Running rich at idle and poor fuel economy after mods and tune

[aminoskee]

Hello everyone,

 

I have been a long time reader of this forum and a first time poster.

 

I have a 2011 FG xr6 Turbo which I purchased second hand back in 2013.

 

I drove my car stock standard since purchase as a daily.

 

However, recently I decided to modify it to get more power and enjoy the modified car experience.

 

The car has the following mods:

 

- Process west stage 3 intercooler

- Process west race air-box kit with 4 inch turbo inlet

- Process west dual entry billet fuel rail

- Process west battery relocation kit

- Process west fuel stage 2 fitting kit

- Process West fuel anti-surge tank with twin Walbro 460 fuel pumps

- Walbro 460 fuel pumps in the fuel tank

- Bosch 1650cc flow matched fuel injectors (from Quickbitz)

- ARP head studs

- Crow cams valve springs

- Garrett GTX3582R Gen 2

- xr6 turbo development 1.06 A/R ford rear housing with 45mm turbo-smart external waste-gate kit

- Xforce full 4 inch turbo back system

- Yellaterra 10mm billet flex plate

- Gj driveline pro series tail-shaft

- IMS diff hat

- Shockworks coilovers

 

The car was tuned using PCMtec and produced about 430 rwkw on a mainline chassis dyno.

 

well, the car drives well and is perfectly derivable.

 

However, the fuel economy is terrible even when normally driving the car around (like a grandma).

 

The car runs very rich at idle even after it reaches normal operating temperature and the instant fuel economy on the cluster only goes as low as 2.4L/100km which used to be around 1.4 to 1.6L/100km before mods.

 

Also the the engine rpm at idle is now increased to 700 rpm compared to roughly 550 rpm before mods.

 

I was wondering what is causing this and should I even be worried?

 

I would appreciate it if you guys can provide me with your valuable insights.

 

Kind Regards,

 

Amin

 

Edited 21/04/23 04:11 PM by aminoskee

[aminoskee]

I should add that the car is only tune on 98 octane fuel.

[k31th]

Nothing sounds too amiss... Sounds like a beast of a car now that it's modified with that list of things

 

Just ask the tuner to see what he can do about off-throttle fuel use, e.g. cruise conditions. Otherwise, it's probably fairly normal.

[hoe]

What's it like on the highway ?

Mine has similar power, runs fine at idle etc. Gets 8.5 to 9l/100km at 115 on the highway.

[Puffwagon]

13 hours ago, aminoskee said:

The car runs very rich at idle

How do you know this? The O2 sensor will be trimming it to run the same AFR as it always has. The only way it can be rich at idle is if the O2 sensor is stuffed or it has been tuned to ignore the O2 sensor feedback.

 

13 hours ago, aminoskee said:

the engine rpm at idle is now increased to 700 rpm compared to roughly 550 rpm before mods.

It has been tuned this way.

 

The high idle data will fark with the overall economy on the dash. Different size injectors and the data used for them will also make the dash inaccurate. Work out your actual fuel economy by how much fuel you're using from the pump and see if there's a problem there.

[aminoskee]

On 22/04/2023 at 8:40 AM, k31th said:

Nothing sounds too amiss... Sounds like a beast of a car now that it's modified with that list of things

 

Just ask the tuner to see what he can do about off-throttle fuel use, e.g. cruise conditions. Otherwise, it's probably fairly normal.

The car is indeed a beast now 😎

 

Its very quick and aggressive when it comes on boost and fun to drive.

 

I'll be paying a visit to my tuner very soon and hopefully we can rectify all of these issues.

 

22 hours ago, hoe said:

What's it like on the highway ?

Mine has similar power, runs fine at idle etc. Gets 8.5 to 9l/100km at 115 on the highway.

I haven't noticed anything abnormal while driving down the highway.

 

Generally the instant fuel economy as shown on the dash cluster varies between 7 to 9L/100km at 100km/h on the highway.

 

However, the fuel gauge on the dash cluster tends to move fast than before which to me indicates that the dash cluster economy readings are not correct anymore.

 

Also, the fuel gauge is not showing the correct reading when I fill up the fuel tank.

 

The gauge needle shows one notch less when the fuel tank is full.

 

I don't know why that is.

 

Maybe a stuffed fuel level sender or the tuner has made some adjustments in the PCM to have this as a safety feature, ensuring that I never run the fuel tank dry.

 

Just wondering what size injectors you're running???

[hoe]

1000cc, nowhere near maxed out.

Unless your planning on e85, yours are probably too big.

Someone with tuning experience will know for sure....

[aminoskee]

Going e85 and flex fuel is definitely on the horizon.

 

I hope 1650cc injectors can be adjusted and dialed down to get near stock idle and accurate fuel readings on the dash cluster.

 

I guess I'm asking for too much and have unrealistic exceptions...

 

A modified car will never be like an stock car.

 

Hopefully other members with tuning experience can chime in and enlighten us.

 

17 hours ago, Puffwagon said:

How do you know this? The O2 sensor will be trimming it to run the same AFR as it always has. The only way it can be rich at idle is if the O2 sensor is stuffed or it has been tuned to ignore the O2 sensor feedback.

I actually connected the car to FORScan to have a look at O2 sensor reading and fuel trim (STFT) graphs and to my surprise the O2 sensor war stuck at 0.85 volts at idle and the STFT was stuck at zero.

 

I think you are right and I suspect that they have tuned it this way to ignore the O2 sensor reading and fuel trimming.

 

But why would they do this?

 

17 hours ago, Puffwagon said:

It has been tuned this way.

 

The high idle data will fark with the overall economy on the dash. Different size injectors and the data used for them will also make the dash inaccurate. Work out your actual fuel economy by how much fuel you're using from the pump and see if there's a problem there.

I think they did not enter the correct injector data in to the PCM such as break-point, high and low slope and minimum pulse width for the new injectors.

 

Well, at the moment the fuel economy readings on the dash cluster seems wrong and the only way I can get a rough estimate of the fuel economy is to check at the pump and see how much fuel goes in and how long I have traveled.

 

Also, the fuel gauge on the dash cluster is not shown the correct reading since I picked the car up from the tuner.

 

The gauge needle shows one notch less when the fuel tank is fuel.

 

I'm not sure why its not working correctly.

 

I guess either the fuel level sender is stuffed or the tuner has set it up like this in the PCM to ensure I never run the fuel tank dry.

Edited 22/04/23 03:12 PM by aminoskee

[Puffwagon]

Trims at 0 and O2 voltage pegged points to a stuffed O2 sensor.

 

See what it does at cruise too, maybe the idle fuelling is sh*t and it's ok at cruise. Watch the O2 readings for info.

 

A vacuum leak could be causing issues too. If the idle timing is very low, less than 10 degrees, you should look there.

 

The intank pump assembly gets modified to fit a 460. The sender will be at a slightly different level than it was before. Accustom yourself to the new fuel level readings and you'll be fine.

[aminoskee]

Thanks Puffwagon,

 

I'll check these and report back.