Z8doc
April 16th 2006, 16:37
I put the Z8 on a DynaJet Dynamometer today at a local BMW Club gathering. This was the first time I have participated in putting a car on a dyno and needless to day, I was not disappointed.
As many of you know, many things can affect the cars performance and the accuracy and validity of the results vary widely depending on many factors including, Ambient temerature, humidity, barametric pressure and altitude. Also, the type of Dynomoter used can skew the results as some do a much better job duplicating real life driving than others do. According to what I have learned, the DynaJet Dynamometer is one, if not the best, at duplicating real road driving and therefore, the results are pretty accurate. The SAE (Standardization of Automotive Engineers) has a calculation coefficient that is built into the software of the DynaJet and will adjust the numbers achieved to account for the variables above. Other factors that affect the outcome are airflow into the engine, operating temperature of the engine as well.
This type of test will read maximum power and torque output to the REAR wheels. The amount you have at the crank/flywheel is a calculated value and generally follows this rule: For automatic transmissions, there is a parasitic loss from the crank/flywheel to the rear wheels (from transmission, drivetrain, rear gears, etc) of about 20 - 25%. For Manual transmissions, the parasitic loss is about 15 - 20%. So, add that amount back to the RW numbers for a close estimate of your engines actual output.
The cars are run through a series of runs, or pulls, as they are referred to. Usually first there is a test run, for automatics, you have to get your car to stay in the RW 1:1 gear (usually 3rd on a 4 speed auto or 4th on a 5 speed auto such as an Alpina Z8) and for manuals (usually 4th on a 5 speed or 5th on a 6 speed, like mine).
The after that, you do 3 pulls. The rear wheels are back onto the top of the DynaJet drums, which creat a load to your rear wheels similar to road driving. The car is then strapped down on all four corners to the floor anchors (we strapped to the suspension arms front and rear). Front tire blocks are place to further protect against movement.
The Dyno readings require removal of one of the electrical covers for the attachment of wires to the spark plug assembly so as to monitor ignition timing and rpms. High flow fans were placed at the front grills with the hood open in order to simulate airflow at speed during each pull. A probe is inserted one of the tailpipes to monitor air-fuel mixture. The Z8 has an H-connection in the exhaust which will equalize this reading so it makes no difference which side this is inserted to.
In order to avoid overheating conditions and to minimize that affecting performance, each pull was spaced about 10 minutes apart to allow the engine to cool between pulls. Next you turn the DSC off, and away you go, first the trial run, then the 3 pulls. Your ABS sensor light will come on but this is no worry, as it is sensing a malfunction on due to the rear wheels turning and the front ones are not. This will return to normal once you are back on the highway under normal conditions.
During the pulls, you start out just like driving, except you shift at about 2500 rpm until you reach your desired gear, in this case, 5th gear. Then YOU FLOOR IT and keep it there until you reach the rev limiter and shut it down after. Standard Z8 that is 6800 rpm, Dinan software, that is 7300 rpm.
My car is modified with the following:
Dinan Stage 1 software (rev limiter at 7300rpm and top speed limiter removed)
Eisenmann Race Exhaust
Quaife LSD with 3.64 gears
CDV removal
Dinan Stage 3 suspension (no affect here)
The results were interesting. The Trial was done with sport mode OFF and the next 3 pulls were done with the Sport mode ON. The Z8 actually increased in performance over each of the three pulls. The last was only slight better than the one before. The conditions were as follows: Ambient Temp: 87.32 deg F. Barometric pressure: 29.04 in-Hg. Humidity: 42%. SAE conversion coefficient: 1.04
Maximum RWHP = 355.40 @ 6300 rpm (5th gear - 160mph:D ) and Maximum TQ = 342.53 @ 3450 rpms with an average Air-fuel reading of 12.8 (the range for normal and best tuning is 12.5 (lean) to 13.5 (rich). In the lower RPM the air-fule was richer at 13.2 and as the RPM climbed, it leaned out to a low of 12.
The conversion range of adding the 15 - 20% to calculate the power / torque at the Crank/flywheel would be a max HP of 408.71 (15%) to 426.48 (20%). The max TQ would be 393.91 (15%) to 411.04 (20%). The DynaJet has a conversion table to estimate power which gave me a reading of Max HP of 418 HP and Max TQ of 404.
Considering the Stock specs listed for the Z8 are 394 HP and 368 lb-ft TQ, that is a substantial gain from just doing a few simple modifications. It was really worth doing and I would highly recommend doing this to your unmodified car to get a feel for where your baseline is and then repeat if after each modification you do to see how much your performance was enhanced. Besides, where else can you drive safely in the USA at a whopping 160 MPH!!:eek: :D
Here are a few pics of the process - enjoy!
For more information on DynaJet and the process you can go to Tulsa Dyno websitehttp://www.tulsadyno.com
As many of you know, many things can affect the cars performance and the accuracy and validity of the results vary widely depending on many factors including, Ambient temerature, humidity, barametric pressure and altitude. Also, the type of Dynomoter used can skew the results as some do a much better job duplicating real life driving than others do. According to what I have learned, the DynaJet Dynamometer is one, if not the best, at duplicating real road driving and therefore, the results are pretty accurate. The SAE (Standardization of Automotive Engineers) has a calculation coefficient that is built into the software of the DynaJet and will adjust the numbers achieved to account for the variables above. Other factors that affect the outcome are airflow into the engine, operating temperature of the engine as well.
This type of test will read maximum power and torque output to the REAR wheels. The amount you have at the crank/flywheel is a calculated value and generally follows this rule: For automatic transmissions, there is a parasitic loss from the crank/flywheel to the rear wheels (from transmission, drivetrain, rear gears, etc) of about 20 - 25%. For Manual transmissions, the parasitic loss is about 15 - 20%. So, add that amount back to the RW numbers for a close estimate of your engines actual output.
The cars are run through a series of runs, or pulls, as they are referred to. Usually first there is a test run, for automatics, you have to get your car to stay in the RW 1:1 gear (usually 3rd on a 4 speed auto or 4th on a 5 speed auto such as an Alpina Z8) and for manuals (usually 4th on a 5 speed or 5th on a 6 speed, like mine).
The after that, you do 3 pulls. The rear wheels are back onto the top of the DynaJet drums, which creat a load to your rear wheels similar to road driving. The car is then strapped down on all four corners to the floor anchors (we strapped to the suspension arms front and rear). Front tire blocks are place to further protect against movement.
The Dyno readings require removal of one of the electrical covers for the attachment of wires to the spark plug assembly so as to monitor ignition timing and rpms. High flow fans were placed at the front grills with the hood open in order to simulate airflow at speed during each pull. A probe is inserted one of the tailpipes to monitor air-fuel mixture. The Z8 has an H-connection in the exhaust which will equalize this reading so it makes no difference which side this is inserted to.
In order to avoid overheating conditions and to minimize that affecting performance, each pull was spaced about 10 minutes apart to allow the engine to cool between pulls. Next you turn the DSC off, and away you go, first the trial run, then the 3 pulls. Your ABS sensor light will come on but this is no worry, as it is sensing a malfunction on due to the rear wheels turning and the front ones are not. This will return to normal once you are back on the highway under normal conditions.
During the pulls, you start out just like driving, except you shift at about 2500 rpm until you reach your desired gear, in this case, 5th gear. Then YOU FLOOR IT and keep it there until you reach the rev limiter and shut it down after. Standard Z8 that is 6800 rpm, Dinan software, that is 7300 rpm.
My car is modified with the following:
Dinan Stage 1 software (rev limiter at 7300rpm and top speed limiter removed)
Eisenmann Race Exhaust
Quaife LSD with 3.64 gears
CDV removal
Dinan Stage 3 suspension (no affect here)
The results were interesting. The Trial was done with sport mode OFF and the next 3 pulls were done with the Sport mode ON. The Z8 actually increased in performance over each of the three pulls. The last was only slight better than the one before. The conditions were as follows: Ambient Temp: 87.32 deg F. Barometric pressure: 29.04 in-Hg. Humidity: 42%. SAE conversion coefficient: 1.04
Maximum RWHP = 355.40 @ 6300 rpm (5th gear - 160mph:D ) and Maximum TQ = 342.53 @ 3450 rpms with an average Air-fuel reading of 12.8 (the range for normal and best tuning is 12.5 (lean) to 13.5 (rich). In the lower RPM the air-fule was richer at 13.2 and as the RPM climbed, it leaned out to a low of 12.
The conversion range of adding the 15 - 20% to calculate the power / torque at the Crank/flywheel would be a max HP of 408.71 (15%) to 426.48 (20%). The max TQ would be 393.91 (15%) to 411.04 (20%). The DynaJet has a conversion table to estimate power which gave me a reading of Max HP of 418 HP and Max TQ of 404.
Considering the Stock specs listed for the Z8 are 394 HP and 368 lb-ft TQ, that is a substantial gain from just doing a few simple modifications. It was really worth doing and I would highly recommend doing this to your unmodified car to get a feel for where your baseline is and then repeat if after each modification you do to see how much your performance was enhanced. Besides, where else can you drive safely in the USA at a whopping 160 MPH!!:eek: :D
Here are a few pics of the process - enjoy!
For more information on DynaJet and the process you can go to Tulsa Dyno websitehttp://www.tulsadyno.com