wrote 5 months ago
Thank you very much for your comments. With how "thorough" I'm attempting to be, I am just a stone's throw away form ECU-land. You first sentence is what I have loved about this project from the get go as the dynamic range of theory is simply immense and enjoyable; albeit, it's a bit overwhelming at times.
I can tell from you comments that you're somewhat familiar with gasoline engines. This is an absolute pressure sensor so I can easily measure vacuum and my test bed is a diesels engine, which do not produce vacuum natively. Though less common in gas applications, diesels commonly use VNT/VGT (variable nozzle/geometry turbos) base turbos. I'm witness to several compound builds where the working pressure is 40-50 psi. I myself run 29-32 psi. Due to the VNT application, exhaust manifold pressures are required to be monitored and are tuned to be no higher than 1.5x IMP/Boost, thought when initially starting out 2:1 isn't uncommon. This is why a 100 PSI-a sensor, ~85 psi-g is a design criteria. Though 0.25% isn't that great across 100 psi, my ECU has little concern keeping me smokeless with a 4-bar sensor with an 8-bit DAC. The sensor's response time is 1 ms, fyi. Because AFR is highly desirable by some using a dedicated WBO2 sensor instead of fudging it, but we'll see how things go.
Yeah, these guys are a bugger. It's relatively simple for either you or I to create a simple calibration profile for a one off design and the application for this device means that it should be a simple technical procedure for those who know enough to know why they want to use a device like this, but including some software smarts is bound to help. with IATs in forced induction, temperature can change really easily. that 3-5 second slew rating is a bit of a concern, but it can be predicted with a little differential equation math, if I recall my Calculus properly. For example, I live is SoCal (Southern California) and this week we will have ambient temps of 100˚F. The output air temp of the turbo at 29 PSI will easily be north of 300˚F. Toss D-DAQ into a car in the Mid-West, mountainous regions, and even Canada and we'll see temps of -20˚F quite easily too. With inherent inaccuracy of RTDs, +/- 20%, these are one of those things I want to make sure I get right.
Anyhow, thank you very much for your comments. I appreciate the thoughtful words and advice more than you know. Despite working on this for the better part of 3 yrs, I know I've not thought of everything so I'm love reading up one any of these aspects to make sure I've not missed anything. I'm trying to make D-DAQ configured to where if I can, it's relatively simple to adjust a bit of code to make a correction and/or make a new sensor board for a new parameter to monitor. Again, thank you very much.
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