Get yourself an AFR meter!

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Superelbert

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Reading through some of the posts here on carb tuning, I recognize a lot of issues I've had my self with regards to tuning carbs, be it for improved performance and response , or simply trying to sort out problems like bad idle, flat-spots, bogging etc..

For the amateur, like my self, the problem is that we just don't know what's going on. We are left with seat-of-the-pants, and trying to interpret all sorts of indirect telltales which can often be symptoms of many different things.

The only way to properly tune a carb to work optimally at ALL engine conditions, is to run an engine on a dynamometer with an exaust gas analyzer and fuel-flow measurement equipment.

That was untill inexpensive wide-band lambda sensors and Air-to-fuel meters became available.

Now, I'm running a fuel,injection system on my 318 (megasquirt controller buildt froma kit and DIY hardware), but I had tuning issues I really struggled to get arround. The narrow band lamda sensor could onlu tell me if I was lean or rich relative to Stochiometric.

I then upgraded to a wide-band lambda sensor twhich allows me to read the actuall air-to-fuel ratio.

Suddenly I could actually see what was going on!

were those cold starting problems due to lean or rich? Did I need to adjust the cranking-fuel, or was it the afterstart enrichment that was out?

Full throttle, or nearly full throttle; was I bordering on lean or was I over-rich thereby burning excess fuel and loosing power?

Suddenly I was able to do exact diagnostics and true fine tuning whilst driving.

Obviously, you will get the benefit of this even if you are running a carb.
And I would say that even if not directly cheap, the price to pay is really small compared to the advantages, not to mention just the fun of actually being able to get somewhere with your tuning and realize the full potential of your engine! :)

I would say that trying to tune your carb or efi without a wide-band sensor/ AFR meter is like trying to set the ignition without a strobe-light; you can sort of do it, but you will never be spot on and you risk doing (costly) mistakes.

The only physical modification required is to weld in a bung for the sensor somewhere in the exhaust system, the rest is a simple wiring excersise.

The one important thing is to make sure the exhaust system doesn't have any leaks as this could cause false readings.

My best spent money so far, and the best advice I can give to anybody here.

Good luck! :)
 
Needsaresto, interresting link you posted there!

Reading that article, this is obviously for a narrow band sensor. The issue with narrow band sensors is that they are only accurate around 14,7 AFR, or stociometric. Apart from telling you if you are lean or rich relative to stochiometric, you can't rely on any ratios outside of that.

But having said that, even with this limitation, being able to tell if you are running rich or lean is certainly better than knowing nothing at all! A possible excemption to this is if you run very rich to the point of getting incomplete combustuion, this can be misinterpreted as a lean condition since unburned oxygen will be present in the exhaust.

Based on my personal experience, I would go for a wide-band solution any day, those extra dollars are really well spent and really not much compared to the time, money and effort most of us invest in our hobby.

Me, I'm running just a sensor and a sensor driver (You can't just hook up a wide-band sensor to a voltmeter or any other external device like you can with a narrow-band unit) which then feeds a voltage analogue to the AFR to my megasquirt unit. So when I hook up the laptop for some tuning or simply to see what's going on, I get a dial on the screen showing the AFR.

I bought an Innovate LC1 package of e-bay for about 130$, really not much compared to what just the sensor costed only a few years ago.

http://www.innovatemotorsports.com/products/lc1.php

Obviously, if you don't run an EFI set-up, you need a set consisting of the wide-band sensor, a driver unit, and a gauge.

You can allso get the same kit with a suitable gauge, and Iæve seen this for as little as arround 170$ on e-bay. Allos great value in my opinion.


http://www.innovatemotorsports.com/products/db.php

There are probably other solutions available, but Innovate seems to be quite serious stuff and seems to get a lot of positive feedback in the various EFI and DIY communities.

When wide-band sensors first started becomming available, the sensors alone could cost as much as 600$ (if my memory serves right). Building a working driver from scratch and calibrating the set-up was allso fairly involved and required an aptitude for electronics slightly above average..

Just how affordable and available wide-band sensing technology has now become is really a DIY tuning dream come true.
 
I have used the cheapo AutoZone narrow band setups for a few years, and they work well. I know there is no comparison to a nice wideband, so I decided to buy one so I could learn a little more about what is going on in my motor. I purchased the same Innovate kit as mentioned above, and it looks like WAY more than what I wanted. Are all wideband sensors similar to this, meaning do they all have the giant control box with them? Its moiré wiring than I want to do at this point in the build, and I think I might be looking to get rid of it.
 
Well, if you had joy with the narrow-band sensor, believe me, you'll love going wide-band!

That controll box sitting in-line on the sensor cable is a must. Not exactly sure what it does down in details, but the wide band sensor is active and requires some feedback loop controll etc to make it work. It is thios circuitry that wasn't initially available when these sensors appeared, thus limiting their use to auto manufacurers or the more advanced DIY experimentalists.

Yes, there are a couple of extra wires, but for running a plain out-of-the-box set up, you don't need to worry about all of them.

The first thing you have to do, is to calibrate the sensor it self. in order to do this, you need a 12 V power source and you'll need to wire up the sensor with a switch and a LED that comes with the kit. You just follow the instruction, it's really easy.

Once the calibration is done (you calibrate it towards air, I remember some of the DIY set-ups required calibration with different gasses etc...)

There is a RS-232 serial port interface for plugging the sensor directly to a laptop for those that want to use a laptop for logging AFR, using a laptop as a gauge, or for reprogramming the output of the sensor. If you're not going to do this, you can simply igmore it, the sensor comes with a factory pre-set anyway.

Once the sensor is calibrated, you can install it. hooking it up is simple. obviously, there is 12V power supply, one wire for ground and one for +12V.

then there is one wire that gives an analogue 0-5 voltage output corresponding directly to the Air-to-fuel ratio. This is what I plugged in to my EFI controller. There is allso a second wire that gives simulated narrow-band output should that be needed for some reason.

How the gauge that comes with the kit is wired, I'm not sure, but in theory, all it should need is a power supply and the 0-5V output.

So just follow the instruction and don't get dazzled by any extra wires or options you won't need and you'll be on your way to wide-band heaven before you know it!
If my experience is anything to go by, you will quite likely experience an "Aha!" moment or two as you start to see what is really going on in your fuel and combustion department! :)
 
If you want the very cheapest O2 monitor, I stumbled across some MSD surplus about a year ago on e-bay. New, in the box, they were designed for monitoring propane engines and generators (Onan). Some were monitors and some controllers. All had O2 sensors and bungs. I didn't pay over $20 for any box, some <$10. The sensors and weather-pak connectors were worth that.

I ran one "emissions warning" box on my Newport for a while, tapped into the O2 sensor for my Holley Projection, but you could run stand-alone. It is just a red light that comes on for rich. Problem was it has ~20 sec averaging time. Too long to help me tweak the Projection knobs, but would be OK for a carb monitor where you can't do anything anyway, though too long to see lean dropouts on acceleration and such. Mainly to see how you run steady on the highway. I switched to the better/faster Holley Lean Indicator, also from ebay. I suspect MSD makes those too.

Not ready to give mine up, but others can search ebay. I got from dealmonger. I saw the same on non-ebay auction sites too. You have to stay cheap if you need to monitor dual exhausts (single for me).

If you want to make your own signal conditioner for wideband O2, it is much more complicated than a simple narrow-band. You can read up on the web. It needs to power a heater and I recall read a modulated signal or such. If you leave it in un-powered the passages can clog with soot and be permanently damaged. There is/was a hobbyist Mega-squirt type project to make home-made boards. I got one off e-bay cheap that a guy started on, plus some sensors for ~$20 (list is ~$50). A future project.
 
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