Measuring AFR

[old_man]

I have been running a 4.7L stroker for around 110k miles and its performance has slowly dropped. I found that my map adjuster crapped out. I originally set it up on a dyno, but I don't want to spend that much money at this point is not a good option.

I have been thinking it might be cheaper to put a wide band O2 sensor in the exhaust. I am an electronics engineer so I would do my own reader using an Arduino. What is a reasonably cost (aka CHEAP) sensor out there? I also would need a O2 sensor bung to weld into my header. Anybody have a cheap source?

Before everybody jumps on me on what I should do first, I am measuring the compression and am planning on measuring the cam lift to make sure the cam hasn't rounded off.

 

[SolarBell]

AEM sells their sensor that you can buy separately. The only challenge is that they do not sell the connector but I'm sure you could find it.

This is a thread I found talking about different Wideband O2 sensors and readers:
http://www.hptuners.com/forum/showthread.php?10510-Which-Wideband-is-right-for-YOU

 

[MoparManiac]

I run a Bosch 17053 with my LC1.

I think I got it for around $70 from Autozone a year or two ago.

 

[old_man]

Thanks for the info. Do you know what it came stock on? I was going to try RockAuto for a deal.

 

[O-Gauge Steamer]

I should think that any vehicle that came from the Factory with Forced Induction will have a wideband O2 sensor in it. There are a ton of them out there...

I run one of these gauges:
http://www.amazon.com/AEM-30-4100-UEGO-Controller-Gauge/dp/B000CFQM4G/ref=sr_1_1?s=automotive&ie=UTF8&qid=1399555456&sr=1-1&keywords=30-4100

I have it sitting in an A-Pillar pod. I also have my Manifold Pressure Gauge and my Compressed Air Gauge in pods as well.

Looks like this:

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At the time of this photo, the third pod had not been added in.

The cost for the AEM part is around $165.00

 

[MoparManiac]

Thanks for the info. Do you know what it came stock on? I was going to try RockAuto for a deal.

'99-01 Beetle apparently.

I just typed the part number into RockAuto and set the manufacturer to Bosch.

Looks like $80.

You can get cheap weld in bungs from Summit Racing. Get one with a plug in case for whatever reason you want (or need) to remove the sensor.

 

[Hoooper]

most 04 and up Nissans came with widebands on the primaries.

 

[old_man]

I should think that any vehicle that came from the Factory with Forced Induction will have a wideband O2 sensor in it. There are a ton of them out there...

I run one of these gauges:
http://www.amazon.com/AEM-30-4100-U...e=UTF8&qid=1399555456&sr=1-1&keywords=30-4100

I have it sitting in an A-Pillar pod. I also have my Manifold Pressure Gauge and my Compressed Air Gauge in pods as well.

Looks like this:

[/URL][/IMG]

At the time of this photo, the third pod had not been added in.

The cost for the AEM part is around $165.00

Thanks for posting that up. I was looking at those, but I am a cheap old bastard.

 

[sidewaysstarion]

You can get a bosche LSU out of an 01 saturn at autozone for ~$30. But I burned up close to 10 Bosch sensors including real AEM sensors before I finally gave up and bought a nice NTK sensor based wideband. I'm still on my original sensor 5 years later.

The main issue with most wideband gauges is they give the heater full voltage and keep it full voltage at all time. what happens is when you start your car up cold you'll get a tiny bit of either exhaust condensation or unburnt fuel that hits the hot sensor and causes the heater to fracture this killing the sensor. The way most OEM's do it is wait for the engine temps to reach a certain point and use PWM to control the wideband temp to prevent issues with the heater. They also have modeling in the ECU that predicts what the exhaust temps will be and will adjust the O2 heater accordingly.

http://www.bmotorsports.com/shop/product_info.php/cPath/103_107/products_id/357/
That is what I run.

 

[Talyn]

I've heard NTKs are the better sensor for widebands.

I run a Dayton Sensors Wego II, which has been good since 2006 and 50,000 miles.

I'd be interested in see how you address the heater using Arduino.

 

[Hoooper]

if nothing else the arduino could be used to trigger a relay. I would expect the heater amperage draw to be well over the arduinos rating.

are you at all concerned about running over 12v to the arduino? I'm working with one right now and not sure if I should try to protect the board by dropping the incoming voltage a couple volts so its always 12 or less.

 

[Dr. Dyno]

I have been running a 4.7L stroker for around 110k miles

Yours has to be one of the highest mileage strokers around. I'm a long way behind you at 76k miles on mine with 250k miles on the Jeep.
You could build another MAP adjuster to reset the A/F ratios once you have the wideband installed.
Does the valvetrain tick any more than before? You could pull the valve cover and check the valve lift just in case any of the cam lobes have flattened. If that was the case, the intake manifold vacuum would be lower than normal and the engine would run slightly rough.

 

[Talyn]

are you at all concerned about running over 12v to the arduino? I'm working with one right now and not sure if I should try to protect the board by dropping the incoming voltage a couple volts so its always 12 or less.

You need a voltage regulator

 

[Hoooper]

why a voltage regulator? Its good for between 5 and 12 volts, if I drop the voltage by 3 volts it should hang around 10-11 volts most of the time and probably never over 12V, but it also wouldnt drop below maybe 8 volts on the low end very often. Assuming youve worked with these before (i havent so I dont know anything), are they susceptible to voltage variances even if the variances are within its range?

 

[SolarBell]

Just put in a 9V regulator. The line voltage can get up to around 13-14V while running. If you drop it to 9V the onboard regulator will be happy and you won't be draining off so much heat with it. Even a cheap one with a lot of tolerance range will be fine.

 

[O-Gauge Steamer]

In a "modern" Jeep, the actual system voltage is temperature dependent. The battery temperature sensor tells the PCM what temperature the battery is and the charge rate is adjusted accordingly. On a "standard" day with the ambient temperature in the high 60s to mid 70s, a charge rate of 14.2VDc is the norm. As the temperature goes up, the charge rate goes down.

Radio shack has voltage regulators. IMO, there should be capacitors on both the input and out sides of the regulator. Just make sure that the regulator can handle the total current draw. Also, unless I have lost my mind (a distinct possibility for sure...) the O2 Sensor operates at 5VDc.

To me then, I would run the entire project at 5Vdc just for the sake of simplicity.

 

[old_man]

When I merge onto the freeway, it will still hit around 90 before I get to the traffic, but it used to do well over 100.

I will give it a good going over, from wet/dry compression, manifold vacuum, and will most likely pull the valve cover and put a dial indicator on each valve as I rotate the engine by hand.

Not that it runs real crappy, it just isn't as peppy as it once was. I still likes to cruise at 94 mph. I hate to take it much higher since the tires are getting worn and weather checked.

Yours has to be one of the highest mileage strokers around. I'm a long way behind you at 76k miles on mine with 250k miles on the Jeep.
You could build another MAP adjuster to reset the A/F ratios once you have the wideband installed.
Does the valvetrain tick any more than before? You could pull the valve cover and check the valve lift just in case any of the cam lobes have flattened. If that was the case, the intake manifold vacuum would be lower than normal and the engine would run slightly rough.

 

[Root Moose]

Tom, looking forward to your final diagnosis. I've always considered your engine build as sort of a reference build for a stroker in the future. If we can learn something from your current state that would be fantastic.

 

[WB9YZU]

There was a AF gauge that came out in the 90's that used an O2 sensor.
Pretty sure it was just a voltage regulated system that was calibrated.
It used a bar meter instead of your standard analog sweep meter.

I'm real sure there was not a micro running it, they simply knew what voltage equaled the optimal AF ratio.

Seems to me it was put out by Holley or one of the other fuel delivery system companies.

-Ron

 

[O-Gauge Steamer]

For those that do not know, the stoichiometric ratio for Gasoline is 14.7:1.

The stoichiometric ratio for E85 is 9.6.

For the "oxygen enhanced" fuel we run here in Colorado (up to 15% ethanol) the stoichiometric ratio is actually 14.2. However, the PCM is going to control the mixture to 14.7 so that means that, technically, all engines that run the E10/E15 are running on the lean side.

Under acceleration, the AFR should "drop" down into the mid 13s. The tune I am operating on has the Heep down to 13.3 (ish, it does vary a bit after all...) when under full boost, RPM dependent. Under boost but not under acceleration, the AFR tends to hover in the low 14s.

The question of AFR could be a thread in and of itself unless it is agreed that we discuss it here. There has been misleading information out there in the past and it is my hope to dispel that information and "put the cards on the table" as they say. Getting the mixture wrong will create issues.

IMO, a F/IC or a tuned PCM is needed for a Stroker. I ran a Stroker (4.7 Litre) back in '01 and it should have had electronic help. As it was, it ran on the stock PCM so suffered from cold engine blahs.

General Terms:
Fat = Rich = AFR lower than 14.7.
Thin = Lean - AFR greater than 14.7.