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Old 04-20-2020, 05:43 AM   #11 (permalink)
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Accelerating with the TDI:
Always depending on size of the engine. A decent 4, or large 5 or 6 cilinder will need less revs. But with every turbo charged engine, to little revs are as bad as too much.
For me - the little TDI - It's pointless to rev it under 1.500 rpm during accelerating. There is no turbo pressure underneath and accelerating will take too much time. The most economic way to accelerate with a small TDI: give enough throttle -> 3/4 is ideal. Never pedal to he metal, only if it's really necessary. Rev it up quickly to 2.200 rpm and upshift. Reving it above 2.500 rpm - in normal circumstances - is pointless. The 'cheapest', most effective power is concentrated between 1.500 - 2.500 rpm.

Once at speed:
It is possible to maintain very low speed in highest gear (less than 1500 rpm or under 50 mph), but when you need to accelerate again, you'll give the engine a hard time. Also taking into account of the size of your engine, a smaller engine will love some higher revs. Due to the extended 4th and 5th gear with recent cars, it turned out better to downshift from 5th to 4th when the speed drops under 45 MPH and to maintain it in 4th gear. It shows no difference in consumption on the on-board computer compared to the highest gear.

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Old 04-20-2020, 05:47 AM   #12 (permalink)
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Quote:
Originally Posted by COcyclist View Post
Safety for all is more important than a few mpg for a Hypermiler.
Indeed, completely my opinion. The MPG you'll win by driving very slowly, will be lost exponentially by all those non-hypermilers who have to brake because of you.
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Old 04-20-2020, 12:49 PM   #13 (permalink)
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Quote:
Originally Posted by ptitviet View Post
Yup happy to share my observations (with my '15 Octavia 3 1.6TDI Greenline Combi). I do not use pulse and glide a lot on my car, as it tends to be less useful when the engine is not too powerful (my former car was a 265hp Renault Megane RS and I could get almost 2l/100km less by using pulse and glide). I only do hill pulse and glide by pulsing up and gliding down. When coasting I switch AC off as it the engine is less efficient when idling.

No mods on my car, only folding passenger mirror on long highway trips.

Until now I have owned the car one winter and got 48mpg (4.9l/100km) which is not bad with short trips uphill to the ski resorts and winter tyres. I am hoping to meet 3l/100km mark this summer with long holiday trips on secondary roads (80-90km/h). With winter tyres and longer trips (30km) I can already get about 4L/100km (58mpg), thanks also to the very good aerodynamics (0.59m2 measured by me thanks to Matlab).

I'd be happy to try front grille cover, but I am not very good with my hands and do not want to put something with no good finish on the car.
In post #4 I stated that I will run the A/C full blast on a 7 mile downhill near me to increase engine braking effect (or heat and wipers and rear window defroster in winter). When I am E-On coasting the A/C and all accessories except the radio are off to reach the highest mpg during the glide phase.

It looks like you are already getting great mpg in your Octavia. I believe it is similar to the Golf AllTrak that we can get here in the States. I used foam pipe insulation (it can be purchased in black) and pushed it between the grill bars on my Golf. I think it looks pretty stealthy and is easily removed if needed.

I fold my driver’s side mirror on the highway and removed the passenger mirror completely. I have small convex mirrors on each side but do head checks too.
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The power needed to push an object through a fluid increases as the cube of the velocity. Mechanical friction increases as the square, so increasing speed requires progressively more power.
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Old 04-20-2020, 01:21 PM   #14 (permalink)
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Drive with a Hot Engine

Diesel engines are most efficient when fully warmed up and fed lots of cool air for combustion. Gasoline/petrol engines also perform better when warmed up but intake air differs in a Diesel. Many Ecomodders driving gasoline engines report much better mpg by using a “warm air intake”. They reroute the intake plumbing to pick up air from near the exhaust manifold so that it is warm coming into the engine. This may reduce peak power but they do most of their driving under low load/part throttle conditions. The throttle plate is mostly closed, the engine is working against high vaccuum, it is not running in its most efficient range. Warmer air is less dense so the throttle can be opened further for the same speed and they have lower pumping losses.

Diesels like lots of cool clean air. Since they don’t have a traditional throttle plate they can ingest lots of air and run very lean, using very little fuel, without creating vacuum. (The vacuum for the power brakes is from a vacuum pump driven by the camshaft). There is no need to route intake air from the exhaust manifold except perhaps to speed warmup. The downside is that extra oxygen can lead to higher NOX emissions so newer diesels have employed lots of technology to lower NOX emissions (and unfortunately reducing efficiency at the same time).

In general, DO NOT modify the intake for warm air in a diesel. Give it plenty of cool high pressure air from the front of the car (stagnation point). There are some intelligent tuners that sell smart tunes to decrease the demand for EGR that help the diesel run more powerfully, cleaner engines with less carbon buildup and return better mpg if that is your priority. Off-road or track use only of course.
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Quote:
Originally Posted by freebeard View Post
The power needed to push an object through a fluid increases as the cube of the velocity. Mechanical friction increases as the square, so increasing speed requires progressively more power.

Last edited by COcyclist; 04-21-2020 at 10:17 AM..
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Old 04-21-2020, 05:46 AM   #15 (permalink)
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Hello!

The Greenline is not like a Golf Alltrak. Green stands for ecological. It is a special version already biased toward mpg :
- small 1.6 TDI 110hp engin
- very long ratio 6 gear manual gearbox (130km/h-85mph is 2000rpm)
- lighter with fewer equipments
- ride height lower -15mm
- various aerodynamic tweaks
- small wheels

I won't modify anything on the engine we don't have the same possibilities to tweak our cars in Europe than in the USA.

Seems we have otherwise quite the same receipt. I will do coasting down test once I get my new grille block and summer tyres to see changes in SCd and Crr.
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Old 04-21-2020, 06:24 AM   #16 (permalink)
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Quote:
Originally Posted by ptitviet View Post

I won't modify anything on the engine we don't have the same possibilities to tweak our cars in Europe than in the USA.
Chiptuning could help reduce consumption with about 5%. Only if you don't make advantage of the extra power, that is. You could save even more if the EGR has been closed and the particulate filter has been deleted. But those things are not recommended (emission-wise)!
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Old 04-24-2020, 06:57 PM   #17 (permalink)
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Quote:
Originally Posted by GreenTDI View Post
Chiptuning could help reduce consumption with about 5%. Only if you don't make advantage of the extra power, that is. You could save even more if the EGR has been closed and the particulate filter has been deleted. But those things are not recommended (emission-wise)!
Of course mine is old enough that it did not come with a particulate filter. I did remove the muffler and replaced it with a straight pipe. It is not loud. The turbo and catalytic converter seem to muffle exhaust noise just fine.
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The power needed to push an object through a fluid increases as the cube of the velocity. Mechanical friction increases as the square, so increasing speed requires progressively more power.
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Old 04-24-2020, 07:46 PM   #18 (permalink)
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Help your engine warm up quicker

The PD TDI has 3 extra glow plugs in the coolant at the top of the engine. This was done by VW to speed warmup and give some heat for defrost and cabin heating during cold starts in winter. That is a large current draw on the alternator until the engine reaches 150 degrees F when the computer shuts them off. This is yet another reason why your TDI gets poorer mpg when it is cold. For optimum mpg you want to do everything you can to help it reach full temperature as soon as possible.

What to do? Here is a partial list:

Park in a heated or insulated garage.

Install a tank type coolant heater. Google FrostHeater on TDIclub. This allows me to plug in a couple of hours before I drive and puts heat in the head for easier starts, and coolant so defrost works better. I highly recommend this mod. I use before I drive even in summer. It really helps the poor engine start better if you have to park outside at 20 below zero like I did this last winter.

Put a small electric space heater in the cabin for a few minutes in winter. I have one with a tip over protection that I put on the driver's side floor. 15 minutes takes the chill off the entire cabin. You can allow the engine to fully warm before calling for cabin heat from the engine.

Grill blocking. I use black foam to block the upper grill year round and put a hard cover over that in winter (partly to protect from rock chips).

Katz stick-on electric heater on the oil pan. This warms the oil and the bottom of the engine. Surprisingly, this heats the whole engine compartment more than the tank heater.

Make sure your noise panel is in place and intact. The VW comes with a partial "belly pan" under the engine. It is molded plastic and easily damaged or sometimes mechanics remove it for engine service and it is not replaced. This allows lots of cold air into the engine compartment and hurts aerodynamics. I have installed a Panzer Plate made from 1/4" aluminum and still have the noise panel next to the engine. It took a little trimming but I feel it insulates better than just the aluminum.

I may add more if I think of something.

I almost forgot. In addition to all of the above, do a few pulls with boost to get some combustion heat into the engine and coolant loop. This is one time where it makes sense to do some medium hard accelerations to get to 150 degrees and get better mpg.
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Quote:
Originally Posted by freebeard View Post
The power needed to push an object through a fluid increases as the cube of the velocity. Mechanical friction increases as the square, so increasing speed requires progressively more power.

Last edited by COcyclist; 06-25-2020 at 09:32 PM..
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Old 04-24-2020, 08:03 PM   #19 (permalink)
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I hope this is still useful

I just noticed as of today this post has 295 views. I suppose I should have posted this years ago, but I seem to have the time now.

Although my timing is all off. We are in a world pandemic so people are hardly driving. Russia and OPEC are in a price war. Oil futures traded at less than zero dollars per barrel. Gasoline was being sold outside Denver for $.99/gallon while diesel was still $2.20/gallon. Tighter emissions regulations and Dieselgate have essentially killed off the small diesel in the US. There is not much incentive to buy a diesel now in the US. We don't get the Greenline versions that are available in Europe and gasoline engine cars are getting much better mileage with direct injection, CVT and multispeed transmissions. Electric cars are becoming more widespread.

Perhaps those of us who are fans of the diesel get it and will be able to keep our cars for a long time and enjoy the driving experience while getting great mpg in these cars.
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https://ecomodder.com/forum/showthre...tml#post621801


Quote:
Originally Posted by freebeard View Post
The power needed to push an object through a fluid increases as the cube of the velocity. Mechanical friction increases as the square, so increasing speed requires progressively more power.

Last edited by COcyclist; 06-25-2020 at 09:33 PM..
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Old 04-25-2020, 06:05 AM   #20 (permalink)
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The positive effect of dieselgate is that new EU6 diesel engines (most recent emission standard) are even cleaner than modern gasolines. But the technology has made them more expensive in purchase as in maintainance and no longer profitable for individuals. Not to mention the higher tax worldwide due to the diesel scandal. To break-even with a gasoline car you should drive at least 22K miles a year and that's a lot.

But I don't believe diesel (or combustion engines in general) will disappear soon. There is still great demand here in Europe. And for those who have to pull loads, there is no equivalent alternative yet. Small low duty diesels however will become (worthless) museum pieces.

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