N75 maps are controlling boost pressure. You would not like your turbo to over speed or over boost after removing Cat and Fap. It also depend on what type of turbo do you have. Look at the pdf, you will know what I mean. Pdf is not exactly for that particular turbo type but it shows what is wastegate. N75 maps are controlling wastegate.

thanks
what about turbo map then?i am confused
what is difference between n75 and turbo map if both are for wastegate operation,or they are not
i have 406 2.2 hdi coupe and if pressure in intake manifold is 1.2 bar ecu will react over westgate.how can removing cat increase pressure in engine?

Dear Friends! Advice please. Did I correctly identified the card vortex valves E0E9C on MB E211 2.2 soft 367129 and, if so, please help me correct them off.

N75 controls the VNT wastegate in the garrett turbos.

1 N75 map = 1 Boost map.
The N75 is a calibration file.
If turbo request = 2000 mbar @ 3000 rpm vs 50mg IQ the....
N75 duty is adjusted to give turbo actual = 2000 mbar @ 3000 rpm vs 50mg IQ.

Basically it is there to make actual boost = requested boost in any cell.
Open the wastegate and actual boost will drop.
Close the wastegate and the actual boost will rise.

Problem is changing the exhaust configuration modfies the pressure difference either side of the wategate.
So the N75 calibration must be adjusted to compensate.

ecuedit wrote:N75 maps are controlling boost pressure. You would not like your turbo to over speed or over boost after removing Cat and Fap.

Relic wrote:Problem is changing the exhaust configuration modfies the pressure difference either side of the wategate.
So the N75 calibration must be adjusted to compensate.

I log about 60 min city and road driving on car with deleted 2-nd CAT and not see any overboost or spikes. Possible one CAT is enough. Other way is replace CAT-s with flame arresters that save resistance in exhaust. This much easier for people without dyno instead divine N75 edit.

N75 is calibrated that turbo has safe delay, when you remove fap / cat than you do not have delay, in most cases it goes fine without calibration n75 in some cases overboost is the problem, or someone has lazy wastegate.

In 10 cars maybe 2 have problems and n75 has to be calibrated, it goes from case to case...

I have one car with strait pipe only for fun not for driving on ordinary roads,
without any resistance and no overboost on stock n75...also no delay.

Useful help for newbies in this thread, and congrats at your rate of progression... I wonder where you are with your understanding now :).

Very usefull thread!!

Very Usefull!!

In 10 minutes i have learn a month :o , but i dont have yet change the ecu of my car because i have a little scare with the result if i do something wrong, but first i need to study a lot more. thanks anyway :)