OT: Redlining cold engines

Just some thoughts I had about what Raby and Macster have beens saying in the "IMS bearing" thread. You know, I used to do this (redline @ cold) all the time in all my V8's. I didnt think twice about it and always found the motors had peak HP when ice cold (obviously). On 50 degrees or colder nights, I would let my cars sit for hours before I raced if I drove it earlier. Once I got into sportbikes, I stopped doing this and let the engine warm before nailing the throttle. Then, I got my first Porsche (996) and became really **** about letting the engine come to full operating temperature before even going over 1/4 throttle. My thoughts are this: an engine should not blow up from redlining cold. If it does, it is on the ragged edge of failure at operating temperature - which we all know Porsche is FAR from. Wear on a cold engine at redline, well thats a whole 'nuther story. Not saying to do what Raby did but jeez, the motor should not be grenaded by this. End of thoughts. Comments, fire suit on.

It is always more risky to redline an engine that has not warmed up. The tighter the engine, the more the risk until all components have expanded to normal. A runner who starts out in a sprint without warmig up has more risk of pulling a muscle, and so does a car. IMO, an engine is ready for redline when oil temperature reaches 150F. However, if the purpose of redlining is to produce power, you are losing a huge amount of power until the transmission has been engaged for at least 20 minutes due to the drag from the cold gear lube.

Totally agree on the tolerances, but it shouldnt fail. Wear, yes. On the trans fluid drag, I think the parasitic drag is more than out done from higher hp/tq IMO. This opinion comes from lots of testing.

Well, this is a new theory for me. I have never run cold engines hard (well fast is a better word) in anything I have owned. I do agree with the thinking. I suppose the reason we dont comes from some old tale from North Dakota where a guy rev'd his tractor in -50 degree winter and the oil didnt lube the motor causing it to seize... then the "warm it up" theory was born and we all just do it without knowing why ? When I first read the manual for the P-car and it said "start the car and drive, do not idle the engine to warm up the engine to operating temp" I was really surprised and it was hard to make that change.. but I have tried - still, I wont be out there reving it up while its cold of course in EU if you just let the engine idle to warm up, meanwhile finish getting your things ready in the house it is illegal (unattended, running vehicle) and even your best friend will turn you into the police (in some countries)

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What puts the car at risk is not wear but the potential of the looseness of certain components to not follow the designed path of movement and seize or break.

I only do that on rental cars (But than I feel guilty..damn)

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Im not advocating to do it (and will never do again), it is just I did it in the past without ever screwing up an engine. My '95 'vette I had, had 126,000 miles on it and I regularly stabbed it cold. It maybe used about a quart every 5k miles. To your point, I think cold wear patterns are established after dozens of runs. There is a "cold" path established over time. I could see a new motor seizing instantly when cold at redline as I have witnessed my dad doing but over time, I think the risk is lowered IMO. HAHA, yeah, done the same.

LOL @ rentals, and yet there is exsists a culture that thinks rental cars are great to buy since they always have excellent service records. (I knew you didnt mean go do it - )

Buddy of mine caught air over train tracks driving a rental on a business trip. Why anyone would willingly buy one of those things is beyond me.

[QUOTE=ivangene;6965597] When I first read the manual for the P-car and it said "start the car and drive, do not idle the engine to warm up the engine to operating temp" I was really surprised and it was hard to make that change.. but I have tried - still, I wont be out there reving it up while its cold QUOTE] The owner's manaul I've had for every German vehicle I've owned has said this. In addition to Porsche an early 70s BMW car and BMW bikes from the 70s, 80s and 90s, air, oil and water cooled alike. I think what is intended by this instruction is what is being advocated by most here and for the same reasons -- start driving but go easy on the throttle until warmed up. Someone will have to explain to me the downside to idling until warm. I can see the downside in certain circumstances, e.g. overheating if you do it for too long, or leaving a boxer motorcycle engine idling while leaned over on the side stand. But barring things like that I don't know what the harm could be. Regardless, I do what the manual says.

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+1 and then I think of the money I paid to rent it and the guilt goes away. Same with doing stunt tricks in icy parking lots after its warm of course...

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The engine may be warm but the rest of the car is not.

I have seen a 996 engine with only 500 miles on it, with a thrown rod from redlining it when before it fully warmed up.

Wear is increased while the engine is cold. The engine will warm much faster if it's running around 3000rpm under load than at 800rpm with no load. So to idle to operating temp will take much longer and result in more wear--at least that's the reason I've always seen. Also, didn't something on 993s get gummed up if you idled too long while cold?

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Nor is your brain, sometimes. Seriously though, there's something to be said for getting everything set before mashing your foot down, especially in a car with power. No need for a quick getaway, it's not like I'm practicing to pull pulled a bank job.

I was told what really hurts the engine when it's cold is "load". Revving the car to 5-6k when cold, stationary, and in neutral - should not really be harmful. In fact u see racing mechanics run out to paddocked cars - start them, run them through the rev range, and shut them off. When I had a S2000 if I blipped the throttle after starting it - I'd swear it would warm quicker once I drove away. But as said above - I would never put a high load on a cold engine - so I never drive over 3k unless car is up to temp.

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Sure, the engine hasnt had enough cold runs to make a good wear pattern yet. I bet if it were 5k miles, the motor would still be around IMO.

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First part, I would think opposite from what I was "taught". Second, why do they do that? What's the reasoning? Just curious.

Thermal shock is a fact in northern climates. Back in the day when I had to travel WAY north of where I live - as in 12 hours north - you would wake up to an air temp of -40F and even with the car plugged in to an AC outlet (without it - wait until spring!) you could hear all sorts of weird sounds for the first few minutes as the coolant in the top of the motor (heater OFF to warm up quicker!) met different areas of the motor that were warming up faster I guess. I'd sit there, the seats made out of ice cold cement (no heated seats!) scraping off the inside of the window wondering how much lubrication I had with semi solid oil trying to flow from the back of the pan and into the oil pick up. I didn't even want to think about what would happen if I rev'ed up the motor! (Another reason other then salt to hibernate my toy until April!) Now this IS extreme but the idea of allowing your motor's internal parts to all reach a uniform temp before high RPM's is valid. We also have issues of very cold gas from the tank and running through injectors into hot cly's to worry about up here in sub zero weather as I have heard of people breaking rings in the first minute after starting the car in these conditions. I bet 0w 0 would sell quite well up around Cochrane Ontario in the winter months!

My understanding has always been that the mechanical argument for warming it up by driving it was that it avoided uneven heating and hot spots. But I also know that this practice was originally encouraged for emissions reasons. Idling is obviously not very green, and the cats don't work until they're hot. A lot of stuff like oil change intervals, viscosities, startup procedures, timing and mixture settings, etc. have nothing to do with performance or reliability. It's all about emissions compliance.

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Yeah, wrapping a motor to redline cold in the North would more than likely have catostrophic effects 100% of the time. In the South where I live, probably be ok even in the coldest conditions. Hmmm. I am trying to figure out how this would create uneven heating. So, your combustion chamber and exhuast side of the engine would be hot while everything else is cool when idling to operating temps. This would be the differentiation I'd assume. So, does the friction from (friction bearing, metal to metal contact) loads really warm up the engine that much quicker or is it the heat dispersed from combustion that ultimately is responsible for engine temps? If it is the former, then I could see uneven heating. We never got that into depth in school for aviation reciprocating engine theory (same as a car engine).

Good thread. I remember seeing a graph in an HP Engine Series book on the Ford FE that showed Engine Wear Vs Water Temp. Very interesting! I know we're all in agreement that "cold running" and "engine wear" go hand in hand, but here is a graph of similar data to what I saw way back when. I love the internet. So the hotter the engine the better it is on wear, from a metallurgical stand point. But excessive heat can and will adversely affect other aspects. Food for thought. And, being an engineer, I love data.

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Funny you mention that. Driving around in our sort of tundra like weather I recall a car I was driving up north was suffering from what aviation people would say was 'carb icing'! Nothing you could do about the problem other then drive it in a lower gear and rev the **** out of it to produce as much heat as you could. Just like a Cessna at 10K and dropping alt from icing - my car was chugging along slower and slower as the intake iced up. I ended up stuffing newspaper in between the rad and the grill, blocking part of the ram air intake and driving without the heater on for over 200KM! Fuel injection was a god send in our part of the world.

I just swapped from a supercharged genuine 500HP mustang to a 2004 996 and IMHO warming up should be done on the move, BUT redlining, in the Mustang anyway was a recipe for throwing a rod, it will always be the weakest component that goes first! Here in Texas it never gets that cold anyway and the motor warms up in a mile or two, until then I keep below 4000rpm

In my case I try to keep the revs down and won't go to redline but to keep it below 5k rpm is tough for me...Reason being that where I live there is a divided four-lane road that I must take a left on. So in order to make it out of my neighborhood I need to give it a little throttle in order to get the car going at the same speed as traffic. It's far from redline but also a bit above the 3k-4k limit some say to keep it under. Granted these aren't sub-zero temperatures I'm starting off from and I do have 0w-40 in the car but I do see the oil pressure gauge is pegged at 5 bars during this maneuver. Hopefully it won't make too much of a difference but my only option is to let it sit there for twenty minutes while it warms up fully.

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You have me at a disadvantage. As I said, this is the story I've always got about this. I think it's even come up on threads here or on Renntech. Either way, I'm bringing a knife to this gunfight.

4-corner piston scuffing is a risk if you over-load at low operating temperatures. Piston will grip the liner at four "corners", leave some marks, then high oil consumption if you're lucky, a seized piston if you're not. The piston doesn't take the right shape until it's up to temperature. Starting the car "cold" and opening it up for a quarter mile is not the best idea. That being said, I don't think there is any issue with starting the car and headed for the grocery store right away... My 2 cents...

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Not sure how much distortion the liner exhibits once the head is torqued. I know air-cooled aviation motors have a tight fit in the liner towards the top and then looser fit towards the bottom when cold. Once at operating temp, the liner is supposed to be as linear and straight as possible for the piston to travel in. This is due to the most amount of heat residing in the top of the bore.

The truth is... its the amount of time that the car reaches to temp. When you redline an engine when cold... The delta temp of various parts of the engine will be at its greatest... There will be cold spots and hot spots.... gradually bringing the car up to temps reduces stress on an engine. This is one of the reason why the 2 radiator line intersects each other so that the delta temps between the 2 rads would be a wash... Oh, did I mention I stayed at the Holiday Inn last night...

My suggestion is not to redline any engine until the oil reaches operating temperatures. Oil pumps put out flow and that's related to viscosity. The colder the oil, the thicker the oil and the less the flow for a given pressure. Porsches in particular have tight tolerances between moving parts and require sufficient oil for lubrication. It's not to say you'll have a catastrophic failure; it just is not optimum lubrication as the engineers designed when the engine is cold. On my M5, the engineers provided lights inside the tach that show maximum recommended RPM until the oil reaches operating temperature. They start off with a max recommended rpm of 4k when cold then they gradually go off as the sensor in the oil pan detects the oil has reached operating temperature. Eventually, they all go out except the last one at 7k rpm. This photo shows some of the lights off because the oil is warm. When totally cold, they are all on initially.

OK, i just got to get in on this one. I bought my first 911 6 months ago, 99 C2, with a factory replacement engine in 03. I've put 13K miles on it and that's more than it had when i bought it. I'm going to go out on a limb and say that the most important thing you can do to preserve your M96 is a slow, careful, loving warm up. Ask yourselves, 'why does Dr. P put the laminar flow oil-water heat exchanger in there?' Why does he put in a thermostat that opens so late? Chevy V-8's are beautiful things, just try to beat a well prepared 944-LS2 conversion on the track. (EVERYBODY hates those things) That has nothing at all to do with a German made small displacment flat six. Apples and oranges. I run swepco 201 in my transaxle, heavier than P recommends, (I would bet that if the engineers did'nt have to account for the everyman the'd spec heavier) I double clutch UPSHIFTS until it's warm. FEEL it people!! That transaxle has cold sincros, and when it's nice and warm the 201 works beautifully. Part of the culprit here is these fantastic computers that make a cold engine run like it's nice and warm.........it's not. Love the site, all very interesting. My 944S2 has 240,000 miles and 2 track seasons and has never been opened, I warm it up very carefully. Cheers!

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For part 1 note the "should". When somebody's willing to put their money behind the claim that red lining cold engines, even in neutral with no load, is not harmful over a population of vehicles... As for #2, remember most race engines are not the mechanic's engine. Somebody else pays for that engine. If someone would pay for my engines I wouldn't care about red lining them cold either. (Well, I would care and I wouldn't red line the engine cause I know the potential for what can happen to a cold engine treated this way.) For races where there is big money involved. a race car engine will not see red line cold. The engine will be treated with all the care and consideration a very expensive and very precision assembly that it is deserves. If I were a race team owner and caught a mechanic redlining a cold engine I'd give him a chance to work for a competing team. Sincerely, Macster.

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The buik of the heat comes from combustion. From cold, even at idle there will be temperature differences. Various areas of the combustion chamber, piston, valves and so on will heat up at different rates. But at idle the degree of heating is at its minimum simply cause the engine is burning so little fuel. A higher load from cold will of course produce more heat cause more fuel is being burned. This also heats up the various components but does so much faster and as a result there are larger differences in temperature between the various components. For instance, the piston crown can get quite warm compared to the cylinder wall and combustion chamber. These have more metal mass and of course coolant around them to absorb the heat. It is possible the piston could get hot enough to momentarily stick to the cylinder wall. This damages the outer diameter the piston and of course the cylinder wall surfaces. This lets more combustion chamber blowby get down to the rings, subjecting them to more heat from the combustion and negatively impacting the very thin but very critical oil film that exists on these rings both between the ring and the cylinder wall but also between the ring and the wall of the ring groove and the top and bottom of the ring. Will this result in catastrophic failure? Probably not. But it does result in accelerated wear/tear. This results in more blow by. The engine is less efficient. Uses more gas. Produces less power. More blow by means the oil gets more contaminated with the by products of combustion. More water makes it into the oil. More unburned gas. More compounds that combine with mainly water to form acids in the oil. All this can affect the oil's ability to provide suffiicent lubrication under high loads and high temperature conditions. Thus failure down the road could occur, but not at the ring/piston/cylinder wall interface, but at a rod or main bearing. Sincerely, Macster.

Regardless of whether or not the IMS bearing prefers high rpms or not, you should always let the engine get up to operating temperature before hammering on it. For those without oil temperature gauges, you have to realize that with upwards of 10L of oil, it sometimes takes a few more minutes for the oil to get up to temp after the coolant reaches that oil. Driving the car hard or 'like you stole it' still means you have to take care of your engine. Just wanted to make sure that one point was clear. Secondly, on the whole IMS and RPM thing, driving habits are what we're talking about. Don't be 5th (or 6th) gear happy. I try to make sure the rpms are above 2500 all the time, if not 3000 rpm.

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+ 1,000,000,000,000

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i guess we have more in common than just owning a porsche...now do you forget to stop before you shift from drive to reverse? It always makes me wonder why rental cars feel like they have 75k miles when the odometer says 10k.

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i was about to mention about the M cars having a cold temp RPM. I always follow the same principal as to warm up on the Porsche. i suppose it couldn't do any harm to be safe than sorry.