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Author Topic: Motronic 4.4 Cam advance & AFR  (Read 2318 times)
mikeak2001
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« on: September 27, 2018, 04:10:56 AM »

Hi everyone.

I don't have much of a problem on tuning this ecu. However I have a question that I hope someone can point me in the right direction.

The vehicle in question is a Volvo s70 2.3T, Automatic AW50-42. the engine does not have VVT! Being an automatic it can be a little sluggish lower down the rpm because the turbo doesn't kick in until around 2700rpm.

While generic tuning of the vehicle. I can hit almost all the afr requests with the standard cam advance/retard setup.

To increase a bit of torque/power lower down I advanced the intake cam and you can honestly feel the difference.

This is where the problems start in regards to AFR. By advancing the intake cam I get more airflow lower down the rpm range and less at redline. This was to be expected but since then I can't hit any of my requested afr's, I'm now at the point of when I boost the car. I hit the cells for higher load(what im expecting), the target afr is  for example 11.5:1 but im pegging out super rich, maxed out on my gauge at 10:1.

This can be reversed by retarding the intake cam back to standard. then I hit my target afr again.

My question to everyone is this:
Is there a bosch map or constant that represents the cam angle? maybe for the calculation of fuel injection or something? then that could be adjusted or am I just barking up the wrong tree?

I understand that the MAF should be reading the intake volume and fuel delivery is calculated around that. I'm finding it odd that the everything runs right with the standard cam setup but the fuelling is totally out when I advance the cam.

I have tested the MAF(Picoscope), tested for boost leaks. tested for leaky injectors(even though they are good on standard cam position setup).

If anyone has any idea's of what I may be missing it would be greatly appreciated.

Thanks all
Mike

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daniel2345
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« Reply #1 on: September 27, 2018, 07:25:56 AM »

M4.4 has no requested AFR, nor will it calculate that.

It has a narrowband Lambdasond, no way to tell which AFR you currently have.

What you are tuning are wrongly interpreted maps for load enrichment.


Injection time is calculated load based, load is affected by cam position.
Since ecu does not not know changed efficency from changed cam, load calculations are not working anymore. Injection based on that works wrong.

Just tune the maps that you have your desired load under a full load pull or lower loads, regardless what the map has for values populated then.
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