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Thread: Z8 Dyno Results

  1. #1
    Z8 Addict Z8doc's Avatar
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    Thumbs up Z8 Dyno Results

    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 ) 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!!

    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
     
    Last edited by Z8doc; April 16th 2006 at 16:40. Reason: information
    Best Regards,

    Jeff
    61995 Silver /// Rot - Original Owner
    Z8 Club of Germany e.V. #102

  2. #2
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    Talking Thanks!

    Thanks for doing and posting this. My car has identical mods, so it's nice to get some idea of their possible effects.

    Mike

  3. #3
    Z8Mania
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    Sounds about right- thanks for sharing the results!

  4. #4
    Team Z8 dwz8's Avatar
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    Very interesting results indeed. I will scan the report I got from my Dyno runs for comparison.

    The first time I did a run I had comparable mods:
    - Quaife plus 3.64
    - UUC clutch & flywheel
    - CDV
    - suspension mods
    I consider none of these as influential with regard to top performance. The gear change has an impact on acceleration and potentially torque at the wheels, but not engine power.

    Since my car was still limited in top speed at that time, all measuring was done in 4th gear. The top result was 376 PS.
    Depending on what hp means in your context, 1 PS equals either 1 hp, or 1 PS equals 0.986 320 073 horsepower. Hence the result was either 376 hp or 370.856. That would be the number to be compared to your 355.40 hp.

    The dyno I was on worked in a similar fashion, but there was one more step in the measuring cycle:
    After hitting the redline, you would disengage the clutch, and the dyno would measure the force it needed to maintain the same speed. Thus all losses in the drivetrain from clutch to wheels can be measured. In my case this added up to about 22 PS, which made a total of 398 PS for a stock engine, extremely close to spec.

    So the losses were much less in my case, approx. 5.85% only. If I use this percentage on your 355.40 hp, you would add about 20.79 hp, giving you a total of 376.19 hp.

    Raising the redline per se doesn't give you any additional power unless the motor management is adjusted accordingly, and potentially using different cams. This can be told from the 6.300 revs that give you already the highest performance.
    The Eisenmann exhaust should result in a minimal increase only.

    So two questions come to my mind:
    - what altitude were you at doing the dyno run?
    - do you have a chance to do a run that measures the losses in the drive train as well?

    I will look for the diagram over here and post it asap.
    Best regards, Dieter

    ....

  5. #5
    Z8 Addict Z8doc's Avatar
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    Quote Originally Posted by dwz8
    So two questions come to my mind:
    - what altitude were you at doing the dyno run?
    - do you have a chance to do a run that measures the losses in the drive train as well?

    I will look for the diagram over here and post it asap.
    The altitude here in Tulsa is 685 ft above sea level. It is my understanding that the software for the dyno corrects for differences in altitude, which is the conversion coefficient that I mentioned as 1.04. The actual numbers are mulitplied by this number which is a coefficient apparently developed by the SAE (Standardization of Automotive Engineers) here in the USA.

    Also, I am not sure regarding measuring the parasitic loss of the drive train directly. I will ask and get back to you.

    Interested in your numbers and graph. It was just fun to see what the car actually did, considering I have never seen or done that before. Made me a little nervous though sitting there on the dyno not going anywhere but the speedo reads 160! I had visions of being a pilot of an F16 on the flight deck of an aircraft carrier and the catapult is getting ready to launch me should the rear tires slip off the drums!
    Best Regards,

    Jeff
    61995 Silver /// Rot - Original Owner
    Z8 Club of Germany e.V. #102

  6. #6
    Administrator thegunguy's Avatar
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    Is that a shock tower deformation meter in the 4th pic?
    thegunguy

  7. #7
    Z8 Addict Z8doc's Avatar
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    No, No... it is a new way to try and correct the deformity...

    Quote Originally Posted by thegunguy
    Is that a shock tower deformation meter in the 4th pic?
    using electrical current. Micro-electrical "shock" therapy! (pun intended) The electrical current forces the electrons in the metal molecules to align themselves in parallel with the electrical current thus straightening the tower deformation. Problem is, when the electrical current is terminated, the electrons and their alignment, snap back to the original shape and the deformation mysteriously returns.

    Disclaimer: Anyone who believes this should have their head examined for faulty wiring themselves!
    Best Regards,

    Jeff
    61995 Silver /// Rot - Original Owner
    Z8 Club of Germany e.V. #102

  8. #8
    Team Z8 dwz8's Avatar
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    Finally, here is the scan of my dyno run, sorry for the delay.

    The green line shows the result of the stock engine before any modifications were made. That would be the one to be compared to your results.
    The blue line shows the result after the modification.


    I looked it up at the Dinan website, they state that there is no performance increase resulting from increasing the redline, which is what I expected. Since none of the mods you have increases the engine's performance, you see the results of a stock engine in the dyno run.

    I noticed that fuel quality may be different in the US, I always use 98 ROZ here. If the engine gets lower quality fuel it may react to this.
    Best regards, Dieter

    ....

  9. #9
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    could you restate your modifications re the blue line?

    Thanks very much!

  10. #10
    Team Z8 dwz8's Avatar
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    The changes include new camshafts, reworking and polishing of cylinder head, finetuning all moving parts, e.g. finebalancing crankshaft, pistons, valves, etc etc.
    Reprogramming of motor management, new exhaust headers, race cats, etc

    Redline is at 7.800 now, power at flywheel after last finetuning between 525 and 530 hp. Everything was done by Nowack auto+sport in Germany, see here and here.
    Best regards, Dieter

    ....

  11. #11
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    These are great results. I am glad that Nowack improved on their promises since our fellow Apples on the M5board wasn't so lucky with Nowack a couple of years ago.

    As for the discussion of drivetrain loss, when I dynoed my stock Z8 it made 338 RWHP corrected. That is pretty close to 15% if you assume 396 as the crank HP. Also that is what most M5ers suggest the magical number should be.

    The 376 PS or slightly less HP is the highest number I have ever seen for a stock Z8 or M5. If the number is correct, consider yourself very luckly. You have the best engine of all of us from the factory. Most owners don't make that power after spending 15k in mods.

    CW

  12. #12
    Z8 Addict Z8doc's Avatar
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    Yes but on any given day, any engine will....

    Quote Originally Posted by clauswagner
    These are great results. I am glad that Nowack improved on their promises since our fellow Apples on the M5board wasn't so lucky with Nowack a couple of years ago.

    As for the discussion of drivetrain loss, when I dynoed my stock Z8 it made 338 RWHP corrected. That is pretty close to 15% if you assume 396 as the crank HP. Also that is what most M5ers suggest the magical number should be.

    The 376 PS or slightly less HP is the highest number I have ever seen for a stock Z8 or M5. If the number is correct, consider yourself very luckly. You have the best engine of all of us from the factory. Most owners don't make that power after spending 15k in mods.

    CW
    perform differently due to the "conditions" of the day with regard to humidity, ambient temperature, altitude, barometric pressure as well as how well you forced the air into the engine compartment during each dyno pull as well as how cool the engine was, etc. etc, etc. Certainly not to discount the the 376PS of Dieter, that is impressive, but that can vary from dynamometer to another as different models (even of DynaJets) will arrive at slightly different readings.

    The best thing I see here is that the engines are performing at least very close to what was advertised (probably an average of several engines tested). Some manufacturers grossly overstate their HP / TQ ratings or understate them. At least we are getting what was advertised.

    My engine is stock except for the Dinan Stage 1 software and the Eisenmann exhaust, of which, only the exhaust will add any HP (advertised as only +10 hp gain) it dyno'ed at 355 RWHP, which with a +15 - 20 % calculation gives a range of 408 to 426 hp at the crank/flywheel. The RW torque is higher than expected on mine I think because of the different gearing (3.64 ratio), and is at 342 lb-ft with a range of 393 to 411 lb-ft (15-20%), but this could be erroneous calculation as the modification that changes the RW torque, occurs AFTER the crank so the amount of torque at the crank is probably the same as Stock, the gears change it after the engine which still results in an increase in acceleration, just differently.

    Point is -- IT"S ALL GOOD!
    Best Regards,

    Jeff
    61995 Silver /// Rot - Original Owner
    Z8 Club of Germany e.V. #102