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I wanted to chime in and see if i could add my $.02 on a few things.
1.) obviously we have beaten this horse to death but 5th gear being 1:1 is best...BUT...it's scary because it's 140ish mph on the dyno. It's even scarier in the Panamera Turbo BUT...i always wear my seatbelt when on the dyno! (not lying.)
2.) Some people tell me that you have to run 5 pulls for the ECU to finish sampling. Some say it's 100 miles. I have seen immediate reactions every time so i know it's immediate but i also see runs #2 and #3 always being higher than #1 no matter what the situation, scenario, time of day or what you had to eat for breakfast that morning.
3.) Fans are good for deliverying more air. What's most important though is being consistent. If you look at your 3rd dyno pull and you use fans every single time and the IATs and ambient temps are the same and you're in 5th gear every time, the Dynojet you are on will be repeateable as hell.
4.) I like to use 12.5% drivetrain loss when looking at power at the wheels vs. crank. this assumes though that i was in 5th gear.
5.) the numbers look low for the baseline but since it's in 3rd gear it's as to be expected and the after looks really strong.
6.) What is important is getting the exhaust air out of the dyno room. You can't see the damage that the CO is doing to the oxygen content in the air and the car is basically running on its own farts.
Every car is different. While the Dynojets are ridiculously repeatable, they may vary by a handful of ponies and torquers. In the end, what's important is the sum of all of your parts. A + B + C is always > just A!
Andy, it has been great chatting with you in regards to the dyno testing you’ve been pursuing, it has been a blast to watch and be a part of it! I think our next modification to your car should be a grappling hook to latch on to that Plaid on your next race haha. As we discussed recently the results on the dyno have not been realistic to those seen for various exhaust modifications on the new 718 4.0L platform, and there’s a variety of reasons that happened. Additionally fueled by some excellent feedback from Scott at Softronic, it is time to turn this into a nice educational post and set up the community with information that can be used to pursue accurate testing in the future. Let’s review our conversations and put some information out here about dyno testing and the basic requirements needed to do this properly and why.
A dyno is a measuring tool for changes to a vehicle. Dynos read very differently from each other, from brand to brand, location to location, model to model, and depending on how the dyno runs are performed by the dyno operator. You have variances from car to car and varying atmospheric / weather conditions on top of that. This is why taking a vehicle to a dyno and doing runs just to see where the car is at currently, or taking the car to another dyno after the baseline runs were done on a different dyno, provides pointless data because the variables are not the exact same. It is important to consider the dynamometer as a measuring tool only for changes to a given vehicle, and a dyno should be chosen and operated in a way that is consistent and accurate to measure that particular vehicle’s changes. Keeping that in mind, here are some basics on how to perform dyno testing on a modern Porsche, specifically the 718 GT4/Spyder/GTS platform.
Suggested Dyno Testing Requirements for Modern Porsches Including 718 GT4/Spyder/GTS 4.0
4WD linked dyno operating within 3% front to rear. A 2WD dyno or 4WD linked dyno that’s not within 3% front to rear requires a Porsche PIWIS diagnostic tool to put the car into dyno mode.
The dyno should be measuring torque. Horsepower is a derivative of torque, and this is how horsepower is calculated accurately and consistently.
Strong fans must blow into the radiator(s) and all intake/engine ducts to appropriately replicate real world conditions of air flow and performance potential.
The dyno should be monitoring rpm so the horsepower and torque lines on the graphs can be compared at the same data points for baseline and post modification runs to accurately show deltas of change throughout the entire powercurve, not just one particular point.
Dyno testing should consist of multiple baseline runs, then multiple post modification runs within as close a time frame and atmospheric conditions as the baseline runs, with no changes in any other variables. The car should also have a minimum of 30-50 miles after modifications installed, or after any ECU reset, for an acclimation / ECU relearn to show accurate performance numbers.
After having great conversations with Andy and using his dyno runs as a case study, there are several areas of low hanging fruit where the testing could have been done differently to more accurately test and show realistic and detailed results of the changes he made.
The car was run on a 2WD dyno - not a linked 4WD dyno - and was not run in dyno mode. This means that the car starts to generate faults because it doesn’t know what the front wheels are doing as far as speed, and it does not matter if you turn the stability control system off as it will still be active in the background. In these circumstances the ECU starts to interact by closing the throttle plate to correct for the traction control as it doesn’t see the front wheels spinning. The car would then need a reset procedure done followed by a driving period to relearn/acclimate before being run correctly. Unfortunately this means the numbers on the dyno runs were impacted and not accurate. To perform dyno runs on this car correctly would require a linked 4WD dyno or a 2WD dyno in Dyno Mode via a Porsche PIWIS computer. This would resolve the issue of the speed of the front wheels moving out of sync or not at all compared to the rear, and would prevent the faults that would close the throttle plate, keeping the runs accurate. If you run on a 4WD dyno and you still get faults it’s typically because the belts/chains have been stretched and the wheels are spinning out of sync more than about 3% which requires a dyno servicing. At that point you’d need to run the car in Dyno Mode, or find another dyno or have the belts/chains serviced on the dyno being run on.
This dyno did not measure torque. Instead it was calculating/estimating HP only based on variables such as gear ratios and tire size. Most dynos measure ft-lbs of resistance - a very accurate variable - to calculate torque and then derive the hp from this. As this dyno was not measuring torque, the HP estimation is not as accurate. A prime example of this is the different gearing on the runs showing different HP results with no other changes. This is not possible, and a dyno showing different power outputs for different gears is not correct. An engine does not produce more or less HP based on what gear is used. If an engine makes 400hp at 7k rpm in 3rd gear it will make 400hp at 7k rpm in 4th gear. Since the dyno used isn’t measuring torque and this car gains a lot of torque in the low-mid rpm range (especially from software), and HP is a derivative of torque on a typical dyno, this dyno isn’t going to give a realistic expectation of HP improvements especially in those areas.
The dyno did not record rpm, only mph. The runs started and ended at different mph, and the HP numbers were taken at different mph. This does not provide any accurate way to overlay runs and show a delta of performance changes at a given point throughout the powercurve. This is why it is advantageous to perform runs recording the rpm the vehicle is operating at, as this is always a consistent direct output of the engine itself. Regardless of gearing and mph, you can then see the exact torque and HP at a given rpm before and after changes, overlay the data, and see an accurate delta of improvement at any area of the powercurve.
The dyno runs did not replicate real world air flow. Fans on the front of the car are good for helping with consistent coolant temps, but not enough for proper intake and engine cooling. These cars were designed with side ducts for air flow to the intake system and for cooling the engine. Normally as speed increases, air goes through a low pressure area on the car and force feeds the side ducts into the intake system and engine cooling fan. By not having realistic air flow into the side intakes, this hurts the accuracy of the runs in two ways. First, you are not cooling the engine properly and this increases heat soak, reducing the performance potential. Second, you’re starving the engine air intake system. The intake system was specifically designed to be force fed air from the low pressure zone of air flow, providing more air than the engine could ever demand with even some positive pressure (think boost!). Instead, the engine is starved and is trying to pull in air through the intake system. Without properly supplied and realistic air flow to the side intakes you’re hitting a diminishing return on performance increases as it’s already struggling to make the power it’s currently at, therefore it won’t show the gains it could be showing with any changes.
Huge kudos where it is due, Andy has enthusiastically attempted more independent testing of his car than most on this forum have ever tried. It is a great opportunity for education on how to pursue this on your own, and do so in a way that accurately represents with data points the difference you feel when you drive the car. If anyone would like to go down the path of testing their car, be sure to consult with someone or a company with a specialty in Porsche vehicles. We are happy to be those people, and/or point you in the right direction to someone locally that meets those expectations. At the end of the day, nothing you’ll see on paper or on a computer is going to replace the experience of living it every day when you drive the car, so put that right foot down and have some fun!
Best Regards,
John Gaydos
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John Gaydos- Owner, Performance Specialist
Cell - (484) 883-6197 johng@soulpp.com
For the sake of pedantry however I'd like to correct the "dyno measures torque" bit.
Some dyno's measure torque, but a dynojet is of the inertia type and it calculates power directly without needing to know anything about the car. It knows the weight and diameter of its drum. That's all it needs. It knows how fast it is spinning and the rate of increase directly leads to horsepower.
A dynojet's torque measurement is calculated backwards from the power.
Now that we have the data can we all agree that the gear in which you're in on the dyno does in fact make a difference? It's a multiplier against a FDR. It's not rocket surgery! 5th gear is always best. Always nice to know other people get the same results. Nice work. You should be very happy. I bet she rips!
4th is enough for good results, just because you get a higher number in 5th doesn't mean a lot. The higher the gear the slower the RPMs climb so you are removing some of the inertia losses. The engine isn't doing anything dramatically different you just see higher wheel numbers. 3rd is probably too short/quick of a run on a dynojet.
Thanks John. That makes sense about the different gears. I was also confused if I must admit. So many different ways for a dyno to do something that seems so simple.
Thanks John. That makes sense about the different gears. I was also confused if I must admit. So many different ways for a dyno to do something that seems so simple.
Hello All,
I wanted to chime in and post the Dyno runs in 5 smoothing and it would be easier to see the base, with exhaust and then tuned with exhaust. While it shows the HP comparisons the runs should be in 4th or 5th gear. The gains will look different as the smoothing gets rid of the spikes also the end spikes can often give a false HP max as the dyno can do this more when hitting the REV limiter.
One did have the HP and TQ as a complete package so people could reference that dyno to other packages that are with a tune and complete exhaust and run on a DynoJet. The 3rd gear pulls do at least show there are gains for each mod so the same would apply to the 4th gear pull. The biggest gains in tuning these isn't the HP necessarily yet the TQ. The tuning we did to the 718 GT4 4.0Lt was along the same lines in gains we achieved with the 2016 GT4 3.8Lt while the engine is 200cc more the TQ was what Porsche mainly detuned the cars in as the 718 GT4 came with 309TQ and the 2016 GT4 came with 310TQ. Yet the 718 increased the HP to 414 from 385 in the 2016 GT4.
Porsche Interseries programmed along with teamed owned Tudor and World Challenge cars in an exclusive with Softronic.
Porsche PCA racing binary check by Softronic for compliance.
08-24-2021, 09:34 PM
