Joseph Davis

Did a writeup on the local message forum, go here.

It doesn't have the fine tuneability of the AFC, but it's meant to be combined with a chip... which the AFC boost hacks should be combined with anyway.

ion_four

I was running something similar to that (but, possibly better) for a while...it allowed me to taper the amount of fuel that was trimmed out, according to MAP voltage, so smaller RELATIVE amounts could be trimmed out for larger or smaller voltages, so you could fix the idle and whatnot...I'll let you know what chip it is, but it's not something you can get from the shack...it's some kind of op-amp that I ordered and used 3 pots to control it.

BTW, I'll sell it to anyone for $50. It's fine and dandy, just not as good as an AFC, which I'm using now.

Joseph Davis

Some ECU's have zero luck adjusting idle mixture via MAP input. The minimum base pulsewidth in the Honda fuel map prevents you from getting a small enough pulsewidth. You can bog the idle with extra fuel so it behaves. Having a few opamps thrown in to be able to fine adjust several different rpm or pressure ranges is what an SMC does - not quite the circuit you describe, but an interesting footnote.

You can probably order the opamp from the Shack, they do have access to a fair amount of stuff. Different stores stock different amounts of smll parts, depending on if it's rated as an A, B, or C class store. Most counter jockeys have no idea what classification their store is, or that there are classifications... . One of my best friends is a manager of a Radio Slack in SC, he emails me pictures of cute girls that come into his store from his webcam/cellphone. You can't ask for a better friend, I assure you!

Anyway, I digress. Part two will be about chipping and tweaking maps to bring idle pulsewidth and ignition curve into line. It requires a bit of mental exertion, but it's easy to follow in someone else's steps than to have to figure it out yourself.

filetofit

http://www.angelfire.com/ab7/diymaplimiter

And ion four is a big fat fibber 'cause he stole my design which I used to sell for $20. Sheesh, inflation.

kenbdSi

It did look familiar. I saw filetofit design a long time ago.

LshatchTurbo

yea wtf, i remmeber filetofit designing this A LOOOOONG TIME AGO. I been using his circuit on my car for some time now. And its was dirt cheap from him.


[Modified by lshatchturbo, 4:55 PM 3/3/2003]

Joseph Davis

The voltage divider circuit needs the op amp with how voltage and current output skews based on varying load. Since filetofit puts his on the MAP output, it works pretty good as the load is constant, but the voltage and current input varies.

I prefer to regulate the voltage going into the MAP sensor, it's the simplest way to drop the MAP input at the ECU and maintain signal integrity, so that when the ECU is chipped accordingly the output is precise as possible... my $0.02.

filetofit and I could argue the merits all day long, I'm sure. Both our approaches work.


[Modified by J. Davis, 2:13 PM 3/3/2003]

filetofit

Actually I wish I had thought of down regulating the voltage on the MAP sensor. But I wanted to have a separate fuel compensation at idle so you could tweak things a little more but in retrospect a constant across the board cut such as is provided by changing the MAP voltage reference would have worked just fine.

Thats what most people do with the AFC hack anyway: a constant across the board cut. Pretty rediculous if you ask me to use a $300 microprocessor driven device to achieve that but hey whatever floats the boat.

technine

I remember buying the circut off filetofit so long ago, still didn't even get my turbo project on my car, but I here from a lot of people it works great. Keep the good work coming guys! for low budget fixes!

liam821

I would have used one of these small devices...but i already had a afc from back in the rice days...

liam