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WB02 and ET per cylinder

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im curiouse about a few things after seeing this photo on the HPA facebook page and wanted to start a discusion about it

1) what is the purpose for monitiring all 4 cylinders so accuratly?

is it to just give us a better understanding how the whole motor is operating?

2) What ecu are capable of tuning each cylinder separtely ?

3) As mentioned of FB how do the WB sensor go operating so close to the exhaust valve

intrested to hear all about this

Each cylinder will have variances. On your standard street car, this isn't really a big deal, but on a race car where every bit counts, this is important to account for. There can be hidden power doing individual cylinder tuning.

Most new ecus have individual cylinder trims for fuelling and timing. Haltech, Link, etc...

The ones closer to the valves are for thermocouples. They dont mind the heat.

The ones further down stream are wb sensor bungs. They are far enough away to be good.

It's not uncommon to get an uneven bias in airflow with many intake manifolds that offers better airflow to some cylinders than others, resulting in a difference in lambda. As 13bjunkie mentioned, this isn't usually a huge concern on a street or lightly tuned engine but as you start pushing the specific power levels higher, a single cylinder running a little lean can spell disaster.

Individual cylinder tuning is available on most modern ECUs these days. Some will allow for just an overall trim on each cylinder while others can be configured with a full 3D trim map on each cylinder for very precise control

The LSU sensors are rated for continuous operation at up to 950 deg C from memory and can handle 1000+ for short periods. Being that this engine is naturally aspirated we won't be seeing anything like that sort of temperature.

thanks for the replys

so when setting somthing like this up do you run all 8 sensors full time?

or are these just a "dyno" set of headers that would then be removed once the car is racing on the track

also do we have a webinar coming up featuring these headers?? i really like toyota 4 cyliner motors and will be intrested in how that motor goes

It's probably more common that the lambda sensors would be removed after tuning but it's not essential. These headers are going on our 1ZZFE Online Practice Dyno engine so all the sensors will be operational full time.

As soon as everything is up and running and tested we will put together a couple of webinars looking at both EGT and individual cylinder lambda.

I've been curious about this exact topic for a while and while I can answer some of the questions, I've got a few too.

1. As Andre has mentioned, variations in intake manifold flow (OEM and aftermarket) can be easily identified. Additionally, I suspect exhaust back pressure in twin scroll turbo applications also is also a major contributor to higher EGTs. I'm only guessing this though because my intake manifold has almost no flow variation on a bench test at 50" water (1.8psi), yet one turbo scroll path sees 400 C at 2200 rpm (2 psi rel), while the other scroll sees 550 C. All temps taken a similar distance back from the exh. primary flange as per the photo.

My question is, should I care? It takes 60% more fuel from 1000-3000rpm and 30% from 3000-6000rpm on the one scroll path to equalise the EGTs. That's a lot of fuel.

2. I run an Autronic SM4. It works a treat, but plenty do per cylinder fuel trims these days.

3. As you can see in the photo, AEM use a finned mount for the sensor to try to cool things as much as possible. AEM claim that they use the 4.2 sensor, rather than the 4.9 sensor because the sensor is slightly thicker, which takes longer to warm up, but that doesn't matter when mounted this close to the valves. If you search the Bosch website you can find the AFR accuracy skew that occurs with exhaust pressure on their 4.2/4.9 sensors. For turbocharged cars this can be massive and AEM supposedly account for this with their pressure compensation adapter. The supplied sensor is 100 psi capable. While AEM claims one sensor is enough for twin scroll systems, my anomaly above suggests otherwise.

Hopefully a webinar we have scheduled shortly will be able to answer a few of your questions more clearly HamR where we will be looking at individual cylinder lambda and EGT.

While EGT is often used as a means of individual cylinder fuel trimming, the reality is that EGT isn't just affected by lambda. What I mean is that if we have all the cylinders running exactly the same lambda, it's still quite possible to see a difference in EGT. This can be due to many reasons - Coolant flow through the head and block may result in one cylinder operating hotter as just one example. When tuning individual cylinder fuelling based of EGT I aim for a 15-20 deg spread from hottest to coldest as trying to get them exact is futile. I also only aim to tune the individual cylinder trims under WOT/full load as you see too much discrepancy in part throttle EGT.

When it comes to EGT placement, this is critical for the readings to be of any use. The sensors need to be identical distances from the header flange and also equal protrusion into the runner. You also need to use the same brand and style of sensor as I've seen differences of up to 100 deg C between two different styles of EGT probe.

I've never measured the pressure difference scroll to scroll in a twin scroll turbo manifold - While I'd expect them to be very similar, I accept there may be some discrepancy - Ultimately the back pressure will be a function of cylinder pressure and it's very unlikely that all cylinders will produce identical pressure. If you've ever looked at the data from turbine inlet pressure sensors though it's incredibly noisy anyway and would require quite a lot of filtering for the controller to make use of it. With this in mind I'm not sure how relevant a scroll to scroll variation in pressure would end up being but in order to make any real decisions you'd need to know the magnitude of the difference.

The SM4 allows individual cyl trimming, but you still need a way of deciding what change to make.

Thanks Andre. I was hoping that you'd say that there's more to EGT variation than just AFRs as many tuners seem to suggest otherwise.

In my case the EGT probes are all the same brand and while not an equal distance from the header flange, they are all an equal distance from the back site of the exhaust valve (it's a Subaru EJ motor). The variation is still small. Protrusion is identical and even sensor placement relative to the dynamic of the gas flow.

Some of the commercial EBP kits provide a dampener to reduce the pressure noise, which may help to at least get an insight of the pressure relativity between the scroll paths. Should be interesting to find out anyway.



There are a couple of techniques to make the EBP signal useable - You can filter it in software or you can build an accumulator. My own experience is that the accumulator might be a better option (yet to test this) as you need to apply so much filtering in software that it slows the response to EBP changes on a gear change to the point the signal is useless if you want to use it for something like a load calculation. I'm not sure how AEM are processing the signal as they don't use or recommend an accumulator.

As always, thanks for the info Andre!

I've noticed that the AEM 4-channel kit doesn't make provision for logging the processed EBP feed, so I guess that data massaging remains their intellectual property. I would expect that anyone attempting to use EBP data for load calculations would need to be fairly sure of their filtering methods.

My intent is/was simply to use the the EBP data to provide the AFR correction required to true up the LSU sensors (see attached), on the assumption that twin scroll paths *may* may see materially different EBPs at different load points. Perhaps it's just easier to use the AEM kit and manually move the pressure feed between the two scroll paths to see if there is any difference reflected in the corrected AFR reading. That ought to be reasonably repeatable on a dyno.

I'd be keen to hear your findings re: accumulator vs data filtering too Andre.



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