NefMoto

So has anyone dipped in to diesel tuning?

I'm just curious if anyone has an explanation of what changes to maps do what in a diesel ECU (VAG cars)?  Like I know people talk a lot about the "smoke map" what does that do even?  Control smoke only? or is there a power limiting issue with that?

I assume pump timing, fuel and boost control will be the main ones along with (apparently) the smoke map.   But I'm sure there is more to it then that even for a "basic" Stage 1/2 tune.

Cheers!

diesel mapping is simple ....
just inject more gasoil at the right time and raise boost enought to burn all the gasoil available .

smoke limiter is just one of injeted quantity limiters .

if it is one thing I've learned when it comes to cars, nothing is simple :)

I understand the basics of tuning a diesel (I used to own an old 1.6L IDI that I modified the pump manually for injection quantity and timing running 20 psi).

But obviously how all the maps in ME7 work together is another issue.

There is tons of info to go on for petrol powered cars... but not much talk about how to even start with the basics on a diesel.

I'm interested in learning this too, possibly with the longer term aim of writing up a good quality technical guide for it, illustrated with maps from a popular engine variant. Aside from the TT, I have had two 2.0 TDi cars before (Peugeot & Toyota) and would go back to a diesel without hesitation. Our next family car might well be a VAG diesel if I have my way and it would be nice to think I could remap it in a quality way myself.

I agree, lots of things including tuning are simple enough to be dismissed in a few sentences by those with knowledge and experience, but very often the subtleties and practicalities are more difficult to master; for instance like raising torque output without sacrificing too much of the good fuel economy diesels are renowned for and without adversely affecting the driveability characteristic.

If somebody wants to point out the key modules of the relevant funktionsrahmen, I'm happy to make a start translating them, making them available on the wiki and understanding the process. I'll run the EDC15 and EDC16 PDFs through Google Translate to get the gist and review what's worth spending time on.

TTQS

Very Basically:

You have a Drivers Wish map, this is RPM vs throttle position.  Units are Injected Quantity of diesel, usually in mg per stroke in EDC15, or in EDC16, in an actual unit of torque, Nm.

You then have a torque limiter map, which restricts IQ, much the same as LDRXN limits boost requested KFMIRL.  The smoke map(s) usually calculate a lambda value from the current IQ and air flow reading.  They limit the lambda to a certain value.  Anything leaner than say 16.5:1 on a diesel will make it smoke.  So, if the drivers wish and torque limiter maps are requesting 50mg of diesel, but the ECU calculates that this will result in an AFR richer than in the current smoke map cell, it will reduce the IQ to such a point as to bring the AFR into tolerance.

Rick

^^^ good info to start with, thanks Rick!

What about tuning for larger injectors?  is there a type of KRKTE?

Depends on what kind of Diesel system, unit injector, common rail etc.

Unit injector, e.g. VAG PD there are duration maps which control how many crank degrees the injector is open for to inject a given IQ.  This is because injector and pump are one unit and actuated by the cam.   For Common rail you have a map of injector opening time, rail pressure with Z axis being the IQ.  Ecu looks up what IQ it needs, looks at the current rail pressure and then determines an opening time.

For old VAG EDC15 VP engines, you work with pump voltage.

Rick

well a friend of mine has an AHU in a B5 A4 (swap)... with bigger injectors.  So I assume that would be the pump voltage kind?

Yea, 90bhp EDC15 Pump voltage.

It's like calibrating a MAF, pretty much impossible out of a Lab.  You can approximate/extrapolate then tune the drivers wish, torque and smoke limiter maps.

Rick

The info stopped here? I feel there is something more! So I may have a million questions but lets start with fueling.
what is a good lambda reading from wot to red line?

Lambda is not as important in diesel Tuning as in petrol tuning. Depending on what car you are working you will have to keep an afr of 16~17 if you don't want to have huge soot and high EGT .

hmm good to know, how do you know your max? ex in pedtrol cars you go till you encounter knock. WHat tells us to back off in diesel tuning?

You need to pick up a book on the fundamentals of compression ignition engines.

As stated above, 1:17 AFR is about what you can run without smoke, that you can calculate max iq dividing your airmass. You can calculate a rough assumption what your airmass will land at by multiplying VE of the engine With boost ratio(this is theoretical). As some has said, there is differences. EDC15 is based in injection quantity, EDC16-17 is based on TQ, but you have NM-iq map that converts injection to tq.

If you inject much fuel, check your end of injection, this cannot be too late or you end up With smoke and high EGT. You can change start of injection a little at high iq and see if you land in a reasonable EOI. But be careful, without a dyno/cylinder pressure sensors you can brake Things here.   

The basic limit maps in edc15 in iq order;

Drivers wish
Smoke limiter(s)
Inj duration 
Tq limiter
SOI

Boost target
Boost limit
SVBL
N75
 
EDC 16 is similar, but based on tq.

It depends which EDC16 you are talking about. For example Mercedes-Benz EDC16 is a hybrid as main torque limiter is still in injection quantity.

It is not a "hybrid" every EDC16 has IQ and TQ limiters.
You can run a VAG EDC16 on an IQ limiter too if you want.

I understand it should be switchable, but VAG seems to use torque in all limiters while Mercedes files may confuse people (IQ in main torque limiter and smoke map, torque in driver's wish and gear dependant torque limiters...).

It is just the way it is calibrated. It does not make the ECU in any way "special", "hybrid" or any other <insert BS term here>.
It is also not "switchable". There is no switch which limiter to use. Almost all of the ECU's have IQ and TQ limiters that are always used in parallel, just in some the map is 1x1 or 2x2 with high values for one of them.

The only switching that goes on (depending on ECU) is Flmng config. Not Engprt, apart from inner/outer torque on some ECU's.

Picking up a 01 jetta diesel tonight. Let the learning begin

I already have a fairly good understanding of diesel tuning, however flashing my 2013 jetta is a problem.