How Does a Lambda Sensor Work in a Common Rail Diesel

[fastlane1]

Well you are correct and well written.

Petrol cars use one wide band lambda pre cat and one narrow band post cat. Usually there are maybe some cars that dont have that setup but they are rare.

I used to tune RX-8 cars and have seen some BMW tunes aswell.

Closed loop on an RX-8 is only under 3400 RPM (if I remember correct, it was some years ago now) and steady state and is only driven by readings from the wide band lambda. Open loop is then you use the gas pedal and then the car uses AFR tables and readings from a MAF sensor.

But modern cars are smart and can adjust them self some. I know when I tested piggy back unichip the RX-8 over time compensated for the Unichip and the tune was almost gone. You have to reset the cars LTFT (long time fuel trim) by disconnect the battery for min 20 minutes.

Thats why remap always is superior to try to foul a modern ECU, I dont know how the GTD ECU works but maybe its the same here. The GTD self compensate with the LTFT to make the Box ineffectly?

I know to little about diesels and the GTD to say it will be like that but one thing is sure. Its always better to remap then try to foul a modern ECU.

 

[chrismc]

Without doubt. I have never argued that.

It's important not to confuse diesel & petrol tuning though.

Tuning boxes DO NOT suffer with this drop in power BS. I ran one on a diesel Leon for 150k miles. Fault free. The box eventually failed so replaced it with a generic remap myself & the car drove absolutely identically as to when the box was working.

 

[fastlane1]

But diesel ECU still uses STFT and LTFT?

 

[chrismc]

Yes as I understand- but this is only in closed loop & only a fine 'trim'

Remember when cruising on a steady throttle the fuelling requirements are nigh on identical between stock & mapped diesels. No extra demand on the system or need for any more fuel...

 

[fastlane1]

Ok there are some differances between petrol and diesel then.

 

[golfhappy]

Here's a thought whilst driving today as regards the open closed loop operation, looking at the MFD at the "which gear you are in" under load gives an indication to change up, so open loop? and whilst say in 4th feathering the throttle, closed loop?

 

[fastlane1]

If I had a more complex software and connect it to the OBD2 contact I could tell how it works exactly... Maybe I get some? What are out there for VW diesels? Vagcom? Is that something useful?

I strongly dont think that GTD only uses STFT and LTFT only in closed loop, it would be a waste of good finetuning for the ECU but I dont know... Yet

 

[chrismc]

Well regardless of whether it does or not- the point I was trying to make is Lambda doesn't 'correct' for the extra fuel thrown in by a tuning-box & trim back to standard power.

If this was the case then remapped cars would also suffer as physics dictates more power comes from more fuel injected (&/or) more boost!!! All spent gasses have to pass across the same said Lambda probe.....

 

[fastlane1]

Sorry but you are wrong.

A remapped car wont try to compensate because it checks in its ECU table and wont try to compensate because its correct values.

A Box that tricks the ECU is a different story, the ECU can try to compensate for the wrong values.

But still, I dont know if this is the case with the GTD ECU but now I am so curious so I have to find out.

Anyone know if there are any tuning software for GTD to buy or freeware?

 

[rapport25]

Sorry but you are wrong.

A remapped car wont try to compensate because it checks in its ECU table and wont try to compensate because its correct values.

A Box that tricks the ECU is a different story, the ECU can try to compensate for the wrong values.

But still, I dont know if this is the case with the GTD ECU but now I am so curious so I have to find out.

Anyone know if there are any tuning software for GTD to buy or freeware?

Agree 100%. A remapped car is running a richer AFR vs a car running a tuning box. IF the car senses a richer AFR via a tuning box, it will trim back the AFR which will result in reduced power.

Not getting into a debate, just stating what is fact in my thread.

VAGCOM should be able to show how the car is running.

Rappy

 

[rapport25]

Have a read of this link..

http://www.aet-turbos.co.uk/blog/story/the-pursuit-of-power-ecu-remapping-vs-tuning-box


How a Tuning Box works...

Tuning boxes work in a different way – essentially overruling the ECU and tricking it into increasing engine performance. Fitted between the engine sensors and the actuator, a tuning box sits down the line from the ECU, and alters the data that the ECU receives and sends to the engine.

This means feeding the ECU inaccurate data about fuel pressure and telling the ECU that the fuel pressure is lower than it is – so the ECU forces the engine to increase the fuel pressure to compensate, boosting engine performance.

However, this can be dangerous, and there’s always the chance that you overstress the engine, causing unnecessary wear and tear and reducing the lifespan of your engine.

Rappy

 

[rapport25]

The only error on my part, is the boost via Lambda comment. I agree that is not correct

Rappy

 

[golfhappy]

AET turbo's are e remapping company...any remapping company would tell you where to shove a tuning box! me guesses it's where the sun never shines!

 

[fastlane1]

AET turbo's are e remapping company...any remapping company would tell you where to shove a tuning box! me guesses it's where the sun never shines!

Can't find any inaccurate information on their homepage.

 

[golfhappy]

To be fair you're right and if you go searching how a tuning box actually works, well it's easier to find out what the masonic secrets are! but over on the Seat forum the guys actually love DTUK boxes and they perform.
I did stick a Racechip box on my mk2 leon and it always performed. I can see how things go belly up when you start to screw at its settings to squeeze more power out of it.