Lean Spool

Lean Spool

I like Merlin’s description best of what exactly this does.

Originally Posted by Merlins ECUFlash EVO Tuning Guide
LEAN SPOOL is a tuning enhancement Mitsubishi employ to reduce the turbo spool time. A gasoline engine will produce hotter exhaust gas and more power at an AFR of 12.5:1 than 10.5:1. It achieves this by running a leaner AFR duing the rapid engine acceleration period than is set-out in the fuel map and in the process produce more torque. All of which results in quicker on-road car.

You must enable this function in periphery 1 bit 0.

Lean spool starts at 3000rpms and stops at 6000rpms. These were the default values in memory. It’s best to edit these values to match when your turbos first start to spool. The default value in the code is 3000rpms, but on most TD04 turbos, you might want to set this to closer to 2200rpms. I don’t see any point in editing the coolant value.

The Lean Spool Load table is the point above which lean spool will activate. Again, since these values are tuned for the more laggy TD05 turbos, you might want to drop them to something more conservative. My stock 98 sees 1psi at about 75-80 load in 3rd gear WOT.

The Lean Spool AFR table is how much leaner your AFR will be off the High Octane fuel table. If you want to run .5 AFR leaner, then set the AFR in this table to .5 AFR leaner than the AFR in your fuel table. I wouldn’t go past 14.7 in this table unless you enjoy playing with fire.

The Lean Spool Trailing Time – Rich Side table controls the time of Lean Spool operation through the RPM band. The units you see in the table are how long it will take to return to the normal High Octane fuel map. You’ll have to play around with this to see what works best for you. The values populated here are the stock DSM values.

The Lean Spool Trailing Time – Lean Side table controls the time to go from the High Octane table to the Lean Spool AFR table. Again, these are the stock DSM values.

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