Self Built Dynamometer accuracy

[Diablo_niterider]

hey guys,

i wanted some inputs regarding the accuracy of self built dynos from any teams that have built their own dynos,

i came across a tech paper from rit on their self built dyno , any inputs from them would be great cause we are thinking on similar lines

we are pursuading the university to buy us a dyno and incase that does not happen build our own

it would be great to have inputs from you guys

thanks in advance

[Diablo_niterider]

hey guys,

i wanted some inputs regarding the accuracy of self built dynos from any teams that have built their own dynos,

i came across a tech paper from rit on their self built dyno , any inputs from them would be great cause we are thinking on similar lines

we are pursuading the university to buy us a dyno and incase that does not happen build our own

it would be great to have inputs from you guys

thanks in advance

[Wesley]

We've found our dyno (using a Land and Sea load cell) to be accurate to the competition dynos to 2-3HP,

We've just finished building our new dyno to replace the aging one we had for the F4i.

Just make sure you have some sort of data acq, because logging data by hand is a real pain.

[PSUAlum06]

I don't think accuracy is nearly as important as precision.

[Steve O]

I have to agree 100%. Ever noticed how different your numbers are going between a mustang dyno and dynojet? The numbers you get out of your dyno do not matter as long as they are consistent. Honestly I don't care if my dyno says I am getting 15 hp or 150 hp as long; if my car is faster than your car does it matter? A dyno is a tool for you to quantify the changes you make to your vehicle so make sure your numbers are repeatable and you should be all set.

[Wesley]

Different words, same meaning.

If it isn't precise, it isn't accurate.

[Jevon]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Wesley:
Different words, same meaning. </div></BLOCKQUOTE>
Sorry to not add to the discussion but I wanted to point out that accuracy and precision are not the same. Accuracy and Precision

[Diablo_niterider]

yes definately accurate ad precise is what i am looking for.

@ wesley - can youshare a few detsils of the dyno you guys built i.e time reqd , cost, type ,problems , anything would be of great help

we are planning for an water cooled absorpton type engine dyno and buying the available data aquisition system and motor control unit.

let me know what you guys think about it

[Superfast Matt McCoy]

The Oklahoma dyno is not a good role model for young and impressionable dynos. It's basically just a land and sea water brake/computer, some electronics, and an engine all welded together with some haste and after-the-fact reinforcement for load paths. It's very loud, very hot, and looks like it was slowly assembled buy four generations of engine team leaders who never talked to each other about it.

A dyno is just a brake, like a very inefficient water pump, and a strain gauge attached to a torque arm. The higher the strain, the higher the torque. If you can log the strain and RPM, you've got a dyno. Assuming you have a limited budget, a dyno computer is an unnecessary luxury if you have a simple data acq and a spreadsheet program.

As far as repeatability, get a strain gauge that doesn't have a lot of thermal creep and spend some time on your cooling system to ensure consistent engine coolant temperature. If you can maintain some consistency with ambient temperature and humidity, that would be ideal. This could be as easy as testing during the early evening and adjusting the time appropriately for different day's conditions.

You can get 80% of the way to a perfect dyno for very cheap if you are careful about the important things. I recently visited a major auto manufacturers racing engine test facility and I was blown away by the millions and millions of dollars that were spent on specialty equipment and facility upgrades just to get repeatability under 1 hp. if you're within 3 hp, I'd call it good.

[Wesley]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Jevon:
Sorry to not add to the discussion but I wanted to point out that accuracy and precision are not the same. Accuracy and Precision </div></BLOCKQUOTE>

Yeah, if all Blips are Bloops, are all Bloops Blips and all that. SAT/ACT semantics.

From a technical point, I agree. But you have to answer him in the context of his own question and intent.


And Matt, we've built a new dyno.