Jump to content
SAU Community

Recommended Posts

I've read a few discussions in the forums on how long people idle their car for (if any) before they drive off, but there's no discussion on WHY it's better to idle for a few minutes or just drive straight off...

Now for the question : I was talking to a thermodynamics professor a while ago and he mentioned that while it is true that oil doesn't fully protect your engine until it is at operating temp, your car is better protected if you drive off straight away and get it up to temp as quick as possible (as long as you don't rev the engine too much); instead of idling for a few minutes to warm it up at the first start in the morning.

Whether you have a turbo or not is irrelevant for this question.

Comments?

Link to comment
https://www.sau.com.au/forums/topic/14177-cold-start-damage-why/
Share on other sites

I cant give you the technical reasons, but I have been told during discussions with a engine builder that once the engine has full oil pressure you should start driving it. Gently of course (off boost).

I would guess this allows for the oil to start flowing properly, heat up more evenly etc.

Basically, before you first start your car from cold (say in the morning) all the oil has drained down into the sump. It's at ambient air temperature, so it's going to be pretty viscous and not likely to flow freely...

You turn the key and start the engine. Since the oil pump only works when the engine is running, and it takes time for the pump to pump cold oil from the sump up into the valve/cam area (and throughout the engine block)

So, you can see that for a certain amount of time the engine is running without any oil!

The exact time it takes for the oil to start flowing freely through the engine depends on many factors - pump efficiency, oil grade, oil temp, climate and the size of the engine. I remember reading that on some older american muslce cars it could take around 2 minutes for the oil to start circulating around the block!!

Since an engine running without oil is BAD, the best thing to do is minimize the wear by not driving off imediately after you've started the engine...Basically you're giving the engine time to become fully lubricated before you put any pressure on it.

Ohh, and turbo motors are even more susceptible to this since the turbo is sitting right on top of the engine - far from the oil pump...

That's how I understand it anyways...:D

After about 15 mins of driving, my oil preasure drops to about 2 Bar, sometimes a little less (on idle that is), while driving it is typically around 4 Bar. I assume this type of behaviour is correct?

I always let mine warm up at least 1 minute, revving it a little (2000rpm - and not continously), so oil can circulate.

yeah i notice that within 10 seconds of turning the key and starting the engine my oil pressure reaches about 4-6bar (depending on how cold it is). After those 10 seconds I'm happy to drive off and after a couple of minutes driving the pressure drops to about 2 bar as the oil heats up. I think most of the damage is done in the first few seconds after startup. Once oil pressure is up then the engine is fully protected.

I let my car idle for whatever time it takes to start it up, reverse out of the garage, shut the side garage door, get a popper out of the fridge in the garage, put the roller door down, get in, put my CD Face in, window down, seatbelt on and get comfortable......

about 2 mins :D

There are many schools of thought on the warm up issue. Some people like to warm their engine up till the temp gauge rises, and then drive off, ensuing their engine is protected.

HOWEVER, you also must remember that the diff and gearbox oil are NOT at optimum operating temp from cold, and even though your engine is warm, doing burnouts etc with cold gearbox / diff is a recipe for a large bang - trust me, i've blown up a number of diffs in my time, a couple backing out and squirting it too hard (not a skyline though).

So, while i think it is important to warm up a bit before driving off (say 2 mins), you should really take it easy for the first 5-10 mins of driving time (under 3000rpm) to make sure diff and gearbox are happy too.

my 2c

Agree with you on that.

In the past I thought I had a problem with my gearbox - difficulty engaging second gear. Turned out that I just wasn't given the gearbox oil enough time to warm up (especially in winter). Not moving, or moving a slow speeds isn't going to warm up the other oils in the car....

okay well from my experience with my old torana race car.... i was young and silly and i had a mate i had to impress so i started it and revved it pretty hard after a little while of idling... about 8k.... went for a spin and wemt to like 8.5k several times and when i put it back in the shed it was fine ... when we went to take it to the drags the next wekend it developed a very bad miss...we changed coild ,plugs,leads,everything......ended up been a broken valve spring......all brand new done like 5 hours on the dyno......was broken from it not been warm enough and the wire in the spring not been ductile(flexible) enough which cause it to break...personally i would rather letting it get to operating temp before driving....reason been that the oil may not be at full protection till operating temp but it has no load on it unlike driving the car......hence idling it will not stress anything till it warms up and you take off..... i alwats warm mine fully before driving.......

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now


  • Similar Content

  • Latest Posts

    • Hi, is the HKS  Tower Bar still available ? negotiable ? 🤔
    • From there, it is really just test and assemble. Plug the adapter cables from the unit into the back of the screen, then the other side to the car harness. Don't forget all the other plugs too! Run the cables behind the unit and screw it back into place (4 screws) and you should now have 3 cables to run from the top screen to the android unit. I ran them along the DS of the other AV units in the gap between their backets and the console, and used some corrugated tubing on the sharp edges of the bracket so the wires were safe. Plug the centre console and lower screen in temporarily and turn the car to ACC, the AV should fire up as normal. Hold the back button for 3 sec and Android should appear on the top screen. You need to set the input to Aux for audio (more on that later). I put the unit under the AC duct in the centre console, with the wifi antenna on top of the AC duct near the shifter, the bluetooth antenna on the AC duct under the centre console The GPS unit on top of the DS to AC duct; they all seem to work OK there are are out of the way. Neat cable routing is a pain. For the drive recorder I mounted it near the rear view mirror and run the cable in the headlining, across the a pillar and then down the inside of the a pillar seal to the DS lower dash. From there it goes across and to one USB input for the unit. The second USB input is attached to the ECUtec OBD dongle and the 3rd goes to the USB bulkhead connected I added in the centre console. This is how the centre console looks "tidied" up Note I didn't install the provided speaker, didn't use the 2.5mm IPod in line or the piggyback loom for the Ipod or change any DIP switches; they seem to only be required if you need to use the Ipod input rather than the AUX input. That's it, install done, I'll follow up with a separate post on how the unit works, but in summary it retains all factory functions and inputs (so I still use my phone to the car for calls), reverse still works like factory etc.
    • Place the new daughterboard in the case and mount it using the 3 small black rivets provided, and reconnect the 3 factory ribbon cables to the new board Then, use the 3 piggyback cables from the daughterboard into the factory board on top (there are stand offs in the case to keep them apart. and remember to reconnect the antenna and rear cover fan wires. 1 screw to hold the motherboard in place. Before closing the case, make a hole in the sticker covering a hole in the case and run the cable for the android unit into the plug there. The video forgot this step, so did I, so will you probably. Then redo the 4 screws on back, 2 each top and bottom, 3 each side and put the 2 brackets back on.....all ready to go and not that tricky really.      
    • Onto the android unit. You need to remove the top screen because there is a daughterboard to put inside the case. Each side vent pops out from clips; start at the bottom and carefully remove upwards (use a trim remover tool to avoid breaking anything). Then the lower screen and controls come out, 4 screws, a couple of clips (including 3 flimsy ones at the top) and 3 plugs on the rear. Then the upper screen, 4 screws and a bunch of plugs and she is out. From there, remove the mounting brackets (2 screws each), 4 screws on the rear, 2 screws top and bottom and 3 screws holding in the small plates on each side. When you remove the back cover (tight fit), watch out for the power cable for the fan, I removed it so I could put the back aside. The mainboard is held in by 1 screw in the middle, 1 aerial at the top and 3 ribbon cables. If you've ever done any laptop stuff the ribbon cables are OK to work with, just pop up the retainer and they slide out. If you are not familiar just grab a 12 year old from an iphone factory, they will know how it works The case should now look like this:
    • Switching the console was tricky. First there were 6 screws to remove, and also the little adapter loom and its screws had to come out. Also don't forget to remove the 2 screws holding the central locking receiver. Then there are 4 clips on either side....these were very tight in this case and needed careful persuading with a long flat screw driver....some force required but not enough to break them...this was probably the fiddliest part of the whole job. In my case I needed both the wiring loom and the central locking receiver module to swap across to the new one. That was it for the console, so "assembly is the reverse of disassembly"
×
×
  • Create New...