Grumpy Bears 2015 Silverado 2WD

2016fifteenhundred · October 17, 2016

What's the magic number for AFR on these motors? I've never done much motor wise to my vehicles but I did a lot of motor work on my old quad and I believe the number was around 13:1. Then again that was on 116 octane race fuel from VP and 13.75:1 compression.

Grumpy Bear · October 18, 2016

You ask big questions. That’s good. The answer is. It varies. Allot. More with wet runner systems than direct injection. Wet systems:

Cold start up around 9:1

Full power 12.5-13.2:1

Normal running 14.5-14.7:1

Light load I’ve seen programs as lean as 22:1 (Honda)

Light load can be downhill. Can be wind at your back. Any situation that gets MAP readings and TPS low enough to trigger the coding. (Honda).

Carburetors and throttle body injections like carburetors feeding unequal length runners, yada, yada run rich enough to cover the leanest cylinder. It gets more precise with individual runner port systems that have an O2 sensor per cylinder even if the air rate is somewhat unequal.

The higher the manifold vacuum the easier it is to vaporize the fuel thus the at the venturi or point of injection mix ratio can be closer to idea 14.7:1.

Nail it to the floor (carb or TBI) and let the vacuum drop low and have large low velocity runners, low quench and low dynamic compression it might take 12:1 to get 14.7:1 in the cylinder.

Cold motors like to puddle thus the reason for stove heat and 9:1. Point is….whatever it takes to get the vapor phase ratio in the cylinder at the point of ignition to 14.7:1. Only vapor burns.

Direct cylinder injection under pressure changes the game. Not for the vapor state requirement but for the actual and instant conditions in the cylinder. Direct injection will not and cannot suffer from velocity/pressure induced liquid phase separation in the port. Much tighter control over ratios can be realized as can about a 5% increase in thermal efficiency. Pretty trick stuff really.

Direct cylinder injection is nothing new but controlling it with a computer with instant closed loop feedback is more so.

Edited October 19, 2016 by Grumpy Bear

Grumpy Bear · October 20, 2016

Did I open a can of worms?

Before anyone asks about BSFC (brake specific fuel consumption) at WOT (wide open throttle) or leanest possible running ratio you have to ask much more basic questions.

How much BMEF (brake mean effective pressure) will it take to get the job done? And as is the case with most questions they don’t have answers until we ask more questions. Like…..well what’s the ‘job’ and ‘how fast’ do you need to have that job done? Under steady rate or some form of acceleration? We as humans are an impatient lot. We what it all and we what it now.

Of these questions, the former ask about torque and the latter set of questions, the needed horsepower which is related to torque by rpm.

Then we go down the Hp rabbit hole. If rpm then at what speed and with which effective gearing? And if that; which transmission gear ratio, final drive gear ratio and tire height. Then the other question, torque related, becomes ‘load’ which is weight, grade and drag in all its various forms.

Finally, as it seems I stepped off a cliff…what has this to do with AFR?

A or air in AFR is displacement, weather and rpm related. F is fuel which provides the ‘potential (kinetic) energy’ to deliver torque and R is the ratio of greatest capture of that potential. What ratio delivers the greatest ‘sensible’ heat liberation? Chemically ‘liberation’ is 14.7:1 but ‘capture’ may dictate otherwise to obtain that ratio in vapor state.

Such subjects are akin to a plate of spaghetti. Each strand a ‘factor’ and thousands of them dropped on your mental plate all at one time.

Net effect? A can of worms. Easy enough to pull an individual strand and look at it under a microscope. Magazines do it all the time. It’s a much larger task to see them all with equal precision and then understand the effect of affect each has on the other and in concert.

My world is meant to feed my personal thirst for knowing a thing. My truck helps me do that. Not the trip you though it would be, eh?

Grumpy Bear · October 20, 2016

It's fall and it's pretty.

Grumpy Bear · October 21, 2016

Seasonal fuel composition. Alky content. Tire wear. Variations in pump cut offs and fill rates. Station pad grades and how you address the pump combine with the normal wear of tires and inaccurate and uncalibrated factory instrumentation can leave you guessing. I don’t guess. I track and verify.

This is a flex fuel motor. Means it “sees” the alcohol as a difference in specific gravity. Also means that some fill variation is counted as fuel suppliers of E10-E85 take full advantage of the +/- 5% rule.

Having collected fuel data for better than 6K of the trucks 11K miles I can report a standard deviation of .667 giving the upper and lower control limits 2 mpg plus or minus the centerline.The centerline dependent upon the speed, load and wind conditions.

The life time centerline is 27.3 mpg to date with upper and lower limits of 29.3 and 25.3 respectively to that center.

Individual speed, load and wind corrected conditions resulted in a data scatter of 15.7 to 32.0 mpg.

Even though the specification for fuel tank size is 26 gallons it is never full when fill is limited by the pumps auto shutoff. About 4%.

There is additional loss of volume caused by the rake of the truck which is load and grade dependent and has averaged an additional 2.5%. and finally there is a 25% manufactures suggested fuel pump cooling related loss.

31.5% volume loss all in all leaving 17.8 gallons of useable fuel volume. I figure of the 6.5 gallons wasted in pump cooling I have access to 5 gallons for emergency. I start looking for fuel when the scan gauge reports between 22 and 25%. Depending on conditions that can mean as little as 280 miles or as far as 570 miles of base range with a cushion of 90 to 160 miles. It’s a pretty big window and a silly amount of wasted volume. Absurd actually.

Not being my first rodeo and having logged near a million miles where I’ve keep track of various vehicles bought new or nearly so I also am aware that the range will continue to increase for the first 40K or so. Yes sir, that is how long it takes for the drive line to reach the linear segment of the wear slope. (gasoline motors only).

11,382 miles done in 297.1 hours gives an average speed of 38.3 mph. This is actually a tick high of the million mile 35 mpg average. Not much dedicated “city” loop driving done on this one yet.

If oil changes are done on the hour meter then 150 hours is close to 5K.

I can’t tell you how useful this sort of information has been to me over the years. It’s saved my bacon more than once. Ignoring it or not having access to it has nearly cost me dearly several times.

Logged a sixth point of the fill ups averaging 500 miles per fill. Still not enough data to nail it but enough to trend it or start to. No corrections over the last three. Still putting in a bit more fuel than it says I’ve used but the error is getting exceedingly small. The gauge mpg function is getting very accurate and what little error remains seems split between a small fill error and a smaller miles driven error. Happy it is they are in opposite directions netting a much improved output that can be trusted. Better yet this will get smaller as the tires wear.

Looks like I might be very close to done calibrating this thing.

Grumpy Bear · October 24, 2016

AMMONYC videos are such a big help. There’s this trick where he paper punches some 2500 wet/dry and with a drop of CA attaches the punched mini disk to a new pencil erasure. A spray bottle with a drop or two of car wash for lubricant. Super small area sanding for spot chip repair. Wowzer.

Repaired two chips today. Using AMMO methods and some tools I’m adding to the maintenance and detailing collection. Like an oil 0/20 angle tip sable brush. Micro drop application. 5000 foam back 3M pads. 4000 mesh sanding film. A high magnification head set and I need a paint light and a small buffer yet.

Unless you clear bra the entire truck or just don’t drive it, which can be done, it’s going to get chips. Keeping up on them keeps the job small and manageable.

The first one is a heart breaker. Then...not so much. In fact the better you get a the repair the less they bother you. I think it's the helplessness that gets to ya. Anyway....

Edited October 25, 2016 by Grumpy Bear

Grumpy Bear · October 26, 2016

BAR, MAP, TPS & LOD. Oh, and yes….those Butterflies.

BAR is say 14.2 PSI. I’m running along at 50 MPH in sixth gear (3.23 axle) on 30% TPS with a 10 PSI MAP. Instant mileage shows 31 MPG and load is 28%.

Come to a hill. I’m in cruise control set point still 50 MPH. Load is increasing so the TPS opens to 50%. MAP matches BAR load increases to 80% and mileage plummets to 11.2 MPG. At which point it reaches equilibrium meaning at this setting the speed does not fall and the throttle does not attempt to open further. Load asked is matched to load delivered.

Some points of note here.

1.) It never down shifts. It just hammers along at 1250 rpm.

2.) The MAP and BAR are equal at 50% TPS.

3.) Fuel use is in direct proportion to load. D’oh Homer.

All have explanations. Down shift in this scenario is controlled it seems by load and the trip point is 99%. Dumb but okay. It has a computer and could be written to pacify an AND/OR gate instead of beating the bearings to death. Manual shift is possible.

See the flow graph of a butterfly valve below. A bit over 80% of the flow is available at 50% TPS or 45 degrees from vertical.

It could have a modified flow to percent position algorithm as it is fly by wire but it doesn’t seem to.

Last one just proves a point. Fuel use is 100% load driven and load comes in a bunch of different forms. The biggest one you have a handle on is speed.

At 65 MPH for instance load increased to 80% with the TPS at 38% and MPG running 20 mpg. MAP 13 and small change. Why the nonlinear response. 100% load is a different base value as rpm increases and more air thus fuel thus power becomes available. Load is the percentage of available power.

Think of it as a load based rolling road dyno.

kstruckcountry · October 26, 2016

That's interesting, my 2006 will pull 28% throttle at 70 mph. 14.6 afr. Usually a 50-60% throttle for a downshift. That's with a tuned 4 speed trans, so it's interesting the newer trans with more gears holds longer.

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Grumpy Bear · October 26, 2016

That's interesting, my 2006 will pull 28% throttle at 70 mph. 14.6 afr. Usually a 50-60% throttle for a downshift. That's with a tuned 4 speed trans, so it's interesting the newer trans with more gears holds longer.

Sent from my SM-G920V using Tapatalk

How did the "tune" change the nature of your transmission? I'm curious. I've done shift kits but never electronic tunes. Yours is Black Bear, right?

kstruckcountry · October 26, 2016

That's right, Black Bear tune. My 4 speed liked to hold gears forever at low speeds and light throttle, and under heavy throttle wouldn't hold them long enough. Now if I'm rolling up to speed under light throttle, it will shift sooner. The shifting under heavy throttle is a bit firmer as well. Overall, I feel like it shifts when I want it to now. The tune changed the habits of the transmission and engine quite a bit.

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Grumpy Bear · October 28, 2016

Another tank logged making the error more visible.

From fill to fill there will always be a bit of variation for dozens of reasons we can’t control.

The “Standard Deviation” over four fills is 0.11 gallons totaling .34 gallons total error on 74.761 gallons of actual pump fill. Meter says we’ve burned 74.425 gallons. Meaning the expected deviation between what the pump charges and the gauge metered has a plus minus of 1/10 gallon per tank which is, as you can see from the graph, a larger variance in fill that there is error in the fill. That kids would be impossible to find and correct without stats. (Visual aids).

The gray line is the ideal fill or zero deviation. The blue line is the actual deviation from ideal or (pump – gauge = plot point) which indeed is showing fills either side of the ‘peg’ (zero line).

The Orange line is the cumulative average. That is the one we are interested in and it is showing we are charging a tenth more that the meter is registering used based on four fills.

There are two ways to correct this meter. Direct percentage…OR…“offset” in gallons. As the error is under 1% and the minimum correction is 1% making the correction just moves the error nearly the same distance the other side of the “peg” (zero line).

But I can make a half percent correction by adjusting the filled gallons offset a tenth of a gallon per 20 gallons and nail it.

Gallons is just one half the mpg equation though and for these four tanks the cumulative difference in percent between the meter and the calculation is 0.34%. Being the opposite direction this will give a meter with a cumulative error of less than 0.05% and that is nutting it I’d say.

That correction will happen at the next fill; then I’ll make a new four fill plot to check my work.

Grumpy Bear · November 2, 2016

Normalized for 100 gallons of gas pumped and on an average fill of 20 gallons the trucks meter recorded an error of .339 gallons per hundred or about an 11 ounce variation per fill with the centerline 1/10^th of a gallon below the zero peg. I made a plus 1/10 gallon correction to the base on the last fill of 19.5 gallons or a shade over 7 ounces. It is now within a half a cup a coffee per 20 gallon fill up. Any variation past this point is a function of the fuel gravity meter for which I have no input for. It’s as fine as I can cut it and with that calibration of the fuel meter is complete.

The odometer was corrected in the kilometer mode and accurate to within .05 per hundred or .03 miles per hundred miles. 0.15 miles per 500 mile fill. There will be some drift upward as tires wear. This has been corrected and verified by GPS, Vascar Radar and mile marker count. As close as is possible without getting the Federal Bureau of Standards involved.

We started with an error of more than 10%. Brought it to within 1% happy. Then 1% pessimistic and now…..time will tell….

I’ve used the same station. Same pump. Same orientation. Same load with the only curve ball tossed at me being the fall fuel composition change. The gravity meter seemed to weather that just fine.

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On another note keeping up with the chip repair has in itself kept me pretty busy. I’m actually getting quite good at it if I do say so myself. Good enough that after I’m done the next day I can’t find where the repair was made any more. More importantly neither has anyone else.

Winter is going to be a major challenge as the temperature will be outside the painting window unless I can find some heated work space to rent.

Riddle me this Batman. Why are the vast majority of the nicks and paint chips on the passenger side and above the body curve? The most protected area on the truck. My best guess? I’ve been peppered by farm and city lawn mowers, power sweepers and from fifty yards out by those three wheeled field fertilizer spreaders. I’d take it personal but they have no more regard for others property than they do for the pets and their own children in their own yards. State maintenance trucks spilling gravel with large signs that state, as they pass you on the right, Not Responsible for uncovered loads. Really? Who is then?

Oh and that bird that flew into it from the ditch. I don’t follow close enough to catch many from the front and even if I did, the masking and the fact that 90% of the nose is flat black plastic keeps them off the paint. The Rhino boards and mud flaps have been very effective at keeping the lower edges chip free.

Edited November 2, 2016 by Grumpy Bear

Grumpy Bear · November 4, 2016

Chart for last 4,000 miles. From 3.5 mpg error at 1,500 miles to 0.03 mpg error at 12,000 miles. Now I can evaluate cause and effect for other modifications with stricter confidence.

Edited November 4, 2016 by Grumpy Bear

Grumpy Bear · November 8, 2016

Already did the seat belt cable recall and today we did the air bag/belt tensioner recall. 40 minute software update so that they actaully work in a crash.