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 Post Posted: Sat Aug 18, 2012 6:25 pm 
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Posts: 348
Hello All,

Those of you that run an innovate logger, that always suspected some error in the rpm trace, I have found some interesting stuff. I have read that people believe for what ever reason that the rpm trace lags. Scott Smith was the one that got me keyed in on this. I always noticed that the car according to the logger would shift before the trigger rpm set in the msd box. I finally got around to hooking up a second rpm sensor. Its setup just like your driveshaft rpm sensor would be and it uses the msd trigger wheel. I got both inputs on my logger at the same time and it shows the lag.

Here is the log

http://farm9.staticflickr.com/8446/7811175574_eb475f85e3_o.jpg


The top rpm trace is using the separate sensor, where the bottom trace is using the rpm input on the dl32 getting its signal from the tach output.

Notice starting at 14 seconds, I am just working the throttle in small increments. See how the bottom trace doesn't really show it and at times shows up to 400 rpms off.

Then at 18.19, I snap the throttle, watching the tach it goes to about 4600,which is in line with what the new pickup shows, where the old input only shows about 3900. Then notice on the decel at 18.60 how the rpm doesn't drop as rapidly as the the new sensor setup.

Its seems to read accurate when its at a more steady state or slowly changing rpms, but has a hard time picking up the quick rpm changes.


I will be running it next week with both sensors to see the difference.

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 Post Posted: Sat Aug 18, 2012 8:14 pm 
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My guess is it's probably something to do with the sample rate of the DL-32, which I believe is 10 x per second. Blipping the throttle will probably exceed that sample rates capability but you're not likely to see that much variance down track except for the gear change.

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 Post Posted: Sat Aug 18, 2012 8:42 pm 
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Joined: Thu Feb 12, 2009 7:52 pm
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You would think if it was a sampling rate issue, both channels would have the same issue.

Not that its much different, but it samples every 81.92 milliseconds which works out to about 12 times a second.

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Best 9.87@131 on the rev limitor 1 Feb 2013
1/8   6.15@110 NEW BEST 27 Nov 11
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