home-brewed vf meter

[suprahilux]

I couldn't find an easy way to monitor vf using a pre-made device. So I decided to design a vf meter for myself. If you read this and don't know what vf is, read this first:

http://www.supramania.com/forums/showthread.php?t=39856

and this:

http://www.supramania.com/forums/showpost.php?p=547633&postcount=16

I am not sure how many people actually pay attention to vf, but it seems important. Those that do, I am not sure how they monitor it. With a voltmeter? I just didn't want to have to take the time while driving to determine the actual voltage then figure what it means. Besides, there are other gauges to watch. I guess it might not be that big of a hassle, I just wanted a vf meter in my dash. So I built my own.

It is small and simple with 3 wires to hook up and easy to read. This unit drives 5 leds, one for each voltage. I set it up so that the red led to the left means 5v lean condition, fuel is being added. The far right yellow led means 0v rich condition, fuel is being subtracted. The rest are green. (Yes, I realize this is opposite to a A/F gauge. That is just how I see the display working for me.) You could set it up in any way that you want for your ease of viewing. It is tunable so if your voltages are slightly different, it can be adjusted. It is a very basic circuit. Anyone with a little experience in electronics could build this simple device.

I have not drawn up the schematic yet, but if anyone is interested I sure would take the time to draw up a final revision. Most parts are available at radio shack. I will probably add a little to the circuit to slightly illuminate the other leds because at night it is hard to tell which green led is lit. Any feedback would be nice. What was your solution to monitor vf?

 

[JimR]

Nifty! I use my maftpro.

 

[mkIIIman089]

drjonez had something like that a while back (maybe still does).

I use my ZT-2 User input.

 

[suprahilux]

I just have a neo and no other fancy elec.

 

[suprahilux]

If anyone decides to build this, post up your results and include a pic if you can. I would like to see other people's work. As you can see it is a very basic circuit. It doesn't take much to build at all. Here is the schematics:

 

[CRE]

Here a some diagrams of an older design(not mine) which was rather popular. I made a couple using comparators too. It is a simple project and a dot/bar generator like the 3904 fits in quite well.

 

[suprahilux]

That's neat. I could not find anything on this site where anyone else had done this. I was beginning to think everyone was using voltmeters or expensive hardware(I guess if you already have it). I would have to say that the vf meter is very fast acting, easy to read and accurate. I could not have gotten the same results from a voltmeter.

 

[steven89]

So are you using this to tune? Or are you using this to just see how the ecu reacts to your SAFC [or NEO] settings?

 

[suprahilux]

So are you using this to tune? Or are you using this to just see how the ecu reacts to your SAFC [or NEO] settings?

Did you read the links I provided? One of them talks about tuning with the vf signal. If your tuning is off a little, the ecu will try to compensate and fight the adjustments. When your wideband reads too lean or rich, sometimes the reason is in the vf signal and you must tune accordingly. I can't really give you much more than that because I have only had the neo for a couple of months and I don't even have my fuel system upgrades installed yet. I have been able to watch the normal operation of the vf signal so I will know how it is supposed to act when the real tuning is necessary.

 

[grimreaper]

Does your safc have a blue wire that is not used on the harness?

You can tune with the vf's or max them out (like many do with VE on the maft pro) to creat your own af ratio at a certain range. However since the safc or neo is rpms based, its not useful except at idle and at constant load situations. Very crude but does work great for an idle that is off due to larger injectors or something.

I would also make sure that EVERYTHING is 100% functional on the car (air leaks, exhaust leaks etc..) before i tuned for vf's as you will just tune around the issue.

 

[isnms]

I just have a neo and no other fancy elec.

If you want to tune your own NEO you need a wideband. VF monitor will not cut it.

 

[suprahilux]

If you want to tune your own NEO you need a wideband. VF monitor will not cut it.

A wideband is on the way. The vf meter is not intended to replace the wideband. The neo isn't doing much but allowing me to get used to using it. No major changes have been made yet to the fuel system.

 

[suprahilux]

Does your safc have a blue wire that is not used on the harness?

You can tune with the vf's or max them out (like many do with VE on the maft pro) to creat your own af ratio at a certain range. However since the safc or neo is rpms based, its not useful except at idle and at constant load situations. Very crude but does work great for an idle that is off due to larger injectors or something.

I would also make sure that EVERYTHING is 100% functional on the car (air leaks, exhaust leaks etc..) before i tuned for vf's as you will just tune around the issue.

It does have the blue wire but it is labeled by the wiring instructions to be a 2nd afm input for the rb20dett(?). Is there another purpose for this wire that I am unaware of?

I wanted to go with the maft pro, but didn't. I decided for my power goals, a safc would be enough. The vf is almost always unresponsive at open throttle conditions. It is very helpful at idle(adjusting fpr), and constant load(highway cruising).

Everything IS 100% functional. Thanks for asking. I just built the motor, broke it in, hks mhg, arp studs, TS rings, 77, new turbo, exhaust, etc...r154!! Just see my sig, essentially everything was done to it in nov. Some pics of build are in my album. No tuning has taken place. I have NOT adjusted values to fix a running issue. All of the electronics are in prep for fuel system upgrades coming very soon. Walbro, 550/lex, afpr kit, wideband, ebc, bpv. I want to be familiar with how the electronics work before I have to rely on them to make my car run properly.

 

[grimreaper]

VF has no bearing on what the car is doing at wot other then to show you that your in open loop (0.0V).

You can toss those diagrams out and save yourself the hassle of making a vf display. hook the blue wire up to the vf output from the ecu. Look under etc. and under check sensor. second one down is the vf reading.

 

[suprahilux]

That's interesting. Oh well, mine is already made and installed. So I will continue to use it.

 

[nikwal]

Did this thing a while back on a lunchbreak at work.
http://hem.bredband.net/nikwal/gauge.gif ,does'nt have to be as complicated as in my schematic though.. I use the same circuit for oil pressure..