The dirty cost of one man's hypermiling?

[euromodder]

Originally Posted by dcb

You jump to conclusions and use sensationalist language without sufficient rigor.

Well, he's not the first to draw that conclusion - see the pulse and pollute thread.

[dcb]

yah, that was a dissapointing thread. Had a gas analyzer and wrecked a $1500 probe. Wrote a sensationalist thread title before having any data, said his engineer friend didn't believe p&g does anything.

[mcrews]

Originally Posted by SentraSE-R

I'm surprised, too, Mark. It could be my 70k engine is as tired as your 255k engine, the listed averages are understated, or?

I remember (vaugely) about 12 yrs ago I installed a long block in my 66 Mustang six cylinder. When i got it smogged the measured results were just 10% of the Max for that car.

[dcb]

Someone still needs to develop a cheap portable 3 gas analyzer IMHO, a snapshot every 800 miles isn't going to tell you much.

[Old Mechanic]

I remember one of my customers who was military and transferring to California, He had a tired old 76 Z car that was Federal emissions (no cat) and it was burning a quart of oil every 500 miles.
I told him I doubted there was any way it would pass emissions in California (no testing here), but he drove it across country and later he called me and told me it had passed.
I had advised him to sell the car and not even try to get it smogged in California since it had never been equipped from the factory to pass. At that time there were Federal and Cali versions of the Z car. In 1981 all z cars were Cali emissions equipped.

regards
mech

[SentraSE-R]

Surprise, surprise. The elephant is still in the room.

I took the xB on a 10.4 mile P&G EOC drive (with mostly 18-32 mph delta), reaching 57.7 mpg. I ran without grill blocks. The engine coolant temperature reached Toyota's warm up temperature of 137F after 4.5 miles. Ambient temperature started at ~40F. Normally, with the grill blocks, EOC P&G warms the engine up to 137F in ~4 miles. At 137F, the blue dashboard temperature warming light goes off. Coolant temperature had reached 172F at the end of the 10.4 mile drive, v. a normal 185F

During the 10.4 mile drive, the cat lit up (exceeded 550F with the engine running) only once, during a pulse while climbing a hill. Total duration the cat was lit was ~1 second during the entire ~25 minute drive.

Let me explain. I watched the cat temperatures during each pulse. When I stopped a pulse, the cat temperatures lagged behind, and typically rose another 75-150 degrees a second or two after the pulse ended. If I ended a pulse at 375F, the cat temps usually rose to 450-525F with the engine off. Only that one pulse exceeded 550F with the engine running, and it was the highest recorded cat temp during the drive at 605F. Cat temps topped 550F half a dozen times in the 10.4 miles, but all these other occurrences had the engine shut off when cat temps were under 500F, and the cat temps topped 550F with the engine already off. In other words, by the time the cat lit, the engine wasn't emitting combustion byproducts.

So, I got 57.7 mpg on a 10 mile drive emitting pollutants the whole time through an unlit cat. I drove the warmed up car on three 10 mile loops in the same area, with engine-on P&G (18-32 and 25-40 mph deltas), and 35 mph cruise control. Ambient temperature rose to ~50-55F, wind <10 mph, sunny and dry.

Results:
18-32 mph 3rd gear NICE-On P&G 46.3 mpg, coolant temperature 185F, cat always lit*.
25-40 mph 4th gear NICE-On P&G 47.7 mpg, coolant temperature 185F, cat always lit*.
35 mph 5th gear cruise control, 45.7 mpg, coolant temperature 185F, cat always lit. Cat temp dropped to 970F on a downhill, stayed in 1100-1200F range most of drive

* Cat sensor 1 was 900F by the time cat sensor 2 topped 550F at 0.8 miles. Observed during cruise control loop.

[California98Civic]

I wonder how often the CAT would be "lit" if you started from cold, running until it is lit, and then did your hypermiling for the remainder of the 10+ mile course you describe. Once it is lit, it would more easily be maintained at higher temps by the short pulses in a P&G routine.

[roosterk0031]

Great data, only thing I wonder is why you removed your grille blocks when reaching 205 dF, I think of that as normal, does you electric fans kick on close to that temp? (mine on at 220ish off 205)

Civic has a good point, but I'd think moving at 30 mph average the cat will cool down pretty quick.

Isn't starting from cold running 2 minutes what the Prius does while still in electric mode(based on reading here)? I'd be willing to bet the new auto start/stops have a temp probe to only shutdown if the cat is hot enough.

Thanks for all the work & expense in getting real data it's a very educational thread.

[SentraSE-R]

Originally Posted by California98Civic

I wonder how often the CAT would be "lit" if you started from cold, running until it is lit, and then did your hypermiling for the remained of the 10+ mile course you describe. Once it is lit, it would more easily be maintained at higher temps by the short pulses in a P&G routine.

I'll find out tomorrow. I suspect there will be no difference, since my 25-40 mph 4th gear P:G ratio is ~ 1:3, and my 18-32 mph 3rd gear P:G ratio is 1:5. My guess is the cat will cool below its light-up temperature with 3-5 times to cool after every pulse.

I also plan a long DFCO test tomorrow to see if I can determine how long it takes to drop the cat from its normal 1100F to below light-up temp.

Rooster, yes, my radiator cooling fan kicks on at 204F, and I get nervous with the grill completely blocked. The fan doesn't do much good when it can't pull air through the radiator. I've wired an indicator light with the fan relay's NO circuit, to give me a visual signal that the fan is on. I'd driven home Thursday and yesterday through Needles and Barstow in the desert, and removed the grill blocks then.

Mech, resident and out-of-staters can bring federal-compliant cars into CA if they bought them OOS.

[Old Mechanic]

Sentra, if you are blocking the grille and not the radiator itself then the cooling fan would just run more but still cool the engine off. Blocking the radiator itself would potentially cause a problem, but not in 40 degree temperatures. If you can monitor the fan operation and see it running excessively then remove some of the radiator block.

Mercedes had a service bulletin out that clearly stated that their engines would not suffer any damage with cooling temps as high as 256 degrees as long as the system was maintaining pressure and the coolant was the proper 50/50 mix. I'm not saying you should run yours that high, just that 204 is not an issue and probably significantly higher than that is not an issue either. MB had alloy V8's with alloy heads on their engines when they issued the bulletin around 1983.

I might get concerned at 220 as a conservative point on your engine.

I am also very pleased to see that you have not totally abandoned your techniques and I still think you may actually be able to come very close to your previous mileage as you gather more information.

It also does not surprise me at all that the cat temps rise after an engine shut down for a short period of time.

Keep up the good work, and never surrender.

regards
Mech