Piggy Back Time!

[fr0st]

I suppose this thread belongs here...

Anyways, a little about myself. I'm doing my engineering degree in Electronics and Communications. Since uni bores me shitless and I got holidays in 2 and a half weeks, I'm gonna need a project. I was looking through the manuals for the Greddy e-manage and Apexi S-AFC and was pleasantly supprised that it was well in my skill level to make my own version

Basically, all they do is take the RPM and AFM signals, add or subtract from the AFM voltage based on a map and feed it to the ECU in place of the actual AFM reading. Am I correct here?

To tune it properly it would need to be able to measure the A/F ratio which is also a fairly easy task. All thats left really is the ability to trace lean/rich conditions to different parts of the fuel map and have the ability to modify it in real time. Since I don't really want another guauge/display, the tuning would need to be computer based.

So in summary

• AFM correction
  
• O2 sensor reading
  
• Computer based map tracing and logging
  
• Real time map editing
  

Am I missing anything out or is there anything that would be usefull to have?

When I get it working I'll probably be either giving out the plans and software for free, so its all for a good cause

At the moment the parts to build it shouldn't be more than $100 using off the shelf stuff.

Any input would be great

Cheers

-Matt

[Sydneykid]

Try the thread on the Jaycar IEBC and DFA, the one on the Apexi SITC and the one on the Tech Edge A/F ratio meter

http://www.skylinesaustralia.com/forums/in...c=61207&hl=IEBC

http://www.skylinesaustralia.com/forums/in...c=80642&hl=IEBC

http://www.skylinesaustralia.com/forums/in...c=91356&hl=Tech

They should answer most of your questions

cheers

Edited June 7, 2006 by Sydneykid

[paulr33]

i like your idea but why re-invent the wheel? its been done by various vendors and are proven well working implementations. each with a good sack of tuners to suit as well.

[PHATR32]

Hey Matt,

Sounds like a great project. I too have thought about designing something simular but have never had the time to sit down and do.

What do you plan on using to controll it?

I use the PIC micro controller for my projects, and the newer range of controllers are pretty hardcore for their size.

good luck

steve

[Medium Dave]

Check out www.rb20det.com it has some good info on tuning and things - Good luck, I will be interested in your results, I have been reading a little into this sort of thing, keep us all updated as to your progress, and I will help where I can (probably not much )

One question tho, rb20 or rb25?

[PHATR32]

rb26 of course

[fr0st]

i like your idea but why re-invent the wheel? its been done by various vendors and are proven well working implementations. each with a good sack of tuners to suit as well.

Well the main reason is I can't afford $600 for a S-AFC

This way I get to learn more about my car and it gives me something to do so I don't go crazy.

What do you plan on using to controll it?

Definately a PIC

The way I figured I'd do it is to have the uC read the sensor voltages and do the map lookup in its internal eeprom. Output that to a digital to analog converter and use opamps to add and subtract it from the AFM signal. The 16F877 is probably what I'm going to use. It's fairly overkill though.

If I can find a smaller pic with integrated DAC aswell as ADC I'd use that to simplify things... but they seem to be fairly rare.

I'd make it for a RB26 if someones willing to give me one

I think the only difference between them is the AF meter. The RB26 uses a differential or dual AFM I think... either way it uses three wires instead of two to read it. RB20 and RB25's have a standard 2 wire AFM's so it'll work for both.

Cheers for the input

[Dose Pipe Sutututu]

something fun to do I guess, if it doesn't work watch his car either lean out or rich out or even won't start.. and maybe fry the ECU lol

[rob82]

Cant wait to see how you do the timing control. Do you move the 6-5-4-3-2-1 crank signal reference point or do you attempt to drive the coils like greedy and fail miserably - 8ms of dwell is tooo much aparently, did they not know this???

[paulr33]

For $960 you can have all these features and much more

[Fly_With_Sky]

$600 for a SAFC. no no no

thats why you would use nengun or greenline. Get it for $390 delivered

[fr0st]

$600 for a SAFC. no no no

thats why you would use nengun or greenline. Get it for $390 delivered

When your a uni student, even that hurts

Anyone wanna give me some full time work during the holidays?

Cant wait to see how you do the timing control. Do you move the 6-5-4-3-2-1 crank signal reference point or do you attempt to drive the coils like greedy and fail miserably - 8ms of dwell is tooo much aparently, did they not know this???

Is modifying the timing really nessecary?

The S-AFC doesn't do it.

If you reset the factory ECU once the have the A/F set right the ECU should adjust the timings for you, athlough on the conservative side. I could always tap the knock signal aswell and just feed the ECU a knock signal when I want it to retard the timing... but I think thats just asking for trouble.

If I was going to do the ignition I may aswell make my own ECU. Seems like too much work considering I could probably remap the factory ecu without to much trouble.

Come to think of it... if I just make a datalogger I could trace A/F and knocking to a standard R32 map if someone hook me up with the technical specs for the maps. All the posts I've seen about re-maps of the standard ECU just seem to be generic... not actually tuned.

The only info I've found is from the silvia tuning site, which is all SR and CA related. Has anyone got any links with more info?

[paulr33]

the stock ecu wont advance timing, only retard when it picks up knocking.

the safc when you piggyback it on the stock ecu and will advance timing for you thanks to bending the afm signal.

[PHATR32]

yeah go for the pics with the inbuilt a/d convertors, as they run a lot quicker, and be less comlplicated.

but yeah, the timing thing may be an issue, and you defnetly need a way to adjust it.

steve

[666DAN]

"Cant wait to see how you do the timing control. Do you move the 6-5-4-3-2-1 crank signal reference point or do you attempt to drive the coils like greedy and fail miserably - 8ms of dwell is tooo much aparently, did they not know this???"

Please refer to my eleventybillion posts regarding the fix for this issue Zener diodes are your friend!

http://www.skylinesaustralia.com/forums/in...=120&p=972512

[MerlinTheHapyPig]

the stock ecu wont advance timing, only retard when it picks up knocking.

the safc when you piggyback it on the stock ecu and will advance timing for you thanks to bending the afm signal.

how does "bending" afm signal change timing? i thought SAFC's could only adjust fuel

[666DAN]

Bending the signal places the fuel map at a lower load point, generally at a lower load point the timing is more advanced.

A good example is when you adjust injector size with the e-manage.

If you change 370cc injectors to 440cc the e-manage multiplies the AFM voltage by 370/440 which gives a load point a lot further down than it really is to match the correct injector firing duration....this is why they don't recommend going more than 150% greater in injector size as it pushes the timing way too advanced.

[fr0st]

the stock ecu wont advance timing, only retard when it picks up knocking.

the safc when you piggyback it on the stock ecu and will advance timing for you thanks to bending the afm signal.

The SAFC wouldn't directly control the ignition timing... it'd just be one of the effects of bending the AFM signal.

For example, you can't say you want an extra 5 degrees advance and get it with the SAFC. You have to increase the AFM adjustment and hope you get extra timing to suit the extra fuel going into the engine.

The e-manage does though as a optional ignition harness.and from the sounds of it not very well.

IIRC when you reset the factory ECU it has the timing advanced by default and retards it slowly when the engine knocks. So if you reset it with higher octane fuel you can benefit from advanced timings. But if you don't reset the ECU it will gradually increase the timing over a few tanks of fuel to suit the higher octane.

[666DAN]

"The e-manage does though as a optional ignition harness.and from the sounds of it not very well.

"

It bloody does!!!!! You just need to modify it, my car worked flawlessly with it...they just realeased it with too many bugs in standard form *shakes fist at Trust*