SGII shows best acceleration load
 

We now have the ability to determine fuel consumption during acceleration under different engine loads. It’s not cheap, as it requires you have access to a Scangauge II with v. 4.06 performance upgrade, a second SG or UG to show engine load during testing, and a cable to piggyback the two devices. I got my SGII v. 3.17 upgraded by Linear Logic for $18 under the Ecomodder Group Buy (regular price for the upgrade is $25).
The upgraded SG-II adds performance data logging, so SG owners can log fuel consumption during cruising and acceleration. I thought I could test fuel consumption during acceleration pulses with the SG alone, but in performance logging mode, it uses all available displays to show time, distance, speed, etc. That meant I couldn’t display engine load to keep acceleration consistent. I already own an UG, so I bought an OBD-II cable splitter, with one J1962M end and two J1962F ends, to plug both my SG-II and UG into my 2006 Scion xB. The UG was used solely to display % engine load during data collection. The SG collected performance data.
SG performance mode automatically logs speed, distance, and time (every .4 seconds for 24 seconds) , plus one user-selected parameter. For the testing, I chose GPH as my user-selected parameter, since the logged time intervals are consistent, while fuel consumption logged as MPG varies with varying distances traveled at different speeds during pulses.
I did three test runs in the same direction in the same location on the same day, November 23, 2011. The road was dry, temperature was 55 degrees F, winds <10 mph, skies cloudy and overcast. I accelerated from 25-40 mph in 4th gear on each run, and added the fuel consumption for the cumulative time during each pulse. One pulse was at 82% LOD, one at 90% LOD, and one at 70% LOD. I’ve been using 83% LOD in my 1NZ-FE engine, having determined long ago that it gives better results than 75% LOD. After each run, I transferred the data to a notebook and then to a spreadsheet.
Following are performance data from my 82% LOD pulse. First column is elapsed time. Second column is GPH fuel consumption rate. Third column is distance traveled. Fourth column is speed. Fifth column is actual fuel consumed during the 0.4 second time interval, calculated from the GPH rate. If I’m burning fuel at 1.51 GPH, I’ll consume 1/3600 of 1.51 gal. in 1 second, and 1/9000 of 1.51 gal, or .00168 gal. in .4 sec.
4 1.51 131 24 0.000168
4.4 1.54 145 25 0.000171
4.8 1.57 159 26 0.000174
5.2 1.57 175 26 0.000174
5.6 1.6 190 27 0.000178
6 1.61 206 27 0.000179
6.4 1.61 222 27 0.000179
6.8 1.65 237 28 0.000183
7.2 1.65 254 29 0.000183
7.6 1.7 271 29 0.000189
8 1.7 289 29 0.000189
8.4 1.8 306 29 0.0002
8.8 1.83 323 30 0.000203
9.2 1.84 341 30 0.000204
9.6 1.86 359 32 0.000207
10 1.89 377 32 0.00021
10.4 1.89 396 32 0.00021
10.8 1.93 414 33 0.000214
11.2 1.93 434 33 0.000214
11.6 2 453 34 0.000222
12 2 473 35 0.000222
12.4 2.08 494 35 0.000231
12.8 2.11 515 35 0.000234
13.2 2.12 535 35 0.000236
13.6 2.12 556 37 0.000236
14 2.16 578 38 0.00024
14.4 2.16 600 38 0.00024
14.8 2.21 622 39 0.000246
15.2 2.21 645 39 0.000246

From the data, I used .005963 gal. gas during 11.6 seconds (29 X 0.4 second intervals) to pulse 25-40 mph at 83% LOD. I used .004688 gal. during 7.6 seconds (19 X 0.4 second intervals) to pulse 25-40 mph at 90% LOD. I used .007563 gal. during 16.8 seconds (42 X 0.4 second intervals) to pulse 25-40 mph at 70% LOD. I had guessed from the collective wisdom here that 90% LOD acceleration would waste gas. I was wrong. We have a better tool than seat of the pants and variable-filled ABA P&G testing to determine best acceleration loads. It’s the Scangauge II with performance upgrade.
I’m including the 90% and 70% LOD data for your perusal. First, the 90% LOD data.
3.2 1.6 110 25 0.000178
3.6 1.62 125 25 0.00018
4 2.05 140 27 0.000228
4.4 2.04 156 28 0.000227
4.8 2.04 172 29 0.000227
5.2 2.04 189 29 0.000227
5.6 2.04 206 29 0.000227
6 2.19 223 29 0.000243
6.4 2.19 240 30 0.000243
6.8 2.22 258 32 0.000247
7.2 2.33 277 33 0.000259
7.6 2.33 296 33 0.000259
8 2.44 316 33 0.000271
8.4 2.46 335 34 0.000273
8.8 2.46 355 35 0.000273
9.2 2.48 376 37 0.000276
9.6 2.48 397 37 0.000276
10 2.59 419 37 0.000288
10.4 2.59 440 38 0.000288

Then the 70% LOD data.
2 1.45 71 25 0.000161
2.4 1.45 86 25 0.000161
2.8 1.43 100 25 0.000159
3.2 1.19 115 26 0.000132
3.6 1.12 130 26 0.000124
4 1.19 146 27 0.000132
4.4 1.2 162 27 0.000133
4.8 2.2 178 27 0.000244
5.2 1.54 194 29 0.000171
5.6 1.54 211 29 0.000171
6 1.56 227 29 0.000173
6.4 1.56 244 29 0.000173
6.8 1.59 261 30 0.000177
7.2 1.62 278 30 0.00018
7.6 1.52 296 30 0.000169
8 1.5 313 31 0.000167
8.4 1.48 332 31 0.000164
8.8 1.54 350 31 0.000171
9.2 1.54 368 31 0.000171
9.6 1.54 386 31 0.000171
10 1.52 405 32 0.000169
10.4 1.52 424 32 0.000169
10.8 1.57 442 34 0.000174
11.2 1.57 462 34 0.000174
11.6 1.55 482 34 0.000172
12 1.61 502 34 0.000179
12.4 1.69 522 34 0.000188
12.8 1.71 542 35 0.00019
13.2 1.71 562 34 0.00019
13.6 1.71 582 34 0.00019
14 1.77 602 36 0.000197
14.4 1.77 623 36 0.000197
14.8 1.75 644 36 0.000194
15.2 1.75 666 36 0.000194
15.6 1.83 687 36 0.000203
16 1.84 708 37 0.000204
16.4 1.87 730 37 0.000208
16.8 1.89 752 39 0.00021
17.2 1.87 774 39 0.000208
17.6 1.87 797 39 0.000208
18 1.97 819 39 0.000219
18.4 1.97 842 39 0.000219

In summary, I used .005963 gal. during an 11.6 second 25-40 mph pulse at 83% LOD, v..004688 gal. during 7.6 seconds at 90% LOD &.007563 gal. during 16.8 seconds at 70% LOD.

Sentra, do you know what the MAP or vacuum readings were at the three different loads? 90% if it is in direct relationship with 90% of available atmospheric pressure should be about 2.7 inches (manifold vacuum) if ambient is 30 inches of pressure. I am wondering if I should apply more throttle to my bike when accelerating or shift to higher gear more quickly or a combination of both

regards
Mech

Old mechanic, thanks for the help on the Metro fan, way off topic but fixed it with zip ties for nothing.

Mech,

I didn't notice. I'm not sure whether MAP or vacuum are supported as gauges for my car. If either are, I'll look to see what they read at the different LODs. I know barometric pressure is reported, and my testing is done at sea level.

No, sorry. UG doesn't support MAP or vacuum gauges on my xB.

Nice data, but which method nets the best MPG, higher load uses the least gas, but also goes the least distance, given the same glide afterwards, you would end up needing more pulses on a given trip.

Assuming the average speed of the pulse is 1/2 way between the begining speed and end speed of the pluse, x the time you could get distance covered, then using the fuel used figure out which is most efficient?

I think then you have to factor over a given distance say 20 miles as more P&G cycles of one method vs different number of P&G cycles at other accelration rates.

Yes, a slight correction is needed. What's needed is compute miles per gallon for 1 pulse and 1 glide. Assuming your pulse in linear then you'll cover 0.104 miles with 83% and 0.069 miles with 90%.

"True" FE for 83% would be (0.104 + X)/(0.005963+Y) where X is the number of miles in your glide and Y is the gallons of fuel in your glide. 90% FE would be (0.069 + X)/(0.004688+Y).

If EOC then Y=0. I ran the numbers for that. As long as your glide is >0.065 miles then 90% is better. That would most likely be true since your pulse distance is 0.069 miles, and I assume your glide distance is greater than your pulse distance. If your glide distance is 0.5 miles then the 90% gives you a 20% improvement relative to 83%

Nice test, BTW.

A typical glide from 40-25 mph in my boxy (8.77 CdA) xB is ~30 seconds, and almost every subcompact to mid-size car does better. Adding a 30 second glide to the data yields the following results:
http://i1179.photobucket.com/albums/...B/PGSGdata.jpg

The results get better with lower speeds. My pulse:glide ratio is 1:3 (10:30) in fourth gear 25-40 mph P&G. It's 1:5 (8:40) in third gear 15-32 mph P&G. It's 1:10 (3:30) in second gear 11-25 mph P&G.

I think the additional data addresses everyone's concerns. The SGII only logs 24 sec. of data, so it doesn't have the capability of recording a complete P&G cycle. I've counted off a lot of 40-25 mph glides, & 30 seconds is very typical for my car.

Not trying to be critical in any way, just bouncing ideas around as you & DD are way above me in number gathering and crunching, but.

Only kind of weak spot I can see is having to use GPH with 2 decimal places to convert to gallons per 4 seconds. I bumped my fuel cost to $10 a gallon, that way TFC (total fuel consumed not Cost) gives accuracty to the 1/1000 of a gallon. Using your data loging you would see where the TFC was at start of the pluse, and at then end, find the difference and I think it would give a better amount of fuel used (elimiate a lot of rounding error).

David