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Rango318 06-09-2014 11:51 PM

TDI, better MPG from hard acceleration?
I read this concept on a TDI forum, and decided to try it out. It was stated on that forum, that it is better for a TDI to accelerate hard to the given speed, than it is to take time to get to it. This statement is completely backwards from what most people do, what i do, and what this site recommends. But i tried it anyway and here is what I have seen.

The last few nights on my drive home from work, I have a stretch a the edge of town where I must stop at a stop sign. After that, it is around 1/2 to 3/4 mile to the stop light, speed limit 35. Most days, i take it easy when leaving the sign, and by the time i get to the light, my torque app is at the same trip MPG as it was when I left.

Tonight when I left the stop sign, the trip MPG was at 47.6. I took off hard, about 75% throttle, and when i got up to speed for OD to kick in (41MPH) i let off and drove 38 mph the rest of the road. When i got to the light my trip gauge said 47.9.

I thought is that it can be more beneficial to do this in my car (02 tdi auto) is i have at least a 1/2 mile for sure before i need to slow down.

I would really like to hear what everyone thinks on this matter.

ecomodded 06-10-2014 12:07 AM

Your using a Auto transmission so it puts a whole new spin on it, But sounds like its a very good Auto trans. To Hit OD at 41mph is Really good for a Auto , with my Standard Trans I go into 5th at 30mph and accelerate to Speed if need be from there.

So I Push the throttle lightly but shift swiftly keeping the engine under constant load, no Lalley gagging about (Im always under 1,900rpms because of rapid gear shifts) but not 1/2 throttle , for me it takes only about 1/2" of throttle to Propel myself Faster then the rest of the cars leaving an intersection.

So I think its wise to be zippy and coast often

Goldenstate 06-10-2014 12:25 AM

I have a 1999 F150 with the 4 speed automatic. In the first three gears, mileage increases but at 40 MPH it will go into 4th gear or overdrive and then the scan gauge really begins to give the higher numbers. I too have decided that the sooner I can reach the magic 40 MPH barrier, the sooner higher mileage kicks in.

Rango318 06-10-2014 10:27 AM

ecomodded, I too was surprised when I found out it was going into OD and not 4th. I have only had this car a few weeks, so it is still taking some time to get use to it. Also this is my first diesel I can run torque with, so I can start to understand what works best.

Goldenstate, Do you watch the load or throttle when you take off? If so, have you found what works best for you (ie mid throttle/load or high)?

Goldenstate 06-10-2014 10:43 AM

Rango318: For years I have followed the common wisdom to drive like one has an egg under the foot. With the egg method, I found I was staying in the lower MPG areas of the Scangauge during acceleration. When I decided to kick things up and no longer use the egg method, I arrived at 4th gear sooner and my overall mileage average picked up a bit. I would estimate a mild to moderate increase in acceleration but still not a hard acceleration.

I have only had the Scanguage a few months and decided it was time to begin trying new things instead of more of the same. With an automatic one is limited to what they can do. I gave the increased acceleration a try and was pleased with the results. I first noticed the improvement when on my regular downhill run from a stoplight. I got to the higher numbers faster when going down hill and decided it might work on the flat land part of my drive as well.

Rango318 06-10-2014 10:47 AM

Goldenstate, That's what I thought was happening as well, just staying in the low mpg to long. Where I live is almost completely flat so it should help when I go test this out. I think I might go out today before work and drive around the mile a few times, do some A-B-A-B testing and see what it comes up with.

oldtamiyaphile 06-10-2014 10:54 AM

I started with full throttle acceleration (having found this works great on my petrol cars). I then tried 80% load (which is often very little throttle) and got the exact same results. I shift at 1500-2000 depending on traffic etc.

I don't trust SG or any ODB tool for instant consumption for diesels. The calibration fluctuates wildly if you change techinique.

Rango318 06-10-2014 11:00 AM

oldtamiyaphile, I'll keep that in consideration. I figure even if it isn't the most accurate, I still have something to look at and keep me motivated to get better numbers.

j12piprius 06-10-2014 12:02 PM

I accelerate at 90% engine load in the civic, then shift to neutral and coast. The chevy is automatic and doesn't have a gauge, but I do the same thing. For example, there are two stretches of a 1/2 mile between stop signs that I drive often in the chevy. I accelerate the first part, then shift to neutral and coast the rest of the way. If there is traffic ahead, then I just accelerate enough to get closer, then coast and repeat. This works well in the civic, so I figure the results are similar in the chevy, as it is a very good coaster.

Cobb 06-10-2014 06:22 PM

I too use to drive like a little old lady, then discovered you can really beat on a car and still get decent fuel economy if not better in some cases. :thumbup:

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