Cold Engine RPM vs Load

S

StillLearning

Joined
May 19, 2018
Messages
98
Location
CT
Hi All,

I recently moved to an area where I have about 1/4 mile drive from my house to the "Main" road, which is about a 7* grade with a speed limit of 50mph, however most traffic averages closer to 60mph. Pulling out going down the hill is no problem, but when I have to turn and head up hill, especially during heavy traffic times, I question if I am causing excessive wear with the engine being worked hard when cold.

I have a manual transmission, so I choose my own shift points. My question is, on a cold engine, when still warming up, which would be the lesser of two evils? Am I better off holding the gears longer under a lighter throttle input, or giving it more gas and keeping the rpms lower?

I realize ideally I would find a way to let the engine warm up more, but on the days when we are having single digit and sub zero overnight temps, that kind of time is not always available. I have been trying to do much like an automatic would and find a "happy medium," but in some cases when I have to get up to speed quickly I am left with the options above, more throttle or more rpm. I avoid full throttle high rpm unless absolutely necessary until the water temp has been in the normal range for a while.

I have friends who claim to go WOT from a cold start all the time and have never had any issues, but they don't keep their cars as long as I do either...

FWIW, the car is an 07 Accord with the 2.4l. Vtec engages around 2200 - 2300 rpm at anything over about 1/4 throttle.

I am really more curious than I am concerned. Is there any science behind this?
 
If it was me, I'd try to warm the engine up some before taking off. Once driving keep RPM around the 2000~2500 range until near fully warmed up. Don't lug, and don't rev high ... happy medium IMO.

What oil and viscosity are you using?
 
So long as you aren't going WOT when you hit the main road, I'd drive normal and rest easy.

FWIW, the automatic transmissions in my last 5 vehicles all keep out of the highest gears or from locking up the torque converter until a sufficient temp is reached in the transmission - meaning higher engine revs on cold starts... Draw your own conclusions.
 
Originally Posted by ZeeOSix
If it was me, I'd try to warm the engine up some before taking off. Once driving keep RPM around the 2000~2500 range until near fully warmed up. Don't lug, and don't rev high ... happy medium IMO.

What oil and viscosity are you using?



I have been running Mobil1 5w30. The car has about 135k miles on it.

It can be somewhat difficult to keep the rpm under 3k in 1st when pulling out. 1st is geared so low that you do have to rev it a bit to catch second gear at any reasonable part of the power band. 3k rpm in first gear is only a bit over 15mph if I recall.
 
I wouldn't mash the gas pedal but it is not worth worrying about. When really cold let it idle a few minutes.
 
ZeeOSix said:
If it was me, I'd try to warm the engine up some before taking off. Once driving keep RPM around the 2000~2500 range until near fully warmed up. Don't lug, and don't rev high ... happy medium IMO.

Agree with this except on the 1-2 shift where you say you need higher rpm to engage. If time was of no concern when returning, just go in the opposite direction which is presumably downhill for a few minutes. Then your engine will be more prepared for an uphill pull. It's better than sitting to let it get warm which takes longer to get to temperature anyway.
Click to expand...
 
Just keep it somewhere in the middle, no high loads or high rpm until warmed up. That is a solid car and solid engine, this shouldn't be too much of a workout for it with the proper oil spec.
 
Rev it and don't feel the need to be competitive every single day. Get in behind a nice 18 wheeler doing the speed limit and you'll have an excuse to go slower.
 
I have a similar problem.

Just climb the hill in a low gear (1st or 2nd) and keep the rpm's between 1200 and 1500
 
That is a tough situation. So your driveway dumps you onto a 50mph road? What if you do go downhill (just asking)?

I would say that is a candidate for a slightly longer warmup (with cabin heat off), and I'd just try to pull out as conservatively as I could.

Good thing CT has four seasons, so the number of times this happens in the worst conditions you can probably count on your ten fingers.

A thought is to fit a block heater. This coupled with a slightly longer warmup idle should spread some decent heat around if done right.
 
I warm up my car for about 3 minutes before I go, 5 mins when it s -20 here in Minnesota and run in sport mode in my Hyundai Kona turbo in winter 90% of the time so it keeps my rpm higher to burn off my fuel dilution better. Plus it keeps me out of the overly rich fuel mapping Hyundai gave the GDI turbo cars to help on LSPI from 1,500 to 2,500. This has helped out my fuel dilution problem immensely. The rpm in sport mode keeps it in the 2,000 to 3,800 rpm through the gears and disables 7th gear on the dual clutch trans.
 
I owned a 1976 Honda Civic. I lived two blocks from the 65 MPH highway, which I took to work every morning. Even in -15f weather. Having a whopping 65 HP engine, it took almost full throttle to accelerate. Did that for 5 years.

I sold the car after 12 years of use, 130,000 miles, and it burned almost zero oil between 3000 mile changes.
 
Originally Posted by Mainia
I warm up my car for about 3 minutes before I go, 5 mins when it s -20 here in Minnesota and run in sport mode in my Hyundai Kona turbo in winter 90% of the time...... The rpm in sport mode keeps it in the 2,000 to 3,800 rpm through the gears and disables 7th gear on the dual clutch trans.


can you switch it on and off "on the fly"?
 
Originally Posted by Mainia
I warm up my car for about 3 minutes before I go, 5 mins when it s -20 here in Minnesota and run in sport mode in my Hyundai Kona turbo in winter 90% of the time so it keeps my rpm higher to burn off my fuel dilution better. Plus it keeps me out of the overly rich fuel mapping Hyundai gave the GDI turbo cars to help on LSPI from 1,500 to 2,500. This has helped out my fuel dilution problem immensely. The rpm in sport mode keeps it in the 2,000 to 3,800 rpm through the gears and disables 7th gear on the dual clutch trans.


I've noticed in my 300 if I use sport mode it helps bring the oil and coolant temps up faster than if I leave it in drive. I guess keeping it in that 2000-3000rpm range helps instead of 1000-2000. If I'm going to cruise down the highway though, back into drive for that 1200rpm@60mph fuel economy boost!

I like the way the trans and throttle feel in sport mode way better as well, that's just a pleasant side affect lol
 
Re the original question...for the period that you have the ability to control to, light throttle more RPM will heat things up quicker.

warmup2.JPG
 
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.
 
Originally Posted by StillLearning
Hi All,

I recently moved to an area where I have about 1/4 mile drive from my house to the "Main" road, which is about a 7* grade with a speed limit of 50mph, however most traffic averages closer to 60mph. Pulling out going down the hill is no problem, but when I have to turn and head up hill, especially during heavy traffic times, I question if I am causing excessive wear with the engine being worked hard when cold.

I have a manual transmission, so I choose my own shift points. My question is, on a cold engine, when still warming up, which would be the lesser of two evils? Am I better off holding the gears longer under a lighter throttle input, or giving it more gas and keeping the rpms lower?

I realize ideally I would find a way to let the engine warm up more, but on the days when we are having single digit and sub zero overnight temps, that kind of time is not always available. I have been trying to do much like an automatic would and find a "happy medium," but in some cases when I have to get up to speed quickly I am left with the options above, more throttle or more rpm. I avoid full throttle high rpm unless absolutely necessary until the water temp has been in the normal range for a while.

I have friends who claim to go WOT from a cold start all the time and have never had any issues, but they don't keep their cars as long as I do either...

FWIW, the car is an 07 Accord with the 2.4l. Vtec engages around 2200 - 2300 rpm at anything over about 1/4 throttle.

I am really more curious than I am concerned. Is there any science behind this?


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 .
 
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?
 
Originally Posted by Linctex
I have a similar problem.

Just climb the hill in a low gear (1st or 2nd) and keep the rpm's between 1200 and 1500


While I would not mind this approach, I would likely be run off the road doing 15 - 20mph (1500rpm in second) in 50mph zone. I have on the other hand been trying to drive my 1/4 mile to the main rd in second gear at 1500 - 2000 rpm to help warm things up a little faster after a couple minutes of idling in the driveway.



Originally Posted by bobdoo
I owned a 1976 Honda Civic. I lived two blocks from the 65 MPH highway, which I took to work every morning. Even in -15f weather. Having a whopping 65 HP engine, it took almost full throttle to accelerate. Did that for 5 years.

I sold the car after 12 years of use, 130,000 miles, and it burned almost zero oil between 3000 mile changes.



This is really good to hear. It sounds like you had to be even harder on your Civic and it held up well.
 
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