple go flat and the straps would hold the car in place.
12-21-2014, 12:15 AM
#85
Rennlist Member
Thread Starter
Matt,
Thank you for doing this. I've been waiting to see what results followed because I have a SW bypass and was told I should keep it off due to Porsche's concern that there is insufficient back pressure with third party exhaust and an inference that installing it could damage the engine. So, I plan to keep it off during break in and wait until after max power is supposed to be achieved after 10k miles per Andreas P as I've read in some thread or another.
Sharkwerks makes claim to very little change in power output change from the bypass installed. When someone tells you that you could have an insufficient back pressure problem, I would ask, "how do you know that?" The Sharkwerks bypass is simply routing the exhaust without baffling surrounding the pipe. What make a GT3 any different than any other car? Factory exhausts are optimized for the masses. Drone, loudness, etc. trump awesome sound.
I would prefer a linear exhaust note through-out the power band sounding like OEM after 3,700 RPM with PSE on instead of the tamer sounds with PSE off or with PSE on and RPM under 3,700. So, my first question is whether that will be achieved with valves disconnected and PSE button always depressed on? Is the best chance of having this sound take place with SW bypass installed, valves disconnected and PSE on? Will pressing PSE matter with SW installed and valves disconnected? These are my questions.
From my test, it appears that PSE button only controls the valves. I don't think the test is definitive, so I will be depressing the PSE button with the valves disconnected just be on the safe side. You will get a linear exhaust not and the valves disconnected with either the bypass or OEM. All the Sharkwerks does is make the factory note louder. I will tell you that disconnecting the valves with the OEM drones significantly more than with the bypass. But the exhaust note is louder at all RPMs with the bypass installed. I would guess 25% louder.
But, the biggest question relates to the above quote and chart. It seems to be the only chart that shows power loss. I wonder whether this is a fluke, one of a kind result or accurate and if something is going on that Porsche knows about but, still has the valve setting in place for a reason despite the power loss by having these valves. And, the question for that chart is, whether Porsche intentionally reduced horse power when PSE is off. OEM settings would be valves connected and I'd like to know if messing with those settings by disconnecting valves and adding SW, or any other after market exhaust for that matter, will create a problem with Porsche's OEM settings. With valves disconnected, that dip in power before 3,700 doesn't exist. In theory, peak performance is achieved by disconnecting the valves.
Run 3 confirms the power loss of Run 1. It just isn't as pronounced due the the X-Axis being much larger. Take notice to the dips at similar RPMs. With the valves connected and PSE off, there is clearly a dip. The part that perplexes me is that the valves still open at a similar RPM with the valves connected and PSE ON. I'm not sure why the power wouldn't dip just the same. This is why I question if PSE button actually changes timing or fuel delivery. The conclusion I draw is that Porsche simply makes the valves open and close for drone. Try disconnecting the valves with the factory center section and you'll see why. It's very boomy an droney.
My thought is, the answer to these questions as to peak performance and linear sound is to disconnect valves, add aftermarket exhaust, in my case the SW, keep PSE on (not sure how this would matter with valves disconnected other than perhaps ECU related changes for something unknown such as timing, air or fuel flow etc.). And, that the only remaining question is whether doing so will somehow harm the car. My guess is probably not. But, then I ask, why would Porsche technicians press for me to not mess with stock settings by adding the SW bypass. I was told "there is a lot going on at 3,700 when the sound changes with PSE on." They obviously know something I don't and perhaps something not being discussed on the forums. I'm not inclined to simply ignore the opinions of my dealership technicians who have received Porsche training, especially on such an expensive vehicle, during warranty and therefore, I have left off the SW bypass and am debating whether or not to install it at all. Responses to my questions will likely affect how I proceed.
Once again, what make a GT3 different from any other car where and aftermarket exhaust is used? Techs are just people make educated guesses. My educated guess tells me there is virtually zero chance of a simple bypass effecting the reliability of the car. I could understand someone saying removing the cats could be problematic, but a bypass? Personally, I am a risk averse person, but this seems to be a rather low if not no risk situation.
Thanks again for getting these results Matt. If you or anyone else has any answers to these questions and thoughts, I'd appreciate further comment or response.
Dan
Thank you for doing this. I've been waiting to see what results followed because I have a SW bypass and was told I should keep it off due to Porsche's concern that there is insufficient back pressure with third party exhaust and an inference that installing it could damage the engine. So, I plan to keep it off during break in and wait until after max power is supposed to be achieved after 10k miles per Andreas P as I've read in some thread or another.
Sharkwerks makes claim to very little change in power output change from the bypass installed. When someone tells you that you could have an insufficient back pressure problem, I would ask, "how do you know that?" The Sharkwerks bypass is simply routing the exhaust without baffling surrounding the pipe. What make a GT3 any different than any other car? Factory exhausts are optimized for the masses. Drone, loudness, etc. trump awesome sound.
I would prefer a linear exhaust note through-out the power band sounding like OEM after 3,700 RPM with PSE on instead of the tamer sounds with PSE off or with PSE on and RPM under 3,700. So, my first question is whether that will be achieved with valves disconnected and PSE button always depressed on? Is the best chance of having this sound take place with SW bypass installed, valves disconnected and PSE on? Will pressing PSE matter with SW installed and valves disconnected? These are my questions.
From my test, it appears that PSE button only controls the valves. I don't think the test is definitive, so I will be depressing the PSE button with the valves disconnected just be on the safe side. You will get a linear exhaust not and the valves disconnected with either the bypass or OEM. All the Sharkwerks does is make the factory note louder. I will tell you that disconnecting the valves with the OEM drones significantly more than with the bypass. But the exhaust note is louder at all RPMs with the bypass installed. I would guess 25% louder.
But, the biggest question relates to the above quote and chart. It seems to be the only chart that shows power loss. I wonder whether this is a fluke, one of a kind result or accurate and if something is going on that Porsche knows about but, still has the valve setting in place for a reason despite the power loss by having these valves. And, the question for that chart is, whether Porsche intentionally reduced horse power when PSE is off. OEM settings would be valves connected and I'd like to know if messing with those settings by disconnecting valves and adding SW, or any other after market exhaust for that matter, will create a problem with Porsche's OEM settings. With valves disconnected, that dip in power before 3,700 doesn't exist. In theory, peak performance is achieved by disconnecting the valves.
Run 3 confirms the power loss of Run 1. It just isn't as pronounced due the the X-Axis being much larger. Take notice to the dips at similar RPMs. With the valves connected and PSE off, there is clearly a dip. The part that perplexes me is that the valves still open at a similar RPM with the valves connected and PSE ON. I'm not sure why the power wouldn't dip just the same. This is why I question if PSE button actually changes timing or fuel delivery. The conclusion I draw is that Porsche simply makes the valves open and close for drone. Try disconnecting the valves with the factory center section and you'll see why. It's very boomy an droney.
My thought is, the answer to these questions as to peak performance and linear sound is to disconnect valves, add aftermarket exhaust, in my case the SW, keep PSE on (not sure how this would matter with valves disconnected other than perhaps ECU related changes for something unknown such as timing, air or fuel flow etc.). And, that the only remaining question is whether doing so will somehow harm the car. My guess is probably not. But, then I ask, why would Porsche technicians press for me to not mess with stock settings by adding the SW bypass. I was told "there is a lot going on at 3,700 when the sound changes with PSE on." They obviously know something I don't and perhaps something not being discussed on the forums. I'm not inclined to simply ignore the opinions of my dealership technicians who have received Porsche training, especially on such an expensive vehicle, during warranty and therefore, I have left off the SW bypass and am debating whether or not to install it at all. Responses to my questions will likely affect how I proceed.
Once again, what make a GT3 different from any other car where and aftermarket exhaust is used? Techs are just people make educated guesses. My educated guess tells me there is virtually zero chance of a simple bypass effecting the reliability of the car. I could understand someone saying removing the cats could be problematic, but a bypass? Personally, I am a risk averse person, but this seems to be a rather low if not no risk situation.
Thanks again for getting these results Matt. If you or anyone else has any answers to these questions and thoughts, I'd appreciate further comment or response.
Dan
12-21-2014, 05:19 AM
#87
Three Wheelin'
When the flappers open they do allow a shorter, more direct path through the cats to the center muffler although the side mufflers aren't closed off and completely bypassed when this happens. Differences in back pressure with different mufflers and bypasses, differences in the length of the exhaust tract; I keep thinking that we're dealing with a complex system so changes aren't always completely predictable, which is no doubt why manufacturers do so much testing.
Try the mod, it's simple, see if the result is what you're looking for.
Try the mod, it's simple, see if the result is what you're looking for.
So not sure how the valves make a cat or side muffler bypass. Am I misunderstanding something?
12-21-2014, 08:21 AM
#88
Rennlist Member
Thread Starter
It looks to me from a quick glance at the car and from not very good diagrams online that the order of events is engine, cats, side mufflers, valves, centre muffler, exit.
So not sure how the valves make a cat or side muffler bypass. Am I misunderstanding something?
So not sure how the valves make a cat or side muffler bypass. Am I misunderstanding something?
With the valves closed gases travel:
Engine > Header > Cat > Side Muffler > Center Muffler > Exit
With the valves open:
You still get all of the same flow above, but open valves give you an extra path.
Engine > Header > Cat> Direct Route to Center Muffler > Exit.
