Dynamometer Questions

[Da1Chief]

OK Guys and Gals,

After my last Fiasco with the truck on the Dynamometer (I was a Virgin) I am thinking about doing it again. Taking what I learned the first time so I can get it right and get accurate numbers.

Last time I only went for the HP numbers. Do I want to have the Air/Fuel/Temp readings as well? (I think they would be helpful later on If and When I start the Modifications)

I have heard a lot about Dynamometers and that the numbers generated can vary greatly between name brand of Manufacturers. I have gone to many websites and looked at more systems than I really wanted to. Each name brand “Claimsâ€￾ their numbers are correct and their produce is more accurate then their competitors.

I understand that this is 99.9 percent BS and is “Sales Hypeâ€￾.

From what I have read and what has been posted on threads here, I understand that there are as many ways to compute HP as there are companies that produce Dynamometers.

Obviously, Age, Maintenance and Servicing (both hardware and software) of the system play greatly into the equation. Given that all are equally maintained and correctly serviced….

Which is the BEST way to read HP? (other than with my ass)

This will direct me to which of the manufactures competing in that field. After knowing who the players are I can then research as to who actually makes the Most Accurate. That will lead me to the best shop in my general area that has the correct equipment and technicians to perform the Dynamometer Test/Pull.

Last Question: What Questions/Variables did I forget so I can get it done right?


ALL COMMENTS WELCOMED!!!!!

 

[Silverback]

Yes, you want to measure all of the variables that can affect the readings.

And it does not matter what brand of dyno you go to, as long as you stay with that brand or company. You are looking for improvements based on the changes you make.

Normally a Dyno-Jet will read 10 to 15% higher than a Mustang Dyno.

 

[Ironhead]

if you dont get a/f at least when you dyno ,,i would think your wasting your money ,,,the hp numbers are nice but a dyno is there to tune your vehical ,i have had two dynos done JUST to see the air/fuel setup

 

[JTS VENOM PERFORMANCE]

worrying about dyno numbers chief is like worrying about the size of ya wanger......

there will allways be someone out there with bigger ones

use it for tuning, and dont look at the numbers

quote of the day, I am going back to my beer now:marchmellow:

 

[Da1Chief]

Normally a Dyno-Jet will read 10 to 15% higher than a Mustang Dyno.

I will assume that this difference comes in the way they calculate the numbers. Which was part of my question on the best method to use. Some use a water brake and some use friction. Any comments as to which is more consistent.....

Stinker: I know it is like who's is bigger and for me that is not an issue (Tweezers with sponge pads attached)

I just want the numbers I get to be accurate...

Thanks Guys, and keep the comments coming. Like I said I was a Virgin when it came to a Dyno and was simply curious as to the HP my truck was pumping (or Pimping) out.

Now that the "New" has worn off I want to do it right so I have an "Honest" Base Line to work from....

 

[Da1Chief]

if you dont get a/f at least when you dyno ,,i would think your wasting your money ,,,the hp numbers are nice but a dyno is there to tune your vehical ,i have had two dynos done JUST to see the air/fuel setup

Thanks Ironhead, that was starting to register in my head as I was typing out the question. I will make sure to have the A/F readings a requrement.

 

[TNVIPER]

Doesnt matter which dyno you use...what is important is the operator. Ask around to see where all the tuners go.

And like Stinker said dont use the dyno for bragging...just tuning. Getting a dyno before modding will give you a base line to work from. Always use the same dyno for later comparisons.

 

[razorbackfan]

Yes, you want to measure all of the variables that can affect the readings.

And it does not matter what brand of dyno you go to, as long as you stay with that brand or company. You are looking for improvements based on the changes you make.

Normally a Dyno-Jet will read 10 to 15% higher than a Mustang Dyno.

Perfect comment, however most people tend to not question DynoJet numbers as much as other brands (been there done that). The best thing to do to get your A/F is to have a bung welded in on your exhaust close to the other O2 sensor to give them a place to screw in the O2 sensor for thier equipement. Do not let them clip it on the tailpipe as this reading is really worthless and way leaner than your truck really is by about 2 points. Also they can unscrew one of the existing O2 holders and screw in thier O2 sensor, they can just leave your O2 sitting off to the side (ECM doesn't use them during WOT runs). This is if you can't get a bung welded in before you go.

Remember no sensor's in your tailpipe (only stinker likes it like that hence the screen name )

 

[razorbackfan]

Doesnt matter which dyno you use...what is important is the operator. Ask around to see where all the tuners go.

And like Stinker said dont use the dyno for bragging...just tuning. Getting a dyno before modding will give you a base line to work from. Always use the same dyno for later comparisons.

Another great comment. Ask the operator how he operates and watch him do a couple of other cars if you can.

 

[rottenronnie]

Hello again Chief-

It looks like you have been doing some homework.
And you are right, the various suppliers will likely argue their dyno unit is better than the other and provide you convincing reasons why.

Personally, I like a dyno that can load (like a Mustang style) and that is the style of dyno we use. Others will argue that a Dynojet is the way to go, blah, blah...

Through tweaking, you can (within reason) have a dyno spit out just about any number you want and those numbers can be used for a variety of evil purposes. As a quick example, key into the dyno that the ambient temperature is 180 degrees F. and watch it spit out a BIG corrected horsepower number! An incorrect Ramp rate or Load number are a couple of others that can taint results... Not saying this could ever be intentional but... it is POSSIBLE..

The same dyno with the same operator should provide you with repeatable results. Those results can then be verified at the track. I think that is the "best" way to measure horsepower. For example a hypothetical 4000 pound vehicle that, according to the dyno (or more often the owner ) made 600 wheel horsepower, is trapping 110 m.p.h. at the track. Well, it isn't making anywhere near 600 wheel horsepower....In this example, it would be closer to 400...

As a guide, a stock Ram SRT-10 with an auto is "somewhere" around 400 "Dynojet wheel horsepower", or a bit less than that. Don't let what you may consider to be low numbers bug you, at the end of the day, they are just numbers.

A/F numbers are typically "fat" (rich) on the stock engines. You might see numbers around 10:1. This helps keep them alive as rich mixtures (gasoline engines) burn cooler than lean. Lean(er) normally provides more power but can be dangerous so a bit of a tightrope is being walked here. I run my own truck around 13:1 which arguably is in a dangerous area but it has proven fine for my application. It is a good idea to include A/F numbers in your pulls and provides you with an important baseline.

We were testing two completely different vehicles last night and one had been there before. So by using the same settings as we used the last time it visited, we can be reasonably confident that the mods and tuning results were being accurately reflected. The other newcomer now has a file that can be used on the next visit and we can go from there, and so on.

There really is no such thing as horsepower (which is just torque measured over a period of time). Look at diesels- Big torque, low revving, low(er) horsepower, compared to gasoline engines.

Rapid (are you confused now?) Ronnie

 

[ZCx]

i agree with the "input data".

when i ran the Dyno at the Pete dealership, i tried my best to be consistent with the input data, temps., weights, fuel weight, etc.

but every once & awhile i had to fudge to get a customer happy, when there was nothing wrong with her & usually puttin out more than the "specs" called for for that engine.

 

[FlyingLow]

Where are you going and when? Maybe I can meet you there.

 

[rottenronnie]

i agree with the "input data".

when i ran the Dyno at the Pete dealership, i tried my best to be consistent with the input data, temps., weights, fuel weight, etc.

but every once & awhile i had to fudge to get a customer happy, when there was nothing wrong with her & usually puttin out more than the "specs" called for for that engine.

Oh, Oh, I guess the dyno secret is out now....

 

[ZCx]

Oh, Oh, I guess the dyno secret is out now....

i guess.

there is a butt load of factors on a chassis dyno for sure.

hell even how its tied down, tire pressures & tread style figure in

:rock: :burnout: :rock: :burnout: :rock: :burnout:

 

[rottenronnie]

i guess.

there is a butt load of factors on a chassis dyno for sure.

hell even how its tied down, tire pressures & tread style figure in

:rock: :burnout: :rock: :burnout: :rock: :burnout:

It is really surprising to me just how a tight tie-down can kick the crap out of power numbers; even on the high(er) horsepower stuff.

 

[ZCx]

It is really surprising to me just how a tight tie-down can kick the crap out of power numbers; even on the high(er) horsepower stuff.

yep:rock:

 

[Da1Chief]

WOW so much GREAT input and information.... I cant thank all of you enough and there are so many/much input. Thanks to ALL of you and yes I have printed it out so I can make a list of what to do and look for.


Please keep the input coming in. The more the better. Heck, this could turn into a "How To" thread for Dyno Days

To Flying Low. I will look at the local shops and provide a list here. I would really like to get together and have a day at the "Torture Booth"... Thanks for the offer..

 

[Da1Chief]

i guess.

there is a butt load of factors on a chassis dyno for sure.

hell even how its tied down, tire pressures & tread style figure in

:rock: :burnout: :rock: :burnout: :rock: :burnout:

Ok, trying to think this one out....

Obviously, I would want the truck tied down securly, but too much down pressure from the tie strap would be bad. That suggests that the direction of the tie straps should be more to the rear and front t cut down on the angle.

However, at a lower angle the tires would spin, which would be bad. This suggests that the tire pressure should be lower as to add better traction to the rollers.

The "Trick" would be figuring out what the ballance between the two are.

Is my thinking correct on this????

 

[HV SRT]

When I was looking for a dyno I went to shops that build Viper and Vette engines to see where they get them tuned. Then I went to the dyno/tuner to see how new the software was. I didn't care what brand the dyno was its all about the tuner. My tuner has a Mustang dyno.

 

[Da1Chief]

The best thing to do to get your A/F is to have a bung welded in on your exhaust close to the other O2 sensor to give them a place to screw in the O2 sensor for thier equipement. Do not let them clip it on the tailpipe as this reading is really worthless and way leaner than your truck really is by about 2 points. Also they can unscrew one of the existing O2 holders and screw in thier O2 sensor, they can just leave your O2 sitting off to the side (ECM doesn't use them during WOT runs). This is if you can't get a bung welded in before you go.

Great input, I would never have thought of it..... Thanks