Someones Bad Tune - Need MAF Scale Confirmation

Pages: [1]

« previous next »

Author

Topic: Someones Bad Tune - Need MAF Scale Confirmation (Read 3585 times)

mikeak2001

Newbie

Karma: +0/-0
Offline

Offline

Posts: 3

	Someones Bad Tune - Need MAF Scale Confirmation « on: April 16, 2018, 07:18:29 AM »

Hi everyone.

I'm hoping someone can help me. I'm not new to tuning however I am new to scaling a MAF. I know there are many questions about this but please let me explain.

I normally tune Volvo's, early Volvo's using the Motronic 4.4 system. A friend of a friend has had a tune dropped on to his Vauxhall Zafira Z20LET with Motronic 1.5.5 which the tuner swears is tuned for an 80mm MAF over the stock 70mm. I find this not the case due to constant positive fuel trims when the 80mm is installed followed by a DTC and limp mode.

I have also confirmed this by reading the MLHFM MAP which is the same as a stock file.

After never scaling a MAF before I made a quick excel sheet to do the job taking into consideration MLOFS of 200.
I could have sworn recently that I read an article, maybe on this forum regarding negative numbers in the map and something needs to be done. Besides the usual subtract MLOFS, scale, then add on MLOFS again.

My main question is just that:
Does anything need to be done to the negative numbers once MLOFS has been subtracted?
My other question:
How does the ecu interpret the negative number once it subtracts MLOFS. I can understand for example 212kg/h - MLOFS = 12kg/s but how would it interpret lower figures such as 160kg/h - MLOFS = -40 kg/h ? or would the ecu just ignore these lower figures?

I have attached a copy of the excel file I put together, The file also has line charts to show the differences. Within the file I have already input the MLFHM from the ecu.

Thanks in advance.

Mike


	Logged

thedrill

Full Member

Karma: +12/-3
Offline

Offline

Posts: 139

	Re: Someones Bad Tune - Need MAF Scale Confirmation « Reply #1 on: April 16, 2018, 08:20:20 AM »

I had a quick look at the scaling, the multiplier between 70mm and 80mm is approx 1.14
your max stock kg is 966, after removing and adding the offset I get 1073kg max.
That should be a good starting point.


	Logged

nyet

Administrator
Hero Member

Karma: +608/-168
Offline

Offline

Posts: 12271

	Re: Someones Bad Tune - Need MAF Scale Confirmation « Reply #2 on: April 16, 2018, 08:46:42 AM »

The reason there is a negative MLOFS is because there is no way for the MAF to send a negative voltage, so zero flow (for a given MAF) is a represented by a small positive voltage. Below that voltage is "negative" flow

So for the scaling to work, you subtract so that that "zero" point doesn't get moved, then scale the values, then add it back so the zero voltage point still results in zero when you take MLOFS into account.


	Logged

ME7.1 tuning guide
ECUx Plot
ME7Sum checksum
Trim heatmap tool

Please do not ask me for tunes. I'm here to help people make their own.

Do not PM me technical questions! Please, ask all questions on the forums! Doing so will ensure the next person with the same issue gets the opportunity to learn from your ex

mikeak2001

Newbie

Karma: +0/-0
Offline

Offline

Posts: 3

	Re: Someones Bad Tune - Need MAF Scale Confirmation « Reply #3 on: April 17, 2018, 04:41:12 AM »

Thanks for the replies.

So would I be correct if I said I don't have to worry about the negative numbers so much? Basically still do the scaling but as long as any number returned as a postive after subtracting MLOFS, is then scaled properly then I should be good to go. After this then do the usual of tuning the correction map if required.

The reason all this has thrown me off is because on the Motronic 4.4 ECU's, the MAF is a bosch however there does not seem to be an offset and the maf scale is pulled from different parts of the ecu. When converted it starts off as 0's all the way to a positive flow then the numbers start increasing. (Info/scaling is in the attached file-Main post)

I suppose the main answer here especially for M1.5.5 is to perform the usual scaling equasion and I should be ok.


	Logged

prj

Hero Member

Karma: +1072/-485
Offline

Offline

Posts: 6041

	Re: Someones Bad Tune - Need MAF Scale Confirmation « Reply #4 on: April 17, 2018, 07:21:24 AM »

The HFM-2 (or earlier) that is used on Motronic 4.4 does not have reverse flow measuring capability.


	Logged

PM's will not be answered, so don't even try.
Log your car properly - WinOLS database - Tools/patches

nyet

Administrator
Hero Member

Karma: +608/-168
Offline

Offline

Posts: 12271

	Re: Someones Bad Tune - Need MAF Scale Confirmation « Reply #5 on: April 17, 2018, 08:47:40 AM »

If MLOFS is zero then adding/subtracting MLOFS is a NOP Tongue


	Logged

Pages: [1]

« previous next »

Jump to:

Navigation

Personal Tools

November 30, 2024, 03:43:17 AM

Welcome, Guest. Please login or register.
Did you miss your activation email?

Navigation

Personal Tools

Search