GM Z20LET Motronic 1.5.5 with Deka 630 FI114961

Good evening to all.

I usually have no problem in the tuning of ECU's and injectors in general, but, this one is cooking my brain.

I am looking for a little help if possible.

The vehicle in question is a Vauxhall Zafira Z20LET GSI. (My brothers car. Why are the freebies always the problem?)

Everyone who mods these vehicles tend to use Bosch injectors however my brother decides against my will and wants to use Deka 630's.

They are genuine injectors direct from Siemens and supplied within the UK. They did not come with any flow test data and the reply I'm getting from them is to use the data sheets already available.

So, here is my problem:

I use the standard injector data for TVUB and KRKTE. He is using a VXR 80mm ID Maf instead of the standard 70mm Maf. I scaled the maf for initial testing by dividing the area of 70mm by the area of 80mm and increased the maf by the scaled value. This gave me a max of 1200kg/hr.

After running the vehicle the data gave me a -4% long term fuel trim. I thought great, not a bad start. Something I can work with.

I trimmed the values of TVUB and KRKTE and got the cruise fuel trims down to -1%.

Now this is where my troubles begin.

I have a target lambda of 0.78(stock) so around 11.43:1 AFR. Took the vehicle for a test drive(road tuning) and on WOT we are achieving 12.3/12.4 afr.

A quick calculation 12.4/11.43 is 1.085 or 8.5% difference.

As we know we would tweak the MAF table to increase the amount and therefor increase the fuelling. Thus getting us closer to target afr.

VXR Maf

I noticed that 99% of people use the vxr mass air flow as a popular upgrade and just pull the maf data from the vxr map and use it in the Z20LET map. In fairness this is close to what I am calculating, my scaling of 1200 * 1.085 would equate to just over 1300kg/hr of air mass and the max air mass of the vxr maf scaling is 1315kg/hr. This made me happy until I tried using the full maf data.

When I entered the vxr maf data and flashed the vehicle, I then started the vehicle which started fine. Almost immediately the short term fuel trim dropped down to max at -25% stft and the ltft started dropping. ltft finally settled around -8% and wot did give me the afr i was looking for, well ...... there abouts before fine tuning.

I can get the ltft to drop to about -4% but this requires drastic reduction of TVUB. (figures below). But, by doing this WOT is lean again by about 0.5 afr.

I am really stuck here because I can get idle fuel trims almost bang on but the maf data seems to be out by around 10% or use the maf data out of the vxr for initial setup and have bad idle and cruise trims but wot afr is almost bang on.

The data in the Deka spec sheet shows TVUB as:

10v 12v 14v 16v (only lists 15v not 16v)

0.9210 0.6360 0.4090 ????

I now have TVUB down to this just to counter act trims.

0.8293 0.4987 0.2800 0.2160

My biggest questions are these:

1) should I just stick to the injector data sheet which gave me the best trims and just scale each of the 512 data points of the maf myself?

or

2) Use the vxr maf data that every tuning company in the UK seems to use and keep playing with the injector data?

3) Has anyone had any experience with these injectors and able to give me any better info than " look at the data sheet!", If you can then this would be much appreciated.

I'm in a bit of a bad situation where all the original parts have been disposed of, I did want to go back to the standard mass air flow. tune the injectors and then change and tune the maf. This is no longer an option without purchasing new parts just to take back off again.

Sorry for the lengthy post, I'm not willing to give up but am frying my own brain trying to work out what is going on.

Thanks in advance to everyone.

Mike.

Hello mikeak2001

I'm a little new in the tuning job. I only did my 1.8T20v with a GT2860RS, and some bosch 630 injectors. Because I made my map mafless I can't point you in any direction regardin maf settings. In my opinion, stick with the settings that make your desired afr spot on at wot, see what are the differences in part throttle and idle (STFT in this Motronic case), and then try to tweak a little the injector opening time in the area where it gives you the problems, hence idle and part throttle I presume. But in the FIRST time do your KRKTE acordingly for those injectors. Do you have in your ecu the FKKVS map? I had a little problem with the afr at cranking and idle-part throttle, it was to rich (something like -11% and fluctuating), and I raised just a little KRKTE about 5%, and lowered the numbers in FKKVS(correction factor for fuel supply system) where my problem still was. I don't know if this is the "correct" measure, but it got my job done, my STFT (-0.87%) and LTFT (-1.3%). My first advice is to put the almost right calculated values for maf, and then try to tune the injectors voltage offset best as you can, and calculate KRKTE with the maximum precision. I don't think you should have any problems after. Beware that Deka are a little known for runing a little richer than bosch. I will atach a picture from my example ecu(ME7.5) with FKKVS map.

Did you sort this? My astra currently runs 80mm vxr maf and deka 630cc injectors. I can pull the fil off for you if you need it

While it's not a platform I've tuned myself, it sounds to me like a very common problem you can strike when swapping injectors and MAF together. As recommended in the Practical Reflash Tuning course, it's always best to make one change at a time unless you have solid data that you've previously generated for either the injectors, MAF, or both. The issue is that an incorrect MAF calibration OR incorrect injector data will both throw off your fuelling and it's impossible to know where the error is coming from.

Thanks to all that have responded so far.

In fairness everything was changed one item at a time and was getting mapped by a local company. It turned out that while being tuned the fuelling and boost was all over the place, after a lengthy investigation we found that the previous owner of the vehicle had also been mapping the vehicle, with a faulty wastegate actuator. Eventually the turbo died. After a total engine rebuild, complete with new intercooler, turbo and all engine parts including manifold, oil cooler etc etc.

I am not a beginner on tuning vehicles and these courses have just reinforced what I know. However these Deka's are beginning to make me doubt my abilities.

@daveymb I don't wont to steal your file but if you could help me out it would be much much appreciated. If it gives me a better starting point then that would help one million percent.

So far the vehicle is running a lot better but the cold weather here is now making the vehicle pull -8% ltft but the afr on boost is now around the 12 mark.

Thanks again to all.

did you get my email mate