[lab rat]

I'm troubleshooting pinging problem with my supercharged M54B30. I will need to learn how the DME fuel adjustment and timing work to help me find the source of the problem.

This is how I think it works:
DME monitors the amount of air coming in through MAF and amount of unburned oxygen through o2 sensor. It also gets data from the TPS and crankshaft sensor for RPM.
Based on these inputs it looks up a fuel table and controls injectors to give it the right amount of gas.

But, how does it sense load? Isn't there a difference between the amount of fuel needed for revving the engine in neutral and going uphill in 6th gear?

Do you have a good link or book that explains it? When I search on the internet I mostly get old articles dealing with carburators.

 

[Bdave]

I'm troubleshooting pinging problem with my supercharged M54B30. I will need to learn how the DME fuel adjustment and timing work to help me find the source of the problem.

This is how I think it works:
DME monitors the amount of air coming in through MAF and amount of unburned oxygen through o2 sensor. It also gets data from the TPS and crankshaft sensor for RPM.
Based on these inputs it looks up a fuel table and controls injectors to give it the right amount of gas.

But, how does it sense load? Isn't there a difference between the amount of fuel needed for revving the engine in neutral and going uphill in 6th gear?

Do you have a good link or book that explains it? When I search on the internet I mostly get old articles dealing with carburators.

Can our unlocked HPF set ups tune individual cylinders for fuel and timing to help adjust a bad EGT? I said "yes" but in reality am not 100% sure. I think this is pretty much on topic since we are discussing capabilities here.

 

[reggid]

I'm troubleshooting pinging problem with my supercharged M54B30. I will need to learn how the DME fuel adjustment and timing work to help me find the source of the problem.

This is how I think it works:
DME monitors the amount of air coming in through MAF and amount of unburned oxygen through o2 sensor. It also gets data from the TPS and crankshaft sensor for RPM.
Based on these inputs it looks up a fuel table and controls injectors to give it the right amount of gas.

But, how does it sense load? Isn't there a difference between the amount of fuel needed for revving the engine in neutral and going uphill in 6th gear?

Do you have a good link or book that explains it? When I search on the internet I mostly get old articles dealing with carburators.

in your case MAF is the load sensor, at idle the engine is throttled so the amount of air flow is low and at WOT the opposite.

in other setups it could be TPS for load (Alpha N) or MAP sensor

 

[SweTurbo]

in your case MAF is the load sensor, at idle the engine is throttled so the amount of air flow is low and at WOT the opposite.

in other setups it could be TPS for load (Alpha N) or MAP sensor

Dunno about our ecu but rpm rate can also be used to sense load.

Our ecu works by :

1. Gets trigger signal from crank to determine where in the 360degree engine cycle the engine is along with RPM
2. Gets trigger signal from camshaft to determine what cylinder bank to fire
3. Gets ECT/IAT temps for trim
4. Gets TPS signal to determinine where in the RPM/TPS table to get values
5. Trims fuel/ign value by load(MAF)
6. Output(drive injector/igniter)

 

[lab rat]

Ok, what about the o2 sensors? Those are used for trimming fuel as well, no?

Let me get into more details about my problem. The engine pings under heavy load pretty much across the RPM range. But, it doesn't do it all the time. It seems to run BETTER when it's warm outside. That goes against logic.
Everybody including ESS thinks it's too much air, too much timing. I tried less boost, restricted airbox a bit, octane booster. Still pings.

Yesterday I noticed another factor. Sometimes the SC builds boost very quick (6-7 PSI at 3k RPM), sometimes it's much slower (4 PSI at 3k and keeps climbing). It runs well with quick boost, pings with slow boost.

So here is a theory:
What if I had bad bypass valve. It doesn't close completely and creates boost leak.
I'm at 3k RPM WOT heavy load. DME thinks I'm boosting 6 PSI so it gives it a lot of fuel. But my boost is lower so it runs rich. O2 sensors catch that and advance timing too much resulting in detonation.

If you have stage2 ESS could you tell me how quickly your boost builds up (cruising at 2k and flooring it)?

 

[Sweed]

Ok, what about the o2 sensors? Those are used for trimming fuel as well, no?

Let me get into more details about my problem. The engine pings under heavy load pretty much across the RPM range. But, it doesn't do it all the time. It seems to run BETTER when it's warm outside. That goes against logic.
Everybody including ESS thinks it's too much air, too much timing. I tried less boost, restricted airbox a bit, octane booster. Still pings.

Yesterday I noticed another factor. Sometimes the SC builds boost very quick (6-7 PSI at 3k RPM), sometimes it's much slower (4 PSI at 3k and keeps climbing). It runs well with quick boost, pings with slow boost.

So here is a theory:
What if I had bad bypass valve. It doesn't close completely and creates boost leak.
I'm at 3k RPM WOT heavy load. DME thinks I'm boosting 6 PSI so it gives it a lot of fuel. But my boost is lower so it runs rich. O2 sensors catch that and advance timing too much resulting in detonation.

If you have stage2 ESS could you tell me how quickly your boost builds up (cruising at 2k and flooring it)?

As long as you have the proper size pulley you shouldn't be over spinning your blower. When are you hitting max boost?

If your bov was leaking you would be loosing boost and running rich based on using a map sensor, but O2 sensor can adjust trim up to so many degrees give or take.

If tuned with a MAF sesnor you might be at its limit on the voltage scale and running lean.

Do you have an afr gauge, that would help.

 

[TxZHP04]

I'd say that theory is pretty unlikely. Might want to check the vac line to the bypass valve though.

Can you induce "pinging" by revving the engine while parked?
You mentioned a new MAF in another thread, is it OE?
Any stored codes?
What are your fuel trims?
Have you monitored coolant temps (this can be done via the cluster if you don't have any other means)?
Are the coolant temp sensor connections secure?

 

[SweTurbo]

Ok, what about the o2 sensors? Those are used for trimming fuel as well, no?

Let me get into more details about my problem. The engine pings under heavy load pretty much across the RPM range. But, it doesn't do it all the time. It seems to run BETTER when it's warm outside. That goes against logic.
Everybody including ESS thinks it's too much air, too much timing. I tried less boost, restricted airbox a bit, octane booster. Still pings.

Yesterday I noticed another factor. Sometimes the SC builds boost very quick (6-7 PSI at 3k RPM), sometimes it's much slower (4 PSI at 3k and keeps climbing). It runs well with quick boost, pings with slow boost.

So here is a theory:
What if I had bad bypass valve. It doesn't close completely and creates boost leak.
I'm at 3k RPM WOT heavy load. DME thinks I'm boosting 6 PSI so it gives it a lot of fuel. But my boost is lower so it runs rich. O2 sensors catch that and advance timing too much resulting in detonation.

If you have stage2 ESS could you tell me how quickly your boost builds up (cruising at 2k and flooring it)?

Forgot about the o2's , they are used in step #5 to trim the fuel value by +/- 15% , any more than that and it wont be able to adjust.¨

Is your car burning any oil ?

Sounds like you could have an oil to combustionchamber leak, this drasticly lowers the octane of the fuel and will result in pinging/detonation

 

[lab rat]

Good info, thanks guys.

The engine will only ping under load. I checked the cooling system and it works (93-96 celsius).
The MAF is new OEM.
It doesn't seem to use unreasonable amounts of oil.
I don't have working OBD reader at the moment (long story of fail) but I did see pending rich AND lean codes last time I checked.
Can I check the fuel trim through OBC?

TxZHP04 - what's your boost at 3K?

 

[TxZHP04]

I checked the cooling system and it works (93-96 celsius).

Do you see a significant temp drop (~10 deg) on a WOT pull at highway speeds?

The MAF is new OEM.

OEM or OE BMW branded?

I don't have working OBD reader at the moment (long story of fail) but I did see pending rich AND lean codes last time I checked.

Interesting. Sounds like either a massive leak (both boost and vac which would imply post compressor) or a sensor problem.

Can I check the fuel trim through OBC?

No, need a scan tool for that.

TxZHP04 - what's your boost at 3K?

Couldn't tell you, I don't run a boost gauge in the cabin and I typically only check idle vac and peak boost when troubleshooting. I thought I had a boost plot from a dyno run somewhere but can't seem to locate it. I'm also running the 81 mm pulley and FI cams so I'm not sure how meaningful that particular number would be to you by itself.

 

[HPF Chris]

Can our unlocked HPF set ups tune individual cylinders for fuel and timing to help adjust a bad EGT? I said "yes" but in reality am not 100% sure. I think this is pretty much on topic since we are discussing capabilities here.

Of course. It is a full stand alone.

 

[Bdave]

Of course. It is a full stand alone.

Cool. Thanks, Chris.

 

[SweTurbo]

No, need a scan tool for that.

Actually you dont , fuel trim both long and short term can be seen using an ODB reader connected to a PC (like an ELM327 & XLSCAN)

 

[TxZHP04]

Actually you dont , fuel trim both long and short term can be seen using an ODB reader connected to a PC (like an ELM327 & XLSCAN)

That's what I call a scan tool. The question I was responding to was whether the fuel trims could be read via the cluster - and they can't.