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Feedback Request: GRT-Supplied VDO Oil & Fuel Pressure Sensors

Canadian_JOY

Well Known Member
I'm currently considering removing our existing engine monitor, an AF2500, and replacing it with a GRT EIS system which will more easily interface with the rest of the GRT gear in the panel.

Over the years I've read several threads here indicating the VDO pressure sensors favored by GRT are less-than-reliable.
1) Is this still the case?
2) What other pressure sensors have been used to good effect?
3) If using other pressure sensors, is the GRT EIS capable of calibration to provide accurate indications?
4) Has anybody re-used in their GRT EIS installation the very sleek 3-wire pressure sensors provided as original equipment with the AF2500?
5) If yes to 4, how did you implement them? (Suspect using 4.8V instrument power to energize the sensor, as well as the existing Common connection, with the "middle" signal wire going straight into the EIS pin should work, but don't want to incur additional down-time of the aircraft should this not work.)

Thanks in advance for your well-considered replies.
 
VDO sending Units

I have had the GRT EIS system since day one on my RV. The only issue I ever had was due to a grounding issue. I had (dare I say it) put Teflon tape on the threads of the sending unit. The unit grounds through the case. This caused an occasional wild swings in oil pressure.
An easy fix is simply add a ground wire to the unit, I believe I may have read about that fix here on VAF.
No problems since.
I have the EIS connected to my GRT Sport SX, works great.
 
GRT EIS 4000

I've used EIS4000 on all my RVs. I've used 3 other brands and always go back to grt for reliability and accuracy. Only recommendation is to use the stainless steel fuel press sendor. All other sensors I've never had a single issue. I do rear mount my EIS since I customize the face a bit but I say go for it - it's awesome. One smaller recommendation is to use a sunlight readable LED warning light which may then require a 10k ohm parallel resistor.
 
Thanks for the feedback. Several previous posts here gave the impression the VDO senders would produce erratic high oil pressure readings, indicating the wiper arm of the sender had lost contact with the resistive element, producing a full-scale signal output to the EIS. I'm glad to hear positive news on this front, too.
 
Had VDO senders in my plane for fuel and oil pressure. Both whigged out around 400 hours. Yhey wear out. Common problem. I switched over to Kavlico. Nice to see my pressures rock steady.
 
paressure senders

When updating my RV6 with GRT, I was told that most of the probs with the pressure senders is caused by the ground going thru the case. I soldered a tab to the case of each and ran a ground wire from that tab.

3 years and no problems.
 
Jesse - would you care to share what steps you had to take in order to get the Kavlico sensors to work with the GRT EIS, please?
 
Worth noting is that VDO makes their sensors both with grounds through the case (what GRT sells) and with a separate ground stud. Summit Racing carries the latter and they can likely be found elsewhere as well. I've had both oil and fuel pressure VDO sensors fail in 600+ hours of service, the oil pressure sensor twice.
 
Thanks for that feedback, Lars - this kind of confirms my concerns about VDO sensor reliability.

I'm not at all concerned about grounding the VDO sensors as I have had plenty of experience in the use of a gear clamp to bond a ground wire to the case of the pressure sensor. I AM concerned about the long-term reliability of the sensors, hence my wondering whether the Kavlico is ultimately the better sender to use, if they can be made to work for oil pressure and fuel pressure with the GRT EIS.

I appreciate the Summit Racing suggestion - after snooping around their electronic catalog I learned a bit as I didn't know these VDO sensors were also available with built-in low oil pressure warning switch. Using one of these would allow me to eliminate the separate oil pressure switch currently in place.
 
Jesse - would you care to share what steps you had to take in order to get the Kavlico sensors to work with the GRT EIS, please?

Sorry, I have an AFS 4500 so not an exact match. I was commenting on the senders, not the EFIS.

That said, the VDO senders provide a varying resistance, whereas the the Kavlico's, needing 5 volts in, I think provide a varying voltage. To make them work with the AFS unit, I had to get help from Advanced Flight. They said either I could send it in, or do the mod myself. They sent me a sheet on how to do it. Pretty simple mod, but I had to take the unit apart and scratch away 2 circuit pathways on the engine monitor printed circuit board. Easy peasy. Took way more time to remove, disassemble, re-assemble and re-install the EFIS than to actually do the mod. The original design of the board had different senders in mind.

Of course, I then had to wire up the new senders and provide the 5 volts from the unit. That was easy though as the manifold pressure sender (which is already on the front side of the firewall) has 5 volts run to it from the monitor board.
 
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Thanks for that clarification, Jesse. To your point, I had been looking at buying an AF3400EE to replace my AF2500 and AFS tech support had provided me with the same procedure to convert the AF3400EE from resistance sensor to voltage sensor.

I pulled the trigger today on ordering a new GRT EIS-66R and Sport EX EFIS to use as the primary display for engine data. Hope to pick them up at OSH and get cutting a new panel in August.
 
Slightly tangential to the current discussion... my ground transportation unit (GTU) is a 1970 Ford Bronco. When I bought it 22 years ago with 51k original miles on it all the instrumentation worked perfectly including the oil pressure gauge (electric, not mechanical). I put another 100k on that engine then moved the sensor to the current engine which now has almost 100k miles on it. I recently tee?d a known good gauge into the pressure port to check the OEM gauge/sensor. Still accurate. The (one wire) sensor is now 48 years old and still works perfectly, or at least perfectly enough. Go figure.
 
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