dyno'd the 997gt3 today ...
01-05-2007, 04:24 AM
#16
Formula One Spin Doctor
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Originally Posted by my911rs
The air consupmtion of the engine should be a function of engine speed and load, not speed. The GT3 can develop 10 or so more HP at full speed due to ram effect. this would not show on a dyno. Quite possibly doing a test in 5th gear is not advisable for wear and tear reasons and maybe safety, but in pricipal peak HP can be determined in any given gear, and the air consumption would be the same regardless of the gear selection.
01-05-2007, 05:05 AM
#17
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on the subject of air flow and normally aspirated cars, I would point this out -
the air flow is of such importance that F1 teams build engine brakes immediately beneath their wind tunnels, so that the airscoop can be fed air at the appropriate speed.
Once again, the shortcomings of relying upon the chassis dyno for absolute as opposed to comparative data are highlighted.
One reason tuners love chassis dynos is their ability to fudge real data and to produce ANY ANSWER THEY WANT. Take your race car to Weissach to be tested, they take the engine out of the car and put it on an engine brake. Why can't more tuners do that? With the right equipment and mechanics, it really doesn't take long to drop an engine.
R+C
the air flow is of such importance that F1 teams build engine brakes immediately beneath their wind tunnels, so that the airscoop can be fed air at the appropriate speed.
Once again, the shortcomings of relying upon the chassis dyno for absolute as opposed to comparative data are highlighted.
One reason tuners love chassis dynos is their ability to fudge real data and to produce ANY ANSWER THEY WANT. Take your race car to Weissach to be tested, they take the engine out of the car and put it on an engine brake. Why can't more tuners do that? With the right equipment and mechanics, it really doesn't take long to drop an engine.
R+C
01-05-2007, 10:31 AM
#19
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Originally Posted by A.Wayne
this is not correct on the Hp issue , on a RR , the hp/tq numbers are affected by gear used . The air issue on a n/a car is being overstated , there is enough air in the building to make it happen ...the air flow is necessary to control temperature on the dyno.
Edit: obvoiusly ram air effects cannot be measured on a static dyno. PAG quote 10 or 15 hp at high speeds, but that's derived (rather than measured) based on quantifying the high pressure zone created beneath the wing.
01-05-2007, 10:45 AM
#20
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Originally Posted by 997gt3north
2nd gear for a gt3 moves the dyno rollers at 137kph / 85mph versus 5th gear in the gt3 which is 287kph / 178mph
Gary
01-05-2007, 11:30 AM
#21
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It is not such a matter of intake air supply for the engine, but cooling air supply.
In 5th gear at redline, the load on the engine has been much greater getting to that point vs 3rd gear at redline.
If you are unable to keep the engine cool during the time it takes to do a full rpm sweep, your data is meaningless.
Due to gear ratios, it takes longer to do a full rpm sweep in 5th vs 3rd. Trying to mimic air velocity for a given road speed is helpful in trying to replicate the cooling needs of the engine at that particular load.
All the 997 models are very susceptible to elevated intake air temps and cooling temps, and the ECU will jump maps, resulting in very erratic power results. Methodical cooling and cool down practices are mandatory for meaningful results.
In 5th gear at redline, the load on the engine has been much greater getting to that point vs 3rd gear at redline.
If you are unable to keep the engine cool during the time it takes to do a full rpm sweep, your data is meaningless.
Due to gear ratios, it takes longer to do a full rpm sweep in 5th vs 3rd. Trying to mimic air velocity for a given road speed is helpful in trying to replicate the cooling needs of the engine at that particular load.
All the 997 models are very susceptible to elevated intake air temps and cooling temps, and the ECU will jump maps, resulting in very erratic power results. Methodical cooling and cool down practices are mandatory for meaningful results.
01-05-2007, 01:36 PM
#23
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Originally Posted by Nordschleife
on the subject of air flow and normally aspirated cars, I would point this out -
the air flow is of such importance that F1 teams build engine brakes immediately beneath their wind tunnels, so that the airscoop can be fed air at the appropriate speed.
Once again, the shortcomings of relying upon the chassis dyno for absolute as opposed to comparative data are highlighted.
One reason tuners love chassis dynos is their ability to fudge real data and to produce ANY ANSWER THEY WANT. Take your race car to Weissach to be tested, they take the engine out of the car and put it on an engine brake. Why can't more tuners do that? With the right equipment and mechanics, it really doesn't take long to drop an engine.
R+C
the air flow is of such importance that F1 teams build engine brakes immediately beneath their wind tunnels, so that the airscoop can be fed air at the appropriate speed.
Once again, the shortcomings of relying upon the chassis dyno for absolute as opposed to comparative data are highlighted.
One reason tuners love chassis dynos is their ability to fudge real data and to produce ANY ANSWER THEY WANT. Take your race car to Weissach to be tested, they take the engine out of the car and put it on an engine brake. Why can't more tuners do that? With the right equipment and mechanics, it really doesn't take long to drop an engine.
R+C
Ohh I'M SORRY I DID NOT REALIZE THE GT3 WAS A F1 CAR , WITH A POSITIVE PRESSURE AIRBOX
Also the numbers can be fudged on any dyno ! if that is your intent and all dyno's are really just comparative tools THEY ALL RECORD AND PRODUCE NUMBERS +/- 5% typically of each other ...Chassis or engine dyno ...Most new engine dyno cells ( the best ones ) also uses a transmission , to simulate the gears , but R/R and engine dynos are just tools both have there strenght and weakness's. Engine dynos are more suited for developement work , so for a manufactuer or a engine builder doing repetitive modifications and developement work a ED makes more sense.. The chassis dyno is better for letting you see what you have as a complete package , testing this complete package or trouble shooting a problem is better solved this way as you are running your car as it is .
They are not mutually exclusive
Last edited by A.Wayne; 01-05-2007 at 02:39 PM.
01-19-2007, 06:20 PM
#24
Originally Posted by Todd/A.W.E.
In 5th gear at redline, the load on the engine has been much greater getting to that point vs 3rd gear at redline.
The local Dyno Dynamics dyno can somehow be re-calibrated but I think it still runs only to a "speed" limit which is below the 275 km/h the GT3 would be turning in 5th and given no wind resistance, it wouldn't have any trouble getting there.
What's the correction for gearing in 3rd to get torque?
01-19-2007, 07:11 PM
#25
The Rebel
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Originally Posted by Nordschleife
on the subject of air flow and normally aspirated cars, I would point this out -
the air flow is of such importance that F1 teams build engine brakes immediately beneath their wind tunnels, so that the airscoop can be fed air at the appropriate speed.
Once again, the shortcomings of relying upon the chassis dyno for absolute as opposed to comparative data are highlighted.
One reason tuners love chassis dynos is their ability to fudge real data and to produce ANY ANSWER THEY WANT. Take your race car to Weissach to be tested, they take the engine out of the car and put it on an engine brake. Why can't more tuners do that? With the right equipment and mechanics, it really doesn't take long to drop an engine.
R+C
the air flow is of such importance that F1 teams build engine brakes immediately beneath their wind tunnels, so that the airscoop can be fed air at the appropriate speed.
Once again, the shortcomings of relying upon the chassis dyno for absolute as opposed to comparative data are highlighted.
One reason tuners love chassis dynos is their ability to fudge real data and to produce ANY ANSWER THEY WANT. Take your race car to Weissach to be tested, they take the engine out of the car and put it on an engine brake. Why can't more tuners do that? With the right equipment and mechanics, it really doesn't take long to drop an engine.
R+C
01-19-2007, 07:23 PM
#26
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All of this Mumbo Jumbo....
Non temp controled environments....bla bla bla
With the chassis dyno no +benifit of the ram-air effect can be accounted for.
Results are just approximations (An inexact result adequate for a given purpose.)
Accurate...not really
Non temp controled environments....bla bla bla
With the chassis dyno no +benifit of the ram-air effect can be accounted for.
Results are just approximations (An inexact result adequate for a given purpose.)
Accurate...not really
