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Old 03-06-2009, 10:20 AM   #1 (permalink)
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Mezzotinter - '94 Volkswagon Golf MK3 CL
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StoneT's adventures with Hypermilling!

Hello people. I've been milling around this forum for a week or so now because I wanted to know If my driving style is as efficient as I thought, or as it could be. I was extremely surprised and heartened to find this site! It is a reassurance to all those outside the US who worry about Americas apparent lack of consideration for the environment.
I believe I've gathered enough info to start posting without sounding like a complete noob.
My car is a 1.8 Golf MK3 CL and I get a reasonable mpg out of it. I've been milling (without realising that it was 'milling') for some time now. However, without any specs to look at I've made a few assumptions / guesstimates:

Engine braking - ECU shuts off injector (single point) at around 1600rpm + closed throttle. (Idles at 1000rpm)
Acceleration - The BSFC sweet spot is between 1600 - 2000 rpm / 75% - 85% cylinder pressure and gives around 25KW (Max for my engine is a whopping 55KW! I have seen no specific BSFC chart but this seems reasonable from looking at others)
Cylinder pressure is not dependant entirely on accelerator (gas pedal) position. I.Eressing pedal down 50% on pedal is not necessarily producing 50% of the possible cylinder pressure. I notice that in most gears you can push your foot down to a certain point and after that it makes no difference. I'm assuming this point is max cylinder pressure
If anyone can correct these or point me in the direction of some better info it would be much appreciated.

Based on the above and recent reading of this site amongst others I have drawn some conclusions and was wondering if anyone could confirm or correct me.

1) 25KW is more than enough power to accelerate the car on the flat, meaning that if I'm in 5th averaging 45mph (1800rpm) I can either use less throttle and therefore worse BSFC, or P+G using most of the throttle until I hit 50mph (2000rpm) and then no throttle (no fuel) until I come back to 40mph (1600rpm) when I 'pulse' again. This ensures all my fuel is used in the best BSFC area and the engine braking effect during the 'glide' in 5th is minimal.

2)I live in Devon UK and anyone who knows it will know there's not may flat roads to be had. This has given rise to my driving style of only using the throttle at around 75% or nothing, in the gear that gives me 1600-2000rpm.
Eg: going up a steep hill in fourth the car cannot produce enough power to maintain speed so I drop to 3rd with 75% throttle This produces more thrust than required so when I reach the speed limit I take my foot of entirely and glide back to 1600rpm and start again.

All coments would be appreciated.

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Old 03-06-2009, 10:51 AM   #2 (permalink)
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2k2Prot5 - '02 Mazda Protege5
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engine braking, although minimal, slows your car. The puny fuel usage used with closed throttle in neutral at idle is worth the added speed/distance you'll be going from just neutral coasting between pulses.

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Old 03-06-2009, 11:04 AM   #3 (permalink)
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Mezzotinter - '94 Volkswagon Golf MK3 CL
90 day: 32.6 mpg (US)
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Thanks Exactly the sort of feedbak I need.
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Old 03-06-2009, 11:11 AM   #4 (permalink)
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Vegan Powa! - '91 Honda CRX DX
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Welcome to ecomodder! DO you have any instantaneous fuel economy feedback?
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Old 03-06-2009, 11:20 AM   #5 (permalink)
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Mezzotinter - '94 Volkswagon Golf MK3 CL
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I was just looking in the instrumentation section as I really want to get something but I don't think my '94 golf has any OBDII port. I may look this weekend.
The ECU is a Bosch Mono-motronic and may have some sort of connection but what info you can get I don't know. Any suggestions? I've been looking at vacuum gauges but what I really want is some kind of cumulative meter so I can try different tactics on my daily commute and see the effect without having to try them for a whole tank and then finding i just wasted 20 litres of fuel
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Old 03-06-2009, 11:49 AM   #6 (permalink)
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Welcome to the site.

For non-OBDII you can use a mpguino!

Current project: A better alternator delete
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