Dr.Boost

It only works off rpm, but the timing would be changed by vac/boost. This is the bad part. IMO the AFC is more accurate than the SMC, but I'm sure it works just as well.
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94geeser

thanks. i'm still confused though. how would a car using a vafc be able to cruise on the highway (without shooting fuel out the exhaust) if it is getting the same amount of fuel under vacuum as it would under boost at a given rpm? i mean technically it should get almost twice as much fuel under pressure (10-11psi) as it would under vacuum, maybe more. i thought jdavis said something about the vafc stretching the map signal so it is boost and rpm dependent (normally 3v is atmospheric; with vafc 3v can be disguised as vacuum to pulse the bigger injectors slower and 5v can be disguised as atmposheric to open the injectors more under boost). if its already altering the voltage going to the ecu from the map sensor, why couldn't it be analogous to pressure changes!?!?! am i missing something?! i would like to try the hack (using fmu now) but not if its going to kill my mpg on the highway! sorry for the long post

45psi

thanks for knowledge

Dr.Boost

The AFC has high throttle/low throttle settings. If you are at full throttle you would be running on a different fuel map(RPM dependent still). The AFC isn't exactly acurate no matter what you do. It is just a hack.

Nope.


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reg22

will a second MAP sensor connected to the throttle input help?

just like the one described here: http://www.alltrac.net/mods/boostedSAFC.html

and:
(What is the "MAP sensor mod"?)
http://members.shaw.ca/costall/1000Q/answers-SAFC.htm

fastcivicboy

i was reading earlier and read that someone said the afc hack isnt good if you are running under 8 lbs. of boost because it advances ur timing to much. I was planning on gettting 450's and a vafc and maybe retarding my timing a little but what do yall think should I just go with another whole fuel managemnt system if im not gonnna be boosting 8 lbs. or more. I was planning like 5-7 lbs of boost for now and maybe bump it up to 7-8 later. My engine is a z6 and my turbo is a TCO5-12 intercooled. What setup do yall think I should run for my fuel management. And the last thing I wanna do is blow my engine! Thanks for the help!

RENR

i dont know who comes up with this stuff mang. take it form a guy that has used the afc in low boost and higher boost(12psi). it doesnt advance yout timing, not so much that it will cause detonation. im currenty runing 10 psi on stock timing. thats how well it works. if ;you do experience detonation, add more fuel with the afc and bam problem solved.(thanks 91accordlx for the tip) AFC! AFC! AFC! Using the afc and 450cc injectors maybe a new fuel pump and youll be set. the afc really is not complicated at all.

Dr.Boost

I don't know how you are getting away with stock timing with no detonation. The AFC does advance the timing a rediculous amount. Also, adding too much fuel will cause detonation.

The reason people say the AFC isn't good for 5-6 psi is because of the timing that it reaches at that point in the map. The ECU is advancing the timing the most at that point. If you can get away with it using stock timing than I guess you are just lucky.
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RENR

well i dont know about that. you say that the afc advances timing, do you have any dyno info or real numbers to prove this? last i remember runing lean caused detonation not runing rich. preignition causes detonation. just want to get the facts straing mang.

Dr.Boost

Well how can you preignite without fuel?

I don't have to prove anything. I can go out to my car, start it up and realize the AFC is advancing my timing. Do you have any dyno numbers or anything that proves me wrong?

Why don't you try data logging your ecu and take a look at the timing maps. Then, disconnect the AFC and have a look at the timing maps.
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