Where do you draw the line?
 

This is really because of another post I saw:

The EGR actually won't even increase mileage when disconnected and if it was working properly this will decrease mileage, FYI, but getting a high-flow cat (or none at all) will leave more pollutants in the exhaust and will pollute more than if the car in question leaves it on and suffers a bit of economy loss.

I guess it really depends on what your mods are for, pure MPG or more earth friendly. While you might think those are synonymous, they aren't, and I'm just wondering where people start to say 'This will give me better mileage, but will pollute more'.

I tend to leave my mods to ones that will pollute less and/or the same while increasing mileage. The mods I do to my car most of the time don't even use new parts, they are off junkyard cars so I'm not paying a company to pollute making me a new electric fan assembly when an automaker already has for the used one that might end up thrown away needlessly if I don't use it.

I don't just consider the "pollute more vs higher MPG" choice, I also consider the "improve my mpg vs decrease someone elses' mpg" choice.

Unfortunately there are a (probably relatively small) chunk of the hypermiling techniques that only work if either you are the only one doing it, or you don't care that you hurt someone elses' mpg. Drafting, pulse & glide (if the road is crowded), some forms of coasting, etc.

So I guess what I'm trying to say is that I consider my vehicle mods and driving technique for what will help the most without hurting someone else.

my theory is if it breaks and doesn't affect mpg or performance then its gone/disabled...

liek the chevette has no cat and disabled the EGR

truck has a cat only because i suffered performance loss (not enough backpressure) but its EGR has been taken completely off because a new one is $80 and we don't have emissions testing

I don't really see how drafting would hurt someone elses mpg. If anything it will also improve the mpg of the truck you ar using for your drafting...

Otherwise I agree that if you could win some mpg's by using irregular speeds on busy highway (pulse and glide) that that wouldn't be very nice for your fellow drivers.

I have the impression though after having been on this forum for a while, that the people that are into hypermiling are not selfish drivers and if anything are safer drivers that look further ahead of what's coming and are considerate of others.

Depends what you are drafting. Yes drafting a big rig won't hurt its mpg, but drafting something smaller can and will hurt the other driver's mpg. I can *feel* my xB slow down when someone drafts me in certain ways. Also drafting too close to a rig is just plain dangerous.

Oh don't get me wrong, I don't think all or even many hypermiliers are dangerous or selfish. It is like anything else, most people are polite and considerate, but there are always a few in any group who take it to extremes and are so concerned with their own benefit they don't think if their actions are negatively impacting others.
Not out of malice or anything, just because they get so caught up in the gains they don't think enough about the downsides.

Disabling the EGR improved mileage for me and it was working properly prior to the modification. In 1989 Volvo installed EGR on California cars while 49 state cars didn't have it. The EPA numbers back this up.

EGR
https://www.fueleconomy.gov/feg/2008c...ef.jsp?id=5651

No EGR
https://www.fueleconomy.gov/feg/2008c...ef.jsp?id=5650

Any idea which other emissions systems decrease or at least don't increase fuel economy?

My point is we shouldn't generalize like the originator of this thread. Modern emissions equipment has come a long way from the 80s and early 90s. Very few spark ignition engines use EGR anymore and most emissions equipment does not hurt fuel economy. Older systems are another story.

Some folks on turbo forums I read, where their state/province emissions test is sniffer only, have removed or hollowed their cats, and passed with lower numbers than stock. The cars that are doing that though have many modifications, are likely dyno tuned with custom callibrations and some are running alcohol/water injection. Some folks with full time HHO are reporting that they can pass emissions with no cat... I'm definitely not saying to go out and rip your cat off, just that it is possible be catless and clean.

I'm new here, but I say any device that is designed to reduce emissions, but decreases MPG is working backwards.

Global warming is real, but has nothing to do with fossil fuels. Thats fact (not that you'll ever hear it on the news). If it weren't for the overzealous environmentalist movement, gas wouldn't be cheaper than it is right now, and we wouldn't be sitting here trying to reverse engineer all the "eco friendly" efficiency-robbing devices on our cars.

I chucked the cat off my SRT-4. I was rewarded with more power and better highway mpg. I dont know if my acclaim will reward me the same way, but it has 82k miles on the original cat, i know its not HELPING mpg. Plus i might be able to fill the tank with the money that recyclers are paying for cats! lol

My Horizon has no EGR, no cat, injectors over 3 times bigger than stock, and passes PA emissions (all except for the visual).