problems with fuel consumption

[kike_kike]

hello
I have a rb25det neo mounted on a patrol GQ and I have problems with fuel consumption and I don't know where to look for the problem.
With 17L I travel 60 km, checking by filling the tank and then refilling.
The ECU is stock and turbo with these features 
Compressor Size:
* Inductor diameter: 52.7mm
* Extruder diameter: 76.2mm,
* A/R: 0.5
Turbine size:
* Inductor diameter: 65.2mm
* Extruder diameter: 48.2mm
* A/R: 0.63
Maximum blowing pressure 0.9 Bar.
Front intercooler with dimensions: 550x300x65 mm.
I attach a photo with ecutalk with the values at idle.
Also comment that I have an AFR watch, it is not connected to the ECU, and with a slight accelerator load and turbo pressure of 0.2 Bar more or less, the AFR measures 13 13.5.
If I accelerate fully, the clock measures 10.5 AFR with turbo pressure of 0.9 BAR
What things should I look at to know that it is failing.
Thank you

[Dose Pipe Sutututu]

You need an aftermarket ECU, you can't just put a bigger turbo on and expect things to be all hunky dory

[Duncan]

Unfortunately, an rb25 in a GQ is never going to be a vw polo, an m3 or some other fuel efficient, error light showing shitbox.

Couple of things

- the ECU will try and run closed loop based on your o2 sensor in most idle and light throttle conditions. That screenshot shows you are running rich (although, we can't tell from one point if it moves around). Basically, your narrow band o2 manages most fuel economy and should rapidly fluctuate above and below 14.7

- a standard ECU with a bigger turbo will go super rich with mid to full throttle

first up, put in a working 02 sensor (can be a standard narrowband, or wire the narrowband output of your wideband to the ECU), and switch to a PowerFC, and get a quick tidy up tune. That will get you 95% as good as you ever will with a little 80s turbo engine in a heavy 4wd at minimal cost. Nistune could also work if you can find a suitable donor ECU.

BTW, it could be much worse, I have a td42 in my gu and it both makes no power AND uses way too much fuel. On the bright side it will keep running well into the apocalypse

[robbo_rb180]

easy fix is LS conversion.
A mate went through this issue a long time ago. The rb doesn't make the torque required for that chassis and I imagine you'll have big tyres too which just makes it worse.

 

[Dose Pipe Sutututu]

Another option is to pop in a RB32 stroker, Samsonas and all the supporting mods.

Big torque, short gear ratio box would help with getting out of situations, towing and economy.

[kike_kike]

Hi everyone

I understand that this engine in a 4x4 will consume much more fuel than in the original car.

The thing is that a colleague has the same car configuration, engine, including the same turbo, 
wheels, gearbox and differential group and his consumption is 16-17 L/100Km, my 
consumption is 30L/100KM, that's why is the query here

So I understand that for everything to work properly I have to mount an aftermarket ECU 
and tune it

Thank you

Edited December 6, 2022 by kike_kike

[kike_kike]

2 hours ago, Duncan said:

Desafortunadamente, un rb25 en un GQ nunca será un vw polo, un m3 o alguna otra luz de error que muestre una caja de mierda que ahorra combustible.

Un par de cosas

- la ECU intentará ejecutar un circuito cerrado en función de su sensor de O2 en la mayoría de las condiciones de inactividad y aceleración ligera. Esa captura de pantalla muestra que se está haciendo rico (aunque no podemos decir desde un punto si se mueve). Básicamente, su O2 de banda estrecha maneja la mayor economía de combustible y debería fluctuar rápidamente por encima y por debajo de 14.7

- una ECU estándar con un turbo más grande se volverá súper rica con aceleración media a máxima

primero, coloque un sensor de 02 que funcione (puede ser una banda estrecha estándar, o conecte la salida de banda estrecha de su banda ancha a la ECU), y cambie a un PowerFC, y obtenga una puesta a punto rápida. Eso lo hará 95% tan bueno como siempre con un pequeño motor turbo de los 80 en un 4x4 pesado a un costo mínimo. 

Por cierto, podría ser mucho peor, tengo un td42 en mi gu y no genera energía Y usa demasiado combustible. En el lado positivo, seguirá funcionando bien en el apocalipsis.

 

The ECUs of rb25det neo are not all compatible with nistune?
In this aspect I am very lost.
I am in Spain and these "cars and engines" are not very well known here.
The td42 was not sold in Spain either...

Edited December 6, 2022 by kike_kike

[Duncan]

6 hours ago, kike_kike said:

...The td42 was not sold in Spain either...

Spain is very fortunate then

I'm not a nistune specialist, but I'm pretty sure rb25det ECU is not supported. PowerFC is cheap, easy to tune and suitable

[kike_kike]

 

ok, I'll talk to the tuner to see the PowerFc.

I have also checked the pressure in the injector rail and I have 2.65 bar at idle and with the regulator vacuum tube disconnected 3.40 bar. According to the manual it has to be 2.45 bar at idle and 2.90 bar with the regulator vacuum tube disconnected. I don't know if this variation is enough to determine that the pressure regulator is not working correctly.

[Dose Pipe Sutututu]

RB25DET R34 NEO ECU is supported by Nistune
RB25DET R33 ECU IS NOT supported by Nistune

Some NOT all NEO ECUs are support, it must be one of these ones:

• R34 RB25DET (JECS) 23710/23740-AA5xx
• WC34 S2 RB25DET (JECS) 23710/23740-0V8xx

[joshuaho96]

1 hour ago, kike_kike said:

 

ok, I'll talk to the tuner to see the PowerFc.

I have also checked the pressure in the injector rail and I have 2.65 bar at idle and with the regulator vacuum tube disconnected 3.40 bar. According to the manual it has to be 2.45 bar at idle and 2.90 bar with the regulator vacuum tube disconnected. I don't know if this variation is enough to determine that the pressure regulator is not working correctly.

You probably have a few different issues. The first is that an RB25DET NEO will require a ton of work the moment you change airflow beyond stock limits as the stock ECU tune has protections built in. This is part of the reason why your fuel economy is aggressively awful. Your fuel pressure regulator may have been modified as well in the past, not unusual for people to tap the top of one with a punch to adjust the spring pressure. Or to drop it on accident. The spec is likely a standard 3 bar regulator, the tolerance there isn't going to be 0.4 bar either way but you can check the factory service manual to be sure.

Even older ECUs like what runs on the RB25DET for R33 they're still going to drop like 5 degrees of timing at least if you flow more air than what is expected as a reasonable max for the stock turbos. I can pull up Nistune to be sure but that's my experience with the RB26.

[Duncan]

21 hours ago, Dose Pipe Sutututu said:

RB25DET R34 NEO ECU is supported by Nistune
RB25DET R33 ECU IS NOT supported by Nistune

Some NOT all NEO ECUs are support, it must be one of these ones:

• R34 RB25DET (JECS) 23710/23740-AA5xx
• WC34 S2 RB25DET (JECS) 23710/23740-0V8xx

I just re-read the first post, it is a NEO so nistune may well be an option (noting that taking the existing ECU out and sending it to be modified might not be convenient compared to a bolt in replacement like PFC)

[kike_kike]

 

hello

The regulator doesn't seem to be punched, so it's probably broken, I'll look for one and try it.

I'll look for a nistune distributor and talk to him.

Thank you all for the answers and suggestions