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Old 07-12-2010, 09:40 AM   #1
Barry Bordes
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Barry do you know your %error on the calculations at all?
The sensor specs are ±1% for Combustion.
The timing trigger that I fabricated adjacent to Mazda’s timing wheel would be the area for greatest possible error.

To check this a test run is then made where the engine ignition is cut at 6000 rpm and the throttle is opened fully. This double-checks TDC in relation to the logged actual compression hump.

To my knowledge the rest are calculations.

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Old 07-14-2010, 10:17 AM   #2
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Originally Posted by Barry Bordes View Post
The sensor specs are ±1% for Combustion.
The timing trigger that I fabricated adjacent to Mazda’s timing wheel would be the area for greatest possible error.

To check this a test run is then made where the engine ignition is cut at 6000 rpm and the throttle is opened fully. This double-checks TDC in relation to the logged actual compression hump.

To my knowledge the rest are calculations.
By sensor specs for combustion do you mean the transducers? Out of curiousity how did you calibrate your transducers? Did they calibrate them for you and ship them with a cert of it (sorry for the questions, it's the engineer in me again--we've been repeatedly told "never trust some one elses calibration unless you absolutely have to"). Would I be correct in assuming the sensors are linear in nature until a certain point, or are they non-linear from min-read to max? (out of curiosity do you know what the resolution of your timing sensor is? ie: can it read only 1 degree or can it read minutes, or seconds?)

If you know the calculations they're running for any given reading you can easily perturb the uncertainties to get a culmulative percentage of error. That way you can at least know the accuracy of your results. From my glances you could be on the mark or you could be slightly off. Without the error it's hard to gage application to different stress/repeatabilty.
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Old 07-14-2010, 05:27 PM   #3
Barry Bordes
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Originally Posted by vex View Post
By sensor specs for combustion do you mean the transducers? Out of curiousity how did you calibrate your transducers? Did they calibrate them for you and ship them with a cert of it (sorry for the questions, it's the engineer in me again--we've been repeatedly told "never trust some one elses calibration unless you absolutely have to"). Would I be correct in assuming the sensors are linear (yes linear) in nature until a certain point, or are they non-linear from min-read to max? (out of curiosity do you know what the resolution of your timing sensor is? ie: can it read only 1 degree or can it read minutes, or seconds?)

You realize at 360º X 8000 rpm it is taking at almost 3 million samples /min. My laptop is the restriction right now and I would like to add 2 more sensors ( for intake and exhaust ports).

If you know the calculations they're running for any given reading you can easily perturb the uncertainties to get a culmulative percentage of error. That way you can at least know the accuracy of your results. From my glances you could be on the mark or you could be slightly off. Without the error it's hard to gage application to different stress/repeatabilty.
Vex, check out this info, (Very accurate and cost effective, an interesting combination).

For aircraft testing instrumentation we had to recertify sometimes every six months. I don't want to certify different dynos for the FAA or DOT. I want it to be accurate but I will pass on recertification.

Really I just want to know is this log an improvement or have I gone too far!
I am using it just like our Datalogit tuning for AFR, transition, etc.

http://www.optrand.com/Papers/fisita98/fisita98.htm

Barry

Last edited by Barry Bordes; 07-14-2010 at 05:54 PM.
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