E38 Economy techniques

[oztracktuning]

Its working well for mine. The 6L Twin Turbo made it 500miles on a tank of Gas. It averaged about 31mpg for a whole tank cruising on our Sydney to Melbourne "Hume Highway".

[swingtan]

Hmmm... where's the thread miner smiley.....

Well, since my last post there has been a lot of changes made. I did the "log trip" but I was towing a big trailer the whole way. From memory I was getting around 13L/100KM but given the weight of the trailer, I was running in PE mode quite often. Remaining in an OLSD tune did help a bit though.

When we got back from holidays, I put in a 220/224 @ 114 cam with 0.550" lift. After tuning it up and looking at a few different issues, I ended up turning the MAF back on and tried OL-MAF for a while. This saw the best economy figures I've ever seen in my car with 8.6L/100km



I did have an issue with leaning out when coming to a stop so I turned on the O2's and am now running back with a CL-MAF tune. It's been very good since then though I'm not sure I'd repeat the above figures.

I've been talking to Jezza about the O2 switch point thing though. We believe that there is a table / parameter missing that has a sanity check on the O2 switch points. I've tried altering mine to below 100mV and saw no change in average O2 voltage when in CL. Maybe this is something the developers might like to look at....... In the mean time, I'd be tempted to remain in CL around town and then go OL if I do a trip.

Simon.

[oztracktuning]

My data from 30hrs of travelling Sydney to port campbell return and throw Heathcote in is that the E38 has incredibly stable AFRs when in open loop in all weather conditions and altitudes. Mine is operating nicely and giving very similar afrs in the bulk of cells every time its logged. Plus that is the race tune as well when on pump gas.

[ringram]

MAF or MAFLESS Ozt?

My SDOL tune is a little wibbly, but Im running 70lb injectors! So she goes a bit rich when transitioning around idle.

Im hitting the dyno tomorrow with the excel sheets and intend to go SDCL long term. (Russo otrcai)

[swingtan]

I found that you could get near perfect AFR's for constant or slowly changing loads when running OLSD. However, getting the dynamics correct for a "single" tune, is impossible ( running a separate "daily tune" and "race" tune you can get an acceptable compromise ). The problem is that the dynamics in the E38 are all calibrated back to MAF airflow. If you turn off the MAF, the ECM can no longer adjust the dynamics referenced to the air flow. So you can really only just set it to max and hope to adjust the other parameters to give an acceptable performance. This is really noticeable in a manual, between gear changes, an auto will not be effected as much. Because of the dynamics issues, you will never get a really smooth WB AFR reading when running OLSD, if the throttle changes, the dynamics will throw off the AFR's

[gmh308]

Hmmm... where's the thread miner smiley.....

Well, since my last post there has been a lot of changes made. I did the "log trip" but I was towing a big trailer the whole way. From memory I was getting around 13L/100KM but given the weight of the trailer, I was running in PE mode quite often. Remaining in an OLSD tune did help a bit though.

When we got back from holidays, I put in a 220/224 @ 114 cam with 0.550" lift. After tuning it up and looking at a few different issues, I ended up turning the MAF back on and tried OL-MAF for a while. This saw the best economy figures I've ever seen in my car with 8.6L/100km

I did have an issue with leaning out when coming to a stop so I turned on the O2's and am now running back with a CL-MAF tune. It's been very good since then though I'm not sure I'd repeat the above figures.

I've been talking to Jezza about the O2 switch point thing though. We believe that there is a table / parameter missing that has a sanity check on the O2 switch points. I've tried altering mine to below 100mV and saw no change in average O2 voltage when in CL. Maybe this is something the developers might like to look at....... In the mean time, I'd be tempted to remain in CL around town and then go OL if I do a trip.

Simon.

Excellent! 8.6L/100. Thats almost 33mpg Imp, 28mpg US.

What AFR to get this ?

[JezzaB]

I feel there is a "Lean Limit" table missing in the E38s. There is one in the E40 computers.

Jez

[swingtan]

Excellent! 8.6L/100. Thats almost 33mpg Imp, 28mpg US.

What AFR to get this ?

Over the 30km trip I did this test on, I averaged 15.3:1 and spark averaged 40'

I feel there is a "Lean Limit" table missing in the E38s. There is one in the E40 computers.

Jez

Exactly right. That and the table to set up the "Air flow modes" to fine tune the O2 switch points.

[gmh308]

Over the 30km trip I did this test on, I averaged 15.3:1 and spark averaged 40'



Exactly right. That and the table to set up the "Air flow modes" to fine tune the O2 switch points.

Was the 30km trip undulating or flattish?

Isn't the air flow mode and O2 data already in B1515/16?

Cheers.

[swingtan]

the trip was down the SE Freeway here in Melbourne, so not particularly hilly.

Map of route

The tables B1515 and B1516 are for referencing the O2 switch points to the air flow mode. There are no tables to define what the ariflow mode actually refers to. If you check an LS1 tune, there is a table ( B4107 ) that defines what each mode actually is in real air flow ( though it's called CL Mode ). The E38 does not have a similar table, it's pretty safe to say there are still undiscovered tables in the E38 tunes.

Simon