Atlanta Dyno Day Pics & Videos (now up)!!
11-21-2004, 11:51 AM
#16
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Originally Posted by Campeck
and I dont see how them not crossing in the right place would make it innacurate or any kind of difference.
Calculation
11-21-2004, 01:28 PM
#17
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Too bad you don't have a picture of where my Blkbird melted the carpet - a 1' diameter hole right under the wastegate muffler
But it is disappointing to learn that I am leaving 50 HP on the table because of a faulty pop-off valve. Have to get that fixed - after all, 331HP at 5200rpm seems weak to me.
But it is disappointing to learn that I am leaving 50 HP on the table because of a faulty pop-off valve. Have to get that fixed - after all, 331HP at 5200rpm seems weak to me.
11-21-2004, 01:50 PM
#19
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To bad my starter went otherwise I would have shown up. By the time I rebuild my 944, my 944 will have already been rebuilt. At least the starter takes less than 15 minuites to change including lifting the car on jacks.
11-21-2004, 09:40 PM
#21
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Finally figured out how to harness my member webspace and got two videos up
First off we have my 2nd or 3rd dyno run to show how our cars were bogging as we first layed our foots down on the gas...we were told our cars were running rich... also proof of the mystery loops!
(right click, save as)
http://members.rennlist.com/tarheel9...684-short.mpeg
Now this is a clip of Mitch's '89 Turbo which wowed us all with 283 hp to the wheels!
(right click, save as)
http://members.rennlist.com/tarheel944s/MVI_1683.mpeg
First off we have my 2nd or 3rd dyno run to show how our cars were bogging as we first layed our foots down on the gas...we were told our cars were running rich... also proof of the mystery loops!
(right click, save as)
http://members.rennlist.com/tarheel9...684-short.mpeg
Now this is a clip of Mitch's '89 Turbo which wowed us all with 283 hp to the wheels!
(right click, save as)
http://members.rennlist.com/tarheel944s/MVI_1683.mpeg
11-21-2004, 09:45 PM
#22
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Originally Posted by tifosiman
Has anyone esplained the loops yet, Lucy?
Cheers
11-21-2004, 09:50 PM
#23
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Riff, I also remember the Dyno operator telling us that our cars were "confusing the computer" when they bogged. I dont know if there is room for Computer error, but it did seem like pretty much every car there had a hesitation at WOT.
11-21-2004, 10:07 PM
#24
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Originally Posted by BlkBird
Too bad you don't have a picture of where my Blkbird melted the carpet - a 1' diameter hole right under the wastegate muffler
(right click, save as)
http://members.rennlist.com/tarheel944s/turbofury.mpeg
11-22-2004, 02:59 PM
#26
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That was a nice day.
THe calibration of dyno unit was not done too well. Operator reguested running 3000 rpm on cars own tach and then he adjusted his rpms to 3000 on dyno computer.
The idea was let the dyno do the braking and hold the car at 3000 rpm for a second or two, then let rpms up to preset cut off point where dyno automatically puts enough load to keep engine from passing that point.
My 944 Turbo couldn't get past 2800 rpm on tach on fourth gear and dyno operator suggested using 2nd gear. I noticed that computer showed 3000 rpm when I was at 2800 on tach, I believe they did not reset tach after previous car and 944 turbo gearing was that much higher and dyno loaded my car there thinking we are at 3000 rpm. By switching to smaller gear he was able to calibrate the unit on lower driveshaft rpms and we could do the pulls.
Normally they use separate rpm feed from engine but this was just a demo and for free to a line of cars it serves it's purpose. It convinced me that everything is at it should have been in the engine, no overly rich or other dangerous situations. Few leaks were pointed out on the exhaust side.
Good info anyway.
THe calibration of dyno unit was not done too well. Operator reguested running 3000 rpm on cars own tach and then he adjusted his rpms to 3000 on dyno computer.
The idea was let the dyno do the braking and hold the car at 3000 rpm for a second or two, then let rpms up to preset cut off point where dyno automatically puts enough load to keep engine from passing that point.
My 944 Turbo couldn't get past 2800 rpm on tach on fourth gear and dyno operator suggested using 2nd gear. I noticed that computer showed 3000 rpm when I was at 2800 on tach, I believe they did not reset tach after previous car and 944 turbo gearing was that much higher and dyno loaded my car there thinking we are at 3000 rpm. By switching to smaller gear he was able to calibrate the unit on lower driveshaft rpms and we could do the pulls.
Normally they use separate rpm feed from engine but this was just a demo and for free to a line of cars it serves it's purpose. It convinced me that everything is at it should have been in the engine, no overly rich or other dangerous situations. Few leaks were pointed out on the exhaust side.
Good info anyway.
11-23-2004, 07:32 PM
#30
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Motor Werks Racing would like to say thank you to everyone who attended our open house and truly hope that you had a good time. This day was designed in appreciation of our customers allowing them the opportunity to obtain a dyno base run for their Porsche at no charge. Motor Werks Racing, an exclusively Porsche shop, deals with 99.9% track cars and very little with street cars.
In keeping with the theme of the day, we wanted to offer all attendees an opportunity to do a dyno run. With that in mind, minor adjustments had to made to accommodate everyone that attended. A true Dyno session requires extensive setup using optical tachometer, TDC markings, ports tapped into manifold for boost on turbo cars and vacuum on N/A cars and lots of practice. In order for all who attended to participate in the free dyno runs we were unable to attach the optical tachometer, vacuum lines and other various items to obtain a smooth and accurate reading. Although the readings appear erratic, the numbers obtained during the free dyno are very close to absolute numbers.
Jim Burke, the owner of PFM Engineering, graciously supplied the dyno for the event and has addressed, in conjunction with DynoPack, the questions presented on this thread.
Gear Ratio:
The DynoPack dyno reads the wheel RPM and calculates engine RPM using the gear ratio. If the actual gear ratio (transmission ratio * differential ratio) is known, this number is entered. Alternatively, the dyno operator can set gear ratio by using the vehicle tachometer.
In the interest of time at the Open House the vehicle tachometers were used to determine gear ratio. For serious dyno sessions, the engine RPM is measured using a calibrated optical tachometer.
Loops in Dyno Sheets:
The DynoPack dyno uses hydraulic force controlled by valves to apply torque to the axles. If the engine suddenly loses power for whatever reason, the computer may not be able to release torque quickly enough to allow the engine to smoothly accelerate. When power loss is severe, the RPM decreases before continuing the sweep. This produces a “loop” in the horsepower and torque curves. The driver also has to smoothly bring the RPM up to the initial RPM and then apply full Power in a controlled manner.
5252:
I don’t know where this urban legend got started, but torque and horsepower curves on graphs only cross at 5252RPM under one special condition!!! Unless the scaling is the same for both torque and horsepower the curves will NOT cross at 5252. By the Way, 5252 is the constant to compute horsepower when torque is expressed in Ft-Lb and speed in rev/min.
Excessive Engine Loading:
This is a problem I have discussed with DynaPack. Engines with low torque at low RPM are difficult to dyno on the DynaPack 3000. Running in a lower gear usually solves the problem, but a poorly tuned or sick engine will not get past the residual torque of the dyno.
As stated before, the dyno base runs and the Open House presented by Motor Werks Racing were meant to be a fun gathering for Porsche enthusiast. As far as the head and exhaust work on the N/A 944 absolutely other mods were performed. Although- stock rods and pistons were utilized as well as compression ratios. This is an ongoing project and not unlike other accredited engine builders, certain proprietary information will be protected. After all, absolute peak power is less important then the overall power under the line. We appreciate your input and welcome any questions you may have concerning our Open House or any of the vehicles that appear on this post.
Thank you
Motor Werks Racing
Exclusively Porsche
(770) 886-0686
In keeping with the theme of the day, we wanted to offer all attendees an opportunity to do a dyno run. With that in mind, minor adjustments had to made to accommodate everyone that attended. A true Dyno session requires extensive setup using optical tachometer, TDC markings, ports tapped into manifold for boost on turbo cars and vacuum on N/A cars and lots of practice. In order for all who attended to participate in the free dyno runs we were unable to attach the optical tachometer, vacuum lines and other various items to obtain a smooth and accurate reading. Although the readings appear erratic, the numbers obtained during the free dyno are very close to absolute numbers.
Jim Burke, the owner of PFM Engineering, graciously supplied the dyno for the event and has addressed, in conjunction with DynoPack, the questions presented on this thread.
Gear Ratio:
The DynoPack dyno reads the wheel RPM and calculates engine RPM using the gear ratio. If the actual gear ratio (transmission ratio * differential ratio) is known, this number is entered. Alternatively, the dyno operator can set gear ratio by using the vehicle tachometer.
In the interest of time at the Open House the vehicle tachometers were used to determine gear ratio. For serious dyno sessions, the engine RPM is measured using a calibrated optical tachometer.
Loops in Dyno Sheets:
The DynoPack dyno uses hydraulic force controlled by valves to apply torque to the axles. If the engine suddenly loses power for whatever reason, the computer may not be able to release torque quickly enough to allow the engine to smoothly accelerate. When power loss is severe, the RPM decreases before continuing the sweep. This produces a “loop” in the horsepower and torque curves. The driver also has to smoothly bring the RPM up to the initial RPM and then apply full Power in a controlled manner.
5252:
I don’t know where this urban legend got started, but torque and horsepower curves on graphs only cross at 5252RPM under one special condition!!! Unless the scaling is the same for both torque and horsepower the curves will NOT cross at 5252. By the Way, 5252 is the constant to compute horsepower when torque is expressed in Ft-Lb and speed in rev/min.
Excessive Engine Loading:
This is a problem I have discussed with DynaPack. Engines with low torque at low RPM are difficult to dyno on the DynaPack 3000. Running in a lower gear usually solves the problem, but a poorly tuned or sick engine will not get past the residual torque of the dyno.
As stated before, the dyno base runs and the Open House presented by Motor Werks Racing were meant to be a fun gathering for Porsche enthusiast. As far as the head and exhaust work on the N/A 944 absolutely other mods were performed. Although- stock rods and pistons were utilized as well as compression ratios. This is an ongoing project and not unlike other accredited engine builders, certain proprietary information will be protected. After all, absolute peak power is less important then the overall power under the line. We appreciate your input and welcome any questions you may have concerning our Open House or any of the vehicles that appear on this post.
Thank you
Motor Werks Racing
Exclusively Porsche
(770) 886-0686