cobalt

This was an interesting read and I am no expert just have some experience. I have access to a mustang dyno and I will say it is a disappointment to most who test their cars on it. Nearly every instance the car was tested on a dynojet the car showed considerably more power and torque. Interestingly one day as my friends just finished tuning a heavily modified Golf R on their dyno which showed 600 whp it was tested again hours later on a dynojet and showed nearly 700 whp. Same car same day similar conditions? What made the difference? I don't want to get into the debate just share my take.

There are so many factors not considered here. As any tool these things need to be maintained. Proper greasing and calibration of the mustang is critical and the grease is quite expensive. If you have ever done it you would understand why many shops might overlook it. Also something you never see is what are the weights of the rollers input as? I have seen some play with these numbers to show better results than they should be seeing. Everything is logged into the system and can be investigated. There was a time someone rented the dyno from my friends and the results were suspiciously high. When we looked at the values later noticed the person renting the dyno changed the values of the rollers increasing their weight showing that more energy was needed resulting in higher numbers. I find this to be a common issue in the tuning world where numbers mean more than actual performance.

We have not seen any measurable differences in numbers based on how the car was ratcheted down or wheel sizes changed, the system compensates quite accurately for environmental conditions.

As jorj7 so aptly put it the dyno is a tool and not about bragging rights as many seem to use it. There are many gains claimed by manufacturers that are erroneous and we have tested some of these products show little to no change and in some applications show loss of power instead of gains also where the power curve has been adjusted. This is where a dyno is best used, testing the baseline against the modified product. If you start with a dynojet I would stick with it and same with mustang although without a baseline it is just another data point without reference.

I thought this was an interesting read and my take on these.

​​​​​​https://www.igotasti.com/vBforum/thr...he-dream-maker

IcemanG17

Dyno's are just a tool. Only as good as the operator controlling it. Getting a perfect dyno tune at sea level and then racing at high altitude like George does isn't super helpful. Opposite is also true.

Its safe to say Georges car makes strong power......I think he quoted mid 500whp.....it takes a healthy amount of HP to push an automatic 928 to 219mph!!!! Yes his aerodynamics help, but power is king at ORR....Example Tim and Cheryl's beast made 515whp at near sea level and had very similar aero plus a 5 speed and their best was 209.9 GPS and I think 208 radar.... IF someone was brave and well funded, add boost to the Beast's stroker.....I would run E85 since the Beast is pretty high compression, but I don't know if it would make it the distance without running out of fuel! I think George got 7mpg on race fuel during his run.....-30% for E85....4.9mpg is cutting it close over 90 mile course and 20 gallon cell

If you took a road racing setup 928 to a ORR it would suffer from too much downforce=drag. I want to say Joe Fan's 928 racer made well over 500whp and hit 180mph at Fontana, I recall MK's hit some pretty high speeds at Road America with just the 5L

Speedtoys

As far as I know, only the Dynojet lab in Belgrade Montana can adjust the hardware stack setting for the drum mass. It's hard coded into the stack.

We have in competition compliance work..which is why we've had to define strict use of the tool, to get 'fair' data from every car in each class being measured. Someone with a hot spec motor could come in 10psi low, and you would miss 5Hp....in a roughly 140Hp class. Nowdays, they roll up with 'iffy' connections to the OBD port to capture timing data, that might be a DQ in the future too.

It's just a tool, use the same one every time, have it inspected by the manufacturer often.

cobalt

Depending on if it is AWD or RWD the numbers need to be adjusted to reflect the force applied against the mass of the rollers being used on the mustang as measured by the strain gage. I must assume the strapping down is an inertia dyno issue vs a load dyno. I see that they recently adjusted the rules to require only dynojets be used to test cars for time trials and eliminated the conversion charts they used for the mustang??

mark kibort

Yes, as we mentioned, air pressure in tires can change rolling friction. this is obviously seen in a coast down test comparison. but if you regulate the tire pressure,, a 4th gear dyno run will not show any measurable variance in wheel or tire size for the reasons ive listed .

again, keep in mind, a mustang dyno is a brake dyno. the car is supported by the mustang dyno attachments. there is a lot of vibration, and that imbalance can effect output dramatically. personally, ive never seen more than a 5 hp variance in using them vs the dynojet 248e. a dynojet 248e is a rolling inertial dyno and by definition, will provide HP output based on the acceleration of the drums. PERIOD. if you do it, you do it. there is no cheating it. KE (J) at time mark 1 vs KE (J) at time mark 2 and divide by the time (seconds) and you get HP (divide by 746). it's very simple.

mark kibort

Sure it's a tool, but a tool can be a very accurate measuring device that is repeatable. the 248e is such a device. there is very little variance between dynos. ive been on ALL of them in the bay area.. some even have changed hands to different shops. never have i seen a variance that is anywhere near significant. same motor, over 8 years, one over 4 years and the stroker over 10 years and the outputs are within a few hp . (for engine HP values of 290, 320 and 375hp) i think i worked out 5mpg at the race track by the way. near 20 on the hyway at 75mph cruise yep, and my 928 5liter with 320rwhp ran up to near the rev limiter and 25" tires in 4th gear (3.2:1) at 156mph on all 3 long straights at RA (and 156 at auto club speedway with the stroker down the main straight at 375rwhp)

ptuomov

Dyno is a tool, sure, but I think you can also race dynos. Some say racing dynos ia stupid. I say that this is undoubtedly true but it’s only marginally more stupid than grown men driving around in a circle.

cobalt

Interesting Mark. I guess we have different experiences. There are several 248e's by us and have a number of charts showing an average of 18% more power from them than the Mustang AWD 500.

mark kibort

what you can be assured, is the 248e is the yardstick for which all others can be measured. its not that it is higher or lower, it is true and correct . why? because you cant fool it. SOMETHING has to accelerate the drums and they are a known size and distrubution of mass, so therefore by definition they will be accurate. repeatable as well, which only will have a few factors to inject a variable..... strap down tension and tire pressure. The mustang awd dyno is much more complex and has many factors that need to be calibrated . again, usually , they should be accurate as well, buts its not a direct measurement of power as it is much more calculated and electronic dependent. ive been on a few of them... (mustang dynos) and again, i was a few hp off my 248e dyno runs with no changes to performance. 18%?? think about how much of a factor that is.......thats 50hp swing and i dont think that is normal AT all. could be operator or correction factor error.

you can see how they work, generally here: https://www.autocentral.com/doc/mode...eel-drive-0001 since its a 4wd dyno, could there be issues while only using 2 wheels? they have an eddy current measuring system to determine and extract hp and torque values. lots of internal programming calculations. i would look there for errors or wheel spin .

cobalt

IMO I believe you have that backwards. The mustang measures torque which is measurable. The Dynojet calculates HP which is not. I believe we will agree we disagree on which is more accurate.

ptuomov

dynojet inertia dyno measures the change in kinetic energy and time. What is measurable and not measurable is a philosophical question given the laws of Newtonian physics. One should rather focus on the bias and variance due to measurement error.

mark kibort

how do i have it backwards? Newtonian physics is very clear about this. rate change of Kinetic energy is defined as HP. (power). so, if you change the rotational rate of the rollers, it takes a certain amount of energy to do it , PERIOD. divide it by the time , you get HP. the mustang has calibrations in electronics (BEMF to determine torque), that are sensitive to many other factors that the dynojet is not. there sometimes is a lot of vibration of the coupling to the mustang dyno, this is not a disagreement, this is knowledge of how the dynojet works and why it is absolutely as accurate as a quartz watch and a scale /ruler to get the drum's dimensions and mass (weight)

Tony

What about the contact patch of the over or under inflated tires? ..and the Venturi effect they impose as they spin in the wheel well.

mark kibort

haha....

GregBBRD

If a single person who brags about absurd 928 horsepower, actually owned a flow bench, they would know how silly their claims are.
The stock heads will flow enough air to make right at 400hp (flywheel), at 100% volumetric efficiency.
....and none of these engines work at 100% volumetric efficiency.

If you figure your automatic transmissions "absorbs" 15% horsepower, 340 rear wheel horsepower equals 391 flywheel.
....anything more than that, with stock heads, is what dreams are made of.