Diesel tuning boxes vs closed loop, pls educate a petrol guy
Discussion
Recently bought my first diesel. Experienced with turbocharged petrol tuning (Subaru, Mitsubishi, Nissan) and ECU hacking (open source on Evo IX and for Cobb on R35 GTR), but not into the diesel world, my ECU would need bench work before it can have OBD access, and I would struggle to trust a mapper not to just put a misunderstood piece of junk copied tune on it. Also have DPF. If I could source the connectors it would not be too hard to make my own two channel box as I am good with microcontrollers, but equally it would not be a good use of my time just for my own car.
If a diesel tuning box alters the common rail pressure sensor signal, will the ECU attempt to lean the richer mixture by shortening the injector times via lambda feedback or would it increase the boost or just ignore? If you also alter the MAP sensor signal to increase boost it could mitigate this, but won't the MAF sensor show higher than target air mass?
Can VDCS show you lambda trims on a VAG diesel?
With a DPF, do you just watch EGT and lambda to tell if you are overfuelling? Unlike a petrol, EGT increases with richer fuelling? What sort of max torque or max power lambda are you looking for, or is it smoke and therefore limited by EGT and smoke/DPF loading?
RPM sensing by tuning boxes, do they look at pulsations on the rail pressure or is it a simple lookup based on pressure in which case why not just have a simple pressure in vs pressure out curve? Anyone have any sample values for rail pressure at various loads/engine speeds?
If a diesel tuning box alters the common rail pressure sensor signal, will the ECU attempt to lean the richer mixture by shortening the injector times via lambda feedback or would it increase the boost or just ignore? If you also alter the MAP sensor signal to increase boost it could mitigate this, but won't the MAF sensor show higher than target air mass?
Can VDCS show you lambda trims on a VAG diesel?
With a DPF, do you just watch EGT and lambda to tell if you are overfuelling? Unlike a petrol, EGT increases with richer fuelling? What sort of max torque or max power lambda are you looking for, or is it smoke and therefore limited by EGT and smoke/DPF loading?
RPM sensing by tuning boxes, do they look at pulsations on the rail pressure or is it a simple lookup based on pressure in which case why not just have a simple pressure in vs pressure out curve? Anyone have any sample values for rail pressure at various loads/engine speeds?
Edited by john banks on Saturday 26th April 21:41
Hi John, you could try asking here
http://forums.tdiclub.com/
or maybe here
http://www.efi101.com/forum/
And as for tuning boxes....given the very few wires they seem to hook up to...I just cant think how good any of them can actually be any use compared to proper ecu remapping with access to all parameters.
http://forums.tdiclub.com/
or maybe here
http://www.efi101.com/forum/
And as for tuning boxes....given the very few wires they seem to hook up to...I just cant think how good any of them can actually be any use compared to proper ecu remapping with access to all parameters.
Your fears are real. A crappy map will fill your DPF up in a very short time, killing performance and costing you boat-loads.
One of my vehicles is a DPF equipped TDI. I found a greek tuner who was happy to follow instructions. All UK based tuners just wanted to sell me their "one size fits all performance and eco map".
But I was concerned about a how the turbo originally intended for a safe 103kw worth of power (which is actually ~120kw according to the torque limiters in the ECU, vag power ratings are conservative) would like producing boost for ~30% more power when I sometimes drive to 2,000m altitude.
The wrong tuner could both kill my turbo and fill up my DPF with soot in a very short time.
I had the EGR shut-down and torque limiters raised but fuelling not increased. This let the engine fuel up to it's next set of internal fuel limiters (based on airflow/smoke) releasing a bit more power and torque but not overdoing it and not creating any more soot.
EGT protection is good, but smokey maps will still cough a lot of soot on take-off at low temperatures before the exhaust system is hot enough for the probe to read the true temperature. In a lot of stop/start you'll fill up the DPF quickly. Of course when this happens people always blame the DPF instead of rightfully blaming the hack tuner.
Tuning boxes are rubbish. They just increase rail pressure. Bypassing almost all the internal protection a diesel ECU has.
One of my vehicles is a DPF equipped TDI. I found a greek tuner who was happy to follow instructions. All UK based tuners just wanted to sell me their "one size fits all performance and eco map".
But I was concerned about a how the turbo originally intended for a safe 103kw worth of power (which is actually ~120kw according to the torque limiters in the ECU, vag power ratings are conservative) would like producing boost for ~30% more power when I sometimes drive to 2,000m altitude.
The wrong tuner could both kill my turbo and fill up my DPF with soot in a very short time.
I had the EGR shut-down and torque limiters raised but fuelling not increased. This let the engine fuel up to it's next set of internal fuel limiters (based on airflow/smoke) releasing a bit more power and torque but not overdoing it and not creating any more soot.
EGT protection is good, but smokey maps will still cough a lot of soot on take-off at low temperatures before the exhaust system is hot enough for the probe to read the true temperature. In a lot of stop/start you'll fill up the DPF quickly. Of course when this happens people always blame the DPF instead of rightfully blaming the hack tuner.
Tuning boxes are rubbish. They just increase rail pressure. Bypassing almost all the internal protection a diesel ECU has.
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