I dyno'd yesterday and picked up 6 more ft. lbs of torque my hp stayed the same roughly. In the upper rpm band the graph becomes rather jagged. I am running pe vs rpm at .97 Autotap is showing my LTFT's at roughly 0 cell 22 0 and 0 knock retard.

All my mods can be found at my site, www.getleaner.com/don
If anyone can help me.


<img src="http://www.getleaner.com/don/images/ls1editdyno.jpg" alt=" - " />

 

Most dynos have a smoothing function. All dyno graphs look like that to a point. It depends what they had their smoothing function set at.

 

Thank you. Smoothing was S-3

 

Smoothing (it depends on the program that they are using) for most dynojets can go all the way up to 5.

 

My Mustang Dyno plots always look like that.

Mark

 

What kind of valve springs do u have. I noticed the roughness at high rpm. U could have a little valve float. My car's dyno sheet was pretty smooth until it got to higher rpm and u could also hear the engine running a little rough. Just my .02 cents <img border="0" title="" alt="[Roll Eyes]" src="images/icons/rolleyes.gif" />

 

Using that smooth function would hide engine conditions.
Wavy line generally points to being too lean and/or knock.

 

It is possible that the jagged curve could be the result of KR.

 

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by Team ZR-1:
<strong> Using that smooth function would hide engine conditions.
Wavy line generally points to being too lean and/or knock. </strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">I don't believe that. Look at his graph, that hardly looks like KR. It looks like an obvious oscillation, which is common.

KR looks more like the rocky mountains rather than a sin wave.
All measuring instruments generate some form of 'noise'. The smoothing funciton is there to take care of this.

I think the last thing we want is everybody getting an un-smooth graph and jumping to the conclusion that it is KR.

 

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by Fbody Man:
<strong> What kind of valve springs do u have. I noticed the roughness at high rpm. U could have a little valve float. My car's dyno sheet was pretty smooth until it got to higher rpm and u could also hear the engine running a little rough. Just my .02 cents <img border="0" title="" alt="[Roll Eyes]" src="images/icons/rolleyes.gif" /> </strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">That sounds like KR.

Valve float in the upper rpm will cause the dyno graph to nose dive.

 

Hmmm, thats odd. I pulled up my dyno's, and pulled them up in dynojet run viewer. It is at 5 by defualt. Your run looks worse than mine at 1 for a smoothing factor.

I set mine to 3, and still did not have the spikes yours has.

Our runs were similar. I Dyno'd my Z06 on Saturday at MTI the two runs were 372.7/363.5 372.8/362.0 HP/TQ. My uncorrected number for those two pulls were 388.9/377.6 and 389.8/379.5. The only mods to the car was to remove the factory Z06 airbox cover, but with the factory paper air filter in place.

Sorry I couldn't be of more help.

 

Two kinds of thing it could be.

One is mechanical resonances (oscillation)
at the higher drum speeds (tire slip/squirm,
driveline resonance, U-joints (which are never
truly smooth, just close enough), even worn
bearings in the dyno drum's axle).

Another is just the resolution of the pulse
pickup & electronics that give the drum
rotational speed readings. As the drum goes
faster, the time between "blips" is a smaller
and smaller multiple of the strobing period,
the increment in frequency-voltage conversion
is closer to electrical noise, or whatever.
The sawtooth pattern is typical of data acq
response when the input is changing a little
too fast for the system to really settle,
and the error on one cycle is made up (or
more than) on the next.

You can only eyeball the center of the "fuzz
band", or apply some averaging / smoothing,
to get a realistic value (not to say correct,
but at least "most likely"). Unless you want
to upgrade the electronics on your paid-for
dyno, and who does?

 

Resonance! It is nothing to worry about. Although, to be on the safe side, I would suggest you wideband the vehicle as well. Does the Dynojet not have one yet?

Have your dyno operator give you your pep files on a floppy disk or ask him to email them to you. Install the Dynojet Run Viewer software located here:

http://www.dynojet.com/downloads.shtml

Then change your smoothing factor to 5. That should help quell that for you on the graph.

FWIW, the Dynojet you used has the old electronics and WinPep software installed on it. This wasn't the most reliable setup compared to their new offering.

BTW, that Cobra of yours is sick! Look at this graph:

<img src="http://www.getleaner.com/don/images/cobradyno.jpg" alt=" - " />

That pulley and DiabloSport chip combo is NASTY!

Sincerely,