2-1) What is an AFC (how do they work, and what is thier purpose)?
Refer to question 1-2 in General.
2-2) What size injectors can be used with the "AFC Hack"?
Injector sizing is key to the AFC hack working properly. This is not because of fuel compensation demands, really, it is more of "how far" you must scale based on your maximum boost setting. To elaborate: As positive manifold pressure builds the MAP sensor signal voltage sent to the ECU builds.
Once ~3.1volts is reached, the ECU shuts down, and goes into "limp mode", rendering the vehicle practially in driveable until it is turned off and restarted. The use of the AFC here is key because depending on how much scale the signal back by direct effects how much pressure is takes to bring the modified MAP sensor voltage up to what the ECU thinks is 3.1v. How does this effect injector sizing?
If your injectors are not large enough, and your maximum boost setting is too high, you'll create a leaning condition or a check engine light.
I have not seen a definative scale as to the corolation of injector size vs maximum boost. If anyone has and solid, proven information on this I would low to post it. Typically, 450cc injectors are used with the hack at 8-10psi reliably. Others have boasted 12psi on the hack without a check engine light.
Link with good info about RX7 Injectors:
http://www.honda-tech.com/zerothread?id=7303832-3) I have heard using an AFC Advances your ignition timing, is this true?
Yes. This is very true. How when the AFC is not connected to your distributor? It all lies in the fundamental basis of how the AFC works. Visualize this, You have a grid of say 15 x 17. This is your OBD0 (10x20 for OBD1) ignition table. As we know, the AFC scales down the MAP sensor input to the ECU, thus, shrinking the resolution of the ignition map to fit more points in the same space. Now, if we look at what happends when we are in vacuum, this part of the table is squeezed into the left most half of the ignition map. If you have ever looked at an ignition table before, you'll notice that this is the most radically advanced section of the table!! This is how your AFC decreases fuel (same thing happends on the fuel table, and to increase, it scales everything to the right part of the table)!! To compensate for this advance in timing, some of used a BTM (Boost Timing Master), retarded their static ignition timing at the distributor, or even chipped thier ECU and modified the ignition table itself.
2-4) What settings should I use for X size injectors with X amount of boost?
This is one of the most misunderstood concepts about using the AFC hack. Lets examine each part to determine your correct settings. To begin, please read question 2-2 before continuing. Now that you understand a little bit about injector sizing with an AFC, we can talk about settings. If you decide to use something other than 450cc injectors, you may want to start with lower boost settings (at the wastegate) and build up from there, keeping the same fuel compensation settings in the AFC.
This will give you the upper limit for the current injector size.
As for obtaining those settings there are a couple of things to explain. Fuel flow rate difference.
This is the difference in flow based on the stock injector flow rate. For a Honda, 240cc injectors are stock. If you increase to 450cc injectors, your flow rate difference is a 46% increase. How do we figure that? Simple math: percent_of_difference = ((240 / new_injector_size) - 1) * 100
Second, an AFC does not control fuel injector pulse duration. This means we cannot compensate for injector latency in the fuel table for our larger injectors. Injector latency describes the scientific characteristic of how long it takes the injector to physically open. The larger the injector, the higher the latency. Since AFCs do not control the pulse duration directly, we compensate with a fixed percentage subtraction, otherwise, we would run lean in lower RPMs, even though our fuel flow rate has been adjusted based on the exact percent difference. The scale for common injector sizes used is 5% for 440-450cc, 4%, 390cc, 3% for 310cc.. then subtract 1 percent per 500 RPM increase. This will give us are starting point. For a boosted application, running stoichiometric is dangerous because of the high volume of air. To "play it safe", you want to run a bit on the stoich/rich side, so we increase fuel flow by 1% per 1000 rpms, trying not to top out a 5% overall increase. Why 5%? ..because your fuel maps are still increasing in pulse duration. So you're increasing pulse duration, and percentage
of flow rate at the same time. You'll get rich, very quickly. If you have VTEC, enrich by 1% more over VTEC VTEC crossover.
So, lets apply everything we've learned, and come up with base settings for 450cc injectors.
1) 240/450 = 0.53
2) 0.53 - 1 = -0.46
3) -0.46 * 100 = -46
So we have a 46% difference, we add our 5% for injector latency compensation, which leaves us with these settings:
1000 - 40%
1500 - 40%
2000 - 39%
3000 - 38%
4000 - 37%
--- VTEC set to 4400 RPMs ---
5000 - 35%
6000 - 34%
7000 - 34%
8000 - 34%
Application of these ideals will find your AFC Hack producing the smooth, safe, reliable power.
2-5) What is the maximum amount of boost I can run using the "AFC Hack"?
Due to the scaling of MAP sensor signal, and maximum read boost amount by the MAP sensor, ~10psi is obtainable. Some of boast numbers reaching ~12psi. Other limitations apply, please refer to 2-2 for more information.
2-6) Will the "AFC Hack" in conjunction with my X size injectors effect my idle?
Yes. However, if the proper settings are applied, and a reliable AFC is used, your idle should be smooth as stock. Refer to 2-4 for information on how to calculate settings.
2-7) I can't find information to install on my car. Where do the wires connect?
Instructions for newer cars are available in the manual downloadable from
http://www.pgmfi.org/~jparker/host/A...AFC_Manual.pdfOr another helpful thread for installing your AFC is located here:
http://www.homemadeturbo.com/forum/i...?topic=44797.0(As posted by mechanic_b)
Apex-I AFC VTEC controller
for PM6 (88-91 civic/crx) or PG7 (88-89 1.6L integra) ecu application only
V-AFC VTEC controller -------> ECU PIN location
Red & Orange wire splice/connect to A15 (yellow/black)
Green wire RPM signal splice/connect to B15 (white1)
Pink wire VTEC signal output to VTEC solenoid (green/yellow)
Purple wire VTEC signal input not used on PM6 ecu
Blue wire VTM signal not used on PM6 ecu
Gray wire Throttle signal splice/connect to C7 (red/blue wire)
Yellow wire Pressure signal output cut/connect to C11 ECU side harness
Si/Hf = white1 , DX = orange
White wire Pressure signal input cut/connect to C11 ENGINE side harness
Si/Hf = white1 , DX = orange
Black wire Ground splice/connect to A16 (brown/black wire)Engine side harness
Brown wire Ground splice/connect to A16 (brown/black wire)has to be connected closer to the ECU
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