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Old 08-04-2013, 07:37 PM   #1 (permalink)
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VW TSi 1.4L 103kw BSFC and tips needed

Hi everybody!
I have a 2008 VW golf (rabbit in the US) with a 1.4l tsi 103kw engine. Transmission is auto, DSG, 6 gear, and I have a couple of questions. If anybody can be kind enough to read/answer any or all, or provide links I'll be grateful.

So, I'm interested in fuel saving techniques (dah!) but I don't want to either turn the engine off or shift to neutral. I'm starting a 2000km road trip in a few hours... And I wanted to test new techniques.

1.I have trouble finding my engine's bsfc. I can only find a newer engine's plot, which turns off 2 out of 4 cylinders. Mine doesn't do that.

2. I was just wondering how efficient pulse and glide with engine on can be.

My sequence will be:
(situation: Cruising at highest gear, engine rpms ~1500)
- switch to the appropriate gear to bring the engine to the lower end of its most efficient area (say 2000rpm)
- accelerate until the engine reaches the high end of the area (say 3000rpm)
- switch to highest gear possible (usually 6th) and let it roll
- when speed goes down, repeat...

Will this be better than steady throttle (not speed) cruising with the same average speed?

3. If my engine's efficient area is 2000-3000rpm, does it make sense to manually shift during an acceleration from stop to say 120kph?

So during acceleration, instead of letting the transmission change to the next gear as soon as possible, I could change gears so that I always keep the engine between 2-3k rpms. Will this be any good?


Thanks a lot for your attention!
Chris

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Old 08-04-2013, 09:18 PM   #2 (permalink)
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Don't be surprised if you find that DWL works better than P&G. I recommend getting good at DWL before trying P&G on the highway, especially since you have such a tall 6th gear.

My truck is geared 1800 RPM at 55 MPH (my normal highway cruising speed), and I only EOC for long downhills and speed limit changes. I did get a really good power off glide a couple hours ago when I came up behind a truck pulling a hay wagon...
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Old 08-05-2013, 06:15 PM   #3 (permalink)
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Quote:
Originally Posted by cmavr8 View Post
Hi everybody!
2. I was just wondering how efficient pulse and glide with engine on can be.

My sequence will be:
(situation: Cruising at highest gear, engine rpms ~1500)
- switch to the appropriate gear to bring the engine to the lower end of its most efficient area (say 2000rpm)
- accelerate until the engine reaches the high end of the area (say 3000rpm)
- switch to highest gear possible (usually 6th) and let it roll
- when speed goes down, repeat...

Will this be better than steady throttle (not speed) cruising with the same average speed?
As the engine stays on, and you stay in gear , you're effectively braking - even if the DSG goes into top gear (6th), it's still braking.

Unless you need to brake, I don't see that being more efficient as driving at a steady speed.

For coasting, you'll need the newer DSG7 with BMT in the new Golf

Quote:
So during acceleration, instead of letting the transmission change to the next gear as soon as possible, I could change gears so that I always keep the engine between 2-3k rpms. Will this be any good?
Coupled to a TDi, in my somewhat limited experience the DSG will shift depending on throttle position and possibly engine load.
If it feels it can change up, it will, giving you the best BSFC due to higher load at lower revs.
Take it easy, keep it out of Sports mode, and don't shift down - DSGs don't like that.
Get used to the limited deceleration you get in the highest gear, and make maximum use of that.

Being something of a hypermiler, but not used to automatics nor DSG, I've tried beating it, and failed, tank after tank, despite driving slower than the car's owner ...
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Old 08-12-2013, 06:00 AM   #4 (permalink)
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Thanks both for your replies!

I read what you wrote before and during the trip and I tried using the tricks but I usually needed to hurry so driving wasn't super economic.

It boiled down to this:
Code:
6.6 lt/100km = 35.6 MPG
1748 km = 1086 miles
81 km/h = 50.3 m/h
21h 39'
Pretty ok, since we had many traffic jams and lots of idling (getting on and off a ship etc).

Quote:
Originally Posted by euromodder View Post
As the engine stays on, and you stay in gear , you're effectively braking - even if the DSG goes into top gear (6th), it's still braking.

Unless you need to brake, I don't see that being more efficient as driving at a steady speed.

For coasting, you'll need the newer DSG7 with BMT in the new Golf
Ok... I did try switching to neutral sometimes during traffic jams, but I'm afraid that the gearbox doesn't like switching back to D without the car being stopped...

Quote:
Originally Posted by euromodder View Post
Coupled to a TDi, in my somewhat limited experience the DSG will shift depending on throttle position and possibly engine load.
If it feels it can change up, it will, giving you the best BSFC due to higher load at lower revs.
Take it easy, keep it out of Sports mode, and don't shift down - DSGs don't like that.
Get used to the limited deceleration you get in the highest gear, and make maximum use of that.

Being something of a hypermiler, but not used to automatics nor DSG, I've tried beating it, and failed, tank after tank, despite driving slower than the car's owner ...
Yes, no downshifts. Sometimes I don't let it do its own changes at D. I switch to "manual" so I can upshift early.

What do you mean by "beat it"?
Try to beat the DSG using a manual?
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Old 09-03-2013, 12:41 PM   #5 (permalink)
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Quote:
Originally Posted by cmavr8 View Post
What do you mean by "beat it"?
Try to beat the DSG using a manual?
Trying to make it behave as you'd want it - in my case, try to use it like I'd use my own manual car.
Didn't work out all that well.

The VW DSG is designed to work best as VW saw fit.
So work with it, don't try to make it do things it won't do on its own.

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