QUOTE(volflo @ Oct 27 2004, 01:57 AM)
Went on the
Porsche Berlin site and they have photograph of their dyno.
Anybody know what it is/ if its good?
Florian,
The projected numbers are for your own good to see how your car develops over time.
Just to bad you never arranged a baseline of your car before the changes. It would have been nice to monitor the progress.
Which dyno totally depends on the system you will be using and how to translate the numbers.
My Volvo's have always been dyno'd at RICA in the Netherlands on a MAHA chassis dyno.
This system can measure the performance of the car by creating a rolling resistance and in a way emulating road situations. This is a so called static dyno system.
There are several ways of testing the car this way. One is to search for maximum output under load at a fixed RPM. The other way is to pick multiple RPM points in a row where the car needs to keep it's RPM point while the load is increasing until power collapses, nice for searching the detonation/ignition retarding limits. Every time the test is completed you move to the next RPM point. At the end the computer can produce a nice graph with the corresponding numbers.
Downside of this test is the enormous amount of heat going in to the car...
A nearly identical test is to increase RPM at the edge of the power delivery of the car. The dyno system can see where the power doesn't develop anymore so it increases RPM and starts measuring again. The amount of load can be set by the operator. This test is really killing for the engine. As a bystander you can see the RPM rise slowly but very smooth, like the car is accelerating in slowmotion. By reducing the load this process takes less time. At RICA they call this a so called quick run and it is a bit comparable to an inertia/dynamic type dyno system.
After performing the measuring of power the car needs to be rolled out until the wheels come to a stop and at this point the dyno can measure the energy going in to the drive train, the so called negative power, which represent the drivetrain losses. When finished the cumputer will calculate the numbers the results are plotted in corrected BHP, uncorrected BHP, torque and loss.
To use these numbers in the correct way you need to look at the corrected/uncorrected BHP numbers, not the wheel numbers because they will be lower compared to a inertia/dynamic dyno result. The cause for these differences can be found in the setup of both systems. Because of the load and the tires being "strangled" between two rollers instead of a big drum the overall resistance is higher.
RICA is using two fan's for different setups. One can produce 100 mph of air stream and the other near 50 mph.
When using a dynamic dyno system basically all you should do is to look at the wheel power results and nothing more. Unless the dyno system attempts to measure the negative power all calculations/conversions to engine power are useless, purely for indication.
Some people use loss figures of 12.5%, others 15% for manuals and between 18-25% for AT's...
Make sure you get the correct wheel numbers with a Dynojet type chassis dyno. Don't let the operator talk you in to a fictive loss numbers which needs to be entered in to the dyno computer.
Loss in non linear. You can't pick an X% loss and calculate through the rev band.
Loss at 1000 RPM is minimal, and AWD will show extreme losses at redline which will be as high 30-40%!. Power at the engine will develop while power at the wheels will drop after a certain point. Peak wheel HP is never in the same spot as peak engine HP.
For me the basic rule of thump, if the dyno is static and can measure losses use BHP.
If the dyno is dynamic use wheel HP which will always be relatively high.
Since US folks mostly use WHP as a base of power output your best choice would be to look for a Dynojet type or dynamic type dyno system and use these numbers to communicate on a forum like this. Using a static system and the results on a forum like this will only bring a lot of unfounded blah and confusion because a majority of the people simply do not understand how to look at these numbers. (No offence)
I did the same, I dyno'd my SwedeDemon at a Dynojet type dyno last year and asked for WHP only results. The results at the time were 284 WHP, the computer calculated 311 EHP, using the rule of thump guess losses the EHP numbers should be between 325 and 335... (Where did that 24 HP go??
)
In a way the results are only good for your car on your dyno system of choice on that time during the ambient circumstances of that day...
Static dyno is the way to go for you because you want your car to perform under constant load on the ring and with a static dyno you will come closest to the real situation. It is the only way to set the car up along the fine line of correct ignition timing. You don't want a high peaking HP dyno queen..
