Is it ok to brake after coasting towards a stop?

[SilverCrown9701]

Originally Posted by suspectnumber961

If you check the page on Elroy (the car) you'll see a BSFC chart that I borrowed that is for a similar engine as mine.

" *BSFC chart...vertical line lower left is typical CRUISING speed RPM vs LOD/torque values....middle vertical line is RPM vs LOD/torque values when accelerating at ~ 2100 RPM...oval represents RPM vs LOD/torque values when accelerating at ~ 32 TPS.

Shows that TPS at 32 to maybe 35-36 (up to 3000 RPM) is more efficient (most efficient = 245 center area)."

...

EcoModder Garage image

On this chart the middle red line shows "efficiency" when RPM is held at 2100...typical easy driving mode.

The oval shows efficiency when throttle held at 32 TPS....more efficient.

I try to stay under or around 37 TPS...which I assume is in the 245 center area...most efficient operation.

If you look at the chart "areas" you can see that efficiency doesn't drop off much at higher throttle positions...so sometimes I'm up into 42 TPS or so.

Main thing you need to watch is whether you are in closed loop (stoch ratio) or not...my 03 Focus will stay in closed loop at pretty high throttle positions....whereas my 86 Nissan truck (1st year fuel injection) will barely stay in closed loop at cruise speeds...slightest hill and it goes open loop.

Another issue is extra wear and tear on the drivetrain...which I figure I compensate for by using synth oils and additives.

I've also found that if I slow too soon for a stop...I can still see some good mpg by feathering the throttle to 17-18 TPS coming up to a stop. Idle for this car is 16 TPS.

I also try to keep my speed up on corners...within reason...and can do this by using some rubber donuts (as tested in police academies nationwide)...one in each spring. This give much better handling than stock. Also tire pressures a bit over door sticker numbers.

Amazon.com: Superior 18-1901 Donut Style Coil Spring Spacer: Automotive

You put these between the coils....sometimes you might need to drill a hole in each end and loosely wire them to the coil.

Thank you for this!

My engine is slightly larger, a 2.2L...would these figures still pally to my car or should they be adjusted up/down?

[suspectnumber961]

I would say that the chart would apply generally to most 4 cylinder engines around the same displacement.

Main thing to notice is that you need to stay under 3K to stay in the most efficient area.

With my SG I use current mpg...avg mpg...TPS...coolant temp. TPS allows me to monitor throttle position relative to current mpg.....I watch coolant temp since I have mods restricting air intake.

Since TPS is directly correlated with current mpg (when cruising at speed)...you can train your right foot TO OBEY. ;-)

What is REALLY NEEDED would be a readout that indicated the actual efficiency at any given time? With my car when accelerating at say 37 TPS ...I see maybe a 12 mpg current mpg...which does not take into account that I'm likely driving more efficiently at 37 TPS rather than at a lower TPS.

[SilverCrown9701]

Originally Posted by suspectnumber961

I would say that the chart would apply generally to most 4 cylinder engines around the same displacement.

Main thing to notice is that you need to stay under 3K to stay in the most efficient area.

With my SG I use current mpg...avg mpg...TPS...coolant temp. TPS allows me to monitor throttle position relative to current mpg.....I watch coolant temp since I have mods restricting air intake.

Since TPS is directly correlated with current mpg (when cruising at speed)...you can train your right foot TO OBEY. ;-)

What is REALLY NEEDED would be a readout that indicated the actual efficiency at any given time? With my car when accelerating at say 37 TPS ...I see maybe a 12 mpg current mpg...which does not take into account that I'm likely driving more efficiently at 37 TPS rather than at a lower TPS.

I have to agree with this. Does this differentiate with an automatic versus a manual?

I notice when I accelerate at a higher throttle position, my instant gallons per hour is over 2 gallons per hour...almost 3 and it seems to make my gas needle drop faster, which is why I have been skeptical of accelerating at higher RPMs and higher throttle.