Dynojets in town?

[whatthe]

I'm looking to pop in and do a quick run or two sometime in the next couple of weeks. Any recommendations like Davenport or one of the others on this list that may still run ye old simple drum style dyno?

http://www.dynojet.com/DynoCenters/D...da&distance=50

I did a baseline on a dynojet at RCTS back in April as an old favor Reg owed me for helping him out one day a long time ago. Something that I didn't think he would actually honor as it's been so long so kudos to him. Way back when, I did over 1000 runs while working there on different cars on that thing and I'd pay shop rate and put down another quick run, but haven't had a response from him for few weeks on this or different things. Which unfortunately leads me to looking for another recommendation.

For a tuning session, there are features on some of the other brands that I like better than dynojet to make things quicker/easier, but for comparing a number against the baseline would prefer the simple drum style.

[Sentry]

Just have the operator set the correction factor to "internet"

[sr20s14zenki]

Originally posted by Sentry
Just have the operator set the correction factor to "internet"

Smashing the imaginary like button here.

Honestly just add like 18% to whatever you get on a proper load bearing dyno (=. Theres your dynojet numbers.

[whatthe]

Originally posted by Sentry
Just have the operator set the correction factor to "internet"

Most people don't realize that there is a nice handy feature called 'uncorrected' on the dynojets. If you want to see how fast your car is going to be at the track, ask for the uncorrected value. It spun that drum of 'x' weight, 'x' fast on that particular day for your car and will be an accurate representation of what it can do.

However, if you want to compare it to the "internet" as you say, then the SAE correction factor is what should be used for those comparisons.

As an example, I dynoed 5-6 different E36 M3s from before mods and after. Different temperatures, different days, different times of the years, different kms on the car... they were literally within a few horsepower of eachother on corrected values. Looking on the "internet" at different m3s, in other cities, with elevations all over the place... the power curves were also similarly very close.

It's still not perfect with issues with gearing, etc. and my personal recommendation if someone is going for a tuning session would be that there are some handy features on the load based dynos that can shorten the amount of tuning time,and offer some advantages.

However for simply comparing to ones own baseline on a dynojet, or even against other dynojets (probably the most common dyno in north america) than stick with ye old fixed weight drum dynojet

[mr2mike]

Originally posted by Sentry
Just have the operator set the correction factor to "internet"

[gpomp]

Originally posted by Sentry
Just have the operator set the correction factor to "internet"

[whatthe]

With all of these great recommendations maybe someone can use crayons to draw me some updated curves and I can just save the dyno cash.

My turbos can support 800hp... and go...

[Silviawannab]

One of the biggest headaches of Dynojet’s go-it-alone chassis-dyno project was figuring out how to assign meaningful power numbers in the face of unknown inertia from the moving parts of the hundreds or thousands of engine, drivetrain, and tire combinations. Wrestling to fully understand inertia and powertrain losses, Dobeck and his team quickly realized that the standard physics formula of weight, time, and distance for converting acceleration into horsepower simply didn’t work-the derived number was always lower than accepted numbers. They poured on resources and burned up time and money investigating it, but no matter what they did, the math never added up.

Dynojet’s final number-fudge was arbitrarily based on a number from the most powerful road-going motorcycle of the time, the ’85 1,200cc Yamaha VMax. The VMax had 145 advertised factory horsepower, which was far above the raw 90hp number spit out by the formula. Meanwhile, existing aftermarket torque-cell engine dynamometers delivered numbers that clustered around 120. Always a pragmatist, Dobeck finally ordered his Chief Engineer to doctor the math so that the Dynojet 100 measured 120 hp for a stock VMax. And that was that: For once and forever, the power of everything else in the world would be relative to the ’85 Yamaha VMax and a fudged imaginary number.

From http://www.hotrod.com/articles/dynojet-chassis-dyno/

[whatthe]

Originally posted by Silviawannab


From http://www.hotrod.com/articles/dynojet-chassis-dyno/

Good article that I've seen and like actually.

Keep in mind that the vast majority of OEM cars don't beat the manufacturer crank horsepower rating with their wheel horsepower rating on a dynojet. So, I would still be pretty confident in assuming mine makes more at the crank after a run (can even confirm with ecu log and see the injector pulsewidth/ mass of fuel, air fuel ratio/etc)..

Don't get me wrong, the numbers are and still do get abused. That 'uncorrected' graph selection has been available since I first used one 16+ years ago. If companies had provided or at least explained the differences, we would probably have less hate in this town and appreciate these for what they can do.. be repeatable and standardized well across the board.


"As long as the inertial dyno’s numbers were repeatable, the critical question (did a particular modification make the engine accelerate faster or slower?) would be answered correctly." ....


The only thing I'm really surprised about is that nobody on this forum has run their car at - Davenport, Concept One, Power Twins or Sports Car Place that would recommend calling them up.

[Silviawannab]

I am not sure about willingness to rent out equipment to self tuners. I know when we needed a awd to rent, we didn't have any luck.

Davenports is the new smaller version, and seems to give reasonable numbers.

[whatthe]

Thanks for the info on their dyno. RCTS used to let guys drive their own car when doing a simple pull, but I don't even need to do that.. They can drive it as long as my laptop is logging.

I know RCTS uses the larger 48" drums, heard of any issues loading up turbo cars on the newer 24" rollers?

A bit of a concern as the rear end is 3.7 in my IS vs 3.1 in the Supra... With the V160 in there, it's a little too short. I found the amount of boost I logged on the 48" rollers was only equivalent to a little more than a 3rd gear street pull (even while in 5th on the dyno).

[LSChevelle]

The reason most shops don't bother with the "uncorrected" numbers is because the dyno is used for comparisons first and foremost. By using the corrected numbers the dyno operator can be confident that any differences in weather from a run today will be compensated for when you run the car again in a week with different mods/tune.

Dynojet is probably the most accurate from dyno to dyno (depending on age) from what I have seen, even still though it's impossible to compare dyno to dyno, there will always be some variations.

People that get hung up on their dyno numbers make me laugh, if you want to know how much power your car makes, weigh it and take it to the track.

From personal experience unless you are using the load feature available on some dynojets the amount of boost a turbo car makes on the roller will not accurately depict what it will see on the street. I usually find ~2psi difference depending on gearing and vehicle weight.

[whatthe]

I agree on it being most accurate from one to another, repeatable. Also pretty sure that fudge factor mentioned in that article was the 'std' correction instead of the later SAE correction factor. If people hate a dynojet because it has SAE corrected values and is consistent, then I think they are missing the point. If they hate it because some guy should have gone faster with 'x' amount of corrected horsepower in an uncorrected world... then there is some blame on both sides for that in my mind.

For peak boost, I was only a couple psi off on the 48" dynojet, but the boost curve came on like 3rd gear. I wasn't aware that dynojet made a version that can add load during the run, but makes sense with the eddy current versions they have. For the 24” dyno, I'm guessing that turbo cars are going to need the extra load as the rotational inertia difference is huge.

I think people should go to the track to see how fast the car is vs. using it for a horsepower number. The generic ET/Trap/HP calculator might give you an idea that you need to make more power or traction to somehow to approach or exceed a theoretical value, but it doesn’t take into account aerodynamics specific to a vehicle, a certain cars ability to launch, how peaky a power curve is or isn't, how much time a laggy turbo kit might need to recover between shifts, etc. The GTR is a great example of being able to defy the formula for the ‘small’ amount of horsepower it came with (near instant shifts with little to no torque interruption, AWD, etc.)… When it first came out, everybody thought it was making a ton more power than it was until Motor Trend and others started to identify the actual source of its speed http://www.motortrend.com/news/godzi...7-nissan-gt-r/ or http://www.motortrend.com/cars/nissa...leration-test/

My car is likely to be the opposite in how it defies the horsepower/ET/trap calculator. 60 foot times are going to be dismal in the 2.3 second (maybe) range using only street tires, my shifts slow trying not wreck my now severely overpriced transmission since it was officially discontinued, etc. etc..

I still plan to head to the track, but the whole point of my setup is that it is a torquey street setup with significantly more power in an rpm range that won't show at the track. The dyno numbers I want to see aren't peak power numbers but torque at street type rpms. Anywhere approaching 550-600whp with a crap load of torque down low will make me happy. Already... from the original dyno it had a lot more torque <3500rpm than every other run of the mill 600+horsepower single or modified sequential 2J, and many V8s.