NefMoto

ok so upon reading i am still unsure about scaling the maf table.
im going from stock 72mm s4 maf housing to 85mm intake tube with filter. (Hitachi)
now i know some of you have opinions about having open element intakes but i struck a deal and it is what i have currently.

i did the calculation for the increase in size - (72mm -- 2.83*2.83*3.14 = 25.15) and (85mm -- 3.35*3.35*3.14 = 35.24) this yields an 18.1%increase in actual size. after dividing the two numbers and getting 1.40 do i multiply the whole table in tuner pro? comparing to a tip file i have that uses 85mm maf it is way off. and i have tried the tip maf table and the car misses at idle and upon acceleration etc.

anyone wants to chime in it would be appreciated. thank you

multiplied the stock table by 18% (* 1.18)and fuel trims are in the +/- 8% range now
i'll figure out what i need to data log and get those tomorrow

In my opinion better gets RS4 linearization (83mm) and multiply to go on 85mm maf. I say that because, some areas are different after multiply than stock linearization compared to bigger rs4.

I show You different method, what i tested in the past. This is my method.

1 + ( 1 - (72mm*72mm*PI) / (85mm*85mm*PI) )  = 1,2825 <- multiplier

Copy table to excel and next, add maf offset to go to non negative values of map, then multiply by x and substract to table Yours added offset.

Example:  (one max value) ((1200kgh + 200) * 1,2825 ) - 200 = 1595gkh new max

If You multipled table by 18% and You have +8% correction: 1,18% * 1,08 = 1,2744 is very close 1,2825.

Normal is You must find new corrections in fkkvs or kfkh map

how do you multiply values for a Bosch sensor to a Hitachi table that doesn't contain negative MAF values? Maybe you have a secret for us here

Yes, for bosch MAFs you have to apply the offset, scale, then offset back

My math is hazy but you may have to scale the offset as well.

i am aware about the bosch offset. but question is do i just disregard those steps in the calculation and stick to the pi equation that leads to the 1.28 for my set up?

wicked info. thank you for all that

Sorry, I forgot! I checked today and i think only multiplying is enough. Additional calculations i use only when i have negative offset. IamwhoIam always watchful  ;D :D


I not saw much binarys, but offset OFS all time is same for different sizes of maf tube (I wonder why?)

i know nothing about what you said but if i were to guess it just has to do with the sensor output. even though housing diameter changed either increased or decreased, the offset stays because the sensor uses it for proper calibration? anybody want to confirm lol

"Only part of the air-mass flow is registered by the sensor element. The total air mass flowing through the measuring tube is determined by means of calibration, known as the characteristic-curve definition." - to quote Bosch. Or same sensor, different housings - temp/deviations as per HFM 5 pdf not withstanding in other words.

I'm fairly certain you dont have to scale OFS.

I never have and it works fine.

If i had time i'd check the math but never got around to it.

Also, I've found that (empirically) the "correct" value is somewhere between proportional to r and r^2

I have no idea why.

what exactly should i log to fine tune this intake? just watching the fuel trims driving around town and steady highway driving they kind of float around more than i would like it to ie above =/- 10%. it is constantly to what i would think is overcorrection but have no faults. havent been able to watch them under load well because im solo riding for it and i need to pay attention to the road lol