Aman Posted October 7, 2013 Report Share Posted October 7, 2013 So I've been noticing a lot of people installing the MAF downwind of the BOV, in areas like the inlet of the turbo. These same people have not-stock intercooler piping going through the driver to the TB. So, why don't these people put the MAF as blow through so they don't get the momentary rich burn from the BOV? Always confused me. Link to comment Share on other sites More sharing options...
ucw458 Posted October 7, 2013 Report Share Posted October 7, 2013 (edited) It wont go rich on decell because the ECU shuts off the injectors on decell above a certain RPM. Whenever my BOV went off my wideband read full lean. I've heard a blow through mass air also has less resolution. Something about the air being hot. If a draw through reads 1-10 a blow through will read 1-7 or something like that. Basicly you can exceed what the mass can read far sooner on a blow through setup. Before the turbo is best. It's also easiest since the stock aircan out and GM 3" mass are the same diameter. Just remove stock aircan. Install GM mass in OEM pipe and install a cheap cone filter. Edited October 7, 2013 by ucw458 Link to comment Share on other sites More sharing options...
Aman Posted October 7, 2013 Author Report Share Posted October 7, 2013 So the MAF is actually more accurate if it's draw through, and it's more worth it to have that momentary rich burn because it only lasts a second and you get more accurate air measurements? Link to comment Share on other sites More sharing options...
ucw458 Posted October 7, 2013 Report Share Posted October 7, 2013 From what I hear a draw through is more accurate. It wont go rich when the BOV goes off. If yours does then you may have a problem. Like I said before, the ECU shuts off the injectors on decel over a certain RPM. Most fuel injected cars do that. Link to comment Share on other sites More sharing options...
tankbob Posted October 7, 2013 Report Share Posted October 7, 2013 From what I hear a draw through is more accurate. It wont go rich when the BOV goes off. If yours does then you may have a problem. Like I said before, the ECU shuts off the injectors on decel over a certain RPM. Most fuel injected cars do that.What if the ECU doesnt shut off the injectors on decel? My wideband always goes really rich when in decel. Sorry if Im thread jacking but I dont run a BOV or GM maf currently. Link to comment Share on other sites More sharing options...
Aman Posted October 7, 2013 Author Report Share Posted October 7, 2013 I run a BOV and it goes rich for a second. What's the RPM that it cuts off at? Link to comment Share on other sites More sharing options...
ucw458 Posted October 7, 2013 Report Share Posted October 7, 2013 I'm not sure what RPM is the cutoff point. I just noticed when I ran through the gears at WOT the wideband would drop to full lean. Also the FSM talks about controling fuel during accel and decel. Link to comment Share on other sites More sharing options...
DMNDSTAR87 Posted October 7, 2013 Report Share Posted October 7, 2013 (edited) When running the BOV after the MAS you are expelling the air u just metered into the atmosphere...the ECU gives fuel based on that value that u just dumped ....i have run it both ways and both worked fine for me after tuneing but the car "felt smoother" with my setup now although I do not have hard data(datalogs) to prove it...Recirculate it would be the best IMOGig out Edited October 7, 2013 by DMNDSTAR87 Link to comment Share on other sites More sharing options...
DMNDSTAR87 Posted October 7, 2013 Report Share Posted October 7, 2013 What if the ECU doesnt shut off the injectors on decel? My wideband always goes really rich when in decel. Sorry if Im thread jacking but I dont run a BOV or GM maf currently. something wrong there...how do you know the ecu is not shutting them off? The injectors maybe leaking.. adjustment on TPS/ISC maybe off..Gig out Link to comment Share on other sites More sharing options...
ucw458 Posted October 7, 2013 Report Share Posted October 7, 2013 The stock ECU has a failsafe mode of sorts. If it detects the Mass is giving weird signals it reverts to a engine speed based map. Says so right in the FSM. Now when you let off the gas and the BOV goes off the ECU sees, the idle switch closed, TPS in closed position, engine RPM going down, Mass air reading high. The first 3 would tell it decel condition injectors off. The last would say, mass not reading right. On the 87-89 cars it will go by the idle switch being closed first. If you jumper the wires to simulate the idle switch being closed the engine will not run right at any RPM. If your car goes rich on decel you should check the idle switch and TPS. You may also need to do a TPS/ISC reset. Link to comment Share on other sites More sharing options...
Aman Posted October 7, 2013 Author Report Share Posted October 7, 2013 I probably need to recirc my BOV. Link to comment Share on other sites More sharing options...
Shelby Posted October 8, 2013 Report Share Posted October 8, 2013 I probably need to recirc my BOV. recirculation is best but as you have been told you need to test the nose swt for proper operationnothing else I can add to what has already been said , they covered it darn well Link to comment Share on other sites More sharing options...
Caliber308 Posted October 8, 2013 Report Share Posted October 8, 2013 (edited) If you mount the GM MAF prior to the Blow Off Valve, you will go rich at Blow Off for a split second. Mount it after the Blow Off Valve...No rich condition at Blow off. I have done it both ways. To me, it doesn't make a whole hell of a lot of difference on whether or not it is placed prior to, or after the Blow Off Valve. There was no change in my cars performance either way. Bill Edited October 8, 2013 by Caliber308 Link to comment Share on other sites More sharing options...
Aman Posted October 8, 2013 Author Report Share Posted October 8, 2013 My TPS is on point since I recently changed it Link to comment Share on other sites More sharing options...
89PalermoSHP Posted October 8, 2013 Report Share Posted October 8, 2013 Recirculate. Link to comment Share on other sites More sharing options...
Shelby Posted October 8, 2013 Report Share Posted October 8, 2013 signal from tps is only part of the requirements,, it also needs to see a closed throddle swt signal Link to comment Share on other sites More sharing options...
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