Money2536's Case Study: Dyno of Connected/Disconnected Exhaust Valves
12-19-2014, 08:45 PM
#17
Nordschleife Master
Being I'm not up to speed as many of you here, my question is why is the GT3 rated at 475 hp and 325 ft lbs. but the dyno reports on Money's car shows much less. What am I interpreting incorrectly? 
12-19-2014, 08:52 PM
#18
Race Director
The big difference is that these read outs are for rear wheel horsepower. I'm no dyno expert, but honestly, given the car's performance numbers I would have expected higher numbers even at the rear wheels. Someone correct me if I have that wrong.
12-19-2014, 09:05 PM
#20
Burning Brakes
Great post Money! All dynos are different, but how conservative did they say their dyno performs? Also, what is the current thinking on drivetrain loss with Porsche's and the 991?
12-19-2014, 09:09 PM
#21
Car should be 425 with such low drivetrain loss or so at wheels.
12-19-2014, 09:24 PM
#23
Three Wheelin'
I am also curious about this. The max HP on the dyno charts seems to be ~380HP. Even with 15% drivetrain loss, the HP at the engine crank would work out to be ~437HP. Did the dyno guys give you a reason why it is reading so low?
12-19-2014, 09:31 PM
#25
Run 2:
PSE ON Connected Valves at Moderate Throttle in 3rd Gear from 2-5K
This shocked me a bit. It leads me to believe there is something more to the PSE button of than just the valves opening. Notice how much flatter the curves are. Remember the valve are still opening around the same RPM, yet we don't see a rather linear curve.
Matt
Can we break the valve operation into 3 areas: 1)Idle, 2) off idle up to ~4000rpm, and 3) above 4000rpm?
My understanding of PSE off based on your comments following Run 2 are:
1) valves closed
2) valves closed
3) valves open
With PSE on, I think the valve position would be:
1) valves open
2) valves closed
3) valves open
Is that correct? I thought PSE effected higher rpm as well.
12-19-2014, 09:36 PM
#26
Nordschleife Master
I think the dyno jet is the issue. I seem to remember back when i did my 996.2-3 back in 2005 at AWE Performance in PA that Mustang Dyno's gave more accurate results. My car with a Europipe exhaust did 377HP at the wheels.
12-19-2014, 09:46 PM
#27
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Hugh Wrote
It would be interesting to see a Z06 or some other radically different motor on the same Dyno back to back to see what kind of losses are being experienced through the dyno. This is really puzzling.
But as far as the work Matt did:I Love SICK engineers!! Its how humanity moves forward!!! On important $hit like this!!!!
Thanks for the work here! More concerning is a 100 hp drop. Drive train I thought should be 15% or so? Well if it will still do the qtr at 126mph as advertised who am i to care...
But as far as the work Matt did:I Love SICK engineers!! Its how humanity moves forward!!! On important $hit like this!!!!
12-19-2014, 09:46 PM
#28
This + US Gasoline is junk if you're using Premium US pump gas it's down 4 to 5 octane than the European equivalent.
12-19-2014, 09:47 PM
#29
Rennlist Member
Thanks Matt you did us all a solid.Great job
BTW does anyone know where the electrical plug for the valves are.?
On my 997 GT3 it was right up on the right side of the engine very easy to disconnect and reconnect (maybe 5 seconds )
Elliot
BTW does anyone know where the electrical plug for the valves are.?
On my 997 GT3 it was right up on the right side of the engine very easy to disconnect and reconnect (maybe 5 seconds )
Elliot
12-19-2014, 09:54 PM
#30
Burning Brakes
As he mentioned in the post the rears are also driving the front rollers which is a greater load. You can do a reverse negative run to calculate loss on dynojets but consistency between changes as opposed to ultimate numbers is more important. Was the throttle position sensor tapped for the various partial throttle runs so they were consistent? Have these been sae normalized? Any chance there was an intake air thermometer set between the runs to monitor loss fom heat gain?