diy mpg gauge

[itjstagame]

Ok, another question in case Skewbe comes back. I recorded a run today (just fuel, no VSS yet) and looked it over. My previous test idling looked like I needed a -20 threshold or so and I think this is still good, but I wanted to ask about the strange things I'm seeing.

If you look at the attached pictures, I'd say 'bumpy' is pretty much the normal output I see, here you can see where I'm revving up and accelerating a bit after a turn. Strange that not only the pulses get stronger but I get a very high 'noise' wave. That is, are there only 3 fuel pulses in this picture? Why is it so noisy at the end?

More bumpy is at the same zoomlevel and further in the trip. Now the noise is getting sharp points. Very strange. Again would you say there's only 3 injections there? The 'noise' is starting to look more like injections. At this point I measured the low points of the noise and it was -16, so it's getting close to my threshold.

Then in the middle of my trip it went 'flat'. This is the same exact zoom level and noise is very very minimal and the injections look obvious. There's only two here now. My TBI is supposed to inject once for each cylinder (I think both injectors fire once per each cylinder or 4 times each per revolution), but here I calculated at at this rate in the 'flat' picture it's only 1100 injections per min. That can't be 300 rpm and even at double that, 650 rpm still seems too low (I have no tach in my truck). Is this some form of DFCO or something? It's injecting once per rev and skipping a bunch of cylinders or something?

Even stranger is my SoundForge chops out dead air in the middle. I had many points where it said it cut out 2-3 secs here and there. That must mean the recording was completely flat with no noise. DFCO maybe? This run was only at 45MPH max and I just left it in overdrive the whole time, so I doubt my revs would be high enough for DFCO (as I understand it).

Thoughts ?

[itjstagame]

Well hooked into the VSS and tested without any resistor or diode using AC voltage. I know it's definately increasing frequency and not voltage but I think it's averaging the voltage and more waves means higher average. Anyway 15MPH was about 10volts and 55MPH was 45Volts, that's a lot. Maybe I should use a resistor bigger than 10k? The diode bridge should clamp to .7, right but still worries me.

[sonyhome]

Aahh... I still have to do this project and spend some time learning Java. i want to use Eclipse to do the R&D, but need time and must make a decision as to which graphic library to use (there's like 3).

Like ItsJstAGame, I've been lazy to find out where that dang Vss wire is, and how to wire the injector wire through the firewall.
Maybe I can get those signals directly from the ECU (?) inside the car.
I have plenty of crappy old laptops to throw at the problem.

Well, first, gotta fix my alternator and change the timing belt and do brakes.

ItsJstAGame:
You're not making much sense in that last post.

i'll just pitch in generalities, maybe it will answer what you ask:
If you have an A/C signal, the longer the duty cycle, the higher the voltage read. If you have a square signal duty 50% and max Vcc 50V, then the voltage you'll read is 25V (1/2 on, 1/2 off).

If your foot is on the gas pedal, you should not DFCO... Idle is 700~1000rpms, so you can use that as a base and play it by ear. Maybe go to what feels like very sluggish in 5th gear... Will be likely 1500rpm 2000rpm, and record when accelerating: no DFCO for sure.
If you like math and know the gear ratios then you can tell what RPMs you do at a given speed, say in 5th gear.

You should be injecting 4x per rotation on a 4 cylinder, right? Then you need to fudge in the injector size (cc/min), and it's trigger delay (it likely has a latency between the start for oozing gas from when the electric signal is on).

Lastly, your pictures have either high amounts of noise making them unusable, or you're soomed out and are seeing 100's of cycles.
Zoom in to 1 "noise" element, and compute it's frequency looking at the time line displayed by soundforge.
Your connection might be crappy: not shielded well enough and drudging noise from random stuff like the alternator, too inductive or capacitive, preventing the injector signal from reaching the sound card.

@#!$ I got to get my *** in gear and try this project... :\

[theholycow]

Originally Posted by sonyhome

Like ItsJstAGame, I've been lazy to find out where that dang Vss wire is, and how to wire the injector wire through the firewall.
Maybe I can get those signals directly from the ECU (?) inside the car.

I think most ECUs are on the far side of the firewall, so you still have to run wires in.

I have difficulty poking wires through existing firewall holes and hate drilling new ones, so I've found a good way to get wires in without penetrating the firewall at all. Just run them to the side of the car, between the sheet metal and the firewall, and close the door on them. Tuck them behind the dash trim and you only see a couple inches of wire when you open the door.

You should be injecting 4x per rotation on a 4 cylinder, right?

One of us is doing math wrong; wouldn't that be 2 injections per rotation? Don't forget the exhaust stroke...

@#!$ I got to get my *** in gear and try this project... :\

I have the same problem all the time, which is why my grilles are still not blocked.

[sonyhome]

What? You don't have your grills yet?



On civics, the ECU is under the passeger's feet. Also found the wires to pull from it...

All OBD-1 Honda/Acura cars:

A1 - INJ1 - Brown - Battery Voltage with KOEO
B10 - VSS Vehicle Speed Sensor - Orange - Pulses 0/12V while spinning front-left wheel

[itjstagame]

Sweet updates! Well I still haven't tested stuff because I don't have stereo line input . But now I'm mostly driving the Festy anyway, the Truck has gone <50 miles in 1 month. But I would like to get it tested and then install on the Festy too.

I can't believe it took be over a year to do becasue it's pretty cool.

As for my 'bumpy' pictures. I really have no idea. I'm quite confident that the larger spikes are the events I want. It's certainly possible the noise could be ignition. It seems to increase with throttle and my unshielded 12 gauge (can't recall actual gauge but not too thick) wire goes right over almost all the ignition wires and the distributor. I mean it's at least 3" away all the time, but still...

As for my confusing post, the VSS is usually a magnet pulsing a coil as the driveshaft or something in the tranny spins, so it produces a AC. Yes I assumed the peak, actual voltage generated would stay about the same, so more AC means higher duty cycle/more AC pulses. Either way it's looking ok when I recorded it, but I used a 33k resitor which may have been a bit too high.

And yes, on a 4 cyl you'd have 2 injections / crank rotation, 4 / cam rotation. On a V8 this is obviously different, but mine is even more different because it's TBI and only has 2 injectors right at the start of the intake runner that feeds all 8 cylinders.

I had originally assumed 2 batch fires / cam rotation (full OTTO cycle), but after reading online it is actually supposed to inject 8 times, I at first thoght this meant 4 times each / cam rotation, but that still looked awefully low, so I decided each one must be firing 8 times, so that's 4 times each / crank rotation. But yeah, definately with it just idling I can see really strange suff, like I can tune so that idle is about 1000 rpm but then when it warms up it can be as low as 350rpm. I'm sure it's just not calculated right, but sometimes I really think it's firing less times/cycle under certain conditions.

[sonyhome]

LOL! Yeah, no way you can be at 350rpm... Unless your truck sounds and vibrates like a harley.

700rpm more likely.

I'd expect you'd go from 1200~1500rpm when cold down to 700~1000rpm idle when warm.

Vss could also be 12V pulled down to 0V, aka reversed.

As for how many injections per cycle, I dunno...
I dunno why you say 2 injections per cycle. (Note
I do not consider the case of cylinders that have 2 or
4 injectors, 8 or 16 valves or what not) For me an injection
is one injection of gas into a cylinder followed by a burn.
I woud expect each cylinder do do one burn per cycle.
However we're veering off topic here.

[theholycow]

Originally Posted by sonyhome

I woud expect each cylinder do do one burn per cycle.

Yes, but a cycle requires two revolutions.

[itjstagame]

Yes, when I say cycle I mean full OTTO cycle, 2 revolutions of the crank and 1 revolution of the cam.

As for the 2 injections it's because I only have 2 injectors on my V8, not 8. The ECU could fire those whenever and how ever often it wants to as long as it's fuel requirements/cycle are met. Which is why I'm wondering if at idle or below a certain pulsewidth time if it doesn't just drop from 8 injections/cycle to 4 injections/cycle with larger pulse widths. I mean depending on injector size and fueling requirements I'd totally program it to do this so who knows what GM did.

[theholycow]

Originally Posted by itjstagame

Yes, when I say cycle I mean full OTTO cycle, 2 revolutions of the crank and 1 revolution of the cam.

Yeah, that discussion was a response to this:

Originally Posted by sonyhome

AYou should be injecting 4x per rotation on a 4 cylinder, right?

Anyway...back to our regularly scheduled programming...

Which is why I'm wondering if at idle or below a certain pulsewidth time if it doesn't just drop from 8 injections/cycle to 4 injections/cycle with larger pulse widths. I mean depending on injector size and fueling requirements I'd totally program it to do this so who knows what GM did.

Measuring duty cycle, which IIRC is what we're talking about (but maybe I'm lost again), makes the question unnecessary. Whether you have 8 small injections or 4 large injections, your duty cycle is the same. This may be a short-attention-span-failure on my part...