Good Lambda/AFR for Diesel

by **ross2482** » Thu Oct 04, 2012 1:04 pm

Well I've tested my file in the 406. I specified fuel values (in MM3) in the smoke table so that AFR was about 17.4 for MAF = 1050mg and 1150mg, tailing off at high RPM. It works fine, I reach the IQ numbers that I've specified in the torque map and there is no smoke! It's as clean as a whistle when accelerating hard.

For reference, I'm injecting 70mm3 at 2000rpm, 72.5mm3@2500rpm, 70mm3@3000rpm, falling to 65mm3@4000rpm.

I need to fine tune the boost levels however, currently running 2183mBar but I think I can get away with lowering this slightly.

Therefore, I think these AFR values are fine in the 406 ;)

PS - My tune file was made in TunerPro, found maps in WinOLS. Also changed axis etc in TunerPro, very easy once you get used to using it!

by **ecuedit** » Thu Oct 04, 2012 1:11 pm

You can go much much lower with AFR without smoke. ;)

by **ross2482** » Thu Oct 04, 2012 1:14 pm

Thats good to know, although I do prefer having a smoke free diesel!
The limiting factor on my car is the clutch I think, before factors such as smoke or the small K03 turbo become a problem!

by **ecuedit** » Thu Oct 04, 2012 1:29 pm

You watch clutch at low rpm, once you reach 2200rpm you can load it more.

About testing the AFR in practice:

Start at AFR 17, than 16, than 15,........etc until it starts to smoke, than go higher for 0.5 and you will get very interesting info :)

Do that at higher air flow.

You can test it like that:
drive at 1700rpm in 4gr and than push it to the max until around 4000rpm.

The tune has to be smoke free.

by **Relic** » Thu Oct 04, 2012 2:50 pm

Thanks for the tips :thumbup:

I am running 2.25 bar (tweaked stock) at the moment which peaks at 3000rpm in a 2.2.
I have my peak torque set at 2750rpm = 73.6mg
Lambda is set at 17:1 but its well above that...I'll look later.

Completely different setup I know...but gives a ballpark idea.

Would it not be better to set the lambda...then lower the boost until it cuts the fueling ?
Then you know its lambda regulating the power.
Otherwise you only know you are providing more air than required rather than the exact amount required.

Main problem with mine is short single exit exhaust with one cat removed.
VNT calibration was spiking badly at 1750-2000rpm.
I'm at the 7th attempt to get requested map = actual map :wtf:

by **lupak** » Tue Oct 16, 2012 11:25 pm

can you share your map ?
I' m try tune my 307 2.0 hdi 107 cv.
Thanks.

by **ecuedit** » Tue Oct 16, 2012 11:38 pm

You can also drive on smoke map... ;)
That means you limit your IQ based on your actual airflow...than you wont provide more air whan you need, you will put as much fuel as you get airflow...

by **rlees85** » Wed Oct 17, 2012 12:29 am

Suppose that is another way to look at it...

How much turbo can i get? .... make turbo maps...
Then make a smoke map based on that... the maximum air I can supply with turbo maps...
Then build a torque limiter around that....

I heard it is a bad idea to be driving on the smoke map as the primary limiter due to the way the signal is .. or something like :wtf:

by **Relic** » Wed Oct 17, 2012 12:41 am

Think the main concern is if the MAF sensor starts misbehaving.
So I can fuel mine for winter....this sets an upper limit.
But I can use the lambda/MAF to cut the fuel as temps warm up...this set the lower limit.
During the year you get somewhere between the two... which is how it is supposed to be anyway from a petrol tuning AFR locked point of view.

Dyno corrections are useless as they assume fueling is lambda locked.
Diesels arent always tuned that way.
Raw values are more useful.

by **ecuedit** » Wed Oct 17, 2012 9:49 am

There is a lot of different approaches (some cars are fueling based on turbo pressure).

For maf, nice approach:

1. You look turbo specification,
2. set safe turbo pressure based on manufacturer graphs,
3. measure new maximum stable airflow just for orientation (here can be some more tricks to do about getting new correct values),
4. make good smoke map based on lambda you want to drive
5. you drive on smoke map some time, to see actual maximum IQ at different RPM
6. than you can set TL just little bit lower, and you get very nice curve...than TL is your primary limiter, to avoid being on the barrier, try to do that on some average year temperature at your climate or temperature ranges you thing that best suites for you
7. when weather changes, you wont have same airflow than in some cases your MAF limiter will limit your IQ as it has to in that moments.