Mustang Dynos are inaccurate?!?

[turbolx]

Well, since people here seem to be more content racing their dyno sheets than actaully going to the track to find out who's quicker, I don't see why I should bother with this debate much further.

I guess I wasted all that time in engineering school too, because someone says I'm wrong on the internet.

The bottom line is as I stated before. The dyno (either one) is a tuning tool, not the ultimate judge of vehicle performance. That's why we go to the track. A competent tuner can certainly tune a car well using either type of dyno, I know I could. The trick is that the load bearing dynos can do a few more things that make the tuning process much easier when it comes to keeping motors together on the track.

If you wish to disagree with me on the merits of load bearing and vehicle simulation, fine. Just realize that this does not make me wrong. Do the homework and actually read some automotive engineering textbooks AND go to the track more often and you'll start to understand a little more. I am confident that I am short on neither technical expertise nor practical "real world" experience on this one, folks.

Your mileage may vary. You wanted my opinion, you got it!

/me hi-fives Fast_351

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Greg Banish
President, Detroit Speedworks, Inc.
'93 LX Turbocharged Road Racer
'00 Bad-Ass F150

[jimberg]

Hmm, I responded to your message in the other thread. I'll also post it here, too:

Originally posted by turbolx:
Well, since people here seem to be more content racing their dyno sheets than actaully going to the track to find out who's quicker, I don't see why I should bother with this debate much further.

One of the problems with making such vague statements is that anyone involved in the thread will take it to mean it was themselves to which you were referring. The quoting feature exists so that we can direct our responses to an individual. A good example is Vector's blanket statement, "You guys don't seem to understand what horsepower really is." I took this to mean that he felt I didn't understand what horsepower means. Then proceeded to give examples that were just wrong.

Originally posted by turbolx:I guess I wasted all that time in engineering school too, because someone says I'm wrong on the internet.

This is simply the nature of the Internet. I don't know you. I have no clue about what's in your mind other than what you communicate via messages. If I feel that someone makes a statement that is inaccurate or doesn't make sense I will challenge it. I expect them to do the same about anything I write, but they better be prepared to back up their challenge with some facts. Do you know that I'm not an engineer? That Unit's not an engineer? Maybe we are, just bad ones. Just having a degrees doesn't impress me that much since I don't have one and I still program circles around people who have them (Yeah, I'm not an engineer). This doesn't mean I have disrespect for a person who has a degree, just that I don't assume someone knows what they are talking about because they claim to have one.

Originally posted by turbolx:
The bottom line is as I stated before. The dyno (either one) is a tuning tool, not the ultimate judge of vehicle performance.

Of course not. There's power transfer from the wheels to the track which would be different based on the weight of the vehicle, suspension components, tire size, tire compound, track materials, track temperature, wind resistance, etc. All of which you are implying that the Mustang Dyno can simulate accurately. Will a Mustang Dyno allow the car to do a wheel stand or a burnout?

Originally posted by turbolx:
The trick is that the load bearing dynos can do a few more things that make the tuning process much easier when it comes to keeping motors together on the track.

If you wish to disagree with me on the merits of load bearing and vehicle simulation, fine. Just realize that this does not make me wrong.

I can only assume that this is directed at someone other than myself since I didn't disagree with you on this particular point other than the fact that it is possible that if the simulation could be flawed to the point that too much load is put on the car causing you to tune out performance that didn't need to be tuned out.

My other problem is with a prior statement of yours where you said "I will gladly put a car that makes 400rwhp on my MD1750 up against any car that makes 400rwhp Dynojet in a race." If you're implying that your car will win, tell us how it could with less actual horsepower. I'd say it can't unless it was inaccurately reporting power.

A dynamometer is a measuring device much like a torque wrench or a thermometer. No matter what torque wrench or thermometer you use, the readings they return should be the same when measuring the same thing. I suppose this doesn't really matter, though, if your only purpose is to make changes to the point that you know if you make more power than you did on a previous run.

It becomes a problem, though, if you are trying to make a statement about how much power you are able to gain by your tuning when comparing it to results of other tuners.

I guess the lesson to be gained from this debate is that if you tune your vehicle on a dyno to always tune it on the same dyno unless you're only concerned about the gains you make during the dyno session.

Oh, and about debating. Simple "I'm right, you're wrong" arguments don't really do much to further the knowledge of the readers. If I'm wrong, I like to be told why I'm wrong. Then I understand why and the people reading will understand why. If someone doesn't take the time to tell me why, I just assume that they don't know themselves.

I think I still have some questions on the table for turbolx. If you don't mind, I would like your learned response. See my previous message in the other dyno thread.



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351W 89 Mustang GT Convertible

[exgmguy]

They both do the job, The MD is just a better tuning tool.

Remember tuning is usually why you put your car on a dyno to begin with.

People just like that higher number though, and we'll never get away from that.

Kinda like Lapeers' trap speeds. (local joke)

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1988 Mustang GT
11.8 @ 123 (7/14/01)
1992 BadAzz Wrangler
1993 Explorer

[jonnyk]

Originally posted by jimberg:
My other problem is with a prior statement of yours where you said "I will gladly put a car that makes 400rwhp on my MD1750 up against any car that makes 400rwhp Dynojet in a race." If you're implying that your car will win, tell us how it could with less actual horsepower. I'd say it can't unless it was inaccurately reporting power.

If a MD reads different from a Dynojet, how do we really know which one is wrong? Maybe we have been brainwashed thinking the Dynojet is the right reading all along when it is in fact reporting incorrectly. I think turbolx was simply pointing out that MD's read lower and 400 rwhp on a MD would be higher on a Dynojet. So if you compared those 2 cars on the same dyno they would show different numbers, hence one in theory would be faster (assuming same weight, traction capabilities, etc.).

Originally posted by exgmguy:
They both do the job, The MD is just a better tuning tool.

Amen.

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'91 LX Hatch, 17 ROH ZR6's, lowered, 3.73's, offroad H pipe, SN Cobra cat-back, ASP pullies, 14° timing, C&L 76mm MAF, 170A 3G, B&M Ripper on a T5
Best ET: 14.593 @ 94.62 2.292 60'
1991 LX Hatch 5.0L

[jimberg]

jonnyk, we actually talked about this point in the other, longer thread. In a nutshell, I agreed that we don't know which is accurate, but that's the problem. Tools that measure the same item should get the same results. turbolx also mentioned that the Mustang Dyno uses strain gauges and the DynoJet uses a known mass which essentially makes a DynoJet more like a balance and a Mustang Dyno more like a scale. I do think that it would be optimal if the DynoJet had a known mass that was the same mass as the vehicle you are testing.

You can read more about this in the other thread.

Just so you know, I have an e-mail into MustangDyne.com to see if there are any nearby since I plan to use one if they are. Not to get a HP reading, but for tuning purposes.

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351W 89 Mustang GT Convertible

[jonnyk]

Cool I will check it out. I glanced at the forum but must have missed that particular thread (disappeared on me).

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'91 LX Hatch, 17 ROH ZR6's, lowered, 3.73's, offroad H pipe, SN Cobra cat-back, ASP pullies, 14° timing, C&L 76mm MAF, 170A 3G, B&M Ripper on a T5
Best ET: 14.593 @ 94.62 2.292 60'
1991 LX Hatch 5.0L

[Unit 5302]

Well, Dynojet does offer all that stuff as well.

At least for motorcycles for sure. You can buy the separate load bearing option for a bike Dynojet, it'll set you back about 10k or so. You can add on airbrakes and all that great stuff. Dynojet's software also comes preloaded with information about different motorcycles for tuning reference. I haven't bothered to look if they have options for cars like they do for bikes, it'd just make sense that they would.

As far as tuning, I'd rather have a real number than one that has been modified by outside factors. The more factors, the more room for error.

I don't buy into hype, or things that are sketchy when all the calc and physics come to a end. Taking a real number, and modifying it with external and non-relating data based on an assumption that the data being applied as a modifier is correct, and based on the assumption that all the data are constant's when in fact they are sometimes variable, makes the Mustang Dyno's readout sketchy to me.

As far as making it easier to keep engines together at the track, I haven't seen any of the bikes that have been dynoed by my friends shop have a problem with that, and Dynojet certainly wouldn't have the reputation it does if their dyno was a part of blowing engines up.

[jimberg]

Unit, as far as just getting actual HP numbers, I wholeheartedly agree with you, but I can see the value of adding load. I can see where the rate at which an engine can accelerate does matter. If the car is spinning a drum that weighs less than itself, the engine will go through the RPM range too fast and not accurately simulate the velocity of exhaust gases and such.

If DynoJet has an option for that, great, but I think the Mustang Dynos come with it standard. The only place that I could find in our area that has a DynoJet and will work on Mustangs doesn't even have a wideband O2 sensor to integrate with the Dyno.

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351W 89 Mustang GT Convertible