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Old 03-20-2014, 12:29 PM   #1 (permalink)
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Need advice regarding vacuum when accelerating

I'm considering getting a vacuum gauge to help find the sweet spot when accelerating, specifically when using P&G. I have an MPGuino for measuring overall economy, but it's not all that helpful for staying in the sweetspot when accelerating. The other missing bit of information here is my engine's BSFC and its correlation with vacuum, but I suppose that can probably be worked out experimentally.

A bit of related info:

I have the very short-geared transmission from a B16A (undersquare) paired with a much longer stroked B18B engine. Peak torque is supposedly at 5200rpm, vs the two peaks around 4000 and 7500 that engines with two cam profiles (VTEC) have.

At 75mph I run close to 4500rpm in 5th. (I don't drive at this speed)

I can shift into 5th at around 15mph and still get up hills, but prefer to do it between 25 and 40.

I have no idea at what vacuum/throttle position/RPM AFR begins to enrich.

At constant speed, I get about the same fuel economy between 48mph and 65mph. Because of this, I suspect aerodynamic improvements would result in better economy at 65 than at lower speeds.

Around 3700rpm/65mph my fuel economy begins to drop sharply.


What do I need to know? What vacuum/load should I be shooting for? Any tips?

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