Engine rpm and load

[kyrix1st]

I've always wondered about the relationship between engine rpm and load on the S65.. there are suggestions that one should keep rpm below 3000 when cold, but there is always the sense of extra load on the car when I put the car into 3rd gear at 40-50kph under 2k rpm. My understanding is DME already defaults certain % of throttle input to have the engine running, so even when you are coasting at, say 50km/h, 6th gear would put the most load on the engine.

That leads to the question: between 2nd gear with a touch of the throttle and 3rd gear with no throttle at 50kph, which one is harder on the engine? The car seems to warm up faster when it is low rpm&high load condition vs. high rpm with touch of throttle.

[SYT_Shadow]

I let it sit for a minute most days, although neither E9X is used in cold weather.

It's a good question though. It's clear you put more load on the engine at 2k than at 3k.

What I try to do is keep it to minimum throttle while it warms up. So if there's an uphill I'll go to 3k rpm and if I'm just coasting I do 2k rpm.

[kyrix1st]

Originally Posted by SYT_Shadow

I let it sit for a minute most days, although neither E9X is used in cold weather.

It's a good question though. It's clear you put more load on the engine at 2k than at 3k.

What I try to do is keep it to minimum throttle while it warms up. So if there's an uphill I'll go to 3k rpm and if I'm just coasting I do 2k rpm.

Good suggestion.

I am hesitant to pull the trigger on cold start delete partly due to possible insufficient oil circulation by reduced engine rpm. I've also heard that cold start is more than just a reved up engine.. I've been told something has to do with VANOS as well to achieve that cold start exhaust pressure, which creates that awesome but loud sound.

[SYT_Shadow]

Originally Posted by kyrix1st

Good suggestion.

I am hesitant to pull the trigger on cold start delete partly due to possible insufficient oil circulation by reduced engine rpm. I've also heard that cold start is more than just a reved up engine.. I've been told something has to do with VANOS as well to achieve that cold start exhaust pressure, which creates that awesome but loud sound.

With the exhaust I use I would have my eardrums blown out in a single cold start, so unfortunately I have it off. But I also don't use the car in cold weather at all.

Yes, it is definitely more than just higher rpms, vanos does change and you can hear the wonderful music it does. It helps it warm up faster than regular revs

[SkiFly01]

Originally Posted by kyrix1st

I've been told something has to do with VANOS as well to achieve that cold start exhaust pressure, which creates that awesome but loud sound.

Don't forget the Aux Airpump for the cats. I kinda wish I could turn it on manually at times. I do like the sound/rumble at times vs the quiet tame warmed idle.

[kyrix1st]

Originally Posted by SYT_Shadow

With the exhaust I use I would have my eardrums blown out in a single cold start, so unfortunately I have it off. But I also don't use the car in cold weather at all.

Yes, it is definitely more than just higher rpms, vanos does change and you can hear the wonderful music it does. It helps it warm up faster than regular revs

My neighbors complain from time to time to the real estate agency, I just tell my agent it can't be helped because V8.

Car is so well insulated I didn't think it was this loud with windows down so I drive off about 5 seconds after turning the engine on, without throttle.

Originally Posted by SkiFly01

Don't forget the Aux Airpump for the cats. I kinda wish I could turn it on manually at times. I do like the sound/rumble at times vs the quiet tame warmed idle.

My neighbors hate it.

[SYT_Shadow]

Originally Posted by kyrix1st

My neighbors complain from time to time to the real estate agency, I just tell my agent it can't be helped because V8.

Car is so well insulated I didn't think it was this loud with windows down so I drive off about 5 seconds after turning the engine on, without throttle.



My neighbors hate it.

I need a button to enable cold start on demand! haha

[Bartledoo]

Originally Posted by SYT_Shadow

What I try to do is keep it to minimum throttle while it warms up. So if there's an uphill I'll go to 3k rpm and if I'm just coasting I do 2k rpm.

Yea, I always prioritize lower load over lower rpm. Steep hills at 2k over 1st gear feel awful.

[roastbeef]

Originally Posted by kyrix1st

Good suggestion.

I am hesitant to pull the trigger on cold start delete partly due to possible insufficient oil circulation by reduced engine rpm. I've also heard that cold start is more than just a reved up engine.. I've been told something has to do with VANOS as well to achieve that cold start exhaust pressure, which creates that awesome but loud sound.

from what i understand, it is the engine retarding timing and using a richer fuel mixture to warm up the catalysts faster. i suppose a number of theories could sprout from the above, but it is mainly done for emissions.

[jcolley]

Originally Posted by kyrix1st

Good suggestion.

I am hesitant to pull the trigger on cold start delete partly due to possible insufficient oil circulation by reduced engine rpm. I've also heard that cold start is more than just a reved up engine.. I've been told something has to do with VANOS as well to achieve that cold start exhaust pressure, which creates that awesome but loud sound.

There is an insignificant difference in oil pressure from 600-1200 RPM, not enough to make a difference when loading is so low anyway.

Cold start is nothing more than a heating routine for the catalytic converters. It is in fact referred to as "katheizen" in the DME. It richens the fuel mixture, opens the exhaust valves early, and delays ignition timing slightly to allow the fuel/air mixture to escape to the exhaust manifold prior to the completion of combustion. In addition the torque manager implements a "torque reserve" which is part what makes them so miserable to drive cold (especially a DCT that isn't warm yet).

The sole function of this was to meet the US emissions requirements imposed around 2001 or so which required new vehicles being approved for sale in the US to meet the standardized NOX emissions levels within so many seconds of engine start from cold conditions. There were several approaches OEMs took to meet this, one of which was "close coupling" the catalytic converters by placing them closer to the engine for ambient heating. Take for example the E46 M3 Euro vs US headers and the associated gains from the Euro version. The downside to these rapid heating methods is decreased life of the catalytic converters. This led to OEMs adding a second set of cats in the vehicles to avoid EPA mandated warranty claims down the road.

I despise the cold start routine and delete it every chance I get.

[CarPoor]

From what I understand bearings generally create suction of the oil from 2500 rpm on, so I keep mine between there and 3000 while warming up with light load/less throttle. Obviously I have to modify my route on occasion so I’m not lugging up hills.

[M3 Number 86]

ill check this with live data today lol

[kyrix1st]

Originally Posted by M3 Number 86

ill check this with live data today lol

Share the results!

[M3 Number 86]

Originally Posted by kyrix1st

Share the results!

There's not much difference once you hit 2000+ rpm with minimal throttle at city speeds. I was in some traffic so it was a little hard to look at the data as I drove.

But I noticed a huge difference if it was below that rpm and giving it just a touch of throttle.

I'll reconfirm on a more open drive.

This was during initial driving (below 3k driving) while getting car to operating temps.