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Discussion Starter #1
I know I asked this in my previous "Now What?" thread, but since it was off topic (and buried among many other questions):

I'm curious if anybody out there knows if upgrading to the Motronic pistons negatively affect emissions on my 82 Bosch L-Jet Spider? I wouldn't mind doing a few things to get a bit more performance out of it, but my two #1 priorities are passing smog and making sure it's still a good daily driver.

I seriously doubt I'll ever track this car, but a little more zip and/or grunt never hurt. :D
 

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1966-2013
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13,741 Posts
Realistically emissions 'should' improve a bit as the higher compression A/F mix is a bit easier to light off and can consume itself more fully than that in a lower compression engine.

We're not talking astronomical amounts here, but there will be a slight improvement, particularly if you don't have to adjust timing. (doubtful you'll need to as the full advance ranges for L-Jet and Motronic are pretty close to begin with)

That aside, the O2 sensor and ECU will work together so that it at least won't get worse. (being somewhat 'dumb', they will try to get to 14.7:1 A/F mixture when in closed loop regardless of the changes in the world around them)
 

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1966-2013
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13,741 Posts
Dunno, but kinda doubt it unless you get pre-ignition issues, and then 89 will likely suffice quite well.

Mayhaps some of the Motronic folks will trip in and tell what they use. (preferably someone who's tried it and uses/used it regularly rather than 'my car has never seen lower than X octane')
 

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But Mad North-Northwest
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11,048 Posts
As with the Motronic engines, I think you'd need at least 91 octane. I filled with 87 once by mistake and it pinged like a mofo.
 
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