The dirty cost of one man's hypermiling?

[user removed]

Originally Posted by SentraSE-R

Starting with a cold engine (~45F), cat sensor 1 reached 550 degrees F in 3 blocks. Cat sensor 2 didn't reach 550F until 7 blocks, at which time sensor 1 was at 800F.

The grill blocks made no difference. EOC after a pulse, and the cat failed to light on the next pulse, grill block or no grill block. Following photo shows cat temp display at the end of yesterday's 10.4 mile P&G drive.


My downhill wasn't long enough. I accelerated to 60 mph at the top of a hill, and went into DFCO at 1100F cat temp. Cat temp rose to 1300F before dropping to 750F at the bottom of the hill, 1.2 miles later. So, unless you're DFCOing 1.5-2 minutes/miles, you can assume your cat stays lit.

Typical cat temps when driving under load.

So Sentra has a new abbreviation CCL. Coast with Cat Lit! He has also created a new level of responsible hypermiling, that is truly clean. With techniques perfected for years, the question remains, how high can you get the MPG while still being environmentally responsible.

I would wager the difference will be very small, and again I heartily applaud your balance of efficiency without sacrificing responsible protection of the environment.

regards
Mech

[SentraSE-R]

We have to remember the cat temp display isn't accurate. There's no way a 1000 degree F lump of metal is going to drop to 100F in 25 seconds (during a glide) with no liquid or air being pumped through it. My guess is it's a UG programming artifact - something like: count six V1s in 1/5 second and add their total to the total of the previous 60 V1s; if <6 V1s are available, start totaling new V1 data log. Cutting the fuel injector signal (going into EOC) interrupts the voltage signals (V1) being counted (DFCO apparently doesn't interrupt the signal). That would explain why each pulse starts from ~100F cat temperature, and it leaves us in the dark as to what the actual cat temp really is.

The DFCO cooling pattern gives us more of a clue to what's really happening to the cat temps, although DFCO is pumping air through the cat, unlike the EOC glide. I'm guessing the O2 passing through the cat during DFCO keeps it lit longer: ergo, the cat stays warmer during DFCO.

So, maybe the thing to do is, do a pseudo P&G on a downhill, using DFCO. It might give us some insight as to how much the cat actually cools during a series of P&G cycles.

Another thing I might be able to do is program Scangauge xgauges for cat temps for the CANSF communications protocol used by my xB, if those data are available. Then I could log the cat temp data for 24 seconds of a P&G cycle using the SG v. 4.1.5 performance features. It's just possible the SG uses a different algorithm to calculate cat temps.

I guess I know what today's project is .

[SentraSE-R]

I had an interesting day. I found the Scangauge CANSF xgauge coding for cat temps, and programmed them in. The following photos show the results:



Starting with a cold (51F) engine, the UG cat bank 1 sensors 1&2 were showing 214F and 134F, while the corresponding SG cat temps were 2499 and 1727.

When the cat reached light-up temp per the UG (sensor 1 = 749F, sensor 2 = 553F), the SG showed unbelievable 7853F and 5889F sensor 1&2 values.

The SG values were roughly 10 times higher than the UG values. I visited Linear-Logic's website and found their xgauge manual, which explained the MTH (math) coding. It explained the MTH coding had three two byte hexadecimal numbers. The first pair made a multiplier, the next pair made a divisor, and the third pair made an add/subtract value. The MTH coding for all the Fahrenheit cat values was 0009 0005 FFD8. The MTH coding for all the Celsius cat values was 0001 0001 0000.

Hmm. The Celsius values get multiplied by 1 and divided by one, so they're unchanged. The Fahrenheit values should get converted by the formula F=9/5C+32. But the values are ~10X too high. The 0009 is the 9s multiplier, and the 0005 is the 5s divisor. The FFD8 is wrong. It uses the high bit to indicate a 2s compliment to be subtracted. I want to add 32, and drop the overall value by a factor of 10. So what happens if I change the MTH coding to 0009 0032 0020? I'm multiplying by 9, but dividing by 50 (0032 hex = 50), and adding 32 (0020 hex). Here are the results.





So, I solved the SG coding error. The SG cat temps followed the UG cat temps closely when my xB was idling. Tomorrow I'll take it for a drive, monitoring cat temps with both SG and UG.

[SentraSE-R]

Well, the SG cat temps follow the UG cat temps pretty closely in routine driving. All I've done is identify a math coding error in the SG xgauge database. When I go into EOC and restart, both the UG and SG cat temp displays restart in the 100 degree range.

So those of you with SGIIs and CANSF communications protocols can probably get cat temps, too.

I'm about to close the book on my P&G chapter. I built and managed legal cases for a living. IMO, we have a preponderance of evidence proving EOC P&G pollutes the air we breath. Ergo, I'm not going to do it, just as I don't litter and I don't steal.

I took my wife to her college today, and out to Valentine's Day lunch. The drive is poor city driving that used to average low 40s mpg. I got mid 30s mpg.

[UFO]

While I admire your dedication and rigor in getting to the solution of your perception of the pollution problem, my perception is different. I think reducing ones overall fuel use is cutting a far more dangerous pollution, not just in the amount of CO2 emissions of ones vehicle, but in the amount of pollution created in manufacturing and delivering the massive amount of fuel to the pump.

But it's all good. Your choices are yours, and mine are mine alone. I have chosen to drive diesels on biodiesel, and that meets my expectations in helping to not pollute.

[Cd]

So at the risk of showing my lack of intelligence, I'd like to ask if it is possible at all to rig up some sort of heater for the cat for times when it is not warmed up.

( Something like a block heater, but hooked to the cat and would run off of your AC port. I imagine this sort of thing wouldnt work at all since it would draw so much current that it would counter the benefits.Perhaps an second battery source could be used for the purpose ...??

I noticed that the cat on my car has vents and have heard of cats going bad when they burn up.
When do cats come on and go off ? Just hypothetically speaking, what happens is if the cat remains lit constantly ?

When i built my aluminum belly pan, I fit it flush with the cat in the hopes that it would allow the cat to warm up faster.
Pretty ignorant eh ? I tried though.

[SentraSE-R]

UFO, my perception is I make it worse if I use 40% less gas, but emit 7500% more air pollution. Obviously, that's a very simplified view. I suspect if someone crunched the data, and I could understand it, I'd be driving a diesel, too. I've owned two diesels in the past, an '84 Toyota Tercel, and a VW Rabbit.

Cd, I hope someone who understands cats will chime in. I don't think preheating the cat helps much. The hot exhaust gases light the cat within a few blocks of driving. N.B. it takes a lot longer (5-10 minutes) to light the cat by just idling the engine. When the cat's metal surfaces are hot enough, they catalyze the HCs with O2 into water and carbon dioxide. Preheating the cat to 550F electrically would take a lot of energy, and be extremely wasteful, compared to heating it with 1200F exhaust gases.

I suspect cat/header wraps on the cat are a wash. They might help maintain heat for better catalysis, but they may also damage the cat by overheating it.

[California98Civic]

Originally Posted by SentraSE-R

I'm about to close the book on my P&G chapter. I built and managed legal cases for a living. IMO, we have a preponderance of evidence proving EOC P&G pollutes the air we breath. Ergo, I'm not going to do it, just as I don't litter and I don't steal.

That's your choice, but there are two easy objections to the logic of this conclusion. For one, it's not as if the testing above--useful as it is--is beyond reasonable objection. Nor is the effor to indify a balanced hypermile/CAT lit technique complete yet. Its by no means clear yet where a balance would be between a lit CAT and fuel economy. Second, the analogies to litter and stealing are not valid. Litter is much more easily demonstrated as a simple analytical fact. You either do it or you don't. You can't balance non-litter with litter as the projected driving technique hypermile/CAT would balance fuel production pollution against fuel burning pollution. A better analogy would be to reducing your plastics usage, where you will have to use plastics and you will have to make judgements about where to participate in the production/pollution stream much like the decision between fuel economy or emissions. The stealing is also not really fair, because it is a normative and moral imperative, not a comparable technological/technique problem. There are competing claims as to whether fuel economy or emissions is the greater imperative. You have an opinion as to which is correct but IMHO it seems a bit strident to imply other opinions would result in actions akin to the mortal sin of stealing.

Anyway, thanks for this great thread. It has been informative and useful.

Regards,
james

[SentraSE-R]

James, my analogy works for me. The burden of proof in civil cases is "a preponderance of the evidence" - an easier test than the "beyond a reasonable doubt" burden of proof used in criminal cases. My car hasn't failed smog. its emissions levels are just higher than average.

Unless someone comes up with something better, my best balanced hypermile/CAT lit technique is probably going to be top gear 35 mph steady state driving (46 mpg winter, 54 mpg summer). NICE-on P&G is a lot of work for maybe a 2.5% gain. EOC P&G yields ~33% gains, from 46 mpg to ~62 mpg, but there seems to be no way to keep the cat lit with EOC.

My references to littering and stealing were not meant as analogies. They were just examples of other things I don't do. I don't buy Exxon or BP gasoline, either, but doing so isn't a crime.

[SentraSE-R]

FWIW, I had to take my wife's new 2012 Elantra in for a smog test, as we purchased it out of state. It passed, of course, being a new car. However, the low speed HC results were surprisingly high for a new car, according to the smog test guy. I didn't want to waste gas warming up the car to drive it to the test station, so that may partially explain the relatively high HCs.


Following are some photos of the smog testing process:
Dyno support plate between roller wheels being lowered.

Low speed test being run. Operator keeps car speed/rpms between upper and lower lines.

Transition to higher speed test has just been accomplished, and is shown on test equipment.

Medium engine speed test segment.

End of test.