MRE Crank / Cam Sensors

[cribbj]

All of you who are tired of those lo-res VR (mag pickup) sensors, and don't want to attempt the not-insignificant task of implanting 36 Hall magnets in a crank wheel, take heart. The Toyota MRE sensor has arrived.

MRE stands for "Magnetic Resistance Element" and Toyota has started using these for crank & cam sensors in the new 4.6l 1URFSE motor in the LS460.

Imagine a sensor that produces a crisp square wave like a Hall, but from a standard crank wheel - no magnets required. It's non speed dependent, so it produces the same square wave during lo-rpm cranking speeds as it does at 7000 rpm.

Denso who make this little gem say this about it:

Benefits and Features (MRE Type)

• High detection accuracy
  • DENSO’s cam/crank position sensors use a unique arrangement of two pair of MREs on an IC chip, achieving high detection accuracy, including just after the engine starts. The MRE cam/crank position sensors have almost 10 times higher sensitivity than Hall element cam/crank position sensors.
  • In DENSO’s MRE cam/crank position sensor, the molded IC chip is installed inside a cylindrical magnet, which means the IC chip is positioned closer to rotor gears rotating with the cam or crank shaft, providing even higher sensitivity.
• High reliability
  • The molded IC chip and the cylindrical magnet are integrally covered with poly phenylene sulfide(PPS) resin for greater strength.
  • PPS resin has high resistance to chemical substances including fuel, engine oil and emissions.

I can't wait to get my hands on one of these and try it out. It should do very good things for stabilising engine timing.

 

[Lextreme II]

Hi John,

Do you know if this part is available yet in local Lexus dealers since the car is not officially out yet. Do u happen to know the part number. I can get a price on it.

 

[cribbj]

David I don't know much more about it just yet - I was going to try my Supra parts guru up in Chicago tomorrow to see if he knows about them yet. They should be a real improvement for anyone who wants to go with a Hall setup for its more precise triggering, but doesn't want to go through the pain of installing a bunch of magnets in a trigger wheel.

I've been studying the NCF information for that new motor, and it's got some other nifty features besides these MRE sensors:

Dual VVTi system with the intake operated by an electric motor

Direct injection plus regular intake port injection (the ECU determines which or both systems to use!)

DIS COP ignition (of course)

A very innovative PCV system which they call blow-by ventilation.

They've abandoned the scissors gear mechanism and have gone with separate drives for the intake and exhaust cams - probably as a result of the dual VVTi system. It also appears they're chain driving the cams, rather than with the usual cogged belt. Perhaps this means they've gone to an interference design now too.

Plus lots more interesting goodies.......

 

[MaxPower]

These are also available for eur12.50 each when bought in qtys of 1-4, airmail delivery to oz is eur12.50. Not sure how good they are but are what some aftermarket EMS companies are selling for around the AUS$60-70 mark.

Here is the data sheet, CYGTS101DC where the ones i was looking at (not direct bolt in though, close though)
www.cy-sensors.com/Gear Tooth Sensor.pdf

And to convert prices.... http://www.xe.com/ucc/

 

[cribbj]

That's a better price than I found. Cherry Switch in the US are also selling them as their model GS1012 here: http://www.cherrycorp.com/english/sensors/gs1012.htm

Their distributors in the USA stock them for between $23 and $26 USD apiece.

I'll see how much Toyota want for them, and then will probably pick up some samples.

 

[cribbj]

Resurrecting this thread as I've purchased a few of these Cherry MRE sensors now and have some pics for comparison.

The sensors are similar in size to the crank pickup sensor, which makes them a little larger than the cam pickup. Actually the "sensing" bit is the same diameter as both, so it'll fit in the holes, however the center line of the mounting tab for the MRE is spaced about 1.5mm further outboard than the crank sensor, and about 6.5mm further outboard than the cam sensor. No biggie for someone with a dremel ;-)

I'll be doing some testing of the MRE over the next week or two, hopefully with a 'scope, to get some idea of its resolution and capabilities. If this thing is as good as it's being represented, there'll be no more need of "standard" magnetic pickups (except in cases where a +5v or +12v supply is not available), nor standard Hall sensors.

It's interesting to note that Toyota have now switched over to using these things exclusively on the new 5.7l Tundra motor, and I would guess the same for the 1UR in the LS460? No magnetic pickups at all on these new motors.

 

[andrew k.]

cribbj,
I am researching every source I can find on MRE's, just to get up to speed. It sounds like a really great upgrade. I think for me it would be best to get my engine done, up and running before trying the MRE's. One less thing to blame, if you know what I mean. I have the SM3 Autronics ECU and MRE's should be a good upgrade. Please keep up the great work and let us know the outcome of your testing.

 

[rms]

John,
VERY interested in the Cherry MRE.
If they hold timing position of the square wave to around 40,000 cycles/min will be great.

 

[cribbj]

Erol, I don't have the detailed spec on the Cherry sensors, but similar sensors from Siemens are supposedly rated to over 100 KHz. With a 36 tooth gear that's equivalent to 167,000 RPM.

What I'm curious to see is if they'll respond OK to a 100mm 60 tooth gear because the teeth on that gear will be much smaller and more closely spaced than recommended for a speed sensor.

 

[turboandrew]

Sounds like this is just a VR sensor and a signal conditioner in one, right? I wonder if not having several feet between the sensor and the conditioner is what makes the sensing range increase so much.

BTW, has anyone really had any problems with the regular VR sensors? I've never heard of anyone having issues with them on 1/2/3UZ.

 

[cribbj]

Andrew, I've read somewhere that it's a pair of Hall sensors feeding a comparator. Here's Toyota's explanation of it, which makes it look more like a VR sensor with comparator. Still think it's a pair of Hall sensors feeding a comparator, however ;-)