What would realistically happen if I floored it and redlined my engine immediately after a cold start?

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National_Word_6091@reddit

I do this with rental cars. I was told by a mechanic friend of mine that its good maintenance for the engine. It also gets your heat up quicker.

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Car companies build cars for people exactly like that. They just recommend you don’t. Of course they know Tina isn’t gonna do more than one oil change a year, change none of the fluids ever, floor it when it’s cold out, and drive it like a dog. They know most of the people that buy cars aren’t literate about anything car related. They know. Some wear and tear from multiple types of metals that expand and contract at different rates would be my understanding. But a detectable amount? Maybe over the life of the vehicle.

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Cbrandel@reddit

Increased wear but I know people who drive like that and their cars last a long time anyway.

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EngFarm@reddit

Diesel backup generators go full throttle as soon as they start every time they start.

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that_dutch_dude@reddit

Those dont need to last long. And proper ones have heaters so they are never cold starting.

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Cofncar@reddit

I’m not a diesel mechanic or anything but, I would assume diesel generators have block heaters or other warming means. Diesel fire pumps are required to have a heater and from what I know they are kept at/near operating temperature as they go from zero to 100 instantly as well

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snorkelsneeve@reddit

Diesel backup at nuclear plants do this as well. They have a keep warm system for the coolant and lube oil

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xHaZxMaTx@reddit

My downstairs neighbor was, for a time, immediately revving their car yo to like 4k RPM when starting it in the morning and would keep it there for like a minute before letting it come back down to idle. I'd try to tell them one morning that that's bad for their engine, but they don't speak English. Haven't heard them do that for a while though, so job well done I guess!

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T_Rey1799@reddit

I usually had to rev my car so it didn’t die after a cold start, catch 22 situation in my opinion

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Neither-Way-4889@reddit

Probably needs to have the idle adjusted then, it shouldn't be dying at idle even when cold.

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Hunefer1@reddit

If they are doing it in neutral it’s not nearly as bad as under load. Still stupid of course.

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Burgermasterm@reddit

express warmup 🤣

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ClickKlockTickTock@reddit

Your 300k mi engine will last 298k miles instead? Lol. It wont immediately blow up unless theres already something catastrophically wrong.

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Downtown_Sun4425@reddit

Isn't this sort of how hybrids work?

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New_Line4049@reddit

You'd irritate your neighbours.

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walnutfillet@reddit

I have absolutely jumped in a car, started it with the throttle flat to the floor, dumped the clutch in reverse and then while still rolling backwards jammed it in 3rd gear and taken off in a huge burnout, i did shit like that constantly in that car. Teenage me had absolutely ZERO mechanical sympathy and still somehow did not blow that car up, gotta love an 80s Toyota! When we had about 40 cattle escape, and again on the day my mum called me to say she was having another bleed on the brain and this one was worse (I made it there in time to say goodbye) I have also done it a couple times in my current car and it's fine too, during a medical emergency that car has also done a 40 minute drive with like 90% of that time being just a few hundred rpm off limiter with no issues. Things like that definitely cause excess wear and can definitely be the exact moment you send parts hurtling into the stratosphere, but most of the time doing it once or twice wont be catastrophic.

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Happy_Sea4257@reddit

I've gone that everyday for years. I have to top up my oil every few weeks.

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metalgod55@reddit

Probably nothing. A buddy had a leased dually years ago that, in the winter, he would drive in first gear floored until it got warm! If it’s a cast iron block you could possibly cold sieze it. That’s where the aluminum pistons heat up and expand faster than the cast iron block and run out of tolerance. I will add that I’ve never seen or heard of that happening in a car engine. I’ve seen it on a 2 stroke dirtbike.

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SlimChris94@reddit

Valve train isn’t warm, increased wear on lifters

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Five_Slow@reddit

You end up throwing the rods [like Rod Knock Rodney. ](https://youtu.be/HhWb9BjNpxA)

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ScaryfatkidGT@reddit

The oil and coolant and block and pistons not being at operating temp cause increased wear and cylinder blow by getting junk in the oil that shouldn’t be and wearing the cylinder walls and cam lobes prematurely

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Exotic_Call_7427@reddit

Ever had hardcore sex in a tight position without any lubrication? Similar thing. Everything works, just with a lot more friction.

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Due_Government4387@reddit

You’d have a few seconds of no lube and shrunken pistons banging around. Depends how cold

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ActuaryFew6884@reddit

I had a friend with a Dodge Neon that did this rather frequently. The engine block eventually cracked with not many miles on it

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gettin-hot-in-here@reddit

So I'm assuming you mean doing this with the transmission disengaged (park/neutral) but putting it in first gear and safely driving up to engine redline wouldn't be much different. Do it once? This is a big nothing IMO. Sure there is wear, but it isn't enough for anyone to care. Do it every time you cold start your car? You're causing unnecessary wear on pistons and piston rings as well as everything else that is supposed to be lubricated by your oil.

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Insertsociallife@reddit

Driving up to redline is different because there's load on it. It's still spinning fast so you have all the inertial forces like you do with redlining it in neutral, but also everything needed to drive the car. Forces in the piston-pin-small end system, big end/rod bearing, and reactions on the main bearings.

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gettin-hot-in-here@reddit

Driving up to redline in first gear is not no-load, but it's low load.

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Extreme-Machine3162@reddit (OP)

I’m just now realizing it could mean either in gear/drive or neutral/park. I made the post with the thought of driving after cold start but either way is interesting.

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OldPuebloGunfighter@reddit

I've always been told reving your engine past 3k epm in neutral is bad for the engine as it puts more centrifugal forces on the crank shaft since its not under load acting against the transmission.

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bradland@reddit

Yeah, that doesn't make any sense. The centrifugal force on the crank is proportional to engine RPM, no matter what, but that's not the primary stress on the crank shaft. The pistons move up and down in the cylinders, so they have to stop and change directions at the top and bottom of each stroke. At this point, the piston can experience around 3,000 g of acceleration near redline, and pistons in high performance engines will experience even more. It depends on RPM and stroke length. A typical piston weighs around 1 lb, which means it exerts 3,000 lbs of force on the crank at that point.

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3579@reddit

I heard that it's more that some resonant frequencies are dampened by having load on the engine. When it's unloaded and just revving some of those build to the point of causing damage.

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bradland@reddit

All of these old wives tales are unsupported. Engines are not some homogenous group with identical resonant frequencies.

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hey-im-root@reddit

It’s more about the mechanics and physics involved, doesn’t really have anything to do with whether or not the engines are built the same. Not one single car even has the same “resonant frequency” regardless of the engine, so that wouldn’t be relevant anyway

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BouncingSphinx@reddit

The engine is mostly what will have issues with hard and heavy acceleration immediately after a start, the transmission and such won’t as much. In an absolute emergency situation, I’m absolutely going to get moving as soon as I possibly can and as quickly as I need to. In a rush, I would still be relatively easy on the acceleration, but I’d still get moving in the first few seconds.

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Far-Plastic-4171@reddit

Anything from nothing to bang and a puddle of oil. Depends on how cold

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pmmeuranimetiddies@reddit

In a modern car? not much The main downside would be a steeper thermal gradient which translates to increased thermal fatigue

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Glittering_Bar_9497@reddit

Could break, could work worse, could be a 50000k mile motor instead of a 200000k mile motor. Sometimes you don’t see the aftermath right away which is one of the reasons I don’t like buying a used car. Not a mechanic so I could be wrong, also I imagine the outdoor temperature would play a huge factor, I think in 100 degree heat the damage would be less than say -20.

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gettin-hot-in-here@reddit

The last sentence is totally true. Engine oil is specifically produced to have some lubricating capacity at a variety of temperatures. So at 100 degrees it can at least partly do what it is designed to do even though it's colder than it should be in normal operation. When the temperature of the oil is -20, it's a lot worse at flowing to where it's needed and preventing wear.

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Friendly-Inspector71@reddit

That's not really a problem with modern 0 or 5W oils. However the engine internals are further from their running tolerances so the oil won't be as effective at preventing wear.

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worstatit@reddit

Had a gas pedal stick on a -5f morning .instantly blew the motor.

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dylmgn@reddit

Sounds like that motor was about to kick the bucket anyway from one redline instance

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worstatit@reddit

It was actually a good runner. It was an 85 Mercury Grand Marquis. No tach. I ended up giving the car away, recipient put a junkyard motor in it. I liked it but wife hated it and wouldn't allow it to be fixed, haha. It's dated fi required a few pumps to get it started in the cold and the throttle cables apparently got iced up. Best riding car of many I've owned.

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tony22233@reddit

Jump in start, floor it and shift into gear.

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Reejerey1@reddit

Not a ton, at least not just one time.

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Simp4Toyotathon@reddit

Increased wear mostly. Doing it to beater cars always makes the boys laugh though.

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aalex596@reddit

I drive every loaner and rental like that. What happens? Nothing.

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Prestigious_Tiger_26@reddit

I hear those are the fastest cars on the road.

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Left-Impress4056@reddit

Got a uhaul to drift the rear tires one time. That was fun a shit.

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hdstenny@reddit

https://youtu.be/mZ3w9saHaTs?si=ekRz3gHtgfRQ9Gvg easily one of the best ads i've ever seen

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Old_Passage6000@reddit

For stock cars they are. Everyone drives rentals with a lead foot and they benefit from the Italian tuneup

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FirehawkLS1@reddit

The fastest car for everyone is a rental, which is why when I buy used cars, I make sure it's not an ex rental car 🤣

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DetectiveNarrow@reddit

That’s why I rent out a Subaru legacy. Rev bomb it all you want but it’s 0-60 is still 9 fucking seconds. ( on a serious note most people treat the car normally)

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aalex596@reddit

I rented a little POS Kia in Colorado once. I had to have the thing pegged at the redline for minutes at a time on some of the uphills. It didn’t blow up, but it sounded like it might.

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Colorful_Monk_3467@reddit

Well nothing happens in the week or 2 you have the car. Probably a different story at 80k miles.

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Extreme-Machine3162@reddit (OP)

I rented a 25 Camry HEV for a couple weeks and boy did I abuse that car lol

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poutine-eh@reddit

even at operating temperature that’s not advised. My ranger has a rev limiter. no car is good revving to redline in neutral

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ImolaBoost@reddit

There’s nothing wrong with hitting rev limiter once up to temp, granted you’ve no other issues with your engine. Sitting at the limiter for extended periods is a different story.

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poutine-eh@reddit

think you misunderstood me… and maybe i’m wrong. Assuming that most modern cars have rev limiters that prevent flooring a car in neutral and hitting the redline. The OP was asking about starting a stone cold car and immediately flooring it not one that’s at operating temperature…. is this ok?

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ImolaBoost@reddit

You stated “even at operating temperature that’s not advised”. That’s incorrect. There’s no issue hitting rev limiter in neutral or otherwise while at operating temperature. The issue arises from low oil pressure, low oil temperature, or sitting on the limiter for an extended period or repeated periods.

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Ashnyel@reddit

I remember a video on YouTube about some corvettes that blew up on cold start, turned out that the guy starting them up, would do exactly that, so they added a limiter…. (There’s more to it than my summary) But I was always told to let the engine warm up so the oil will be less viscous, and you’ll have less wear on the engine’s components,

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AlphaDisconnect@reddit

Chevy tahoe. Dosent care. Chevy impala. Dosent care. Japanese hino dutro. Dosent care. But a Ford Taurus or dodge Durango might care.

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Weekend_Donuts@reddit

Well, your oil will be thicker and create more oil pressure. Will depend on engine design, but could…… Flood the pcv system/consume oil. Blow the rear main seal of the particular engine is prone to that. Most likely though……. a small amount will f accelerated wear you won’t notice.

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Legitimate-Duty-5622@reddit

Lots of engine wear. Possibly worse. Engine is rich at cold start. Oil is thicker and is not properly circulated.

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TuzzNation@reddit

Temperature is not optimal so the fuel won't burn clean. You need up having carbon build-up all over the place. You get carbons at valves and it would affect the seal when compressing. You lose mileage and power.

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Dieselfumes_tech@reddit

Knock knock

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TheCamoTrooper@reddit

I've killed an engine once doing that lol, 30 year old honda with almost 600k on it and it got plenty of abuse lol But newer, good condition engine doing just once isn't likely to cause any issues, doing it repeatedly or on an engine already pretty worn out is gonna cuz issues

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Successful_Piano8118@reddit

Lots of wear on your motor. Like 50k miles worth of wear on your internals within seconds at minimum. Could possibly throw a rod bearing that was on its last leg Whatever is grasping for life decides it's time. Not in that order btw

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KiraTheWolfdog@reddit

Lol what the fuck are you talking about? 50k worth of wear all at once? 🤡

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Successful_Piano8118@reddit

Uh yeah. Did you not read the question? A completely dead cold motor immediately floored after start up? We know what happens when this occurs, Chevrolet found out during the development of the ZR1 with the LT5 because an intern would do this very thing every morning. Motors were blowing up left and right. But sure, convince me otherwise

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KiraTheWolfdog@reddit

Im not arguing that its bad for the engine. Im arguing that saying something completely arbitrary and made up like "50k worth of wear all at once" is asinine.

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Successful_Piano8118@reddit

Literally we figured it out almost 40 years ago https://youtu.be/6Vs2tdR-9C8?si=aS6zk4N-bMVRXzLD Time stamp 1330 motors were blowing up before they left the factory. It's genuinely incredibly destructive and easily on par with 50k miles worth of internal wear, there's no oil film on a cold motor like there is on a warm motor.

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KiraTheWolfdog@reddit

"Easily on par with..." he said, with absolutely zero data to back it up. Like I said, yes. It's bad for the engine. But you randomly making up wear figures doesn't help anyone, and makes you look like a twat. Spouting off with horseshit about "that will do 50k mi worth of damage to your engine" blah blah is stupid. The fact that you're digging in your heels and arguing for it speaks more than your stupid comment ever did.

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Successful_Piano8118@reddit

Dude you can't even build a PC without problems, why TF would anyone want to listen to you about building or protecting a motor exactly? "Making up figures" is not stupid it's reinforcing how detrimentally stupid it is to floor it on a cold start. So detrimental in fact that some of the best built motors with the most insane durability standards couldn't even make it out of the factory. But go ahead, punch it. Let me know how it goes.

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6speeddakota@reddit

Watch zip ties n bias plies on YouTube. He does it all the time. Basically you're just putting massive amounts of wear on components because the oil can't get to it quickly and protect it.

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Bulvang@reddit

I used to work with a guy, who was a lube tech at a shop btw, who would cold start his personal car everyday with foot to firewall and rev the piss out of it. He still managed to find his way home safely everyday but I will never forget that insanity.

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bigworm35@reddit

You will likely spin a bearing.

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uncleduddly@reddit

Well, if you bought a diesel Rabbit in 1984, and drove it like that because you were a kid, you'd get 256,000 miles on it before you sold it to someone that put however many more miles on it.

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Dnlx5@reddit

I di it like once a week. Its no big deal as long as you have good oil.

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El_Pollo_Del-Mar@reddit

Honestly, probably nothing.

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Cambren1@reddit

You could possibly spin a bearing.

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Fancy_Chip_5620@reddit

Nothing

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1995LexusLS400@reddit

You’ll increase wear. It’s not really going to make a difference if you do it once or twice, but if you do it all the time, that’s when the issues start happening. A 50K engine that’s been consistently redlined from cold is going to have the same sort of wear on pistons, conrod bearings and cylinder walls that you’d expect from a car with 100K-150K miles.

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Kootsiak@reddit

It depends on the engine but most should rev up but do it slowly because of how cold everything is and the ECU being cautious with rich fuel mixtures and delayed spark timing (you know the word but I can't type it) that will keep you from destroying everything. It's just that cold start that will take a few months off it's life, but it should soldier on. Check out Zip Ties and Bias Plies on Youtube. He owns a bunch of 7.3L IDI Ford diesel trucks in northern Alberta and will spray half a can of ether into them, pin the accelerator to the floor and cold start them like they owe him money. It's almost a ritual at this point.

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ColdSock3392@reddit

Why can’t you type it? The timing I retarded, it’s not offensive to the engine or anyone else…

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OldGeekWeirdo@reddit

I'd expect excessive wear on parts that haven't gotten oil yet. So, likely nothing you'd notice right a way, but something that will appear over the life of the car.

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BouncingSphinx@reddit

Extra wear, potential failure at the very most extreme.

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skinisblackmetallic@reddit

You will feel guilty.

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series-hybrid@reddit

High revs consumes lots of oil, putting it into the top half of the engine. Cold oil is thicker and doesn't drain back down as fast, possibly leading to the oil-pump sucking air. Race engines increase the diameter of the drain-holes, and add a larger oil-pan (or a dry sump system).

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bigtony8978@reddit

Spin a bearing

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sinph1@reddit

The biggest issue is the premature wear on the camshaft bearings due to limited oil pressure. The special coating will wear/burn off, after that it will be metal on metal. You won’t notice the damage until way later down the line. By that time it might be someone else’s problem. Also typically in the cold engine the tolerances might be too tight on the piston rings. As the engine heats things expand into more natural fit, so when you rev it when cold you are just accelerating wear. Now here the impact will be immediate, each cycle of this exercise you very gradually lose compression to blow by and the engine will make less power.

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Green_Report_9503@reddit

your camshafts will get a nice lil wet sandpaper job on them probably will do 30-40k's worth of damage to the cam lobes assuming this is a OHC engine

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Ok-Highlight-3402@reddit

Judging by the people that live next door to me that do every single morning even below freezing: nothing.

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ze11ez@reddit

i do this all the time with a work car. Runs fine so far. And a few weeks ago it was like -45000 degrees it was so cold. still nothing. usually this is from work where there's room to gun it. From my house its not as open field to go ham

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pbgod@reddit

It only takes a moment to build full oil pressure in a modern car because typically there is a valve that holds the oil prime through the engine. The cold oil would be at its thickest, so anywhere that oil can reach actual has the most protection that it can have. Most modern cars, especially with auto/dct trans, have a limiter if you're in park/neutral with no wheel speed. If you rev the engine up in neutral, it will probably pin at 4k or something, not redline. In that circumstance, there is almost no load on the engine. If there is no load, there is minimal force on the rod/crankshaft bearings in the ways that would cause failure. So, despite all the people saying otherwise... it's really not that big of a deal.

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PckMan@reddit

A lot of accelerated wear on the engine basically. In extreme cases you can straight up grenade your engine doing that. It's not like doing it once or twice will do that but usually the people who do that do it all the time so they do indeed grenade their engines. Something just gives be it the piston rings or a valve and shit just explodes. Don't do that. Literally takes 5-10 mins of regular driving to warm up an engine.

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ReptarSonOfGodzilla@reddit

Sort of depends on the car. As your car sits after running, fluids drain down and thicken as they cool. Your engine is intended to run at a certain temperature, the various fluids are designed to provide correct lubrication in those temperatures. So hard acceleration just with a cold motor is bad, since the fluids are out of spec, immediately after start is all of those issues, plus a lack of any lubricants in some areas. Worse case scenario would be scorching parts, best case is accelerating wear on basically every moving part in the engine and transmission.

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