Tuning jtd maf upgrade 70mm to 80mm

sussexa · May 11, 2013

ok so will start this thread with what I have so far
mafs are usually rated in kg/h so to convert some used on jtd from kg/h to mg/I
http://www.alfaowner.com/Forum/atta...ilo-jtd-16v-maf-kg-h-to-mg-inj-conversion.xls

from this you can see what the max readable airflow would be at set revs.
now the jtdm 150hp uses the 640kg/h sensor so you can see at the upper end say 5000 revs the max airflow it can read is 1066mg/I now that is no problem but eventually at the upper edge of tuning envelope this is no longer high enough to see the real airflow(which engine is breathing but maf not sensing so not fueling for?)

here is a comparison 640kg/h to 850kg/h mafs with air temp and some afr max fuelling calculations
http://www.alfaowner.com/Forum/atta...-4-maf-limits-and-max-mm3-inj-afr.xlsx-640maf

http://www.alfaowner.com/Forum/atta...16v-stilo-jtdm-644-maf-boost-max-iq-chart.xls

heres air consumption
http://www.alfaowner.com/Forum/atta...720-stilo-jtd-16v-1.9-jtd-air-consumption.xls

heres air consumption converted to velocity
http://www.alfaowner.com/Forum/atta...ir-consumption-and-velocity-70mm-maf-and-80mm

heres colour coded to usable range ,borderline and out of range
http://www.alfaowner.com/Forum/atta...ir-consumption-and-velocity-70mm-maf-and-80mm

there is nothing to be gained performance wise going to larger maf until well over 200hp id say.
will post pics up after

sussexa · May 11, 2013

70mm original next to an 80mm maf

an adaptor could be used to go from 70mm to 80mm but I decided to upgrade intake so 80mm into the airbox lid

now I have some final tweeking to do as space is very tight

not enough room for a reducer here 80-48 either

when I have overcome alignment issues I will update
if anyone does similar I was going to cut the trumpet so it sat right in the corner but went against it for perfect airflow into maf , unfortunately I wont have it after maf
more planning and measurements instead of winging it at construction stage was required.

also be aware fitting a larger maf to a std car will see lower airflow and actually reduce performance.
a remap with maf relinerisation would be required.

all the work done is interchangeable and spare airbox lid has been modified I wouldn't recommend chopping your only car parts.

sussexa · May 11, 2013

I will put pics of snorkel intake mod on here also as sort of related
as close to original pic as I have
http://img807.imageshack.us/i/march2011egtgaugesetc00.jpg/

the scoop bulge in the corner was designed in incase I needed a drain for any water but after several checcks in wet weather no water has settled in there
this is as close to ram air as id like to go but still working as designed by using the high pressure air at the gap from grill to bonnet

although as you see in this pic I have nibbled a bit off the grill but with the bonnet down there is no direct path for rain etc to enter the scoop.
there is a drain hole in the bottom of the airbox so wont really give ram air but will help to reduce restriction at high boost .

as far as the snorkel pipe I calculated that upto 3200mbar the velocity in the snorkel pipe should stay under 45m/s so not bothered to increase pipe size(the alfa boys have a 45mm restriction(107m/s at same airflow)

anyway no downside detected to snorkel mod maf readings have increased slightly and temps are usually same as ambient unless parked up when airflow stops and temps increase as hot air from rad rises up through grill.
here was a log in cold temps and cold start as can be seen by maf and map temps very close
http://www.alfaowner.com/Forum/atta...-16v-sat-9-03-13-start-up-temp-baro-press.xls

and once again this is by no means necessary to reach 200hp and over easily as I did 210+with almost std intake before this mod.

fruchty · May 11, 2013

I am gradually reading all your posts here and on the Alfa forum and I just want to say you're doing amazing things with your stilo!

I also have a Mjet 16v that I plan to tune a bit and your posts are a goldmine!

Thank you and keep up the good work!

sussexa · May 12, 2013

I will always try to stick to the facts , evidence and be honest and this is definately not needed on a std jtd even a quite well tuned one!!.
Even i may find with my hybrid that the std intake and maf is not maxed out and become a restriction.
But this summer i may tweek map pressure over 2900mbar and that is over 70mm maf range.
If i ever get it finished i will update this thread.

philipb82 · May 13, 2013

Hello Sussexa

I don't know much about MAFs or the technicalities. When my mate plugged his diagnostics in my car the MAF was giving a reading of 0.4 when revved at idle. Sorry but i don't know what unit of measurement this is, like i said no idea about the figures! Does this sound right for a Bosch MAF? I hope i'm making sense

Thanks

Phil

sussexa · May 13, 2013

The 8v jtd is most likely a straight maf voltage linearisation curve set up,
Ill post a couple of bosch data sheets and try to find some data on the std ecu map on the curve figures.
But basically if you imagine something like no airflow=0v and max airflow=4.8v maybe and each maf would have a different curve depending on flow rating of the maf
I know mine is 640kg/h yours may be only 480kg/h say max flow 5v so if i put your maf on my car ecu would think 5v=640kg/h even if airflow was only 480kg/h
If you put my maf on your car your ecu would see a lower airflow when maxed out 5v you could be flowing 480kg/h expecting to see 5v but my maf would only give say 4 v at 480Kg/h , your ecu would see 4v as say 350kg/h and reduce fueling to suit smoke maps in ecu, lower power.
Davidthelodge had this exact fault a year or so back someone had fitted a 16v maf by mistake and he had big power dips on rolling road, had been to dealers for diagnostics if i remember right, and they missed it.
Make good reading if you can find it.

philipb82 · May 13, 2013

Thanks for the info. Also is it possible for an ECU to be 'sensitive' and blow a MAF? I was told this by the garage because they know my car has had some issues. Is this true or rubbish?

Phil

Shadeyman · May 13, 2013

philipb82 said:
Thanks for the info. Also is it possible for an ECU to be 'sensitive' and blow a MAF? I was told this by the garage because they know my car has had some issues. Is this true or rubbish?

Phil

I would expect the MAF to be more robust than the ECU so if an ECU did manage to "blow" the MAF the ECU would be seriously fried IMO.

sussexa · May 19, 2013

here are some examples of maf v curves
http://tuning-diesels.com/Pierburgh/pierburgh.htm
a pdf her tdi related but bosch v pieburg
http://www.google.co.uk/url?sa=t&rct=j&q=&esrc=s&frm=1&source=web&cd=1&cad=rja&sqi=2&ved=0CC4QFjAA&url=http%3A%2F%2Fwww.auto-consulting.it%2FDWN%2FMass_Air_Flowsensor.pdf&ei=PamYUfuvMq6d0wXhkIHwCg&usg=AFQjCNFwZ-vBm9lmhQS49bWvT3bfwEh7pw&sig2=FBPrXHFOMqGVooaKcjdpBA‎
and bosch only stuff here
http://www.maseratilife.com/forums/...nsor-cleaning-bosch-hfm-5-sensors_airmass.pdf

as for robustness? theyre designed to sit in an airflow that could be bone dry or very damp(on high humidity day) and read airflow from less than 0.1m/s velocity to 45m/s velocity accurately with chances of getting wet and oily from reverse airflow from ccv breather inlet just after it.
I would say thay are designed to be pretty robust, when cleaning a maf I never touch anything though just spray through mesh in normal airflow direction, I see no reason why a maf would blow other than bad plug connection, getting totally soaked maybe ,or short circuited somehow?

also the maf reading may not change much between idle and revving you would automatically expect it to follow revs up but it wont it will follow boost pressure up, so at idle parked and then revved to 2000-3000 etc the boost pressure goes up very little maybe 100mb or so as no load.so the maf doesn't go up much either maybe from 485mg/I to 550-600mg/I .
as its calculated from ingested air per stroke and already converted in fes /mes the only thing that would affect maf at no load no boost would be the engine ve /breathing