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[All] [Generic] AEM AFR Wideband monitors - how do they work?

 
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monkeyra
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1990 Toyota MR2 Mk2 V6

PostPosted: Sat Sep 09, 2017 5:58 pm    Post subject: [All] [Generic] AEM AFR Wideband monitors - how do they work? Reply with quote Reply with quote including images

I'm running a supercharged 2GR-FE currently on a standard ECU. I'm a bit paranoid of running lean and popping the engine, so want to get an AEM AFR gauge.

About to push the button on purchase, but one niggling question I'm wondering if any of you know the answer to. How does it determine what is lean and what is rich? Is there a magic number which applies to all petrol engines which determines rich or lean?

This is the one I've got my eye on:

http://www.aemelectronics.com/products/wideband-uego-air-fuel-controllers/wideband-failsafe-gauge

It carries out it's own configuration by the driver pulling some runs (or on a dyno) and then determines what is rich or lean. Does it do this by sniffing the exhaust fumes then for fuel content?

Has anyone got experience of AEM? (I'd be surprised if no!)
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Essex2Visuvesi
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PostPosted: Sat Sep 09, 2017 9:02 pm    Post subject: Reply with quote Reply with quote including images

Blatently robbed from Garret's website but it explains everything:-

Why lean makes more power but is dangerous
When discussing engine tuning the 'Air/Fuel Ratio' (AFR) is one of the main topics. Proper AFR calibration is critical to performance and durability of the engine and it's components. The AFR defines the ratio of the amount of air consumed by the engine compared to the amount of fuel.

A 'Stoichiometric' AFR has the correct amount of air and fuel to produce a chemically complete combustion event. For gasoline engines, the stoichiometric, A/F ratio is 14.7:1, which means 14.7 parts of air to one part of fuel. The stoichiometric AFR depends on fuel type-- for alcohol it is 6.4:1 and 14.5:1 for diesel.

So what is meant by a rich or lean AFR? A lower AFR number contains less air than the 14.7:1 stoichiometric AFR, therefore it is a richer mixture. Conversely, a higher AFR number contains more air and therefore it is a leaner mixture.

For Example:
15.0:1 = Lean
14.7:1 = Stoichiometric
13.0:1 = Rich

Leaner AFR results in higher temperatures as the mixture is combusted. Generally, normally-aspirated spark-ignition (SI) gasoline engines produce maximum power just slightly rich of stoichiometric. However, in practice it is kept between 12:1 and 13:1 in order to keep exhaust gas temperatures in check and to account for variances in fuel quality. This is a realistic full-load AFR on a normally-aspirated engine but can be dangerously lean with a highly-boosted engine.

Let's take a closer look. As the air-fuel mixture is ignited by the spark plug, a flame front propagates from the spark plug. The now-burning mixture raises the cylinder pressure and temperature, peaking at some point in the combustion process.

The turbocharger increases the density of the air resulting in a denser mixture. The denser mixture raises the peak cylinder pressure, therefore increasing the probability of knock. As the AFR is leaned out, the temperature of the burning gases increases, which also increases the probability of knock. This is why it is imperative to run richer AFR on a boosted engine at full load. Doing so will reduce the likelihood of knock, and will also keep temperatures under control.

There are actually three ways to reduce the probability of knock at full load on a turbocharged engine: reduce boost, adjust the AFR to richer mixture, and retard ignition timing. These three parameters need to be optimized together to yield the highest reliable power.

The AFR Sensor as you say "sniffs" the fumes in the exhaust and can tell how rich/lean you are running
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pbmr2
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PostPosted: Sat Sep 09, 2017 11:12 pm    Post subject: Reply with quote Reply with quote including images

Monkey, you hit the nail on the head. Yes there is a 'magic number' or the right mixture of fuel and air.

The above post explains it well.

You will need a threaded fitting in the exhaust about 45cm down the lengeth of the exhaust from the exhaust ports. Much closer and the heat will kill the sensor over time and the readings won't be a accurate as they could be.

With a V6 install you will have a custom exhaust, make sure it's got the port for the sensor or arrange for one to be welded on.
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Dale_V




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PostPosted: Mon Sep 11, 2017 5:24 am    Post subject: Reply with quote Reply with quote including images

Stock engine and stock ecu... There's nothing to be paranoid about, I'd be inclined not to bother buying one at all.
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Gazza_DJ
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PostPosted: Mon Sep 11, 2017 10:42 am    Post subject: Reply with quote Reply with quote including images

Dale_V wrote:
Stock engine and stock ecu... There's nothing to be paranoid about, I'd be inclined not to bother buying one at all.


There is when you've added a supercharger... Stock map can only compensate so far!
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Dale_V




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PostPosted: Mon Sep 11, 2017 11:36 am    Post subject: Reply with quote Reply with quote including images

Gazza_DJ wrote:
Dale_V wrote:
Stock engine and stock ecu... There's nothing to be paranoid about, I'd be inclined not to bother buying one at all.


There is when you've added a supercharger... Stock map can only compensate so far!


balls, i missed the supercharger bit

in that case, wideband [thumleft] , but get a standalone and have it mapped
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monkeyra
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PostPosted: Mon Sep 11, 2017 12:13 pm    Post subject: Reply with quote Reply with quote including images

I've ordered an Innovate MTX-L Plus, ticks all the boxed.

The standard 2GR Ecu is quite adept at altering itself, but it has it's limitations. Exactly what the upper limitations are I'm not quite sure, hence getting the AFR gauge to keep an eye on it.

Standalone - easier said than done. The only ones on the market that support the 2GR cost an arm and leg.

There are people who can hack the standard ecu, they just haven't found all the required tables inside yet.
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Gazza_DJ
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PostPosted: Mon Sep 11, 2017 12:54 pm    Post subject: Reply with quote Reply with quote including images

How much head room is there on the stock injectors when adding boost?
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androo007
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PostPosted: Mon Sep 11, 2017 1:17 pm    Post subject: Reply with quote Reply with quote including images

Not to mention that for optimum power each engine has its own preferences.
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monkeyra
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1990 Toyota MR2 Mk2 V6

PostPosted: Mon Sep 11, 2017 8:44 pm    Post subject: Reply with quote Reply with quote including images

Gazza_DJ wrote:
How much head room is there on the stock injectors when adding boost?


With the stock ones, they should be right on their upper limits. I do have bigger injectors waiting to fit, but waiting for Gouky to either remove the immobiliser on his TRD tune, or find the appropriate sections in the standard tune.
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