Dyno smoothing

[KenH]

With the Dynojet graphs, you can apply different amounts of smoothing from 0 to 5 with 5 being the highest amount of smoothing. I noticed the shop I went to printed their reports using 3. If I went all the way up to 5, the peak HP dropped down by about 2HP. If I smoothed less, I could get the numbers to jump up about 13HP.

Anyone know what smoothing level 'should' be used? Unsmoothed data is obviously bogus, but I wonder if that is why some of the reported dyno numbers are as different as they are.

--- Ken

 

[BlueGTS]

I never thought about that but it is a great point. I have watched maybe 100 cars dyno including some of my own and have noticed big differences in the graphs from different facilities. Some have very jagged lines and some are very smooth. I never knew you could adjust the level of smoothing. It makes a lot of sense, as many of the "peak" numbers are spikes.

 

[KenH]

Here is an example of what I am talking about. Top chart is using basically no smoothing and the bottom one is using a level of 3. If the smoothing is set to 5 (max), it drops HP to about 429. Basically a range of 429HP - 441HP using the same dyno run and same SAE correction factors.

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--- Ken

 

[Jack B]

Ken:

I have the WinPep (Dynojet)6.03 software and have on file about 100 viper pulls. With my software version the factory default is a "2". For those that just have the hard copy, the smoothing can be done anytime after the run. It is not a hard setting used during the pull. The actual uncorrected curve (no smoothing) has a mild slope, however, it is comprised of a saw tooth line. The smoothing makes the graph more readable. There is very little real change when you use a smoothing of greater than 2.

What is really interesting is that using a smoothing factor of greater than "2" can actually increase the hp/tq, because it starts to distort the root curve. The "2" setting gives the most accurate curve. The "1" setting gives the highest reading, however, it obscures the intent of the dyno.

Another consideration is the fact that the correction factor can alter the hp even more. If you use "STD" correction you will show the max hp/tq. If I use STD (versus SAE) and a "1" smoothing, the hp/tq can be increased approximately 2-3%. If the car had a very peaky curve like an NOS car without headers, the correction and smoothing could alter max power rating even more.

 

[BlueGTS]

This is a great thread. I am willing to bet a lot of the difference in stock and near stock Viper's is due to the level of smoothing. 10-15 rwhp differences is huge to anyone with a stock car. Thanks for the graphs. I will take note of the smoothing from now on.

 

[Motor City Mad Man]

Wow, I dynoed my Viper again today and am wondering the exact same things you guys brought up. I had them copy my runs for the last 3 years onto a diskette and then download the Dynojet viewer software free off dynojet's website. Anyways my max hp is 457.51 and max torque is 507.41 with std correction and smoothing of 1. The number the shop reported out to me was SAE correction factor and smoothing of 3. It came out to max hp 436.22 and max torque 484.24 with those factors.

I always thought maybe something was wrong with my car because I see other people with the same mods as me putting down 20 or so more hp and torque. Now I think the difference may just be in the correction factors and smoothing used. Should I change my signature now to say 457.51 hp and 507.41 torque? It will make me feel better.

 

[BlueGTS]

I only look at SAE number as they give an apples to apples comparison. I guess the new thing should be to ask for SAE and level 3 smoothing. Boy isn't it fun to play with numbers? Now we see how stock cars can dyno so high, and how exhaust can give 65rwhp.