"Cruise Ratio"

[robertisaar]

new idea i'm toying with...

basically, i'm taking the vehicle speed and dividing it by the calculated airflow to get an idea of load on the engine(not unlike LV8 for OBD1 MAF setups).

the theory behind this being less airflow per MPH means better fuel economy/more power per unit of fuel used. could be VERY useful for spark tuning... if the theory holds water anyway.

i'm tracking it with the histogram feature on tunerpro V5 and i'm getting very sensible numbers...

55MPH at 55kPa is showing 1.100 (meaning 60.5 grams per second of air)

on the high end, 5MPH at 55kPa, i'm seeing 10.562 (52.81 GPS).

on the low end, 60MPH at 25kPa is .327 (19.62 GPS).

i iz excite!

opinions?



at the very least, it should be a decent indicator of where an engine is most efficient...

[86FieroSEv6]

Hmmmmmm, knock me in the head if my understanding is wrong, but isn't this a mathematical representation of the old vacuum type fuel economy gauges they used to put in cars? Or, are you doing on paper what the fuel data center in a Cadillac is doing?

[robertisaar]

Hmmmmmm, knock me in the head if my understanding is wrong, but isn't this a mathematical representation of the old vacuum type fuel economy gauges they used to put in cars? Or, are you doing on paper what the fuel data center in a Cadillac is doing?

those referenced vacuum alone, not speed or calculated airlfow... they also didn't record their positions for various vacuum/MPH combinations either...

fuel data center? sorry, i haven't been around any recent Cadillacs to know what they do or don't do.

[ssdurango]

How did those old vacume/economy guages work and what did they tell you?

[robertisaar]

How did those old vacume/economy guages work and what did they tell you?

AFAIK, they were just a regular vacuum guage, with one end reading higher(high vacuum) and another reading lower(low vacuum)...

then again, the last one i've seen was in a mid-late 70s station wagon with a big block IIRC...

[Superdave]

I use my vacuum gauge for this. Basically the higher the vacuum you can maintain at cruse speed the better economy you are getting. It's quite handy coupled with a wideband when using LCM and tuning the SA. The more input the better and since i was raised on old school tuning it's nice to see how the engine reacts to different loads.