Rb26 Fuel Pressure Sensor Tap Location?

[etang789]

Where is the best location to tap for Fuel Pressure Sensor for RB26? Between fuel rail and fuel regulator or fuel regulator and fuel filter?

I have found this sensor adapter for 350z fuel rail, I wonder if it works for RB26 stock fuel rail? this will look the install much more stock looking I think?

I want to use this AEM Stainless Steel PSIg Sensor

http://www.aemelectronics.com/?q=products/sensors-connectors-accessories/map-pressure-sensors/stainless-steel-psig-sensors

Edited December 16, 2015 by etang789

[GTSBoy]

Anywhere between the outlet of the pump and the inlet of the reg is at the same pressure. Doesn't have to be on or near the rail. Unlikely that there is enough similarity between ancient 1980s designed RB fuel rail and 2000+ designed VQ rail that you'd hope to mount it there either.

[sneakey pete]

I'd do it after the filter though, if that starts blocking flow you'd want to know about it

[Paulusc44]

As above, pressure is equal from outlet of pump through to the FPR.. Would be suprised if an VQ35/37 Item would directly fit to an RB26 rail but the thumbnails youve provided actually look very close?

[burn4005]

not actually true. you will have pressure drop over the fuel line from the pump to the rail, which is exacerbated the smaller the diameter it is and the higher the flow. if you have to mount sensor before rail, put it as close as you can to it. after rail position is less important. anywhere between rail and reg is fine.

[GTSBoy]

not actually true. you will have pressure drop over the fuel line from the pump to the rail, which is exacerbated the smaller the diameter it is and the higher the flow. if you have to mount sensor before rail, put it as close as you can to it. after rail position is less important. anywhere between rail and reg is fine.

Wow. So you're going to quibble over 0.2 psi out of 45 or 50?

[zebra]

Wow. So you're going to quibble over 0.2 psi out of 45 or 50?

When reading from a uncalibrated Chinese pressure gauge

[Dose Pipe Sutututu]

just don't tap it on the return line (I've seen this before on a car I went to check, tried to contain my laughter).

[sneakey pete]

Friend just put a bronze tee on his line from filter to rail, then ran a line the 10cn or so to the sensor moubted on the strut tower.

Pressure will transmit fine. At the end of the day it's only going to be an indicator anyway. Pressure doesnt always colloratre with flow.

[GTSBoy]

You actually want to the pressure to be constant regardless of flow. Hence the measuring location and the presence of the regulator.

[89CAL]

Pressure = Resistance to flow

Drop in pressure MAY indicate a drop in flow

Pressure should be equal, shouldnt matter too much as long as you dont put it in the return line as stated above. I'm going to use the gauge port in my turbosmart reg, that is what its there for after all

OP Hasn't really stated the reason for wanting a fuel pressure gauge. Generally they are there to set the FPR, then almost forgotten about unless there is an issue or you happen to be looking under the bonnet while the car is running and glance at the gauge. If OP Is using a standard rail, and wants to put that adapter in, then use the stock reg, thats probably the nicest way to do it on the reg side. Otherwise, as above, easiest option is probably to just tee off the feed line. A barb fitting tee piece, some fuel line and a few hose clamps will cost next to nothing, do the connection down out of sight and run the hose up to a gauge where you want it. Mount the gauge through a bracket to a fitting with another barb and job done?

[GTSBoy]

Actually, he hasn't said he wants a gauge. He does say "fuel pressure sensor" and I was taking him at his word that he was running a decent ECU that will accept a fuel pressure input for safety shenanigans.

[burn4005]

Wow. So you're going to quibble over 0.2 psi out of 45 or 50?

you'd be surprised.

ethanol (@ 1.2cP) at 400lph in an 2.5m x 8mm pipe with a typical surface roughness is more like 4-5psi. add things like bends and it's even higher. if you are using a fuel modelling calc in the ecu that requires injector pressure delta, a 10% error is certainly significant.

example, courtesy of fuelab:

Edited December 18, 2015 by burn4005

[Ben C34]

What kind of dick head would measure fuel pressure at the pump?

[zebra]

Who is using 250gph on a street car?

Unless you're out to win dragweek

cause that is like 2500hp worth of pump.....and if I had 2500hp....I would be using more than one half inch fuel line.

[89CAL]

That graph isn't really too conclusive If you don't know the application it was tested on.

What is at the end of the line? You can imagine that there is a vast difference in pressure drop if you block off the end, or if you have the end open. Its not useless information, but its also not too relevant if there is no information on the test. In theory if the line was dead headed (Blocked) there should be equal pressure along the line (There will be a slight difference from the start to the end)

So for example. if I used a -6AN 14' line, with a 12psi set fuel regulator at 200gph and use that chart, I will get a 12psi pressure drop. How does that work?

[GTSBoy]

Cal,

I wouldn't stress too much over some of the concerns you raise. For one, if you dead head the pipe then there is no flow and you find yourself down at the origin point of all the graphs - no flow and no pressure drop.

The biggest concern about the data is something that you alluded to - which is that the people conducting the test are more likely to be marketing types than product development engineers. So there is a reasonable likelihood that they do not know how to measure static pressure in a line without introducing errors. For example, they might have started the measuring line lengths by connecting the inlet end of the pipe to some larger volume block off which they have tapped the pressure gauge. They'd get a fairly accurate pressure measurement from that location, but they'd get an unrealistic entry loss for the flow going into the pipe. The same might be true for the exit coefficient from the pipe. Were they flowing it out into open space above the receptacle, or was the end of the pipe submerged? Either choice means you introduce factors that you need to either report or account for.

Ultimately it doesn't really matter though does it? Because the simple truth is that NO-ONE ever plans to have their fuel pump unable to keep up with the pressure demand. You always choose a pump that has sufficient capacity so that it is the fuel pressure regulator that sets the pressure in the fuel rail. If you deliberately choose a pump that can't keep up then you are a moron, because now you really are at the mercy of the exact performance of the pump, which might work better on one day than the next, or with variations in ambient or fuel temperature or battery voltage, etc etc. Accidentally finding yourself in a situation where the pump can't keep up (which is how most people find out it's not big enough) is fair enough. But you do not then choose to model the bloody fuel pressure vs flow curve in the ECU so that you can do injection time corrections off of it. You upgrade the pump.

/engineering 101

[89CAL]

I'm not stressed

To me the best place to put a fuel pressure sensor would be Immediatly before the reg or on the reg. That way you know without a shadow of a doubt what your end of line fuel pressure is. Maybe its 2psi more at the rail inlet, maybe its 0.00000001psi more

But like I said, I'm not going to stress about it, doesn't appear as though OP is to stressed either

[etang789]

Pressure = Resistance to flow

Drop in pressure MAY indicate a drop in flow

Pressure should be equal, shouldnt matter too much as long as you dont put it in the return line as stated above. I'm going to use the gauge port in my turbosmart reg, that is what its there for after all

OP Hasn't really stated the reason for wanting a fuel pressure gauge. Generally they are there to set the FPR, then almost forgotten about unless there is an issue or you happen to be looking under the bonnet while the car is running and glance at the gauge. If OP Is using a standard rail, and wants to put that adapter in, then use the stock reg, thats probably the nicest way to do it on the reg side. Otherwise, as above, easiest option is probably to just tee off the feed line. A barb fitting tee piece, some fuel line and a few hose clamps will cost next to nothing, do the connection down out of sight and run the hose up to a gauge where you want it. Mount the gauge through a bracket to a fitting with another barb and job done?

Yes, I want to have a stock looking engine bay so want to use Stock Fuel Regulator and Stock Fuel Rail

Actually, he hasn't said he wants a gauge. He does say "fuel pressure sensor" and I was taking him at his word that he was running a decent ECU that will accept a fuel pressure input for safety shenanigans.

Yes, safety precautions is what I have in mind. And I am running Haltech Platinum PnP so it will be helpful when doing dynos and logs.

I'm not stressed

To me the best place to put a fuel pressure sensor would be Immediatly before the reg or on the reg. That way you know without a shadow of a doubt what your end of line fuel pressure is. Maybe its 2psi more at the rail inlet, maybe its 0.00000001psi more

But like I said, I'm not going to stress about it, doesn't appear as though OP is to stressed either

All I am concerned is if I use this adaptor location would it still be a good reading for safety precautions and monitor health of fuel pump ...etc Edited December 19, 2015 by etang789

[GTSBoy]

Yes it would be perfect, so long as you actually set the Haltech to call off the fun if the pressure drops below some threshold.