Cold Engine RPM vs Load

[StillLearning]

Originally Posted by Panos
You worry too much.My Kawasaki 249cc engine does not operate smoothly under 2500rpm under acceleration and breathes nice only after 6000rpm.I use it daily to go to work short tripping it (today work spot is 9kms,but for most years was 4kms)...since 2009.So everyday "the little engine that could" is seeing 6000-8000rpm with cold oil temperatures (10W40 viscocity is all I ever used) for 70.000km and still going strong,with zero oil consumption (every 6000km OCI) and a nice UOA I did last year for the first time.So your redline rpms is my everyday midrange rpms when cold with no issues.I would keep rpms no lower than 2000rpm and no higher than 3500-4000rpm and call it a closed case.


I think this all relative. As a percentage of your usable rpm range, you are really not revving that much higher than a typical car engine. I have a little 250cc Suzuki, which is similar, and it has a red line of just under 10k rpm from what I have read (no tach on the bike). I would correlate 5000rpm on the bike to about 3200 or 3300 rpm in my car, or half of red line rpm.

Also, props to you if your riding that thing in sub freezing temperatures!! I have ridden in weather as cold as about 45 degrees F and that was plenty cold for me. I actually tried to start it one morning after sitting in my shed overnight on a single digit temperature night, as it was blocking my snow blower and I figured it wouldn't hurt it to run it for a while, and it wouldn't even turn over fast enough to start. That was with Valvoline 20w50 motorcycle oil.

 

[StillLearning]

[/quote]
Have you considered installing a block , oil pan , dip stick or coolant heater ? That should help your problem / concern , plus several more benefits .

I would not run WOT with a cold engine , unless I was about to get run over . Not very often , any other time .

If I have time , I try to idle at about 1500 RPM untill the temperature starts to warm up , before taking off . This gives me some heat to defrost the windshield , if needed .[/quote]


The car does actually have a block heater or some kind of heater installed (there is a plug hanging by the front bumper) but it does not seem to do anything or make any difference when plugged in for a few hours. The engine turns just a slow as it would normally with cold fluids. I will probably investigate a little further in the spring when I do my next oil change and possibly a coolant change if the heater is installed in place of a freeze plug. I am hoping it is something simple.

 

[badtlc]

Originally Posted by StillLearning

That said, hypothetically, if you were merging onto a highway with your insufficiently warmed engine and had to get out of the way of a speeding semi, would you choose to...

a. Accelerate in third gear at full throttle from 3300 - 4000rpm
b. Accelerate in Second gear at half throttle from 5000rpm to 6200rpm

I guess I am asking if the stress put on an engine/oil by the centrifugal force of a fast spinning engine is greater than the combustion force(s) of an engine under high load?



I wouldn't go above 2500, maybe 3k, RPMs until it was warmed up a bit. When I had my MTX Mazda3, I kept it below 2500, even getting on the interstate until the cold coolant light went off at a minimum.

 

[Shannow]

2,500 to 3,000RPM is fine.

 

[WyrTwister]

Originally Posted by StillLearning
Thanks everyone for the replies.

It sounds like what I am doing with my "Middle of the road" approach is the right way to go about it. It also sounds like I am better off erring on the side of higher rpm vs higher load to help warm the oil at a faster rate.

Also thanks Shannow for providing the graphs. It is nice to see some data to support what most have been saying.

That said, hypothetically, if you were merging onto a highway with your insufficiently warmed engine and had to get out of the way of a speeding semi, would you choose to...

a. Accelerate in third gear at full throttle from 3300 - 4000rpm
b. Accelerate in Second gear at half throttle from 5000rpm to 6200rpm

I guess I am asking if the stress put on an engine/oil by the centrifugal force of a fast spinning engine is greater than the combustion force(s) of an engine under high load?


I would not think centrifugal force is an issue . Combustion force ? You mean , the force applied to the top of the piston ? Again , do not think this is the issue . As long as you do not exceed the engine " red line " .

I think the issue is / would be , are the bearings getting sufficient lubrication with the cold oil ?

The first consideration is to do ANYTHING to keep from getting hit .

 

[Anduril]

Run a 0w oil if it's really cold and let it idle for a few minutes.

 

[Shannow]

Originally Posted by WyrTwister
I think the issue is / would be , are the bearings getting sufficient lubrication with the cold oil ?


If the "W" rating was appropriate, and as the OP posted, hes already been running it for many seconds, how in the world would the bearings not have enough oil ?

 

[CBR.worm]

I have a less drastic, but similar situation. I have a long driveway that ends at a road that people are travelling ~70 MPH on in both directions. I usually leave the car in 2nd for the length of the driveway (about 2,500rpm) - not ideal, but it certainly warms it up more under light load than idling down the driveway - enough to get the gauge off the C. I try to pull out when there is a long break in the traffic - but sometimes it is not possible. It causes me pain (especially since my truck has a lot of cold piston slap), but sometimes I just have to squeal out into traffic and try to get up to 70 without going over about 3,500 rpm.

 

[bobdoo]

Originally Posted by StillLearning

I guess I am asking if the stress put on an engine/oil by the centrifugal force of a fast spinning engine is greater than the combustion force(s) of an engine under high load?



I think somewhere in here: https://www.cycleworld.com/authors/kevin-cameron

he covers that. High RPM generates MUCH higher loads.

 

[Avery4]

This is something that bothers me also. I live on a sort of busy state highway with a 45 MPH speed limit, but people regularly go 55+ so I need to get up to around 50 reasonably quickly after pulling out. In the summer I don't feel too bad about it, but especially in the winter I let it idle for a minute before pulling out and try to take it easy and shift around 2.5-3K RPM with light throttle. I don't push it until the oil temp gets up to at least 140-150 degrees.

On the other hand, I don't think I am stressing the engine too much because I live in Tennessee and park in an attached but unheated garage, so my car never really gets started at below around 45-50 degrees and it always warms up pretty quickly because I don't use the heater until the coolant is fully warmed up. Looking at the positive, my engine always warms up pretty quickly since I get moving as soon as I pull out onto the highway about 50 feet from my house. Hopefully the fact that my engine doesn't spend much time running cold somewhat makes up for needing to accelerate decently fast shortly after a cold start. I think I worry too much