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(WARNING, SMALL BOOK BELOW!)

Since the dyno debate will continue to rage on, I'm going to chime in once again and combine several posts I've made on the matter on various forums.
The dyno comparison thing is a tough one, and there is no set way to prove one vs another.

The dyno arguement gets so old. I constantly have people talking crap about the Dynapack - reads too high, you manipulate the #'s, blah blah blah.

All BS, people talking crap with zero or not enough real experience tuning both n/a and boosted cars on different dynos to get a feel and understanding of how things work and what variables (both in the dyno and vehicle) come into play when comparing dyno brands/types.

Just let it be what it is, a tuning tool. If you want to know more in-depth differences/strengths/weaknesses between them (some do certain things better than others), talk to someone that is honest and has tuned cars on several different dyno types for some real input. There will always be some bias based on personal preference of course. :detective:

I'm guilty of talking crap like that about Evans Dynapack in the past based on knowledge/understanding level at the time (which wasn't enough).

I've now tuned enough cars (1000+) on Dynapack(hydraulic load cell), Dynojet(inertia roller), and Mustang(eddy current load controlled roller) dynos to speak with some authority on the subject. My tuning tool of choice is the Dynapack for several reasons, of which repeatability is of utmost importance.

I've seen different Dynojets read differently from each other as well. I have had several 400-500whp cars leave my dyno and then get on a Dynojet and make 20-30whp more there. :uh:

On the flipside, I've also had cars leave my dyno and then read less power on a Dynojet. :uh: again.

There are just too many undocumented variables involved, and those doing the comparing/criticizing are often making too many assumptions and/or going off of misinformation about the car, etc. :confused:

A related story for you guys to think about:

I recently had a car that made 500whp on my Dynapack go to a Dynojet for a dyno day a few weeks later telling everyone it made 500whp, and it only layed down 437whp!

This led to a bunch of crap talking about how my dyno reads way too high. So, I had him bring the car back to re-dyno it. It then lays down only 445whp on my dyno.

So what happened? It turns out the boost level was a few psi lower than when I initially tuned it, and the owner was having issues with the FPR so he messed with it and it was now running super rich (high 10's afr's). So we clean up the AFR's and bring the boost back to where it was, and 500whp again. Yet all those people that saw it at the dyno day will continue to talk crap without ever knowing the whole picture, only what they heard. Just something for you guys to think about, in addition to the info below.
;)

Comparing dynos, technical discussion, etc:

We recently took part in a Dyno Dash magazine article (not yet published) that compared readings of several different dynos all within a few hours on a mildly modified EVO. 2 Dynojets, 1 Mustang, 1 Dyno Dynamics, 1 Dynapack. If I remember correctly, the car made ~350whp, and all the dynos read within about 10whp and torque. Interesting, huh?

All I know is that the weight vs trapspeeds calculations are the only true proof of power. You can't argue with the laws of physics. It takes XXX amount of power to accelerate XXXX amount of mass to XXX speed in XXXX distance, provided traction is decent and the shifts were well executed, etc.

BUT.....The weight vs trapspeed method needs to be better thought out by most people, and I see it used improperly all the time for 3 main reasons:

1. Often a car won't trap what it should've because of how well the car hooks and is driven. I've tuned cars that never trap what they should because of lackluster driving or traction, and other cars that trap exactly what they should, and were driven well.

2. Gearing, or lack thereof. If a car doesn't have a well matched tire size/rev limit/gearing combo, it won't trap what you would think based on a dyno sheet because it's not putting down that power for the whole run. This is closely related to #3 below.

3. People tend to blindly enter the peak whp number the car made on the dyno into those calculators. That is a big and very common mistake.
You need to analyze the dyno graph first. If the car had a really peaky powerband with say a 45* angle climb to the high peak hp number, you shouldn't expect it to pull a trapspeed based on that number. You need to find the average hp during the rpm range that the car was run in and use that number.

If the car had an "umbrella" shaped torque curve and the hp number floated at about the same constant number in that rpm band that the car was run in, then it would be appropriate to use that number and expect a trapspeed based on that number.

To take it a step further, turbo cars typically have a small period of re-spooling (and thus less power) after shifts which needs to be taken into account.

To take it another step even further, turbo cars running different boost levels in each gear again require a lot more math. You have to average the power made in each respective gear in the rpm range that the car was run in.

In Conclusion:

So..........this leads to alot of crap talking about "so and so's dyno reads high/low", when in actuality, these factors and the misuse of these weight vs trapspeed calculators are skewing things.

My car last year was a perfect example of this, it hovered at 460-470whp in the rpm range that the car was run in, the gearing kept it in that range, and it trapped 139mph weighing 2300lbs. - exactly what it should have.

We have a few customers that have similar charts and drive well, and they all trap exactly what they should as well. So I know my dyno is accurate enough, and there is no possibility of wheelspin or losing tach signal on the Dynapack to mess the chart up. Not to mention that tire size/pressure/alignment/strapping technique/etc are all variables that are eliminated. The Dynapack is a superb tuning tool, and the one that I personally prefer after using quite a few different brands.

Also if you like math you can do some injector duty cycle vs whp calculations to see if a dyno chart is in the ballpark, provided that you have all the relevant info.
 

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Brokedick Millionaire
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With Dynapacks, the numbers will vary between the small cells and large cells, as well as playing with the slew factor.

Was helping with a Dynapack last night.....but know enough to make all three lie.

Dyno numbers make for great bench racing :)
 

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From a end user, I think the Dyanpac is much safer to use.

It doesn't look as cool, but it's not what the car makes on the Dyno that's important. It how it run's on the track or as a DD that really matters.

But most people like to debate so let the people talk.
 

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personally... in terms of design I think the dynapack has one of the best features, which is bolting to the hub... it eliminates several variable in one shot

but as JFK 1992Si said it doesn't look as cool... but I would rather look not cool on the dyno and be faster on the track :twisted:
 

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good informative post, i'd like to see some more info ont he dyno dynamics dynos...i seem to have a softspot for those dynos because of their bling factor..when is this artuicle coming out in the dyno dash magazine? can it be found online too when its out?
 

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very good info.
and i have to say that ive been re-educated thinking the same about dynopacks.
i think it more important to see the dyno as a tuning tool rather than how much power it prints out.
if im going to get my car tuned on a dyno, i want one that reads the whole powerband and allows the tuner to do his job properly. hp numbers may be off ~ by a small margin, but id rather have a great tune throughout the entire powerband. when it comes down to it at the end a good tune will result in good fuel economy, reliability and great numbers at the track.

one thing id like to see is the differences between the various dynos ( constant load, no load, awd, practicality etc..)
this is great quality info and all of us are learning.
keep it up guys. its good to hear from the guys who use them on a daily basis
 

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formerly Kit88
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More to learn, thanks guys
 

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Hi hater!
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At the shop that my tuner tunes at they use a land and sea dynomite dyno (or something to that effect). I have seen all the features and could understand how any number of things could cause it to skew numbers. I have seen that same dyno read way different numbers for the same car on different days. As others have stated people get to hung on the numbers it a tool plain and simple. I do like what JFK was talking about when he said that its not always peak power its consistent power. This throws people off so much especially when there car makes good power but cant run what they think it should at the track.

This is great love the tech stuff
 

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This definitely needs to be stickied. Great informative post.

I personally don't get hung up on the #s a car makes. Its definitely great to have and know, but on average its not that big of a deal. The dyno is a tool and should be used as one. The #s arentwritten in stone, they will vary. I've seen plenty of people get their panties in a knot when the # in theire head doesn't match the # on the printout. I've seen my own car swing several hp on different days w/ no changes other than crazy heat in the room. (Dynojet btw) There's a lot of factors that go into what the car is going to mke on that particular day.
Let it make what its going to make, get out and run it.
Enough of my non technical rambling, this is a great topic :bigok:
 

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Brokedick Millionaire
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Why do most of the top end tuners use Dynapacks????

No worry about tire slippage, but a PITA to mount/dismount the car.

Above ground Dynojet is the easiet if just making 3 pulls for $60 on a dyno day.
 

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Do dynapacks put a full load throughout the entire rpm range allowing for part throddle tuning? That's one thing that I hear about with the dyno dynamics
 

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Discussion Starter #16
With Dynapacks, the numbers will vary between the small cells and large cells, as well as playing with the slew factor.

Was helping with a Dynapack last night.....but know enough to make all three lie.

Dyno numbers make for great bench racing :)
Yes, there will always be variances from one dyno to the next. And on ANY dyno you could manipulate the numbers if you were that sort of person. It won't do you or the people you tune any good, though! It'd be shooting yourself in the foot.

Clarification on the term "slew factor" (where did this term come from? "slew" sounds like "skew" aka manipulating or something) for those who don't know. This refers to the run time of the pull. Especially on a turbo car, too short of a run time will give a slow spool time and not place a realistic load on the car.

good informative post, i'd like to see some more info ont he dyno dynamics dynos...i seem to have a softspot for those dynos because of their bling factor..when is this artuicle coming out in the dyno dash magazine? can it be found online too when its out?
Not sure on that. I'll post in here when it comes out.

Why do most of the top end tuners use Dynapacks????

No worry about tire slippage, but a PITA to mount/dismount the car.

Above ground Dynojet is the easiet if just making 3 pulls for $60 on a dyno day.
Yup. That and you cannot lose rpm/tach signal as is so notorious on dynojets.
Roller dynos are definitely faster/easier for doing dyno days. But with practice, it only takes 5-10mins to load a car on the Dynapack, so it's not too bad.

A Dynapack is much more consistent and repeatable IMO, and allows you to see small changes easily. You need a dyno to be be consistent to see the results of changes to the tune. One of the biggest reasons why most shops don't use a Dynapack is cost. They are easily one of the most expensive dyno's out there, yet most casual observers think they are "cheap" because it isn't a gargantuan piece of steel that takes up the whole room. Very backwards in fact. Higher tech, smaller package = higher price.

Do dynapacks put a full load throughout the entire rpm range allowing for part throddle tuning? That's one thing that I hear about with the dyno dynamics
Of course. It is a hydraulic load cell, that controls wheel speed and measures the actual torque level being generated at all times. Another thing is that there is no roller noise (which is very loud) which makes it easier to hear whats going on under the hood.

thanks for posting this that whole craigslist post shit was rediculous..

I do think i will be going to you guys for my tune after all
You were really buying into that? I have to vent a bit about that.

That is/was all being posted by one guy acting like many different people trying to discredit our shop and ruin our business because he made a bad choice by coming to our shop and pulling a gun on another customer. We told him to leave, he refused and was causing a huge scene so we called the police and gave written reports (there were ~8 witnesses), so now he's pissed. The state is prosecuting him, and in retaliation he has made threats on our lives and business "if we don't recant our statements to the police". So.... he is being prosecuted on multiple counts including threatening a witness. All of his ranting, BS posts that he is making on the internet trying to ruin our business is just working against him. :wacko:
 

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Brokedick Millionaire
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JFK78, please.

"SLEW" setting is right on the Dynapack screen, it is the rpm per time setting.

SAME setting can be used on a engine dyno to control the rpm vs time setup. Only difference is no driveline involved :)

IMHO, I wish that all that use a Dynapack to TUNE agree on similar settings, list which pods where being used, then MAYBE numbers would be useful.

I know the numbers involved, sorry if I cannot explain them. I've worked with Blundell on all three dynos, and even before I met him, to notice the little differences.

See in 1999 Dave had nothing to do with Honda's, period.

My mind needs break......
 

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Discussion Starter #18
JFK78, please.

"SLEW" setting is right on the Dynapack screen, it is the rpm per time setting.

SAME setting can be used on a engine dyno to control the rpm vs time setup. Only difference is no driveline involved :)
Huh????

That is what I said minus the the word RPM, assuming that everyone realizes that "run time of a pull" requires going from one rpm point to another. Same thing, different words.

Clarification on the term "slew factor" (where did this term come from? "slew" sounds like "skew" aka manipulating or something) for those who don't know. This refers to the run time of the pull.
 
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