83turbo280zx Posted May 14, 2008 Share Posted May 14, 2008 ok, as far as my automotive knowledge goes, this should still be ok to route your afm like this, i want to put an intercooler and run the pipes through there the stock airbox was, and in turn put a high flow filter on the turbo, and route the afm inline with the turbo, and the BOV before the afm, so unmetered air escapes rather than metered air like welding a bov to the stock J pipe, see attached diagram for what i mean im sure it will run, but i just want to know all possible pro's and con's and what should i expect, thanks!! btw its an 83 zxt, with the afm on the suction side of the turbo heres the link to the diagram http://www.zcar.com/forums/read/1/1929400 Quote Link to comment Share on other sites More sharing options...
xxjoeyxxeb Posted May 14, 2008 Share Posted May 14, 2008 I think most people have put the AFM in front of the turbo air inlet. Quote Link to comment Share on other sites More sharing options...
83turbo280zx Posted May 14, 2008 Author Share Posted May 14, 2008 I think most people have put the AFM in front of the turbo air inlet. yes, i know that is how the stock set up is, im trying to put an intercooler in, and would like to place the afm inline with the turbo outlet and throttle body, so im trying to get all the details i can on doing this Quote Link to comment Share on other sites More sharing options...
ShaggyZ Posted May 14, 2008 Share Posted May 14, 2008 You can technically do it, of course, but it's apparently harder to tune; I don't really know why. Also, you're likely to blow your AFM apart in higher boost (don't know what might be considered "high") - turboford guys who run blow-thru VAM/AFM often do this, but we're running 15psi from the factory. You're better off using one of the multiple proven intercooler routing techniques and leaving your AFM in place. Quote Link to comment Share on other sites More sharing options...
stprasinz Posted May 16, 2008 Share Posted May 16, 2008 I have trie dthat and the engine would pop and fall on its face as soon as positive pressure (boost) was acheived... not sure why.. I was kinda stumped.. The reason I did it was Because you would be able to flow more air through the meter if it were pressureized as apposed to ambient air...... Wow I just found out why... thought about it visualized air being vaccumed into the engine causing the flapper door to open.. then air is pressed into the afm instead of sucking... then the spot on the door is pressed closed somehow.......... In threry in my head looks better than full visual.... Maybe it was just me.... try it and see... Quote Link to comment Share on other sites More sharing options...
Brad-ManQ45 Posted May 17, 2008 Share Posted May 17, 2008 The AFM and ECU are set up to measure the flow of non-pressurized air and supply the appropriate amount of fuel. Your car won't run right at all - leave it in front of the turbo - not after. Quote Link to comment Share on other sites More sharing options...
HowlerMonkey Posted May 19, 2008 Share Posted May 19, 2008 It's not the pressure but the warmer air fooling the intake air temp sensor to skew things leaner..........since it was designed to report the temperature of the air just as it enters the intake tract and not after being compressed. Quote Link to comment Share on other sites More sharing options...
hughdogz Posted May 19, 2008 Share Posted May 19, 2008 It's not the pressure but the warmer air fooling the intake air temp sensor to skew things leaner..........since it was designed to report the temperature of the air just as it enters the intake tract and not after being compressed. I think BradManQ45 hit the nail on the head. The AFM wasn't designed to measure compressed air. Say that you add an intercooler that is 100% efficient (for sake of argument) so that temperature doesn't play any role. The mass flow rate of the air is the same regardless if it is still atmospheric, pressurized or even a higher temperature. Say for instance, you are boosting at 14.7 psi. That is twice the atmospheric pressure (on the absolute scale). If the pressure is doubled, the velocity must be halved since mass flow rate is the same (assuming same diameter tubes). Therefore, the AFM is only "seeing" half the flow in the pressurized pipe (versus the atmospheric location) . The ECU then adds only half the required fuel. [Edit: This logic seems right to me, but I'm not 100% sure.] Quote Link to comment Share on other sites More sharing options...
HowlerMonkey Posted May 21, 2008 Share Posted May 21, 2008 This car uses a flap door air flow meter. Quote Link to comment Share on other sites More sharing options...
hughdogz Posted May 21, 2008 Share Posted May 21, 2008 This car uses a flap door air flow meter. Exactly. That was the premise of my post. The "flapper" OEM AFM on the L28E's don't measure or take into account the air pressure, rather they measure the air velocity. I'm probably talking over my head here. I need to bust out the FSM to know for sure. Quote Link to comment Share on other sites More sharing options...
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