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Old 05-01-2009, 09:15 PM   #11
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Things seem to be going good with my mileage. I'm averaging, roughly, 27.05mpg in a V6 car that the EPA rates at 19mpg combined. Not only that, I still do gas hoggish things like rapid acceleration & driving at 60+mph with the windows down and sunroof open. I've not closed up my wheel wells, though I have blocked off most of the openings in the front of the car.
This weekend, I'm changing the oil. I just bought the car, used, about 1.5 months ago and I've probably already put a good 3K on it (86mile round trip commute, per day, 5 days per week times 6 weeks gives us 2580 just in commuting for work). Since I've no idea what the condition of the present oil is, I feel like an idiot waiting so long to change it. I'm hoping fresh oil will push me closer to that elusive 30mpg mark.

Presently, I've got some plans that could improve FE:

Lighting:tail lights, brake lights, marker lights, and turn signals are all going to be swapped out with LEDs. My morning commute happens before the sun comes up, so the alternator is pretty well taxed on the way to work. On top of this, the LEDs are way brighter than incandescents, so I'll be easier to spot as well. Other lighting changes will include some super bright 12W LEDs for the DRLs vice the 45W incandescents they use now. Then the low beams will be swapped out with single filament 55W bulbs.

Powertrain Performance: Smoothing out the intake tract and piping cooler air into the airbox should help out a little. I did this on my 1995 Chevy Cavalier and noted improved throttle response, and shaved .2sec off my quarter mile times. Piped some cold air into the air cleaner on my 1988 Chevy Caprice, and it rewarded me with .3sec improvement in quarter times. We'll have to see how it helps with a German car.
The exhaust on this car is WAAAY over engineered. It baffles me as to why they saw fit to put a resonator just downstream of the cat, a ginormous canister muffler just downstream of that, and a standard muffler downstream of that. I plan to get rid of the resonator and canister muffler. I'll replace those with OEM sized piping (not worried about Mandrel bent piping... I'm not convinced it does any good for cars under 300HP). The last muffler is showing signs of decay, so I will likely replace it with a nice Magnaflow. I figure I'll pick up 1 or 2 mog just in weight savings with this job.
A performance chip might be a viable option.

Suspension Performance: The Koni dampers with Neuspeed racing springs make for a tight set up, but there's a wee tad of understeer. I've read that jumping up to a 28mm (vice 25mm OEM) front anti-sway bar and staying with the OEM 25mm bar makes the GTi pretty nuetral. I'm thinking of trying that out. Also, my GTi has over 160K on it. I'm willing to bet that replacing some worn out suspension system bushings could be in order. A heaping helping of low deflection polyurethane bushings could be just what the doctor ordered!

This will all happen pretty slowly, so I can see how each thing affects my FE. Except for the exhaust and suspension, anything can be undone if it has no effects.
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Old 05-02-2009, 04:32 AM   #12
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What oil will you be using? On MKVs, VW doesn't specify a viscosity rating; instead, they merely require that the oil be VW-approved. I'm using Castrol Syntec European Formula 0W30. When I switched to it I did not have stable enough conditions to be able to measure if it increased my FE or not.

You might want to reconsider the cold air. Theoretically, hot air should increase your FE (at a slight cost in power), while cold air would increase power (at a slight cost in FE). This has been proven for some cars and disproven for others. I don't think I've even seen any attempt on a car like yours, let alone credible data. It may also depend on driving style.

As for freeing up exhaust and intake, keep in mind that while driving even vaguely for gas savings, you never move a fraction of the quantity of air that those systems are already designed to flow. They have to flow the maximum power your engine can make when running WOT at redline; any less than redline, or any less than WOT, and it's moving a small fraction of that. Enjoy doing those mods because you want them, but don't hold your breath waiting for FE improvements -- and if you get improvements look for other causes too. You can't do double-blind testing so you can't rule out placebo effect on driving style, though long-term results can support stuff that seems like it shouldn't work.
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Old 05-05-2009, 12:31 PM   #13
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What oil will you be using? On MKVs, VW doesn't specify a viscosity rating; instead, they merely require that the oil be VW-approved. I'm using Castrol Syntec European Formula 0W30. When I switched to it I did not have stable enough conditions to be able to measure if it increased my FE or not.
I went with Castrol GTX 5W30. I don't have the owner's manual for this car, and there's no recommended oil weight on the fill cap. I asked the people in the Wal-Mart service department what the recommended weight was. They showed me some book that had a listing for "fuel economy, all temperatures." They listed 5 and 10W30 and 5 and 10W40, so I went with the least viscous of the 4.
Since all my "testing" is based on miles traveled and gallons filled, and I've not yet had to fill up since Friday, I can't say if it did me any good. I can say that the stuff that came out did not look too good.

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You might want to reconsider the cold air. Theoretically, hot air should increase your FE (at a slight cost in power), while cold air would increase power (at a slight cost in FE). This has been proven for some cars and disproven for others. I don't think I've even seen any attempt on a car like yours, let alone credible data. It may also depend on driving style.
Well, I don't plan to spend too much money on the intake. I'm going to pretty much build the thing myself. If I lose out on FE, I just might have to design it so I can swap between the stock set up and the "aftermarket" set up when I go racing (which I WILL do once I start getting paid right). If I lived much closer to work, I'd be willing to give up FE for performance sake. This is not the case, though. My daily comute is over 80 miles, so I need to focus on FE over performance. Still, stress relief is important also.

One thought I had while admiring my engine (I'm wierd that way) after doing my oil change was to see if I can get a TB with a larger opening. Hesitation on this comes in the form of not knowing how FE will be affected, and having limited knowledge on how well VW engines respond to such things. An overhead cammed VR6 is a lot different from a pushrod Chevy engine.

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As for freeing up exhaust and intake, keep in mind that while driving even vaguely for gas savings, you never move a fraction of the quantity of air that those systems are already designed to flow. They have to flow the maximum power your engine can make when running WOT at redline; any less than redline, or any less than WOT, and it's moving a small fraction of that. Enjoy doing those mods because you want them, but don't hold your breath waiting for FE improvements -- and if you get improvements look for other causes too. You can't do double-blind testing so you can't rule out placebo effect on driving style, though long-term results can support stuff that seems like it shouldn't work.
Here's my opinion on the exhaust mods I want to do. I know I can get more performance out of the motor with a freed up exhaust. I also know not to over-do it on size (which is why I'll just go with OEM pipe size). I know not to expect much by way of FE because the exhaust is freed up. What I do expect, however, is a slight improvement in FE because I'll be dropping upwards of 50lbs off the weight of the car. I'm going to have the car weighed, as it sits, and then have it weighed again after I do the exhaust just to see how much of a weight savings I get.

I've been contemplating lately what I can do to lighten the car or to negate the effects of my sound system (2 amps, stiffening cap, subwoofer). I've not got anything super fancy, but I rather enjoy having an above average sound system in a vehicle that I spend so much time in. It's an odd dichotomy {sp?}... I want good FE, but I want a fair amount of comfort also.
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Old 05-05-2009, 12:48 PM   #14
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I wouldn't recommend worrying about weight for FE. However, it will certainly affect racing and if you're going to race that's a good reason.

Weight loss does not help most cars with FE unless they're being driven horribly wastefully. A driver who even makes a vague attempt to drive for FE will not see a difference except in certain cars -- I think it's cars that are very light, and underpowered or need to rev high to make power. A heavier or torquier car, such as yours, won't see measurable gains in FE until you remove a huge portion of weight, I'd guess 20% or more. If you can knock 500 pounds off the car you might get somewhere.

I'd be more worried about a large sound system's electric draw on the alternator. The alternator doesn't make extra electricity, it is controlled by the computer to not drag on the engine when there's no need for generating any electricity.
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Old 05-05-2009, 01:23 PM   #15
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I wouldn't recommend worrying about weight for FE. However, it will certainly affect racing and if you're going to race that's a good reason.

Weight loss does not help most cars with FE unless they're being driven horribly wastefully. A driver who even makes a vague attempt to drive for FE will not see a difference except in certain cars -- I think it's cars that are very light, and underpowered or need to rev high to make power. A heavier or torquier car, such as yours, won't see measurable gains in FE until you remove a huge portion of weight, I'd guess 20% or more. If you can knock 500 pounds off the car you might get somewhere.
Interesting thoughts. It's still worth looking into. Besides, I noticed while I was under the car for the oil change that the big canister muffler is rusting through, and the resonator and other muffler aren't fairing too well either. My exhaust mods may end up being as much for my own edification as for complying with local laws.

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I'd be more worried about a large sound system's electric draw on the alternator. The alternator doesn't make extra electricity, it is controlled by the computer to not drag on the engine when there's no need for generating any electricity.
Where I will admit that the extra amplifiers will be additional load, I'll also point out that the stiffening cap is designed to ease this. When the sound system demands a particuarly large surge of power, the cap fills in to ease the burden on the alternator.
Truth be told, I'd like to get ahold of a Golf or Jetta TDI. I've been pretty interested in running diesel engines off of used cooking oil for quite some time, now (for money saving "stick it to the man" reasons, more so than "green" reasons). If I can find one of these in decent shape at a decent enough price, the GTi will become my racing/hobby car.
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Old 05-19-2009, 06:13 PM   #16
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So, I have finally gotten new tires for Dubba. I bought a set of Falken Ziex ZE912's in 205/50-15. This is smaller than the 205/55-15's that were on the car, but are the OEM size. Right now, I'm running the tires at OEM recommended pressure. When the long weekend gets here, I'll bump them up. Max pressure listed on the sidewall is 51psi... I think I'll set it at 45psi. This pressure should be a good compromise between FE and comfort.
I'm going to need to fix the speedo at some point, though the odometer seems to be spot on. With the 55-series tires, the speedo always matched up to my GPS unit. Now, the speedo reads about 2MPH faster. As for the odometer, it seems to match up with the GPS unit, still. I also did the "mile marker to mile marker" test... the odometer was spot on over a 15 mile stretch of US-17.

As for the tires and FE... I haven't been able to determine FE since putting the new tires on. Some absent mindedness has resulted in a couple partial fill ups here and there. I've done this before and just used the cumulative gallons pumped and let the trip odometer keep going. Certainly not very accurate, but it still keeps me concentrating on my hypermiling goal. My last gas log entry shows over 29MPG with new oil. I'm contemplating making fairings for the rear tires. They'll be removable so the car will still pass tech in races. I just want to see if I can push this car over the 30MPG mark.
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Old 05-20-2009, 07:00 AM   #17
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I done a total grill block on my old '88 Escort and didn't seems to see any difference in FE, but when I did the warm air intake the FE made a tremendous jump. I would say approximately 10%. After doing the warm air intake the car got it's best mileage ever and that's saying a lot since the car is nearing 500K miles. The best previous highway mileage was 50 MPG, but on a short trip about a month ago I got 52.446 by the mileage on the odometer and 54.629 by the mileage my GPS measured. Pretty good for a car rated at 42 highway.
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Old 05-24-2009, 06:05 AM   #18
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So it turns out that the Firestone guy that installed my new tires pressed them up to 45psi. I'm just going to leave them there.

I'm still going to see what I can do to get this thing over the 30 mpg mark while still NOT sacrificing much.
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Old 05-24-2009, 08:59 AM   #19
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Filled up today. See my gaslog for more info. I took a hit on this one, as this round's FE was below my average (less than 27mpg this time).

I've been reading on some VW forms about guys opening up the inlet to their airbox such that more air gets in there while driving. Since I will eventually be racing in this car, I think I'll do this mod anyway. We'll see how it affects my mileage.
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Old 05-26-2009, 09:18 AM   #20
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You might want to reconsider the cold air. Theoretically, hot air should increase your FE (at a slight cost in power), while cold air would increase power (at a slight cost in FE). This has been proven for some cars and disproven for others. I don't think I've even seen any attempt on a car like yours, let alone credible data. It may also depend on driving style.
Ok, I've been contemplating this lately. I'm a little confused on how reducing power increases FE and vice versa. In my mind, more power means the engine holds a given speed with less throttle, which translates to less fuel consumed. I'm confused as to how the opposite could be true.
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