Understanding a Dynojet

[shark77]

whats the point of running the car through teh gears on the dyno....pointless...if you dont dyno in the 1ot1 or teh closest to it you will get a inaccurae reading due to gearing

The point of running through the gears, is to see how power delivery is during actual real-world accelleration. When you run a big turbo, you want to see how it builds power through gears. Also, based on your findings, you can fine tune a final gear ratio selection.

But back to the understanding of how a dynojet works...

No car has a 1:1 ratio.

Every car underdrives the wheels. Meaning, for every time the wheels make one rotation, the engine rotates more than once. Therefore, you cannot have a 1:1 ratio.

The MS3 actual ratios are as follows. Each number represents the number of rotations the engine turns for every time the wheels make one rotation.

1st = 13.95
2nd = 8.83
3rd = 6.07
4th = 4.61
5th = 3.65
6th = 2.85

Losses in low gears can be explained by 3 things.

1. The friction is substantially more.
2. Turbo spool-up
3. Dyno sampling.

By dyno sampling, the drum being spun by the drive wheels makes less rotations during a run in 1st gear through the RPM band than it does in 6th gear. Therefore, the lower the gear the more likely the dyno will error in computing its outputs.

A run in first gear, may only rotate the drum ~20 times. Whereas a run in 6th gear will rotate it ~200 times during a pull. However, error rates with modern computers today are fairly minimized.

What is important is that you are measuring what is translated through the chassis. Most people on here are just concerned with WOT pulls, but dyno tuning extends well beyond that.

For instance, while engine tuning you may want to control a boost spike while inputing 3/4 throttle in 5th gear at 50mph. There is a myriad of scenarios that a full tune should incorporate. Not just WOT pulls in one gear. Because, how many times are you driving under that exact condition?

 

[Haltech]

Well unless your using a Dynojet 224Xlc full load dyno like the mustang dyno, you are forced to tune at WOT... Finish your tune on the street at real world load to smooth out the rest of the tune. Very few shops have the 224Xlc, so you may have to call numerous places to find one, even out of state.
I also see the best tuners, either tuning in 3rd gear on a 5 speed tranny, 3rd gear on an automatic or 4th gear on a 6 speed.

Ive seen people run through the gears on a mustang dyno, since its designed to do this for various tuning applications. However, dynojets shouldnt be used like this. I had one guy i worked with try running 1-4th on a dynojet last year... Needless to say, coming home from his dyno run, he split the yoke on his driveshaft and also popped a seal on his right rear diff.

To each their own.

 

[$inCitySpeed3]

The point of running through the gears, is to see how power delivery is during actual real-world accelleration. When you run a big turbo, you want to see how it builds power through gears. Also, based on your findings, you can fine tune a final gear ratio selection.

But back to the understanding of how a dynojet works...

No car has a 1:1 ratio.

Every car underdrives the wheels. Meaning, for every time the wheels make one rotation, the engine rotates more than once. Therefore, you cannot have a 1:1 ratio.

The MS3 actual ratios are as follows. Each number represents the number of rotations the engine turns for every time the wheels make one rotation.

1st = 13.95
2nd = 8.83
3rd = 6.07
4th = 4.61
5th = 3.65
6th = 2.85

Losses in low gears can be explained by 3 things.

1. The friction is substantially more.
2. Turbo spool-up
3. Dyno sampling.

By dyno sampling, the drum being spun by the drive wheels makes less rotations during a run in 1st gear through the RPM band than it does in 6th gear. Therefore, the lower the gear the more likely the dyno will error in computing its outputs.

A run in first gear, may only rotate the drum ~20 times. Whereas a run in 6th gear will rotate it ~200 times during a pull. However, error rates with modern computers today are fairly minimized.

What is important is that you are measuring what is translated through the chassis. Most people on here are just concerned with WOT pulls, but dyno tuning extends well beyond that.

For instance, while engine tuning you may want to control a boost spike while inputing 3/4 throttle in 5th gear at 50mph. There is a myriad of scenarios that a full tune should incorporate. Not just WOT pulls in one gear. Because, how many times are you driving under that exact condition?

ok i agree with the last couple statements,...im not gonna go through teh back and fourht...your are very right, a dyno is a tuning tool it just happens to tel you the horse power and torque, as for running the through i understand tuning each gear... But just so you know you are supposed to sample between 1700---and redline of gear....and your whole there is no 1 to 1 is true but pretty much bs there is a gear close enough to test true horsepower in cars...the 04 cobra has a 4 gear of 1.0 and i can name countless others...here is the link go to teh last page and check for your self....http://www.svt.ford.com/flash/svt_pdf/SVTCobra_brochure.pdf

 

[$inCitySpeed3]

Heres something for you to understand dynojet

all this talk about dynojet is getting old

Just so everyone realizes this, weight load and airmass load are completely two different things. Theoretically, a MAF equipped vehicle will see the same incoming aircharge whether it is "weight loaded heavily" or not much at all.

all of your fuel and spark tables are based on load, or more specifically, calculated load. This "calculated load" has NOTHING to do with the weight, or simulated weight that is imposed by the dyno. This is a common misconception that has been spread by Mustang Dynamometer, and it's really a representation of their ignorance on modern engine management systems.
Your primary concern is getting your spark and fuel tables calibrated properly for the boost and octane of the fuel you're using.


Check out the link below, it's a spark vs. load table. The load, again, is calculated load (not load imposed by the dyno). The calculated load can be looked at as VE% (volumetric efficiency). Notice as RPM's and calculated load go up, the commanded timing goes down. There are many things parameters that effect the actual delivered spark advance, but your "tuner" should have all that handled......
http://www.diablosporttuning.com/ima...sparkvsmbt.gif



The turbo Civics, SRT-4's, or any other speed density type engine management system are not as precise as a mass air system. A speed density sytem (uses MAP, TPS, RPM) is only inferring the airflow, or airmass entering the motor. If you have enough range on the MAP sensor, and the PCM calibration is set up properly, you can maintain consistent fueling, even when you turn up the boost.

You don't need a dyno that can impose additional load, that is, a physical weight load above and beyond what the inertia provides, to tune a speed density EMS. An eddy current load absorption dyno (our 224 can be had with or without a load / power absorption unit) is very helpful, but not mandatory, in order to map a car from idle to redline and all VE points inbetween. I'm talking about an 8-20 hr session of holding the car steady state at various VE / RPM points and fine tuning the calibration. When someone makes the call to run a stand alone EMS and starts a calibration / map from scratch, then having a dyno that can hold you at various VE / RPM points becomes very handy.

If these guys are crying about "not being able to keep the boost up", that's a bunch of s***. The fastest Evo in the land has a Dynojet, and guess what, it was mapped with inertia only. I'd look at the efficiency of your turbo set up before I'd blame the dyno for not "loading the car properly".

For the record.....the largest, most successful, and most popular manufacturer of performance chassis dynamometers in the world is Dynojet Research Inc. Properly equipped Dynojet dynos can operate in 1 of 2 capacities, either inertia only load, or inertia with eddy current load absorption.



like i said before, i owned one for years and will have another dyno...not trying to be rude to anybody but this isnt my first time around the block

 

[shark77]

your whole there is no 1 to 1 is true but pretty much bs there is a gear close enough to test true horsepower in cars...the 04 cobra has a 4 gear of 1.0 and i can name countless others...here is the link go to teh last page and check for your self....http://www.svt.ford.com/flash/svt_pdf/SVTCobra_brochure.pdf

The 04 cobra 4th gear is 1.0, but before it drives the wheels, it is leveraged by the 3.55 final drive. Meaning the engine turns 3.55 rotations for every time the wheels turn 1 time. This is not a true 1:1

Even 6th gear which is 0.63 x 3.55 the engine turns 2.23 times for each rotation of the wheels.

For a car with a final drive of 3.55 to run a true 1:1, a gear would need to be ~0.28.

 

[bast525]

can I please repost my own dyno thread now and you guys keep your debate out of it now that you have you're own thread?

 

[Haltech]

all this talk about dynojet is getting old

Just so everyone realizes this, weight load and airmass load are completely two different things. Theoretically, a MAF equipped vehicle will see the same incoming aircharge whether it is "weight loaded heavily" or not much at all.

all of your fuel and spark tables are based on load, or more specifically, calculated load. This "calculated load" has NOTHING to do with the weight, or simulated weight that is imposed by the dyno. This is a common misconception that has been spread by Mustang Dynamometer, and it's really a representation of their ignorance on modern engine management systems.
Your primary concern is getting your spark and fuel tables calibrated properly for the boost and octane of the fuel you're using.




Check out the link below, it's a spark vs. load table. The load, again, is calculated load (not load imposed by the dyno). The calculated load can be looked at as VE% (volumetric efficiency). Notice as RPM's and calculated load go up, the commanded timing goes down. There are many things parameters that effect the actual delivered spark advance, but your "tuner" should have all that handled......
http://www.diablosporttuning.com/ima...sparkvsmbt.gif



The turbo Civics, SRT-4's, or any other speed density type engine management system are not as precise as a mass air system. A speed density sytem (uses MAP, TPS, RPM) is only inferring the airflow, or airmass entering the motor. If you have enough range on the MAP sensor, and the PCM calibration is set up properly, you can maintain consistent fueling, even when you turn up the boost.

You don't need a dyno that can impose additional load, that is, a physical weight load above and beyond what the inertia provides, to tune a speed density EMS. An eddy current load absorption dyno (our 224 can be had with or without a load / power absorption unit) is very helpful, but not mandatory, in order to map a car from idle to redline and all VE points inbetween. I'm talking about an 8-20 hr session of holding the car steady state at various VE / RPM points and fine tuning the calibration. When someone makes the call to run a stand alone EMS and starts a calibration / map from scratch, then having a dyno that can hold you at various VE / RPM points becomes very handy.

If these guys are crying about "not being able to keep the boost up", that's a bunch of s***. The fastest Evo in the land has a Dynojet, and guess what, it was mapped with inertia only. I'd look at the efficiency of your turbo set up before I'd blame the dyno for not "loading the car properly".

For the record.....the largest, most successful, and most popular manufacturer of performance chassis dynamometers in the world is Dynojet Research Inc. Properly equipped Dynojet dynos can operate in 1 of 2 capacities, either inertia only load, or inertia with eddy current load absorption.



like i said before, i owned one for years and will have another dyno...not trying to be rude to anybody but this isnt my first time around the block

Other than an aftermarket FAST system or a few manf still using speed density, 75% of the cars out there use MASS AIR. We can debate which is better for days, but the point i want to make, Dynojets dont tune 100% on MAF cars with inertia and hell, a dyno is for doing a base tune anyways. I like Dynojets over Mustang Dyno's anyday, however, they both have their place in the tuning world.

From my own experiences, ive seen 03/04 Cobras, Lightnings and GT's with blowers that experience tip in detonation or detonation found on street load. To say that inertia tuning is the end all, be all tuning is completely wrong. My own truck had a problem at 3840 RPM just after a second gear shift... I had a slight stumble and tad of tip in detonation that was only found while driving on the street. The dyno couldnt duplicate this problem. In goes the laptop, wideband with real time datalogging and the tuning software to solve the problem while driving on the street. Not every car/truck will have issues on the dyno, but theres those that will.

This isnt my first time around the block neither. Theres more to spark and fuel tables.. You need to look at the duty cycle of your injectors, fuel pressure, MAP and the additional fuel trims. You and I have a FORD background. We seem to know the FORD ECU quite well but its unfortunate the Mazda doesnt use and of the FORD ECU stuff, otherwise, tuning these suckers would be a breeze.

 

[$inCitySpeed3]

You and I have a FORD background. We seem to know the FORD ECU quite well but its unfortunate the Mazda doesnt use and of the FORD ECU stuff, otherwise, tuning these suckers would be a breeze.

man do i wish ............