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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Powertrain and Drivetrain Discussions > N54 Turbo Engine / Drivetrain / Exhaust Modifications - 335i > Lean Spool?



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      08-07-2013, 10:33 AM   #1
Ilma
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Lean Spool?

Does anyone know what the effect of "enabling" lean spool would be?

The stock map has it turned on, while the OTF maps have it disabled.

I assume it would probably help increase spool up time, but am wondering what the side effects would be by turning it back on in the OTF maps

Also found a table for maximum spool rpm = 2000. Wondering if this is this connected to lean spool in any way?.
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      08-07-2013, 10:49 AM   #2
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Increasing EGTs via leaning out AFR during spool decreases the amount of turbo "lag" as perceived by the driver.

Until the procedeflash, it was perfectly acceptable to use the procede with the OEM lean spool tables (since it was unmodifiable to the end user) at initial full boost with no detremental effect, as stated by your tuner.

However, from recent OFT logs it appears that "lean spool" is actually occuring at tuned spool up, and AFRs are stabalizing just prior to maximum boost.

Lets see which of the two shiv perfers now.
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      08-07-2013, 11:26 AM   #3
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I don't know how much of a difference it really makes on the road but BMS disables lean spool as well with their flash maps. Their reasoning was they did not observe any spool up improvements with it on and preferred the AFR stability on tip in with it disabled.

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      08-07-2013, 11:39 AM   #4
Carl Morris
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I prefer it disabled but setting/clearing the checkbox in the Cobb map didn't seem to disable it in either case. So I set the max spool mode rpm to 500 to get it out of the way and that has worked.
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      08-07-2013, 12:41 PM   #5
shiv@vishnu
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Since the fuel (spool) and regular fuel maps are similarly mapped, enabling or disabling lean spool won't make much of a difference. Certainly not enough to induce an EGT induced spool up benefit as Tzu suggested. Bigger contributor to how the car runs is the spool mode (max rpm) value as that will actually have and effect on boost control/wgdc. Set that value too high and you will see some low end boost abnormalities in flash-only applications. Doesn't apply to Procede use because it bypasses dme boost control.
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      08-07-2013, 01:10 PM   #6
Ilma
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Quote:
Originally Posted by shiv@vishnu View Post
Since the fuel (spool) and regular fuel maps are similarly mapped, enabling or disabling lean spool won't make much of a difference. Certainly not enough to induce an EGT induced spool up benefit as Tzu suggested. Bigger contributor to how the car runs is the spool mode (max rpm) value as that will actually have and effect on boost control/wgdc. Set that value too high and you will see some low end boost abnormalities in flash-only applications. Doesn't apply to Procede use because it bypasses dme boost control.
So OTF flash map stacked with Procede (for meth control only) = No impact?
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      08-07-2013, 01:12 PM   #7
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Quote:
Originally Posted by Ilma View Post
So OTF flash map stacked with Procede (for meth control only) = No impact?
I hate saying absolutes like no or none. But the effect is minor and not significant

The bigger effect the ProcedeFlash has is increased DME boost targets which gets the DME to target a richer AFR in the 3000-4000rpm range. This is why we set the entire AFR offset table (in the Procede tuning software to 50) since we no longer need the Procede-induced enrichment.
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      08-07-2013, 02:21 PM   #8
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And hence why targets are met faster, and the so-called "lean spike" is not significant on flashes with lean spool disabled. I see approximately stoich with a flash during spool and periods of 18 AFR with piggy only.

As an example, the "spike" can be tuned out entirely as shown in threads on another forum, when ATR was first released.
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