Mazda Rotary Club

General => General Technical => Topic started by: Brett on April 25, 2008, 07:44:17 AM

Title: AFM positioning
Post by: Brett on April 25, 2008, 07:44:17 AM
Is there any advantage to positioning the AFM on the pressure side of the intake?  (I saw a car advertised on a Japanese auction site a few months back with its AFM moved to the poistive pressure side and it got me thinking.)

:wave
Title: AFM positioning
Post by: SiH on April 25, 2008, 07:48:13 AM
On a turbo car it can mean better fuelling if you have a VTA BOV (If the BOV before the MAF, if you see what i mean) as it\'s not metering the air before it is expelled, so you don\'t get momentary richness when it releases meterd air.
Other than that, not sure, but bear in mind that a MAF that usually sits by the filter may not be designed to run under pressurised conditions, so may havea reduced life expectancy, and may leak air.
Title: AFM positioning
Post by: Prof on April 25, 2008, 08:52:50 AM
There is an ambient air temperature sensor in the AFM unit as well, so that would now be reading the increased air temp caused by compressing the air.  Given the ECU was set for fuelling based on the ambient air which was going to be compressed, it\'s going to give falsely high air temp readings.
 
I\'ve only seen this done with the series 5 AFM - the cone sensor ones, rather than the flapper type on the older FC\'s.
Title: AFM positioning
Post by: antnicuk on April 25, 2008, 10:31:37 AM
i have seen it on a 20b cosmo before, I dont think i would bother, AFM are sensitive enough as it is,  just get a microtec and stick a nice big filter on the front of your turbo and bin the AFM  :)
Title: AFM positioning
Post by: DRIFTMOTION on April 26, 2008, 12:10:48 PM
I\'ve seen this alot on modded Jap FC\'s exceeding 350hp, afm fitted after a fimc, As Prof as stated only with series 5 cone afm. I think the main benefit is for bigger turbo\'s (td06 t77 etc) If the afm was fitted before the turbo as standard then it will cause air flow restriction at high boost / rpm