2021 Bmw M340i

[sage drum]

How long to warm up engine?

[ornate stag]

20-30 seconds before driving, operating temp before approaching the limit

[sage drum]

Is it okay if I just start driving immediately? But not press the gas pedal. Like to move one spot to another ?

[ornate stag]

Yep that won’t hurt anything, just don’t start it and rev it immediately

[sage drum]

Thanks dude

I got scared because the car kind of jerks into gear. Since it’s at a higher rpm for cold start. But maybe that’s just my motor mounts

[zinc zinc]

Shouldn’t jerk, and if you’re only just moving it gently it’s unlikely to be engine mounts. How old is the car and has the gearbox been serviced?

[west zealot]

Some cars do start at a honestly ridiculous RPM, looking at you suburu with 1700 I saw one do

[zinc zinc]

He’s talking about it jerking into gear, not jerking on start.

Also, as the owner of a Subaru, it idles around 700. Not exceptional by any means.

[west zealot]

At that RPM it was hard not to jerk putting it into gear

[sage drum]

I work on m340i's and the most common failure we see is vanos actuators and camshaft or eccentric shaft scoring. My shop traced this back to lack of oil FLOW on cold start. We find that the cars that are allowed (especially more performance based engines) to sit and warm up and thermally expand for around 2 minutes typically have significantly less wear on the valvetronic eccentric shaft and camshafts.

[sage drum]

Thanks dude! But let’s say I want to cold start but just move to a new parking spot. That would be fine right.

[sage drum]

Na I would still personally wait at least a full minute to allow oil to circulate and the vehicle to go into closed loop fuel trim correction… basically once you hear it idle down it’s ok to move it to a new spot. If ur actually going on a drive let it warm up longer

[cerulean wadi]

just redline it the moment you start it to warm it up as quickly as possible.

[sage drum]

Great way to ruin a motor if ya got to get rid of it

[cerulean wadi]

It's best to do it especially in colder climates.

Limi bash the bugga

[sage drum]

redlining a cold motor is extremely bad for it... thats coming from a guy who floors his car at least 20 times per drive and I am at 120k miles on an unreliable platform (infiniti vr30ddtt)... I actually let mine get around 120 degrees of coolant temp then drive nice and slow under 2k rpm until oil and trans are at op temp. Oil changes every 3k miles, trans drain and fill at 10k miles. Thing runs like new. If you dont allow for smooth thermal expansion dont expect things to last

[ornate stag]

It’s possible the sarcasm of the recommendation to redline didn’t translate too well into text

[sage drum]

im well aware he was being sarcastic i just didnt want someone to believe that dumb fuckery

[west zealot]

Me who starts it, sets my music and goes, 10 seconds or so and I keep it under 2k for the 1st mile

[cerulean wadi]

Limi bash the bugga

I just don't put oil in my motor since it warms the motor up way quicker.

[sage drum]

lol i love u bro.... i know some ppl who do that. those chevy v8's are unkillable

[west zealot]

I know someone who starts it and immediately full send, it lasted over 200k miles

Some of that was burnouts and drifting

[sage drum]

Wow that’s wild… 5.3L?

[west zealot]

Yep, everything around that engine blew first, transmission once and diff twice

[sage drum]

Wow

Anything before afm seems to last forever

[sage drum]

Is it fine to rev a cold engine to show off the sound to your friends, like let’s say let it idle 30 seconds and rev it up to 4-5k rpm like twice? You see how you say drive slow and nice under 2k rpm’s. I agree with this. But some people say 4k rpm is fine? Do you believe that?

[cerulean wadi]

here in australia we do something called a limi bash its when you rev it until it hits the rev limiter and just keeps hitting it. you should be able to limi bash it for as long as you like

oil pressure has left the chat

[sage drum]

I mean I’d just redline it cold hold it for 2 minutes it’ll be fine

[cerulean wadi]

no im joking

you should never rev a car the moment you start it you need to let it build oil pressure first

it will take 30-60 seconds to build pressure

[west zealot]

That was the 90s turbo whatever, it's like 5 seconds max now

[cerulean wadi]

i dont even have a turbo

[cerulean wadi]

got my engine built and the engine builder told me to let it sit for 30-60 seconds. then just cruise until she is up to temp. gotta let everything else get up to temp as well before i flog it

[west zealot]

That's about the time that it should idle down as well

[cerulean wadi]

she stays in the high idles until she is moving or up to temp for my car.

[sage drum]

Not at all man. If the motor is warm then yes, if it’s cold that will do a lot of damage. You really shouldn’t ever rev a cold motor

[cerulean wadi]

Nuh absolutely redline that thing

If you redline it enough you'll start to hear a cool slapping noise

[sage drum]

I would also highly recommend removing “auto start/stop” with bimmercode… that system is actually pretty harmful to a motor since it will start the motor and immediately let you move… oil pressure does take a second to build so over time it will cause some damage

[sage drum]

That is true but wouldn’t there be an oil film from the existing cycle

[sage drum]

Film goes away real quick when ur at 1500+ rpm on a cold start before it goes into closed loop fuel trim correction

[radiant drift]

I usually wait until the idle RPMs settle down before moving. Then I keep it under 3k RPM until at least 5 minutes after coolant reaches operating temp

[west zealot]

Wait it pops back to open loop? Why the fuck

[sage drum]

Ya on cold start they’re in open loop and then once the upstream o2 sensors are warm it will idle down and go into closed loop

[west zealot]

Oh I thought you meant the like 3 minutes at a light

[sage drum]

Ohhh na lol

[sage drum]

Would it be fine to cold start my car. But chill inside of it to use the AC or heater, listen to music smoke a blunt, for like 30 mins. Like I didn’t drive it I just kept it idling. Would that be harmful? I see that the only thing I’m doing is wasting gas? + I’m up my oil change cycles and things like that knowing I idle more

Also, after cold start and waiting a few, what rpm is the best to keep it under for the m340? Also is it fine to enter a highway with cold engine as long as rpm’s are low?

[frail shoal]

GG @sage drum, you just advanced to level 5! Chat more to level up and earn top roles!

[sage drum]

I personally keep it under 2300rpm when its still cold. I would wait for at least coolant temp before hopping on the highway. Keep in mind oil and trans fluid are still gonna be cold.

As for idling since you have a hybrid powertrain it will most likely shut off the motor unless you disable auto start stop. I wouldnt idle for more than 15 minutes on a regular basis just because it is a lot more strain on your cooling system specifically that cooling fan motor which is an absolute pain in the butt to replace

[cerulean wadi]

Just redline it

Limi bash as the kids would say

[sudden cradle]

i have an infiniti with a vq30hr, i like to floor it a lot, it has 200k miles and going strong 💪🏼 don’t wanna jynx it, just wanna point out that the cars aren’t a totally “unreliable” platform. i do oil changes frequently and i do not know when the last trans fluid change was but i’m sure a while ago

[sage drum]

Some people say 3,000 rpm is okay. If we were to put wear and tear on a time scale, if I were to just keep it at 2300 rpm vs 3000 rpm maxium what’s the difference? Like a 5 hour time difference?

Because me personally I start the engine let it settle then I don’t go over 2,000 out the neighborhood. Then main streets I’m at around 2.7k max and slowly build it as engine gets warmer for even thermal expansion

Also @sage drum please suggest me some YouTube videos/channels or forums about this topic or things from the base like cz I’m new to the game I’m tryna learn the ins and outs and mechanics of cars. Not even for just my m340 but for all the cars that I ever encounter

[sage drum]

The best thing to do is go to school or get a internship or apprenticeship at a shop…

[sage drum]

What about the regular question I asked up top. And thanks

Also depends more on the load than rpm… if ur in a manual car you can be at extremely light load and still rev out to 5k rpm… I think load is what kills an engine more than rpm. I would recommend staying below 3k rpm and below 30% of throttle input. You can go onto a scan tool and watch your throttle position if that would help but basically don’t give the motor a lot of load. The main reason of that is with more load the engine will have to compress more air and therefore will be working harder, with low load and medium rpm it will still be compressing a lot of air but at a more linear rate if that makes sense

[sage drum]

Modern engines do have tighter clearance values than old engines so they don’t expand quite as much as an older engine would… however aluminum does expand quite a bit with heat. I’ve personally seen these exhaust manifold get up to 800 degrees which is pretty dang hot especially for aluminum. I would just recommend treating it nice if you want it to last if that makes sense… don’t beat on it til it’s warm basically is the general idea

[sage drum]

Ya I had a 3.0 turbo in a q50 and it got to 250k… that being said I’ve had countless non maintained infinitis and ones that were not warmed up that have dead turbos or dropped valves or had chain guides fail as low as 50k…

[sage drum]

Like I know it sounds dumb but Once you build a couple engines or have to remove one you will be like ya ok let me never do this again I’ll just warm this shit up because it can be a pain in the ass 🤣

Thank you lockops

💯