Dyno 3.2 graph is "rough" = WHY??

[Sboxin]

Dyno test on 1984 3.2 (1978SC track car) shows a very rough line (zig zag shape).
What would cause this?

Ideas: dyno spark lead is loose, spark plug wire problem = miss fire, Dyno equipment error, SAE smoothing set to zero
Dyno from 7-17-2010


Dyno from 2005 for comparision





Thanks in advance for your help and ideas

Roy

[jpachard]

Yes, the smoothing will help, you can download the software yourself and play with it if you have the original file from the dyno run.

Cheers, James

[Sboxin]

Thanks James for the tips - I will talk to the Dyno operator and try to get the data file. After looking at the older dyno info it appears the "scatter" occurs in both. This may be a function of the equipment/sensors used to measure the forces from the drum.

The Porsche engine sounded strong through the dyno measurements. We completed 6 runs - 3 in fourth gear and 3 in fifth (0.96 gear). But, we do have 1 spark plug wire that may need to be replaced. The engine is recording the same HP/torque output since the rebuild in 2005 - and an excellent leak down test results also.

I will look further into the SAE smoothing process and programs.

Take care,
Roy

[jpachard]

Roy, forgot to mention the software is available at Dynojet's website. I have added the link below

Dynojet Research Inc. - Software - Downloads

Cheers, James

[al lkosmal]

It's hard to read, but it looks like the smoothing on the 2005 run was set at 5 vs. smoothing at 0 for your 2010 run. I expect that, depending on the datalog interval, you're going to see this type of "noise" without some smoothing, or averaging of the data points.

[Sboxin]

I downloaded the DynoJet software and am now waiting for the Email with the data files. And, yes the 2005 dyno had an SAE=5 smoothing.

The software looks really easy to use.

Thanks again guys

Roy

[Sboxin]

Well, here is the smoothed version of a Dyno graph -- but it still needs some work with maybe updated Dyno software (note MPH instead of RPM). Also, no Torque or A/F ratios. Anyway,I am interested in figuring out the cause ripples in the graph.



Do any of you have a dyno graph to compare with this?

Thanks again,

Roy

[jpachard]

Roy, I have a dyno graph on Steve Wong's website. If you look under dyno charts you will see mine ( James Achard) with an AFR trace too. Also, if my memory serves me right, you can change the values in the X and Y axis of the graph in the software. Let me know if you need any more help.

Cheers, James

[Sboxin]

James,
Thanks for the tip on SW's web site -- it has been a while since I looked at that.
That clears up any concern I have on the rough graph lines.
And, i found your graph also.

After looking at the DynoJet software tutorial I am able to change the graph axis to show HP, Torq and AFR with RPM.

Thanks for your time to help with this question,
Roy

PS: You may know this car - Chris' UPS 911 from POC
Son's car at NASA Nationals at Miller in SLC Utah 9/09 still running fast w/ SW chip

[JeremyD]

I had the same thing too - and same concern -





From the file - Steve Wong can not only analyze the results - he can also do a custom chip to make sure you are getting everything out of your engine (and make sure your AFR is optimal)

[Sboxin]

Thanks for all the responses and help!

Here are the smoothed graphs for HP, Torque, and AFR.
We have a SW chip that was programed for the 2005 Dyno data.
The engine is all stock spec and stock cams (for POC classing)
And, the 2010 data looks very close to the 2005 data. So, we won't be having the
chip reprogrammed at this time - if we feel the need for more HP we'll bump
up to the 993 class

I discussed the data with our local Porsche Indie tech (expert 30+years) and
the only suggestion was to think about adding an adjustable fuel regulator to
increase the pressure slightly to remove the lean curve at 5000-5800rpm. I don't
think we will do this at this time - maybe later (because we just did a gearbox
rebuild/refresh)

Conditions for this Dyno Temp=110F Hum=5% Pres=28.9






Well...anything else someone wants to contribute...I'm ready to move on to
the next improvement (weight removal- could use 100# less(driver diet!!)

Take care,
Roy

[jpachard]

What kind of exhaust system are you running? Also, do you have a lightweight flywheel?

Cheers, James

[Sboxin]

James,

The flywheel is standard (heavy) weight stock w/puck type disc.
The exhaust is custom 3 into 1 each side and single out open pipe.








Take care,
Roy