Mike Chaney's Tech Corner

Mike's Software => TT Dyno => Topic started by: srt8-in-largo on June 10, 2010, 03:22:48 AM

Title: howdy mike
Post by: srt8-in-largo on June 10, 2010, 03:22:48 AM
Great piece of software you got here.

I've followed threads you've been involved with on some of the Hemi forums and couldn't resist, so I bought a copy! I believe I have the latest version (v2010.110) but I don't seem to have the "lock" feature where two graphs can be compared... do you think I need to reinstall it or something?

Also would you mind giving your thoughts on 2nd gear "pulls" as far as effect on hp/tq numbers?

I drive an SRT8 Hemi with a 5-speed auto. My 2nd gear is 2.19:1, 3rd is 1.41:1, and 4th is 1:1. I haven't done 3rd or 4th gear pulls yet but numbers from 2nd gear pulls look WAY low. Even though I'm new to the software I've followed enough to know how to correctly input all the parameters, and I understand TT Dyno to be remarkably accurate in terms of correlating well to actual dynos. So I'm a little concerned that maybe my car isn't running properly... unless the pull in 2nd gear accounts for low readings.

Title: Re: howdy mike
Post by: admin on June 10, 2010, 01:28:59 PM
The lock button is on the middle/bottom of the window just under the text output.  It becomes active (enabled) as soon as you graph a dyno run.  Just click it to lock the current graph and then load a new one to compare.

My SRT8 is also a 5 speed auto and I do all my runs in second gear because that tops out close to the speed limit here.  What kind of numbers are you getting?  Most chassis dynos are run in 4th or 5th gear to give close to a 1:1 transmission ratio.  When you test in lower gears like second, parasitic losses increase, giving lower numbers particularly on automatics.  I've found the parasitic losses of second gear on the SRT8 auto to be close to 25% rather than the typical 18% you'd get for an automatic running in a higher gear on a chassis dyno, so you have to factor that in.  I typically get around 330 lb/ft of torque and around the same (330) HP.  My only mods are a Predator tune and K&N drop in filter.


Title: Re: howdy mike
Post by: srt8-in-largo on June 12, 2010, 01:02:11 AM
Oh, yes I do have the lock feature then. I thought I saw it in a different location before.

Here's one of my 2nd gear pulls showing about 300/300 hp/tq. With 25% loss I get 404/398 which still seems low. But if you're showing 330/330 with tune and filter, idk, I'd have to say 300/300 on my 100% stock machine can't be far off.

Further below is a 3rd gear pull showing 357/348 hp/tq. With 20% loss its at 446/335, where I'd expect these numbers to be closer to the 2nd gear values at 25% loss.

I might be getting a little confused here...but I do concede the ballpark nature of these loss figures.



Title: Re: howdy mike
Post by: admin on June 13, 2010, 02:09:47 AM
Your graphs certainly seem reasonable.  I did two 3rd gear runs and they were both right around 350 RWHP and 350 RWTQ.  As long as you do your runs in the same spot on the same road and in the same gear, your graphs should be very consistent.  For me, I just do all my runs in second on the same stretch of road.  I know the frictional losses are close to 25% for that gear so that'll get you close to comparisons for any other dyno.  The best thing is the consistency though which is great for modding.


Title: Re: howdy mike
Post by: srt8-in-largo on June 15, 2010, 11:25:47 PM
I have to admit I'm having tons of fun with this and appreciate your expert feedback.

I completely agree with good consistency being the best indicator. I've decided that I'll no longer do 3rd gear pulls on public roads because the top end is just too high. I have a nice stretch that I pull onto out of my subdivision that's mostly flat, mostly barren, and no problem getting up to 80mph on. So with a patch of road selected to be used everytime, my next consistency problem is throttle control.

The pulls below were done within a few minutes of each other... on exactly the same stretch of road. I think the correlation would be quite remarkable... if I had just operated the throttle more similarly in each run. Correct me if I'm wrong, but I think the differences on the low-end are due to how quickly, or not, I mashed the pedal. Even though I believe these are both valid runs, it's impossible to compare avg tq because of whats happening below approximately 2500 rpm.

Do you agree?

If I wanted to compare avg tq, which I do, it seems that I need to edit the csv, lop off data points below about 2500, and then reload. I haven't tried it yet but I'm sure the tool will accept user edited files like this... and then its now possible to custom arrange any rpm range you want, right? Along these lines, what are the odds of you incorporating an rpm range selection feature into TTDyno?

Final thoughts, this time about the differences on the top end. I *believe* the solid curve is where I bounced off the rev limiter. Why does the tool show a premature dip when this happens? The dashed curve is where I was able to let off the gas almost exactly as I hit redline and which is where... 6200 rpm... I'd expect peak hp.

Can you offer any tips in being more consistent on the top end?


Title: Re: howdy mike
Post by: admin on June 16, 2010, 01:06:44 PM
Average torque is only calculated for the last 2000 RPM of the run just for that reason: to eliminate any start/throttle issues.  So if you stopped at 6200 RPM, average torque will be computed for 4200 RPM through 6200 RPM.  Also, that dip in the curve was not caused by the rev limiter.  TT Dyno will end the run as soon as it sees the first decrease in RPM so bouncing off the rev limiter should have no effect whatsoever.  Have you turned off ESP (traction control) completely?  I'm not sure if you can do that on the 300 or not but I know if I don't turn off ESP completely, I get some strange dips in the curve sometimes.


Title: Re: howdy mike
Post by: srt8-in-largo on June 29, 2010, 02:20:53 AM
Ahh ok, only the last 2000 rpm for avg tq calcs. And thanks for the explanation about how the tool ends the runs. I've been playing with it quite a bit lately and it really helps to have a little insight into what the SW is doing. One thing I've noticed recently is that, on occasion, there's a discrepancy between the KR-ST max value plotted in TTdyno and the KR-ST max value shown when I replay runs in the Diablosport Dataviewer. Have you seen this before?

Another issue I'm running into at times is that my auxilliary PIDs seem to disappear once in a while. Several times I go to plot IAT, for example, and ttdyno gives me a blank auxilliary graph. The first few times I thought the Trinity mucked up the data, but when I view in Dataviewer, IAT is there.

Here's a case of this, or something possibly related, happening. I modified this csv file by deleting about 5MB of unneeded data at the beginning of the file. Now when I plot in ttdyno, KR-ST does not plot or appear as an auxilliary PID... yet it exists in the csv file. Any idea for what needs to be done to get KR-ST to show up when I plot this file?

http://docs.google.com/leaf?id=0AoIzNq_s9RArdDNLcXpRNEFoUFh4QXR3WU5UVlJ6ZGc&sort=name&layout=list&num=50 (http://docs.google.com/leaf?id=0AoIzNq_s9RArdDNLcXpRNEFoUFh4QXR3WU5UVlJ6ZGc&sort=name&layout=list&num=50)

I haven't paid much attention to whether ESP is on or off, so you may be right about the blip. As far as I know the ESP button functions the same on all SRT's: a single press disables it a little bit and an extended press disables it further, but not quite 100% off. As far as I understand the closest we can get to turning it 100% off, including aftermarket and DIY mods, is to use dyno mode in the Trinity or Predator. I'm off for some more testing!  ;D

Title: Re: howdy mike
Post by: admin on June 29, 2010, 10:52:14 AM
You're right, it does help to have an understanding of what the software is doing (internally) sometimes.

On the KR, keep in mind that data is plotted at every 100 RPM, yet in your actual data log, you likely have not a single sample that matched RPM at even 100 RPM segments.  For example, your actual data may have captured a sample at 4089 RPM and another at 4126 RPM but we need a reading at 4100 RPM.  This means the data must be interpolated.  In addition, not all parameters are captured at the same time stamp so each parameter is interpolated and smoothed in its own time axis.  So long story short, you are seeing data that has been "corrected" for 100 RPM increments and that's why you may see a small difference here and there between TT Dyno and your data log.  FWIW, TT Dyno is actually giving more accurate data because it can accurately calculate an accurate picture of all parameters at a given time stamp.  Contrast this to your data log where all the parameters are being captured at a slightly different time.

On the second question, the aux data only plots changes. So if your IAT was 84 degrees for the entire run, no line will be plotted because there is no range (y direction).  In a future version I plan to add a message that shows the static value on the graph.


Title: Re: howdy mike
Post by: Mike_Levy on August 09, 2010, 04:44:49 PM
Any idea what the parasitic losses are on the Jeep SRT8? Gotta be pretty high. She only put down 392/384 on the AWD chassis dyno, yet runs 11's @ 115, so its gotta be at least 25% if not more. Waiting for the password to see what this software says she's putting down.

Title: Re: howdy mike
Post by: admin on August 09, 2010, 10:14:37 PM
Any idea what the parasitic losses are on the Jeep SRT8? Gotta be pretty high. She only put down 392/384 on the AWD chassis dyno, yet runs 11's @ 115, so its gotta be at least 25% if not more. Waiting for the password to see what this software says she's putting down.

AWD setups are normally right around 25% parasitic losses.  Remember too that running in lower gears is going to result in higher parasitic losses as well, so your numbers will be slightly lower doing a second gear pull than they would a 4th gear pull on a chassis dyno.