91 octane, straight gas, $3.00+/gal

Planning to do some max acceleration tests, I bought a gallon of 91 octane, straight gas, in a spare can. It was nearly $3.50/gallon. Still, it will take about 100 miles to run out of gas before I can put in to 1 gallon and then fill the tank.

I've got a good place for testing acceleration and hill climb. With Auto Enginuity, I can record generic data and I have GPS mouse with one second resolution. The only piece of the puzzle missing is vehicle weight. Any suggestions?

Bob Wilson

 

My interest is to measure the HP output as a function of octane and I'm down to my last two gallons of Shell, E10, 87 octane. So I'm going to use my hill climb test. It has the advantage of:

• standing start - the problem with a dyno is the inital speed. I really want a map from 0 mph to xx - whatever the maximum
• hill grade delay - the ~8% grade slows the acceleration so we can get more accurate dE/dt
• no police issues - I'll be starting from the sheriff's substation with a clear view of on coming traffic. My first pass, just to climb the hill at a set speed, will partially normalize the car
• normalized starting state - descending the hill in "B" will leave the ICE and traction battery in the same state-of-charge and temperature state

Now that I have a clue about how to get the vehicle weight, this will work!

I'll do a dry-run in a few minutes using Auto Enginuity to record the 'stock' values along with a reset, Garmin GPS.

Thanks,
Bob Wilson

 

Preliminary Report

Date: Oct. 17, 2010 ~5:00 PM (CDT)
Temp: 77 F indicated on last run
Gas: Shell 87, E10
Estimated weight: ~3,300 lbs (~1,500 kg)
Hill heigth:~ 525 ft (~160 m)
Vehicle: 1.8L, ZVW30 Prius, 14,800 ODO
Tires: 15" wheels, Sumitomo T4, ~50 psi, 5k miles
Vehicle metrics recorder: Auto Enginuity, generic power train
Emphemris record: Garmin nuvi 260 w
Hill climb:

Starting location: police substation just below lower left of "Heart of Dixie Highway
Ending location: first road at top of hill

Runs:

• 87 mph (indicated) - warmed car at 55 mph to sub-station, 10 miles, standard battery bars. Started from drive with a maximum acceleration and right turn onto drive. Drove car at 55 mph after crest until battery started showing charge bars, did a U-turn and returned to crest of hill. On downgrade, set cruise control to 50 mph and car fully charged battery to 'pink' top bar. In last 200 meters, engine note changed suggesting peak traction battery charge and use of ICE to continue speed management. Made a U-turn and returned to police substation drive.
• 97 mph (indicated) - When traffic passed, did a maximum acceleration and sharp right turn to head up hill . . . faster than before. I waited for some traffic, a pickup and car, to pass and then another lone car about 1/4 mile behind. After the lone car cleared the first turn, I was off. Unexpected, I caught the first pickup and car at the last turn . . . and at 97 mph (indicated) flew past them.

I want to integrate the GPS data with the Auto Enginuity. However, there was distinct change in the exhaust recirculation behavior between the first and second run. Initial data views:

• 50% throttle became 81% when EGR kicked in - this showed up on the first run suggesting. However, the MAF did not significantly change.
• +7 mph difference between indicated and OBD recorded velocity speed - this is where the GPS data will be critical to determine what the car actually was doing.
• minimum 70 mph (OBD) for max MAF and ICE rpm - we need the GPS data but it really looks like maximum ICE power requires 70 mph on the (OBD).

I have been at 90 mph indicated in my NHW11 at the crest of the hill and that is more excitement than I want. But in the ZVW30, it felt much better, more in control.

Well that is all I have for now. I need to get the vehicle weight and improve my protocol:

• pull onto road way
• hold brake with left foot
• max accelerator
• count 1, 2, 3
• release brake

This should be a much better standing start. But I'll do that with the high-octane, straight gas.

Questions? Comments?

Bob Wilson

ps. Yes, it was fun!

 

I've attached the raw data in a two, page, excel workbook. This can be opened using OpenOffice. Issues to be aware of:

• Time (Mac) - Auto Enginuity reports time to 1 millisecond resolution. However, Excel has trouble dealing with 1 millisecond time resolution. The raw value is there and an approximation based upon text conversion down to 10 milliseconds. OpenOffice may handle time more sensibly.
• Time (Mac) - Auto Enginuity reported the local time in 12 hour clock, not 24 hour clock. A straight 0.5 day addition in Excel offset the 24 hour value by approximately one and a fraction second . . . (grumble: quality.)
• Sampling - Auto Enginuity reports each value captured at a single point. They are roughly spread out between each frame but rapidly changing values can be sampled in different vehicle states. The usual practice is to toss out the easily identified 'end points.'
• Time (GPS) - The Garmin nuvi reports GMT time in seconds without the fraction.
• Fuel consumption - use the stoichiometric air/fuel ratio of 14.7 to one and ~2,790 gm/gallon (NOTE: gasoline density varies based upon the specific mix of hydrocarbons. I will try to measure the density of the high octane gas.)

I won't be able to work on this until this evening. However, I would use the GPS data to calculate the total vehicle kinetic and potential energy as a function of time. This also includes calculating the speed. This would result in a set of interpolated values between each GPS point with x, y, z, velocity (m/sec), kinetic E, and potential E (kW hr).

I would use the Auto Enginuity data to calculate fuel consumption and treat low values of vehicle velocity as 'zero points' to figure out clock offset between the Macintosh and GPS.

Finally, I would merge the two sets of data and interperlate to a common time scale to approximate the total vehicle state at any given time. Ploting this data makes it understandable.

Please fell free to harvest whatever data you find interesting in this data. I prefer collaboration.

Bob Wilson

 

I wanted to see the relationship between maximum ICE rpm vs speed (OBD uncalibrated.) :

Obviously, I need to begin at a standing stop with max accelerator and brake and then let off on the brake. Still the car does scoot on MG2 while starting the ICE. With the ICE already running, we should establish better metrics.

Bob Wilson

 

Uh Oh!

• 89 mph peak - Pure, 93 octane, no ethanol gas, standing start, brake holding max accelerator
• 91 mph - Shell 87, E10, rolling, right-turn start

I am seeing slightly higher, MAF rate on the Shell 87.

Bob Wilson

 

Uh Oh!

• 90 mph peak - Pure, 87 octane, no ethanol gas, standing start, brake holding max accelerator
• 89 mph peak - Pure, 93 octane, no ethanol gas, standing start, brake holding max accelerator
• 91 mph - Shell 87, E10, rolling, right-turn start

I am seeing slightly higher, MAF rate on the Shell 87 than the 93 octane.

Bob Wilson