RPM on cold engine?

[Jelle]

Hello there,

I am very new to this forum, and I gotta say, it was a bit confusing to get to this point

Anyway, I have been thinking a bit lately, and I hope that you guys can help me.

You see, constantly I get told that when my engine is cold, I have to run on low RPM's, however, I do not completely agree to that.

Now my engine is quite strong, so it doesn't have much trouble on the low RPM's too, but heres my idea of how it should be:

My father, who works for ZF (transmissions) says that a cold engine should never run more than 2k RPM, the same thing I am told from both my sister and her boyfriend, who both have an education in the area. Still, I do not really agree.

My point of view in this matter is that an engine should never "laboring" (that's what google translate told me, I have no idea what the word is in English). What i mean, is when an engine is having trouble to pull itself and the car at very low RPM's, I'm sure you know what I mean.

Anyway, my engine has a bit trouble at those low RPM's, it is a straight 6 with 200HP, and even though it has Vanos (yeah, BMW) it is still quite slow at those low RPM's.

Back to the question: What are the appropriate RPM I should run my engine on when it is cold? I normally just change gear when I hit 3k RPM, but almost everyone is nagging me about doing so, "It is not good for the engine" they say.

The car is a BMW 525 E34 with a BMW 2.8 M50B28 engine which very few modifications to it. The intake manifold has been ported a bit bigger, and it has a bigger exhaust manifold, yet the rest of the exhaust is stock.

Thank you for reading my novel

 

[GregLocock]

I'm pretty sure that heater hoses are on the engine side of the thermostat, at least in British cars.

I once tried to persuade the chief engineer on this

http://www.youtube.com/watch?v=UQuzHU3JVWU

(the first car ever to use a part designed by me!) that cold passengers were less important than a warm engine, but he ignored me.



Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

http://eng-tips.com/market.cfm?

 

[patprimmer]

Steve.

On my 1989 model Honda Integra, the heater core is plumbed into a thermostat bypass line. It akes water from the head before the thermostat and feeds back into the pump suction side of the thermostat housing. I just looked to check to make sure. That is the logical way to get the heater/demister to clear the screen in minimum time although it does increase engine warm up time. Also the Honda does have a cold start "tune" in the ECU and is sluggish and limited to probably about 4000rpm until the ECU decides it's warm enough. I only know because of the rare occasions where I had to pull directly onto a freeway from a dead cold start and getting up to speed was more on my mind than preserving the engine.

dgallup

Sure, BMW might do those cruel tests to prove their engines can stand up to the ignorance and abuse of it's most extreme users. That does not mean it is recommended or ideal.

OP

Rod has it right. Common sense is all that is required. This is a stock factory engine I presume so it is designed to withstand the much of the abuse some users throw at it, however it is still desirable in my opinion to just keep the engine lightly loaded but happy.

I am not going to bother looking up your particular oil.

Also even if I did, I don't know how it compares to the recommended oil and I also won't bother looking that up.

The reason I asked if you where an engineer is that this site is designed for engineers to discuss engineering work related problems. The non engineers not welcome rule is so we don't get to bored spoon feeding clueless lay people with endless questions that to us are basic.

As you have been polite and not completely clueless you have not been red flagged and deleted despite your falsely claiming to be an engineer when signing up for the site.

Don't start expecting to much spoon feeding if you wish to stay. Also phrase your questions in a concise precise manner with all relevant detail, but no padding or to much flowery politeness. The guys here are often at work and have no time nor inclination for flowery small talk.

Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers &

http://eng-tips.com/market.cfm

for site rules

 

[Jelle]

Evelrod:
I get what you are saying, but if I change down, I will go over the limit of RPM's which I have been told to keep it under.

Benta:
Well, that is what I am told the name for it is. It is not the 2.5 from E34 with VANOS, but an engine from a whole other car. It is a 2.8 liter. I believe the car I took it from was an E39 cabriolet, but I can't seem to figure out BMW's way of naming their models, it's just ridicules.

My 2.8 is very weak at low RPM's, even with VANOS, which just adjust the valves when going low and high. Once I hit 4k RPM, it starts to deliver some power.

In Denmark such a car that I have is not very common, and really not with such an engine. Many people over here drives 1.6'es (My dad, Opel Astra F 1.6) It is only when we gather at friday night we see a few cars which is as powerful as mine.
Cars are not only expensive over here (180% tax when you buy a new one + the price of getting it shipped here and all that stuff.
But not only are the cars extremely expensive to buy, they are also extremely expensive to get insured. I pay about 4300 dollars each year, and the state also want me to pay what they call is "weight tax", there I pay about 1000 dollars a year.

Back to topic... My dad always lets his engine labour when it is cold, because he does not want to rev it. I can't imagine that is good for it, especially when it is such a small engine.

 

[Lou Scannon]

Pat, fair comments; I think an oil pump drive failure or filter canister rupture would constitute a catastrophic bottom end failure, unless the engine was shutdown immediately. If excessive oil pressure doesn't cause something to break, the result may be hydraulic lash adjuster pump up, which will tend to reduce rpm and hence oil pressure.

 

[Jelle]

Thank you all for your advice.

 

[patprimmer]

Jelle

Common sense is actually quite uncommon.

Take advice from the manufacturer. They have yested and know their particular engine. Every engine is different.

Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers &

http://eng-tips.com/market.cfm

for site rules

 

[patprimmer]

Greg

I was of the opinion that the heater bypassing the thermostat was for quick demist, hence safety, not passenger comfort.

The comfort aspect was simply a desirable side effect. The slower warm up was an undesirable side effect, but safety got priority.

Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers &

http://eng-tips.com/market.cfm

for site rules

 

[Lou Scannon]

Safety for society as a whole. An individual's safety would be adequately served by not driving with frosted or misted up windows.

 

[SomptingGuy]

I used to drive rental cars with the brakes on to increase engine load and get the heating working.

- Steve

 

[Tmoose]

There's a 30 page NHTSA test defrost system procedure.

http://www.nhtsa.gov/DOT/NHTSA/Vehicle Safety/Test Procedures/Associated Files/TP-103-13.pdf

I did not read the whole thing.

classic Binks model 62 spray gun used to apply mist and create frost (or ice?) to the outside surface of the glass at 0 F.

%80 of "critical area" to be defrosted after 20 minutes. controls on 100% defrost

No mention of heater performance testing.

 

[NormPeterson]

I think what I'm hearing in the background is a touch of youthful impatience.

When I really push my engine by going sideways, it often starts to tick in the valves pretty quick, no matter what oil I use. I cannot imagine that it is good for the engine, and I am told that it shouldn't happen. I bet it can be pretty much anything, but when it only happens when the engine is working hard at high rev's (I never do this on a cold engine) may tell a bit about what it can be?

Never? Or never below what temperature?

Suggests to me that oil is sloshing away from the pickup or that the pickup tube is otherwise able to suck air under those conditions. If so, definitely not good.


Norm

 

[benta]

Norm, what you need to read is the original post.
There is no such thing as an M50B28 engine from BMW. The OP also admits that it's not original.
So, we're talking about a "Franken-BMW" here, probably a home-shop bored-out M50B25.

So all bets are off.

Cheers,

Benta.

 

[NormPeterson]

Umm, reading the original post is exactly what prompted the 'impatience' line of thought. I've seen this particular topic from both sides of the coin, and it's apparent that there's some fishing for outside justification of his warmup technique going on, most likely to use the next time it comes up for discussion elsewhere.

The car make/model/extent of non-OE content is immaterial.

That said, upshifting a cold gearbox is apt to be easier if enough revs are reached just before upshifting, and this can easily mean briefly revving over 2000. It's either that or double-clutch (the 1-2 upshift in particular).


Norm

 

[BrianGar]

Benta,

Although that engine was not made by bmw, they exist so commonly now due to people building them, that they are a used engine number among the masses.

By what he is saying re single vanos, his engine started out as a M50B25TU, and then had 2.8 internal bits added to the block.

BUT having said that, he also did say that it came from and e39 ''cabriolet'' so god knows what it could have been.

I think the entire thread would have been better off on a Bmw forum to be honest, as he sounds young, and very ''new blood'' driving this ''sophisticated machine''.

Now had it have been a brm v16, where he would have had to machine new parts if the originals screwed up it would be entirely different. But in this case I dont think its anything to worry the op. The rear quarter panels may see 'wear' long before the hydro lifters.

Brian,

 

[SomptingGuy]

I'm lucky to get any warm air from the heaters in my diesel on the way to work. If I take the "scenic" route, the needle lifts on my temperature guage and the heaters start to blow warm air.

For cold starts, there is a button I can use to switch on the front/rear window heaters, and the door mirror heaters. Otherwise, it just blows cold air at the side windows.

I have read/heard of diesels having heaters to suppliment the engine's heat for those few cold minutes, but it does seem a bit extravagant.

- Steve