Digital $30 trans PSI sending unit, works great!

[Mr. P.]

This is not a how-to but more of an FYI -

I found a cheap accurate pressure sending unit on eBay for $30 shipped (pigtail included!), I verified its output with several known sources (air compressor & gauge, and mechanical trans pressure gauge) and it works a treat. The seller is "renbusan" and the eBay store is named "Industrial-stuffs". The sending unit I used is labeled "500-psi", is accurate to +-2%, runs on a +5-volt source, and has a third wire which is the sensor voltage output which can easily be monitored as a Flashscan analog input, the formula for the custom PID = "iff({EXT.AD3} > 0.4, ({EXT.AD3} - 0.4) / 0.0077, 0)".

Mr. P. :)

PS - the same seller has a 100-psi sending unit that would also work well for monitoring fuel pressure, for $30-shipped - this is by far the cheapest option I have seen for a fuel pressure sending unit, although I don't know what the PID for it would be (you would have to determine that with testing). The next cheapest fuel pressure sending unit that I know of is the $65 one sold by Aeroforce.

[Chuck L.]

Here's the link..
http://cgi.ebay.com/ebaymotors/Pressure-transducer-sender-100-psi-oil-fuel-air-_W0QQcmdZViewItemQQhashZitem3a64d155b6QQitemZ25079 9543734QQptZMotorsQ5fCarQ5fTruckQ5fPartsQ5fAccesso ries

Sure beats the $135 from Summit!

[Mr. P.]

For all we know they might even use the same ASIC inside!

[ScarabEpic22]

Hmmm thats really tempting, and Id probably get the 500psi for trans and a 100psi for fuel. Not running boost yet, but for $30 its cheap insurance that your pump is putting out the correct pressure. And be able to see what you're actually getting vs commanded trans line pressure...

[ryans1000]

anyone try the 100psi? i think I'm going to buy one. says linear output. would this work for turbo backpressure also?

[nevinsb]

Probably not, the exhaust side is pretty hot.

[ls327]

much less expensive than summit...

[Chuck L.]

You could use the sensor with a length of copper tube as a heat sink. I did that w/ a common gauge and had no problems..3' of copper tube.

[Racing2Fast]

Here's the link..
http://cgi.ebay.com/ebaymotors/Pressure-transducer-sender-100-psi-oil-fuel-air-_W0QQcmdZViewItemQQhashZitem3a64d155b6QQitemZ25079 9543734QQptZMotorsQ5fCarQ5fTruckQ5fPartsQ5fAccesso ries

Sure beats the $135 from Summit!

why cant i find that kind of price these days. sigh.

[ryans1000]

i ordered that ebay one yesterday

[joecar]

Ryan, let us know how you go with it.

[ryans1000]

did a test and here is what the 0-100psi sensor output

voltage-----Air Compressor Gauge-----1.5" Liquid Gauge
--------------------------------------------------------
1.47v-----30psi-----24psi
1.91v-----40psi-----35psi
2.36v-----50psi-----46psi
3.57v-----80psi-----77psi
4.35v-----100psi-----97psi
4.48v-----???-------100psi

Not sure but I'm guessing the 1.5" liquid gauge was more accurate because it is 0-100psi vs the air comp gauge was 0-200. Also note the 1.5" gauge and sensor was at the end of a 50 foot air hose.



Looks like the formula may be psi = (voltage-.5v)/.04 . What do you guys think?

11770

[ls327]

yes, the liquid gauge looks more accurate..

[Chuck L.]

In the FWIW dept:
I've tested many of the small gauges, [Summit, Jegs type], against the certified gauge on my injector flow bench... Most don't come close.
However, once the deviation is established, it will repeat at most all the test pressures...
I've also seen the liquid filled units be affected by under hood heat. [Were rail mounted].

[joecar]

did a test and here is what the 0-100psi sensor output

voltage-----Air Compressor Gauge-----1.5" Liquid Gauge
--------------------------------------------------------
1.47v-----30psi-----24psi
1.91v-----40psi-----35psi
2.36v-----50psi-----46psi
3.57v-----80psi-----77psi
4.35v-----100psi-----97psi
4.48v-----???-------100psi


Looks like the formula may be psi = (voltage-.5v)/.04 . What do you guys think?

Yes, that's what I get...

you can simplify it to: psi = (volts*25)-12.5

[ryans1000]

i'm going to feed the sensor in through the 3 egr pins 41, 47 and 55. When I enable egr in b1301 will that effect any other areas/tables?

[joecar]

Table B5907 EGR Spark Correction will contribute to final spark.

[ryans1000]

got it installed, seems to be working fine. so on the stock fuel rail with dual walbro pumps, I'm getting a fast fluctuation from 54.5 to 60psi . Base pressure is set to 58psi. Regulator is before the rails obviously as there is no return port on the rails. This image is with the car off and just the fuel pump turned on. Haven't had time to drive the car yet, maybe tomorrow. Is this normal????

click here
11828

[ryans1000]

well my sensor started reading about 10psi too low all the sudden after only a few weeks use. contacted the seller and he sent me a new one. so i'm not sure if this sensor is cheap junk or just a freak defect. I'll keep you guys updated on the new one.

[joecar]

Thanks for the update.

[ryans1000]

my 2nd sensor for this company also is not working correctly after only a couple weeks. Can the e85 be causing this or is the sensor just a piece of junk? does the e85 actually touch anything sensitive on the sensor?

[joecar]

Ask the company if this sensor is affected by fuel touching it... and ask if they have any fuel specific sensors.

[LReiff]

Any updates on these sensors?

[ryans1000]

the company sent me a 3rd new sensor but I haven't tried it. i would just go with a different one if I were you :)

[ryans1000]

I ended up buying an autometer sensor to replace the ebay sensor.

before I installed it I was checking voltages on the 3 sensor harness wires and noticed the harness ground wire has .8 volts when I check it with the voltmeter to chassis ground. The harness ground wire is directly connected to blue connector pin 41 (EGR Pintle position ground) . Is this normal ?

[ryans1000]

and to add more information the red 5v wire shows 5.8volts when referenced to chassis but shows 5.0 volts when referenced to computer ground.

[badls1]

do these sensors work better when just using air? thinking of getting a couple and logging back pressure/intercooler pressure drop.

[ryans1000]

do these sensors work better when just using air? thinking of getting a couple and logging back pressure/intercooler pressure drop.

I wouldn't waste your time, they are probably cheap china sensors. I ended up putting an autometer sensor in and its been fine since