Shop OBEX P1 Docs P2 Docs Learn Events
Low pressure sensor — Parallax Forums

Low pressure sensor

sidecar-racersidecar-racer Posts: 82
edited 2014-10-19 12:31 in Accessories
I'm looking for recommendation for a low pressure air sensor; 0-5psi (other ranges considered) it's to be used to measure intake airbox pressure (expected to be positive value at high speed due to ram air effects). Output can be 0-5vdc, i2c or spi (I have different data acquisition options. Existing a/D is 12bits. We're seeing a lean fuel air mixture at high speed at 5000ft so thinking the fuel injection computer isn't smart enough to adjust. Plan to adjust external.
Rick Murray

Comments

  • pmrobertpmrobert Posts: 673
    edited 2013-03-21 13:49
    Motorola MPX series is what I would use. I have used them extensively for manifold, pre- and post- turbo absolute pressures, exhaust backpressure (w/isolating stainless tubing), crankcase pressure, etc.They make them in several different ranges, I think they make a 4100 which has 100 kPa as max, lower ranges may be available. I have a little experience with airflow/ram effect, etc. - ram air usually doesn't work as common sense would dictate. NACA ducting, etc., have been more effective in this regard than the more obvious concept of scoop-on-a-hood type arrangement.
    -Mike
  • sidecar-racersidecar-racer Posts: 82
    edited 2013-03-21 15:35
    We're running two 6" Naca ducts with short stright runs into airbox. The ducts are part of factory (LCR) body so one would think they should be in right place *grin*. Fuel Sonoco 105 had stochastic(sp?) value of 14.0, talked with Sonoco engineer and he felt 14.7 was way lean. Engine was dyno-tuned (at sea-level) so should have been rich at Bonneville. Would love to compare notes with you, we're shooting for world record in August.
  • pmrobertpmrobert Posts: 673
    edited 2013-03-23 06:45
    Rick, that sounds extremely awesome! LCR as in LCR Honda? 14.7? If any significant load/power, that's going to turn some expensive aluminum into cool expensive melted shapes, but you know that. As far as altitude effects I've found the only sure thing is that there's less ambient pressure. Depending on your intake and exhaust tract harmonics, restrictions, cam timing, presence or absence of either MAP sensor and/or baro sensor, etc., etc., etc., it can be a Smile shoot. The lower ambient pressure, while reducing potential mass flow in the intake, also makes your exhaust flow better - it's exhausting into less pressure and into a potential lower pressure area due to aerodynamics - this can cause lean areas to appear when actually underway. What class are you running at Bonneville? What ECU are you using? What's the base engine? PM if you wish, I'd like to speak with you at your convenience.

    -Mike

    After 5 seconds of research you must be speaking of the Swiss sidecar chassis manufacturer LCR...
  • sidecar-racersidecar-racer Posts: 82
    edited 2014-09-25 20:01
    Hello Mike, It's been awhile but I thought I'd let you know what we found. We had done a gear position lockout on ECU placing box in 5th gear (this increases advance/torque in lower gears and increases redline in 6th [186mph limit required by DOT]). Well, it also disables airbox pressure compensation circuit! Therefore caused 14.7 reading. Removing resistor gave us 13:1. Salt sucked so did only 151.6mph. I did build up a pressure sensor setup using bosch sensors (cheap) but never installed it after finding our about ECU issue.
  • driveno11ferdriveno11fer Posts: 1
    edited 2014-10-17 21:14
    Low sensor's?
  • pmrobertpmrobert Posts: 673
    edited 2014-10-19 12:31
    Thanks for the followup - that's a cool story illustrating "the devil is in the details". 151.6 is still moving down the road for sure - I envy you!
Sign In or Register to comment.