Topic: What Dyno?

[PubliusE]

I posted this on the "Big" board last night and didn't get a single reply.  So, I figured I'll try over here and see what you guys have to say.  I think this is more down your alley anyway.

OK, I'm thinking about putting my car on a Dyno just to see what numbers I can get. Just curious to see what the GMPP tune, CAI and RPI exhaust will produce. I know very little about this. So I figured I throw it out to you guys. One shop has a AWD Dynpack 5500 and a Mustang 1750DE dyno. Another has an AWD Mustang 500SE dyno. Both seem to claim the AWD models are better. I guess if I had an EVO I might understand but I don't. Can some of you guys offer your opinion on one system/model over another and why? Educate me! 

[Critterman]

I don't know that much about dyno's but it is my understanding that the Mustang will give you higher numbers.

[DeepBlueGXP]

Eddie (spl?) dynos are the most accurate.
What you need to do is get the runs on a thumb drive afterwards and post them here.  There is software you can download for free to see the graph on your PC.  WinPEP 7.  Thanks for the tips Dave and Randy at DDM

It's really difficult to compare as each car acts differently on different dynos and depending on your Altitude, Temperature and Humidity, values can change.   

[PubliusE]

Eddie (spl?) dynos are the most accurate.
What you need to do is get the runs on a thumb drive afterwards and post them here.  There is software you can download for free to see the graph on your PC.  WinPEP 7.  Thanks for the tips Dave and Randy at DDM

It's really difficult to compare as each car acts differently on different dynos and depending on your Altitude, Temperature and Humidity, values can change.   

I understand that those factors will effect your reading.  What I'm wondering is all things equal which is best for a real wheel Solstice?  One tuning site states:
From the Mustang Dyno site:

"It's true -- any dyno will spin the tires, do some figuring and print a graph. But some can do more than others. Here are some facts: Mustang Dynamometers are unique. All Mustang Dynamometers are loading dynamometers designed to duplicate real world operating conditions. Our patented control system uses eddy current power absorbers to load a vehicle exactly the way it would be loaded on the street -- including wind resistance, which is a significant factor in high-speed testing. Mustang dynos also feature a load cell to measure the power being applied to the rolls."

Without going into a lot of theory, a Mustang dyno gives you a real world tune, every time. The model that XYZ Company uses to tune some of the fastest cars in the tri-state area is an all-wheel drive model that is capable of testing both axles under the same imposed load, while at the same time syncronizig front and rear wheel speed. This ability allows us to test the newest in assymetrical AWD systems safely without risk to the car's differentials.

The other site which has two different Dyno states:
The Dynapack AWD setup with full feature Wideband 0/2, boost pressure sensors, and a variety of other small features that make this dyno our favorite and only chassis tuning device. Mustang Dyno With the growth of XYZ Company and our client list becoming more diverse, we realized that many of our domestic customers felt that a roller dyno was the only true way of getting an accurate reading of a cars power potential, though we may not agree with this, we wanted to please our clients.  With that came the decision to purchase our latest dyno, the Mustang 1750DE. It is an above ground chassis dyno, and has some neat features that we believe our 2WD customers will appreciate. The mustang dyno also has a full MoTec 5 gas Wideband 02 setup, boost pressure sensors, and a very cool 1/4 mile simulation system that is being added this month.

The marketing of the second site sounds better, but I really don't know if it is just BS. 

[lil goat]

OK the AWD or not of a dyno has absolutely no relevance to our cars, I believe that all of the dyno's you mentioned are eddy current as they are newer dyno's. They will all give you fairly accurate numbers, Dynojets (inertia type) are usually a bit higher than others, Mustangs are whatever the installer had a mind to do, I have seen them read higher AND lower. I just steer clear of them. I think if you can find one a Super Flow will give the most accurate numbers, all be it the lowest usually by a lot. Now for the truth, dyno numbers don't matter period. Unless you have a dyno sheet from the car before the mods and one from it after, hopefully on the same dyno they numbers mean nothing. I know on a Dyno Dynamics dyno there is actually a setting to make the numbers read like they would on a DynoJet inertia (drum) dyno, this is called compensation. It can be set to anything the operator wants, in other words the dyno can give you any output you want to see. I can get a dyno sheet for my car that says 400 HP if I want, it won't mean anything but easy enough to get. The delta or change from before and after is the only really relevent number. A Dynapack and a DynoJet are not the same company here is some reading.
http://home.earthlink.net/~spchurch/churchautomotivetesting/id12.html

[lil goat]

OK did a bit of searching and found this, while I don't necessarily agree about the Mustang Dyno, the theory about Eddy Current dyno's in general

Here's how I like to explain the difference. . . by Mike Hornback

DynoJets are inertia dynos, and have been around for years, much longer than any type of load cell dyno. Inertia dyno's work on the principle of the acceleration of a known mass over time. Their rollers are the known mass. Weighing in at over 2500lbs or so. Your car gets strapped down to the machine, and the dyno collects it's data. It is able to calculate horsepower by measuring the acceleration in rpm of the rollers in regards to RPM. This is why gearing can affect the dyno results, more on that in a bit. Now that the dyno has recorded the horsepower curve, it can take the integral of that curve and get the torque curve. Since the dyno’s power calculations are based on the acceleration of mass over time in regards to RPM, gearing is very important. Since a vehicle with a lower gear ratio can accelerate the mass to a higher speed using less engine RPM, it will show a higher horsepower number than a car with a higher gear ratio. If a car is able to accelerate the dyno’s rollers from 200rpm (roller) to 300rpm (roller)in 1500rpm (engine), then the dyno is going to record more power than a car that did that in 2000rpm (engine).

Now we go to Mustang dyno’s and other loaded dyno’s. Our Mustang MD-1100SE dyno’s rollers weigh 2560lbs. That is the actual mass of the rollers, much like the DynoJet. That's about where all the similarities end. When we get a car on our dyno, we enter two constants for the dyno’s algorithms. One being the vehicle weight, the other being what's called Horsepower At 50mph”. This is a number that represents how much horsepower it takes for the vehicle to push the air to maintain 50mph. This is used as the aerodynamic force. Mustang dyno’s are also equipped with a eddy currant load cell. Think of a magnetic brake from a freight train. This magnetic brake can apply enough resistance to stall a big rig. Off one side of the eddy currant load cell, there is a cantilever with a 5volt reference load sensor (strain gage). As the rollers are spinning this load sensor is measuring the actual torque being applied. So as the rollers spin, the load sensor is measuring the force being applied, sending that information to the dyno computer, taking into account the two constants entered earlier, computing the amount of resistance needed to be applied to the rollers to load the car so that the force of the rollers resistance is as close to the force the car sees on the street. The dyno is then able to calculate the total force being applied to the rollers in torque, and then taking the derivative of that torque curve to arrive at the horsepower curve. Since torque is an actual force of nature, like gravity and electricity, it can be directly measured. Horsepower is an idea that was thought up by man, and cannot be directly measured, only calculated.

I like to state it like this. . . I start by asking how much your car weighs, lets say 3500lbs. Now you take your car and you make a make a WOT rip in your tallest non overdrive gear, how much mass is your engine working against? 3500lbs right? Now you strap your car on a DynoJet and you make a WOT in the same gear, how much mass is your engine working against? 2500lbs right? Now you strap your car on a Mustang dyno, how much mass is your engine working against? 2500lbs. Plus the resistance being applied by the eddy current generator. We’ve seen anywhere for 470lbs of resistance to over 700lbs of resistance as measured in PAU force in the data logs. So which one is more accurate? Well they their both accurate. If a DynoJet dyno says you made 460rwhp, then you made 460rwhp. If a Mustang dyno says you made 460rwhp, you also made 460rwhp. Now which one of those numbers best represents what your car is doing when its on the street. That's a different question.

The most important thing to remember is that a dyno is a testing tool. If the numbers keep increasing, then you’re doing the right thing. We try to look over at NET gain, instead of Peak HP numbers. A 30rwhp increase is a 30rwhp increase regardless of what dyno it is on.

Now I can address how to calculate the difference between one type of dyno and another. Simply put, you can’t. Because Mustang dyno’s have so many more variables, it’s not a simple percentage difference. We’ve had cars that made 422rwhp on our Dyno, two days later make 458rwhp on a DynoJet the next day. We’ve also had cars that made 550rwhp on our dyno, make 650+rwhp on a DynoJet a few days later at another shops Dyno Day. For instance, my 2002 Z28 with a forged internal LS6 Heads/Cam/Intake, makes 460rwhp on our dyno. I thought that was a little low, since I’ve had cam only LS6 Z06 vettes make 450rwhp. So I overlaid the dyno graphs. Guess what, the PAU force for my car was almost 200lbs more than the C5Z06 that made 450rwhp with cam only. So I entered the weight and horsepower at 50 number for a C5Z06 and did another horsepower rip with my car. The only reason I did that was to compare Apples to Apples. This time my car made 490rwhp, no other changes. Now I don’t go around saying my car made 490rwhp, I say what it actually did with the correct information entered into the computer. It made 460rwhp. Now if I ever get a chance to take it on a DynoJet (which I plan to in the spring), I have no doubts it’ll be over 500rwhp. I know this based on airflow and fuel consumption on the data logs.

But since we’re asked this question constantly we're fairly conservative, and hence tell our customers that the difference is closer to 6-7%, but as you make more power, and the more your car weighs, the difference increases as well. You must remember, Dyno's regardless of the type are tuning tools, and are in no means meant to tell people how fast their car is. Now which one is more "real world" is a totally different question. I like to explain it like this..... If you drive your car in a situation in which you have no mass and you're in a vacuum, so basically if you do intergalactic racing in space, use a DynoJet. If your car sees gravity, and has an aerodynamic coefficient, and you race on a planet called Earth, then use a Mustang (ie Eddy Current) Dyno 
__________________
Mike Hornback @ Straightline Performance

[Deep-GXP]

I only read towards the very end but this is interesting....so I guess we should be using Mustang Dyno's (Eddy current)

[lil goat]

Eddy Current yes, it is worth reading it all, I don't like Mustang dyno's at all but it is just a brand. The point is for many many years the DynoJet inertia dyno was the only game in town, with a DynoJet you can not tune a car, you can only quantify the change a mod made. With HP tuners on many of the GM cars, not ours, you can actually live tune the car while on the dyno under different loads, at different speeds and different rpm's.