Home made fuel controller/babypiggyback

[Mk34ullboost]

Mods list
-modify stock afm housing ( drill out plug so u can adjust the screw)
-basic narrow band, wideband if you got the cash more accurate, (to make sure you dont go lean)
-basic boost conttoller or elec if you got the cash
0-2000 ohm variable resistor(linear with a knobb to adjust resistance) or "pot" potentiometer
Splice the "pot" into the coolant temp sensor wire at the ecu (find a ecu pinout for your year very easy)
As you turn the knobb (adjust only when engine is warm ) resistance will increase telling the ecu the coolant is colder.this will raise injector pulse width. Giving a richer mixure.
I have just set this up in my 87at t and havent done much tuning with it yet. Before adding the "pot" it would take 4-5 psi to get in to the rich area of my a/f gauge at a 10 psi max, I wanted a little more safety so if I want as soon as I start to accelerate I can get a rich mixture or when crusing never get a rich mixure with the turn of a knobb . I call this a piggybabyback for under 10 bucks

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[Mk34ullboost]

What do you guys think any problems with this better ways to add fuel? Im just experimenting and trying to get the most out of an otherwise stock set up. My fuel pump is next upgrade any input good or bad is appriciated.

 

[mecevans]

If anything the 7M runs too rich. Gains will be from leaning it out. Your better off spending time and money on an MBC, downpipe and full exhaust.

 

[hvyman]

And a wideband and safc.

When you add or subtract fuel it changes timing as well.

And you don't want your car running in warm up enrichment.

 

[IndigoMKII]

And a wideband and safc.

When you add or subtract fuel it changes timing as well.

And you don't want your car running in warm up enrichment.

I was thinking the same thing..

Just spend the money for a safc and the afpr kit..

300-400 bucks is cheaper than rebuilding the engine because you tried to do something the cheap way.

What's that saying? Fast, reliable, cheap. Pick two.

 

[Mk34ullboost]

I do have a narrow band a/f gauge I know they're not too accurate but I'm not tuning for 500 hp either just so I can see if I go lean and to make sure I'm rich under boost. So from what I've read spark is controlled by load and rpm not fuel intake and would it advance timing or retard timing I'm thinking timing would be retarded due to ecu sensing a colder temp right me if I'm wrong. Seriously nobody on this forums tests consents they just buy these controllers that do the same hint as what I'm trying out ? Add resistance to a circuit or clamp the afm signal to bypass fuel cut (that's dumb) fuel cut is great 7ms already have a bad rep imagine if they didn't have fuel cut. Just need some help Some people that have done something similar or know about it not just trying to tell me to buy some thing I know my options theirs a lot of them not all of them need to be paid hundreds for. Mk3 gurus (the open minded ones help me) shine some light on this for me. Please!!

 

[hvyman]

That's where a narrowband is no good. A narrow band o2 sensor is not fast or accurate enough to tell you your rich or lean in boost. It doesn't tell you what your afr is.

Get a wideband.

 

[radiod]

Narrowband is like having a tachometer that has 3 readings, low rpm, cruise, high rpm. It gives no inidication of what the actual values are. A wideband is a must if you are going to be playing with fuel, you absolutely need to know those values if you want to do things properly.

Personally I wouldn't be trying to adjust the fuel mixtures by tricking the ECU coolant temperature sensor.