Why would I want to change down?

Rochdale Pioneers · 07-31-2011, 01:36 PM

Just driven the boys home from the park in my less than a week old 520d. Doing 30 mph on the flat on the speed limiter, in 5th (6mt) and the shift indicator is asking me to drop to 4th.I

I'm doing the legal speed limit, at 1,000 rpm and the engine is returning 60 mpg on the economy gauge.

Why would I want to change down?

HighlandPete · 07-31-2011, 03:02 PM

BMW have decided 1,000 rpm is too low for the 2.0d engine, driving at a constant speed.

I'd suggest at that rpm you could load the crank/con rod bearing oil film quite hard, without knowing it. Seeing as there appears to be crankshaft issues with the 2.0d engine, I'm not surprised the indicator is showing the need for a down change.

BTW, BMW autos down change at something like 1,100 rpm on the lightest throttle/loadings.

HighlandPete

Rochdale Pioneers · 07-31-2011, 03:21 PM

With the Limiter on the engine was basically trundling along on tickover with momentum pulling me along. If there was any load issue with tickover it didn't feel like it!

And I do short spells at tickover - my street is 15mph 3rd gear foot covering the brake. I don't want someone running my kids down and I don't want to kill theirs either....!

LuvMyE92 · 08-01-2011, 07:43 AM

A slow speed in a high gear like you describe puts a load on the engine and is not good for it. With a petrol engine you'd be hearing noises. A diesel makes so much noise already that you probably can't tell. I'd suggest that you will damage the engine if you keep doing this.

I think it's a good idea that you drive slowly and avoid running over kids, just do it in first or second gear...

Z4C_luvver · 08-01-2011, 09:45 AM

With mine, I have noticed that as a guide, it runs well when I run my car at (minimum) 10 times the gear selector position, so 20mph = 2nd gear, 30mph = 3rd gear and 40mph = 4th gear and so on. It normally leaves it around the 1500 -2000 rpm range.

As above posters have noted, you will do damage to your engine by driving it at too high a gear for the speed. Apart from other engine interactions, the pistons are being worked so hard that they are no longer running true to the bore, but at an angle to the axis of the bore.

Just my 2 pence...

07-31-2011, 01:36 PM	#1
Rochdale Pioneers First Lieutenant 23 Rep 371 Posts Drives: F10 520d SE Join Date: Apr 2010 Location: Stockton on Tees UK iTrader: (0)	Why would I want to change down? Just driven the boys home from the park in my less than a week old 520d. Doing 30 mph on the flat on the speed limiter, in 5th (6mt) and the shift indicator is asking me to drop to 4th.I I'm doing the legal speed limit, at 1,000 rpm and the engine is returning 60 mpg on the economy gauge. Why would I want to change down? __________________ Had: E91 320d ES Titanium Silver Now: F10 520d SE Alpine White, Cinnamon Brown leather, Business speakers
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07-31-2011, 03:02 PM	#2
HighlandPete Lieutenant General 6659 Rep 15,858 Posts Drives: BMW F11 535i Touring Join Date: Mar 2007 Location: Scotland, Highland Region iTrader: (0)	BMW have decided 1,000 rpm is too low for the 2.0d engine, driving at a constant speed. I'd suggest at that rpm you could load the crank/con rod bearing oil film quite hard, without knowing it. Seeing as there appears to be crankshaft issues with the 2.0d engine, I'm not surprised the indicator is showing the need for a down change. BTW, BMW autos down change at something like 1,100 rpm on the lightest throttle/loadings. HighlandPete
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07-31-2011, 03:21 PM	#3
Rochdale Pioneers First Lieutenant 23 Rep 371 Posts Drives: F10 520d SE Join Date: Apr 2010 Location: Stockton on Tees UK iTrader: (0)	With the Limiter on the engine was basically trundling along on tickover with momentum pulling me along. If there was any load issue with tickover it didn't feel like it! And I do short spells at tickover - my street is 15mph 3rd gear foot covering the brake. I don't want someone running my kids down and I don't want to kill theirs either....! __________________ Had: E91 320d ES Titanium Silver Now: F10 520d SE Alpine White, Cinnamon Brown leather, Business speakers
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08-01-2011, 07:43 AM	#4
LuvMyE92 Occasionally frequent poster 3000 Rep 2,744 Posts Drives: CT5V-Blackwing Join Date: Jan 2008 Location: RTP NC, USA iTrader: (0)	A slow speed in a high gear like you describe puts a load on the engine and is not good for it. With a petrol engine you'd be hearing noises. A diesel makes so much noise already that you probably can't tell. I'd suggest that you will damage the engine if you keep doing this. I think it's a good idea that you drive slowly and avoid running over kids, just do it in first or second gear... __________________ Current inventory: F22 & G05 Cadillac CT5-V Blackwing w/3 pedals Past: E24,E28(3),E34,E36,E37,E38(2),E39(4),E46,E89,E92 (obviously),F01,F06,F10,F30,F87,G12,G30(2),G82(2)
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08-01-2011, 09:45 AM	#5
Z4C_luvver First Lieutenant 67 Rep 322 Posts Drives: Phoenix Yellow Z4C Join Date: Feb 2011 Location: Wiltshire iTrader: (0)	With mine, I have noticed that as a guide, it runs well when I run my car at (minimum) 10 times the gear selector position, so 20mph = 2nd gear, 30mph = 3rd gear and 40mph = 4th gear and so on. It normally leaves it around the 1500 -2000 rpm range. As above posters have noted, you will do damage to your engine by driving it at too high a gear for the speed. Apart from other engine interactions, the pistons are being worked so hard that they are no longer running true to the bore, but at an angle to the axis of the bore. Just my 2 pence...
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