Acceleration - how hard?

SentraSE-R · #11 03-02-2009, 11:26 PM

You should get a ScanGauge to monitor your engine load while you're accelerating. To achieve best BSFC, you want to keep LOD between about 75 and 85, and RPM between about 1500-2200 rpm (for most 2.0 liter class engines). Full throttle wastes too much gas. You need much less throttle climbing a hill, and much more descending a hill, to achieve the same load. We're talking about aggressive accelerating during pulses, not maintaining speed - which should be done with light throttle.

PaleMelanesian · #12 03-03-2009, 07:50 AM

For steady-speed driving, yes, you want the minimum throttle possible, like a granny.

But we want more. So we pulse and glide. This article hits on the technique for the pulse part.

run500mph · #13 03-03-2009, 11:12 AM

I have a question. I have done 75-80% throttle and had great results. I have now been pulsing from around 40 mph at full throttle and achieved the highest numbers in a year. Someone said that it is my scanguage reading incorrectly because it is wot. Can't thr SG read wot correctly? The mpgs have gone up significantly by doing this. I accelerate from a stop at about 40% throttle at 1st gear then about 100% from 2nd through 5th gear to a max speed of 60 then FAS on the glide. The tires have been at 75-85 psi so the glides are very very long. The change seems logical to me, but what say you all?

ksstathead · #14 03-03-2009, 11:18 AM

If it goes open loop at WOT, then SG may not be accurate. Need to confirm with tank averages.

run500mph · #15 03-03-2009, 12:38 PM

Can you seen on the sg if it goes open loop?

Right Lane Cruiser · #16 03-03-2009, 12:57 PM

You should be able to see it on the LP gauge. I'd pull it up and see what happens while you are accelerating with your foot planted. If it opens, the air/fuel ratio the SG uses to compute consumption won't be valid anymore.

JusBringIt · #17 03-03-2009, 02:53 PM

at wot, loop is open, sg wiill most likely read 9999mpg.

SentraSE-R · #18 03-03-2009, 03:10 PM

SG won't read 9999 mpg unless you've got open loop and fuel cutoff. My SG is set to monitor fuel cutoff at idle thottle position sensor (1) plua 4 (5). At WOT, the TPS would be 35 or so, and I'd have <5 mpg fuel economy.

JusBringIt · #19 03-03-2009, 03:13 PM

If there is a significant change in throttle position, wot to no throttle, or vice versa, the sg has a tendency to read 9999 for a brief period.

Right Lane Cruiser · #20 03-03-2009, 05:56 PM

All that can be said for certain is that in WOT circumstances most vehicles depart from the stoich air/fuel ratio and dump enough fuel in to make sure that the cylinders don't burn (ie, they run very rich).

The SG measures air flow and uses that to calculate the fuel consumption using the stoich ratio and will continue to do so during WOT. This means that it will report less fuel used than what is actually burned -- a higher mpg readout than reality would dictate.