Mountain Climbing Tdi Style

I Must Cross A Mountain On My 50 Mile Trip To Work {one Way} Each Day And I Have Been Trying Different Things To Increase My Mileage. Today I Went Up At 55 Mph Instead Of My Regular 65 Mph. And I Placed It In Neutral And Coasted Down The Other Side. I Can Reach Speeds Of 80 Mph Coasting And Must Use The Brakes Quite A Bit, When I Change My Pads I Will Get The Best I Can Find And May Upgrade To Drilled Rotars On The Front. My Regular Mileage Is Around 42 Mpg On My 2002 Nb With Auto Tranny. I Am Also Going To Amsoil In The Tranny {full Senthectic}. I Will Run This Way A Couple Of Weeks And Let You Know If I See A Increase.

RAMP said:

I Must Cross A Mountain On My 50 Mile Trip To Work {one Way} Each Day And I Have Been Trying Different Things To Increase My Mileage. Today I Went Up At 55 Mph Instead Of My Regular 65 Mph. And I Placed It In Neutral And Coasted Down The Other Side. I Can Reach Speeds Of 80 Mph Coasting And Must Use The Brakes Quite A Bit, When I Change My Pads I Will Get The Best I Can Find And May Upgrade To Drilled Rotars On The Front. My Regular Mileage Is Around 42 Mpg On My 2002 Nb With Auto Tranny. I Am Also Going To Amsoil In The Tranny {full Senthectic}. I Will Run This Way A Couple Of Weeks And Let You Know If I See A Increase.

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Isn't fuel only injected when you push on the pedal? Going to neutral seems like it won't gain you any mpg's. Also, keeping your car in gear & downshifting going down the hill will keep your brakes lasting longer & you'll be less likely to warp them. Correct me if I'm wrong.

~ryan

I do the same kind of driving everyday for work too. With my manual tran, I just leave it in gear and have no problems coasting down. I regularly have to use the breaks to keep the speed down.

Not sure how the auto will work but doesn't hurt to try leaving it in gear.

I Don't Know How Much Fule It Uses To Coast But My Rpm's Drop A Bunch When It Gose Into Netural.

Leave it in gear when your going downhill, it uses 0 fuel. When you put it in neutral it uses fuel too keep it idling. Its win/win, no fuel and save on brakes.

agreed with the leave it in gear comment. Downshift if you can for more engine braking. When above idle with the throttle at 0% it won't use any fuel, but if you put it in neutral it uses fuel to spin the motor at idle speeds.

BTW, most of the energy loss in engine braking, IIRC, is in compressing cold air, heating it up, and then exhausting it.

I may be mistaken but I thought with the auto. tranny there was much lubrication going on when in neutral. So going 80mph in neutral would be a bad thing. But maybe Im wrong on this one. Kory

The oil pump in an automatic is run off the outer casing of the torque converter, directly connected to the crankshaft, so if the engine is running there's oil pressure. It has to be this way, as all the transmission's controlls are hydraulic...

TooRoundTDI said:

Leave it in gear when your going downhill, it uses 0 fuel. When you put it in neutral it uses fuel too keep it idling. Its win/win, no fuel and save on brakes.

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__. Totally correct. I can't see a time when you'd ever need to coast in neutral. I drove from Knoxville to eastern NC this weekend (I-40) with a side trip up to the top of Mt. Mitchell. Gee, these are great cars for driving in hilly country!
'

Just to confirm this. I recently got a scan gauge, and going downhill, even with cruise control on, the mileage jumps to 9999MPG. Mine's a 5-speed, but I can't see any reason it'd be different with an auto.

Just stick with quality OEM rotors or even ATE Powerslots...drilled is for looks only.

Thermo1223 said:

Just stick with quality OEM rotors or even ATE Powerslots...drilled is for looks only.

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Slotted is pretty lame as well, at least for street applications.

REAL drilled is nice because of reduced weight and better venting, but that is only if they are produced that way and not actually drilled (like Porsche brakes). Many times drilled rotors results in greater likelyhood of cracking and warping rotors.
Usually a good pad and fluid upgrade is all these cars need.

milehighassassin said:

Slotted is pretty lame as well, at least for street applications.

REAL drilled is nice because of reduced weight and better venting, but that is only if they are produced that way and not actually drilled (like Porsche brakes). Many times drilled rotors results in greater likelyhood of cracking and warping rotors.
Usually a good pad and fluid upgrade is all these cars need.

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Not really, the ATE's are not knife edged like other slotted rotors I've seen causing a lot of pad wear. They just provide a way for the gas effect to not lift the pad off the rotor. A simple yet effective upgarde that won't cause you to use brake pads every year and enhance stopping power a bit.

True with the drilled rotors though, also the lack of surface area on the rotor to do the actual braking. I was under the impression that casting the holes in the rotors is better then actually drilling them even when increasing the rotor size to compensate for lack of surface area.

mrGutWrench said:

__. Totally correct. I can't see a time when you'd ever need to coast in neutral. I drove from Knoxville to eastern NC this weekend (I-40) with a side trip up to the top of Mt. Mitchell. Gee, these are great cars for driving in hilly country!
'

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I agree on a hill where you can maintain speed with the engine in over run, but, I do coast on the flat in neutral from time to time. If I see a traffic light up ahead that is red, I slip the tranny into neutral and just coast up, rather than have the engine 'brake' the car too early and then I have to apply throttle again. Seems more sensible to me to have it idle all the way there as I gradually slow. This is also on empty roads too! if the light turns red while I'm approaching, I let the engine brake me and downshift as well. VERY little brake use. And yes, I can drive a manual properly so I don't wear out clutches. I've had over 250,000 km on cars with the original clutch. One even went over 400,000 km's. Granted, two thirds of thier lives were also spent on country two lane blacktop!
I have one traffic light at the intersection of two major county roads that I can't see until I round a gentle curve. It's then about a kilometer away. Over the years, (commuted this route to work for 13 years) I have learned that if it's red when I round the bend, and stays that way for 5 seconds at 80km/h, it will turn green and stay green when I get there. No brakes, no loss in inertia. If it's already green, I lift off, slip into neutral and coast. Since I'm on the "A" road, (the light stays green longer for mine than the crossroad), by the time I get there, and having coasted down to 60 km/h, it turns green and I'm through with minimal loss of inertia.
I used to drive 130 km one way to work in the early morning and could get almost all the way there with VERY little use of the brakes. Got 100,000km out of a set of front brake pads on a regular basis! Just takes planning and familiarity with the route.

I keep hearing the theory that running in over-run does not use any fuel, but I recently purchased and installed a ScanGuage and it is either very wrong or the over-run idea is wrong.

I work on a mountain and I climb from about 6000ft to about 9000ft in the scretch of 3.5-4 miles. I have done the runs down the mountain when I get off work using both methods described for over-run and just coasting with the clutch depressed either in gear or in neutral. The ScanGuage clearly shows that I get the same results for coasting with clutch in and in gear or in neutral. ScanGuage tells me that my fuel economy drops if I just leave the car in gear and let it coast down the mountain in gear using the engine for braking. The speed limit is 40 mph on this road with 25 mph curves. I generally don't have to touch the gas but twice to get off of the moutain, and the rest is coast until the bottom.

So either my ScanGuage is wrong or something is amiss with the in gear over-run theory. Maybe I am doing something wrong, but my test runs so far have not shown over-run to even come close to coasting and letting the car just idle.

So far I haven't seen my ScanGuage go to 9999 or anything of the sort, so maybe there is something wrong with my ScanGuage.

Longsnowsm

Longsnowsm said:

I keep hearing the theory that running in over-run does not use any fuel, but I recently purchased and installed a ScanGuage and it is either very wrong or the over-run idea is wrong.

I work on a mountain and I climb from about 6000ft to about 9000ft in the scretch of 3.5-4 miles. I have done the runs down the mountain when I get off work using both methods described for over-run and just coasting with the clutch depressed either in gear or in neutral. The ScanGuage clearly shows that I get the same results for coasting with clutch in and in gear or in neutral. ScanGuage tells me that my fuel economy drops if I just leave the car in gear and let it coast down the mountain in gear using the engine for braking. The speed limit is 40 mph on this road with 25 mph curves. I generally don't have to touch the gas but twice to get off of the moutain, and the rest is coast until the bottom.

So either my ScanGuage is wrong or something is amiss with the in gear over-run theory. Maybe I am doing something wrong, but my test runs so far have not shown over-run to even come close to coasting and letting the car just idle.

So far I haven't seen my ScanGuage go to 9999 or anything of the sort, so maybe there is something wrong with my ScanGuage.

Longsnowsm

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MPG in neutral with my scangauge is 140 MPG or so, MPG in over-run, 9999 MPG.

You may not have it configured right. What does the book say for Diesel A or Diesel B for small cars? (I don't remember what mine said off the top of my head)

Your right, I don't have my ScanGuage set correctly. I just reviewed the book and I need to set the engine size, and fuel to Diesela. I didn't do that. I will set it and test it out again on my mountain drive to and from work and see what I get with it set correctly.

Thanks for pointing out the ScanGuage settings for diesel. It helps explain why my mpg readings are not what I expected.

I will report back what I see with the corrected settings.

Longsnowsm

I made the changes to my ScanGuage today and I now see what everyone has been talking about. I too see the 9999 Over-run condition. The question that comes to mind is just how accurate is this over-run status? The reason I ask is when I coast down the mountain from work and if I have my window open I can still smell the diesel exhaust. So I know the car is still burning enough fuel that I can smell it. So just how accurate is the ScanGuage in the overrun? Does anyone know for sure?