Chris Harris

its been explained 1000+ times so you really dont need to worry about it...plus you arent really doing that good of a job, because whether you can back up the theory or not...they advance the hell out of your timing

RENR

there was a guy on here once that dyno'd the timing on his car with the hack. he got 7 degrees advance aroung 6-7psi and said at 10psi timing was practically stock`

TurboEF9

I've not posted here in a long while since Chris (xenocron) is handling business quite well... but I believe I need to chime in on this one.

First off, where the hell did you get that it modifies your short and long term fuel correction? That's just ignorant.

Are you trying to make yourself sound like you know what you're talking about by using fancy terms that a lot of novices know nothing about?

First off, your AFC doesn't modify ANYTHING in your ECU. Plain and simple. And your short and long term fuel corrections are stored in the ECU.

Second, an AFC works by intercepting your MAP/MAF output (input to the ECU), scaling it by a user defined percent, and spitting it out again. (Jesus, didn't I write all of this in an Engine Management FAQ a year ago? ..oh wait, I did. Section 2, Question 1)

Anyway.. once this signal is modified, and fed back to your ECU, your ECU thinks it's at a different pressure reading than it actually is, therefore, based on the ascending flow of your fuel map, decreases injector pulse duration.

"Well, wait a minute Jason, if it's decreasing injector pulse durations, how are you using an AFC to increase fuel flow for boost?"
That's a great a question... You're using larger injectors. Instead of decreasing fuel flow on your stock 240cc injectors, using larger injectors, say 450cc (most common) you're actually flowing more fuel, at the same pulse rate (without getting into injector latency characteristics).

Now, that is the kicker. That is how the whole thing works. Make sure you understand this:

Say you have a pulse width of 10 milliseconds (arbitrary number used for example) with your 240cc injectors, to get the same amount of flow from your 450cc injectors, you would have to scale the pulse with back (OMG! That's what your AFC does by modifying your MAP) 46%. This means, a pulse duration of 5.4 milliseconds would be needed to flow the same amount of fuel.

Last two concepts.. stay with me..

"How does this let me boost?" ...easy, since you're scaling back the MAP (Manifold Absolute Pressure) voltage, you're making the computer think you're at less pressure than you actually are. Therefore, it takes MORE pressure to bring the ECU to a point where it freaks out and thinks there is a problem.

Now, the all important, how does this advance timing...

Easy.

Look at a fuel and ignition map. Apply the concept of how we increase fuel, tot he ignition map and what do you get? Increased timing.

For those of you who are too dense to do that, looking at a fuel map from left to right, the numbers get greater as the MAP pressure increases, it's reverse on the ignition map. From right to left, as MAP increases, ignition decreases.

So, if we're scaling back our MAP signal making the ECU think we're at a lower pressure (which would give us less fuel pulse because it increases from left to right) it would give us MORE timing because ignition maps decrease from left to right.


Got it?

tranceminister

Great explaination once again Jason. Good to see you back, but sorry it had to be to correct something thats already been covered quite a few times.

jecu

so for people using the hack, couldnt they just run smaller injectors than 450cc say 310's and tune it from there. Would it not advance the timing? or at least not as much? Sorry if this is totally wrong, just trying to learn

TurboEF9

Thanks, TM! I've missed you buddy!

Heheheh..

As for your injectors, yes, you can you smaller injectors (Did I leave this out of the Engine Management FAQ a year ago? Oh wait, no.. I didn't. Section 2, Question 2).. but anyway)

Yes, you can use smaller injectors, but you won't be able to boost as high before "freaking out" your ECU. This is because your injector flow differential will be too small.

Try and follow this..

With 240cc injectors, unmodified MAP voltage, your Honda ECU will drop to limp mode with a CEL(10) at 3.1v. Your stock Honda map sensor will measure about 5v (for sake of argument, and easy math.. with the diaphram design you won't actually hit 5.0v, you'll hit 4.8 or so). 3.1v is about 1.3psi of boost.

For sake of argument, and easy math, we'll say 5 volts is 10.3psi of boost.

With that, you can calculate how much boost you can run on a set injector size, based on the flow differential percent.

(Mind you, this is entirely too much ------' thought to put into an AFC hack.. but, I'll show you anyway..)

OK, so you have a 5v MAP sensor, 3.1v is 1.3psi, 5 volts is 10.3psi, how many volts per psi? 0.18v

450cc flow 46% more fuel than 240cc (240/450 - 1 = .46)
310cc flow 23% more fuel than 240cc (240/310 - 1 = .23)

You scale -46% of 3.1v, and you get 1.67v @ 1.3psi (mod'd voltage). How many psi can you run before you get to 3.1v cut off? About 10. (.18 * 10) + 1.67 = 3.4v (keep in mind this math is not exact due to my arbitrary number use, but you get the point)

What about 310cc?

-23% of 3.1v is 2.39v @ 1.3psi (mod'd voltage).

(.18 * 5) + 2.39 = 3.2v ..so around 5psi..

..but, I wouldn't recommend any of this crap. Do it right. Don't skimp on the last, most important, part of the turbo setup.

Dr.Boost

[Hotrex]------- pwn3d punk bitch[/Hotrex]


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jecu

oh no Im not going to use an safc, Im going turboedit myself. I was just trying to gather up some info for a buddy of mine doing his setup with the hack.