Mustang dyno numbers = low?
 

Is this true? I am pretty effin pleased with my dyno @ 423rwhp cam only. But is it possible I make more?

Mustang dynos do read lower than dyno jets, but mustang dyno's can be adjusted to read the same as a dyno jet

Yeah I am assuming its pretty dead on, I dont think I have heard of to many cars making 420+ with a cam and LS6 intake

Not many, but it does happen. Great numbers! What cam and how much torque?

I made 389rwhp on a Mustang dyno & 463rwhp on a Dynojet
Anyone who asks how much it makes to the wheels I always
say 389rwhp :devil:

They can read lower or higher. All depends on the setup.

Thunder racing Trex cam, 395tq, I am extremely pleased with the set up. Stock 2000 heads and LS6 intake.

I've had a few cam only LS1's make 420+rwhp on our Mustand MD-1100SE dyno, so it's possible that it'd show more horsepower on a Dyno Jet.


I have written pages and pages of posts on this topic on various forums. Here's a little write up I did a few monthss ago. . .

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 Dyno.

gearing does not have major effect on horsepower output.

From what I have seen its about 5-10 hp. Also, some differential builders require heavier fluid (75W-140) which will result in further parasitic losses on the dyno.

I was referring to 1st gear vs. 4th gear and so forth, not final drive ratio. I probably should have stated that, and that will greatly affect the amount of torque recorded at the wheels, and since horsepower is a derivitive of torque, it will affect the horsepower numbers as well. If you've ever seen a 1/4 mile simulation run on a Mustang Dyno, and graph the horspower over time, you will see how the gearing effects the output to the wheels.

Thats the problem I have with a mustang dyno. The user can enter in to much data to control the output of the dyno sheet. When I had my dynojet dyno there was no way for me to alter the number by changing anything in the computer. I have seen in person the guy running the mustange dyno I rented change stuff in the computer to change my numbers when I asked about them being low, then magically I had a higher dyno number.

To me a dyno is just a tuning tool, and as long as you can see a before and after and see your gains or loses for what you did that's all that matters. BUT I also know 99% of customers want dyno numbers and dont care if you have a eddy brake or its a load bearing dyno. I personally like tuning on a mustang dyno, just dont like the fact I can skew the numbers.

Any dyno that can recieve input for weather corrections or weather stations can be used to manipulate numbers. I understand that Mustang dyno's, since there are more variables, a user can manipulate the numbers in various ways. Two being the vehicle weight and horsepower at 50mph values, but those are printed on the reports, so if they're skew'd, then it's right there in black and white. The second would be to change the "air" under the weather correction data, and the third would be to change the parasitic loss multiplier. Changing the last one however, will drastically effect the amount of load on the dyno, resulting in different horsepower levels.

As you said, a dyno is a tuning tool, over the years we have learned that we'll never compete with the horsepower numbers from a DynoJet, but in the corse of those years, we have also educated the customer base to understand the differences as well.

We have a real time weather station, the dyno recieves this data real time for it's weather corrections, we use the provided data (Mustang supplies it from the EPA database) for horsepower@50mph, and vehicle weight, and the parasitic loss multiplier is always a value of "1.00", if any customer asks to see it, then I have no problem showing any of the presets on our dyno.

We started off asking customer if they wanted to see what the horsepower of their car would be in "DynoJet" mode (changing parasitic mulitiplier to 2.50 it simulate an inertia dyno), but that only further confused most customers. We learned it was best to keep things as they are, regardless if some one thinks they are high or low.

There is no high or low when it comes to comparing chasis dynos, just different. Since inertia dyno's and loaded dyno's are different in so many ways, I was trying to explain the difference in they way they work, so that people would better understand the difference in horsepower numbers between the two different type of dynos.

When I first went to a mustang dyno I was on two dyno jets before. I went from 400hp to 370hp. I was ready to cry like a lil bit*h. I ran 12.1 at 115mph on that 370hp reading. But then built up to 463hp on that same dyno. In my case,it read lower. People say it can be messed with to read higher. Maybe it can,but a jet may be able too.

The goal is to shop around for the highest reading dyno you can find. That's what you make. Then you post it here.

With the mods in my sig i made 419/385 CAM ONLY using Straight Lines mustang dyno..

Informative read.

Bwhahahahahahaha!!!

I had a cam only LT1 prior to my current LS1 car. it was a very large cam, 242/250, and it really did run well. better than my 383 years prior. I put it on a local mustang dyno and it laid down 389 rwhp. the dyno owner suggested I run in 2nd gear because I still had 2.73s and running out 3rd gear with 2.73s would put me close to 200 mph. he had me hold the RPMs at about 3000 rpm in 2nd gear but the converter never locked since its 2nd. I also had a yank PT4000 stall.

now shortly after my buddy with a 2002 vette went on the same dyno, ran in his 1:1 gear, had LT headers, catback, and an intake of some sort, and made 340 rwhp which leads me to believe the dyno is pretty accurate.

how far could my numbers be fudged considering the following:

I may not have been at 3000 rpm when he told me to hover around there due to the converter not being 100% efficient or locked up like in 3rd gear.
running in 2nd gear (1.62:1) as opposed to 3rd gear?
And finally would my big stall help my #s? I noticed my dyno graph didnt look like that of a big stall car on a dynojet.

I realize im splitting hairs but it has always made me wonder if the car really put down the power or it was a fluke. it sure felt good, it felt better than my 383 that was trapping ~112-113 which would lead me to believe the numbers were somewhat close. It also was a LOT stronger than my current '99 formula so I know it made more than 300 rwhp lol.

Mustang dyno's measure actual torque, with lower gearing it multiplies torque, since Horsepower is a derivitive of torque in accordence to RPM, the peak horsepower numbers might be close, but slightly inflated, but the torque, especially through the Yank conveter would show a large torque spike at the begining of the test, and have it rapidly fall off. This is due to two things, the torque mulitiplication of the gear, and the flash of the converter.