Money2536's Case Study: Dyno of Connected/Disconnected Exhaust Valves
12-19-2014 | 11:53 PM
#47
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Joined: Aug 2013
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From: The Villages, FL
Anybody else notice in the video how the front wheel rotation is fractionally behind the back ones? If I am correct this probably explains some of the unexplained horsepower "loss." The car is pushing the dyno to move the front wheels and the lag would indicate friction losses that sap horsepower. IMHO.
12-20-2014 | 12:00 AM
#49
Nordschleife Master
Joined: Oct 2014
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Dyno Jets normally give higher results than Mustang/DynaPak dynos. I asked the guys at Titan what their experience has been with their dyno. "Does it give similar results to other Dyno Jets?" Their answer was yes, but we are dealing with an AWD dyno. AWD dynos show greater drivetain losses than typical rear wheel versions.
I wasn't concerned with Peak HP numbers, but remember that this is a rear wheel drive car driving an AWD dyno with a link to the front wheels. So we are easily seeing an additional 10-15% in losses due to mechanical disadvantage. Thanks to Porsche finicky ECU you must drive the front wheels at the same time as the rear of the car will go into limp mode. Heck, I got a traction control and parking brake error that took about 10 miles to go away.
These are SAE numbers. Realistically the car is put somewhere between 410-430 at the wheels, but I was more concerned with the comparison of connected to disconnected which we accomplished.
I hope that makes sense.
I wasn't concerned with Peak HP numbers, but remember that this is a rear wheel drive car driving an AWD dyno with a link to the front wheels. So we are easily seeing an additional 10-15% in losses due to mechanical disadvantage. Thanks to Porsche finicky ECU you must drive the front wheels at the same time as the rear of the car will go into limp mode. Heck, I got a traction control and parking brake error that took about 10 miles to go away.
These are SAE numbers. Realistically the car is put somewhere between 410-430 at the wheels, but I was more concerned with the comparison of connected to disconnected which we accomplished.
I hope that makes sense.
It's interesting that the GT3 motor is putting down these numbers to the wheels. Given rear engine / RWD, I would have expected higher (low 400's).
Dynojets are very comparable. I'll throw mine on an AWD Dynojet when I get it in March to compare.
12-20-2014 | 12:40 AM
#51
Pro
Joined: Nov 2009
Posts: 548
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From: Georgia
like I said if the car will do 126mph in the qtr then I am a happy camper. I had a GT-R with 560rwhp on a dybo jet that did the qtr at 11.01 at 126.8. Best trap speed was a 127.8 at a slower et. Car was fast Even in a mild tune. If my car (picking up tomorrow!!) is even close to the as tested trap speed of 126 I will be very happy indeed. Thanks again money2536 for the efforts!!
12-20-2014 | 06:21 AM
#54
Racer
Joined: Aug 2014
Posts: 431
Likes: 1
Fantastic data. Many thanks Matt.
A couple of observations. First, perhaps the fan isn't blowing enough air over the top of the car to actually simulate the amount of air which would be entering the engine for the maximum ram effect which would occur when driving on the road. Maybe this would cause some amount of diminished HP/Torque during testing.
Second, I would have repeated the first run. It is anomalous enough that a repeat to confirm the result would have been nice to see.
Finally, the disconnected vs connected runs are similar enough in output as to be considered statistically insignificant differences.
If I'm reading this correctly, it seems that the default position for the GT3 should be PSE "on", regardless of whether an aftermarket system has been installed, and that disconnecting the valves has little effect on peak HP.
A couple of observations. First, perhaps the fan isn't blowing enough air over the top of the car to actually simulate the amount of air which would be entering the engine for the maximum ram effect which would occur when driving on the road. Maybe this would cause some amount of diminished HP/Torque during testing.
Second, I would have repeated the first run. It is anomalous enough that a repeat to confirm the result would have been nice to see.
Finally, the disconnected vs connected runs are similar enough in output as to be considered statistically insignificant differences.
If I'm reading this correctly, it seems that the default position for the GT3 should be PSE "on", regardless of whether an aftermarket system has been installed, and that disconnecting the valves has little effect on peak HP.
12-20-2014 | 06:58 AM
#55
Racer
Joined: Mar 2012
Posts: 363
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From: West Des Moines, Iowa
Your sapphire is beautiful, thanks for the info.
My Vette put down 450 RWHP on a new 4 wheel dyno on 91 octane, and just at 500HP on a rear hub dyno.
I would probably have skipped a 4 wheel dyno for the GT3, as the results were obviously lower than expected as everyone else has indicated.
12-20-2014 | 07:22 AM
#56
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Joined: Mar 2014
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From: Midwest
Can some one sum this up for me:
Okay, I also have the SW Bypass. If I plug the valves on my exhaust there should be no issues( no loss in torque/Hp)??
The PSE now is deemed obsolete because it is no longer needed?
Sorry - too early for me to think
Okay, I also have the SW Bypass. If I plug the valves on my exhaust there should be no issues( no loss in torque/Hp)??
The PSE now is deemed obsolete because it is no longer needed?
Sorry - too early for me to think
12-20-2014 | 07:55 AM
#57
Burning Brakes
Joined: Apr 2014
Posts: 960
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To sum it up Jimmy, the valve is there to eliminate drone at lower rpms, and it actually reduced performance. Regardless if the button is pressed or not. Unplugging the valve gives marginal performance and drone.
12-20-2014 | 08:02 AM
#58
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From: The Villages, FL
12-20-2014 | 08:06 AM
#59
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Joined: Aug 2013
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From: The Villages, FL
dont understand this comment. Dynos have no idea what kind of induction you are using and they don't lie.
Your sapphire is beautiful, thanks for the info.
My Vette put down 450 RWHP on a new 4 wheel dyno on 91 octane, and just at 500HP on a rear hub dyno.
I would probably have skipped a 4 wheel dyno for the GT3, as the results were obviously lower than expected as everyone else has indicated.
Your sapphire is beautiful, thanks for the info.
My Vette put down 450 RWHP on a new 4 wheel dyno on 91 octane, and just at 500HP on a rear hub dyno.
I would probably have skipped a 4 wheel dyno for the GT3, as the results were obviously lower than expected as everyone else has indicated.
You must have missed the comment that a RWD 991 911 won't work on a rear-wheel only dyno. If the front wheels aren't moving, the car goes limp.
12-20-2014 | 08:11 AM
#60
Thread Starter
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Joined: Aug 2013
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From: The Villages, FL
Fantastic data. Many thanks Matt.
A couple of observations. First, perhaps the fan isn't blowing enough air over the top of the car to actually simulate the amount of air which would be entering the engine for the maximum ram effect which would occur when driving on the road. Maybe this would cause some amount of diminished HP/Torque during testing.
Second, I would have repeated the first run. It is anomalous enough that a repeat to confirm the result would have been nice to see.
Finally, the disconnected vs connected runs are similar enough in output as to be considered statistically insignificant differences.
If I'm reading this correctly, it seems that the default position for the GT3 should be PSE "on", regardless of whether an aftermarket system has been installed, and that disconnecting the valves has little effect on peak HP.
A couple of observations. First, perhaps the fan isn't blowing enough air over the top of the car to actually simulate the amount of air which would be entering the engine for the maximum ram effect which would occur when driving on the road. Maybe this would cause some amount of diminished HP/Torque during testing.
Second, I would have repeated the first run. It is anomalous enough that a repeat to confirm the result would have been nice to see.
Finally, the disconnected vs connected runs are similar enough in output as to be considered statistically insignificant differences.
If I'm reading this correctly, it seems that the default position for the GT3 should be PSE "on", regardless of whether an aftermarket system has been installed, and that disconnecting the valves has little effect on peak HP.
We actually did the first run twice. It looked odd, so we reset the Dyno Jet and did it again with the same dip. You can also see similar dips in power/torque in the WOT/connected,PSE OFF run.
I also agree with you that the results of connected versus disconnected are very similar, which is what I was hoping to see. I just didn't want to see a low-end decrease in power. To confirm my suspicions, that data shows that we may even get a slight power increase, although largely insignificant.