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YOUR RESEARCHWhat RPM Do You Drive At
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carbureted engines and only
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This fuel dumping issue was for carbureted engines and only when the choke was on and only required to make the engine run with black clouds of smoke exiting the exhaust.
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It's a Tip so I have to pay a little more attention, manual mode probably used more that auto mode.
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I use a proprietary blend of the top 10 oils to counter the inevitable argumentative-ing around the subject.
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Also, if you see lower AFRs that some folks are reporting, it�s likely an older engine technology.
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It is also, true that running your car at operating temperatures, for a continued period of time, the unburnt gas in the oil will be burnt in the combustion chamber.
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Car will warm up faster being driven at lower RPM's and...I believe...importantly it is better for the car (oil and cylinders) not to be dumping gas into a low rpm running engine.
When carburetors were used in cars, it was necessary to idle the engine for a couple of minutes on cold mornings to facilitate a smooth running engine.
Run with black clouds of smoke exiting the exhaust
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This fuel dumping issue was for carbureted engines and only when the choke was on and only required to make the engine run with black clouds of smoke exiting the exhaust.
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carbureted engines and only
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Reported cause
This fuel dumping issue was for carbureted engines and only when the choke was on and only required to make the engine run with black clouds of smoke exiting the exhaust.
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I recently watched a PCA video with Jake Raby talking about the IMS and good failure prevention. He suggests a minimum of 3,000 RPM to keep the bearing moving. My 04 996 feels good at 3,000 driving from here to there. I have a tip because I have a week left leg from an Achilles injury and a clutch isn't for me anymore, so I drive in manual in 3rd mostly, when driving on roads around home. How about you guys?
Cruising around at 3500 just wastes gas and makes you look like a tool. run the car at whatever gear is appropriate for the situation. sometimes thats 2000rpm, other times its 4500rpm. dont lug it (pretty hard to do in a 996) but no point zinging along at 3500rpm when you arent planning on accelerating either
I do, three of them in fact, and yes, I worry about gas. If you like to waste money for no reason, be my guest, but its pointless. If you feel that porsche owners aren't concerned with the use of gas, you'll likely be surprised to find that frugality is what caused them to be porsche owners in the first place.
I have a Tip, so most of the time it's whatever the tranny is at while driving, but yeah, about 3500 is perfect. In TX we have pretty swift highway speed limits so setting the cruise at 85 is pretty common and it pegs about 3000 from what I recall.
I have a Jack Raby Stage II engine and he advise not to run at 2,200 - 2,400 RPM - stress on the valve train components is highest there. It's a Tip so I have to pay a little more attention, manual mode probably used more that auto mode.
And I'd rather spend my money on upgrades and maintenance and fun driving opportunities than extra gas so I am also mindful of unnecessary revs.
Manual, 987S I drive between 4-5K on the tach. 6K not uncommon. Pretty much never below 3K unless I am still warming up.
The car is away for the Winter but I don't remember any torque at 3K and not sure why I would drive there. And if I am mostly going on the highway, my Boxster is staying in the garage. That's why I have my RS4 and it also stays above >4K most of the time, even on the highway.
Actually, even though you tried to be cute, 2000rpm is not between 2200 and 2400. nevertheless, there is no reason to be at 3500rpm while just cruising. none.
Snarky bunch in here. Generally, just be reasonable. My reputable indy gave me the following pointers:
1. Don't warm the car up in idle, take off right away and keep in under 3K when cold (I interpret as ~20 min)
2. When warm, don't shift under 4K (which probably means don't drop below 3) - even in stop and go traffic (i.e. keep in 1st)
I don't follow that last part so strictly. I generally just try to keep it above 3 when warm unless in stop and go traffic. That means sometimes driving at ~4 because speeds don't allow 3 in the next gear up. Canyons consistently at 4 - 6.5. Note, if you drive like this, your emissions readiness my may not clear if you've detached your battery at some point.
When you're knickers-deep in pedantry, such use of 'gray area' logic need not apply! I should say, good man, don't you realize this gentle man has three, ahem - I say threeee, Porsches? They shall sooner expire from bearing wear than suffer from low gas mileage! Harrumph
Sorry
I cannot agree with don't warm up car.
Disclaimer, that is generally speaking.
I guess if you live on the southwest, where 100 degree days are normal , I can see your point .
But in the Northeast, even during warmer months, mornings can be down in 40s.
So driving any car, without a warm up is not good for cold metal parts that have not expanded to normal, within operating temperature.
my 2 cents
I think "don't warm up the car", i.e. idle..is pretty standard advice nowadays. Car will warm up faster being driven at lower RPM's and...I believe...importantly it is better for the car (oil and cylinders) not to be dumping gas into a low rpm running engine. 3000 rpm is better than 850 rpm or whatever these cars idle.
Not an expert but that is my take.
I shift so smoothly that people think my 911 has a CVT or maybe it's the electric version 😜 Which dial is the one that tells you what your RPMs are again ?
I have to agree with Alexander Hamilton on this one.
The main issue with the warm-up is you douse the cylinders in fuel. Similar to leaky injectors, which is a major contributor to compromised cylinders in the m96, rinsing cylinder walls in unspent fuel is not the preferred approach. As fuel's a solvent, it can break down cylinder walls and contribute to things like scoring, d-chunk & ovalling. This is summarized from a recent PCA video, but it's a fairly common misconception that's been addressed formally on the forum. It's not an ego-petting match, it's just common sense. The safe way to warm up is to get out and drive reasonably until the car warms up.
Of course, once it's warmed up, I trust that you'll take exceptional care to maximize your fuel economy because that's why we drive 911s. For the fuel economy.
It was -13F here in MN this morning and the shifter hardly wants to shift because everything is so cold... i find it hard to believe that this is better for the car than allowing it to warm up a little.
Thirty to sixty seconds would be fine, but after that you are doing more bad than good. The cars are designed to be driven lightly when cold in order to warm up faster, not idled for warm up for reasons already mentioned.
I should be clear about letting car
warm up
My statement was vague, so I will explain what I meant.
I usally wait until I can see temp gauge move the needle off the bottom.
Then I drive, but I keep rpms under 3500, until operating temperature.
I know that cold running puts a lot of unburnt gas in the oil.
It is also, true that running your car at operating temperatures, for a continued period of time, the unburnt gas in the oil will be burnt in the combustion chamber.
It is also true, there is a reason why we run synthetic oil like Mobil 1, that will protect our cylinders during a cold start.
David
Streets I try to keep above 2,500 rpm so 60kmp/h usually 3rd gear and highway as close to 3,000 as possible - 5th gear 100kmp/h is just under 3,000rpm. Also no acceleration over 3,000 before the engine is warm.
The LN retrofit website also makes a point of "trying to keep the rpm above 2,500".
I'm aiming for longevity - wish me luck
The Tiptronic controller uses ATF temperature as one of the sensors to select the proper shift map (i.e. RPM). I wonder if the algorithm also assumes something about the engine oil temperature.
Revs should not drop below 1500 (as stated in the manual).
I keep mine close to 3000 when cruising normally, which is a sweet spot to keep the oil frothing vicsouly, but not so fast that it�s wasteful.
Where you keep the revs for low load should be a lot different than when you have higher load. If you have a very weak load, such as cruising at 35mph on a flat or declining surface, you can run into the 2,000s all day long.
But if you want good acceleration, I would shift to get the revs well above 3,000 for moderate torque (using 50% throttle) or for maximum torque (80% or higher throttle), above 4,000, as 4200 on up is where the highest torque starts.
I always get a kick out of these RPM threads. I guess Audi wants me to destroy my engine.
When I turn the Audi on, the screen says I should keep the RPM's below 7000 before the oil is warmed. Not 4000 rpm, not 5000 rpm, not 6000 rpm but 7000 rpm. So why are so many Porsche owners fretting about 4000 rpm?
I didn't even know my Porsche could run at 2000 rpm. If I drop below 3000, I'm downshifting. The car runs better, drives better, feels better at higher rpms. Maybe in my vintage sports car I might shift at 3500 with a 5500 rpm redline, but never in a modern performance car. OK, in my BMW X3 manual I probably shifted at 4200-4500 rpm, because it had to be. The car will tell you when to shift.
BTW, if I am driving around home, I am probably in 2nd more than I am 3rd. If I remember correctly, I need to be in the mid 40's (mph) before I am even contemplating 3rd. 3rd can take my up into the 70's pretty easily. ( It's winter here, and I haven't been running the much car lately so I am doing this from memory.) With the tall gearing, I am 1,2,3,6. Never did figure out what to do with 4 and 5.
I prefaced my original post with my 987S/MT. I jumped in because I have an M96 engine. I don't have the Tip either.
I don't have a 996...don't give me any ideas, please. I'm out of garage space.
Lots of people in this thread wasting revolutions per minute on USELESS engine noises and STUPID decisions sacrificing MPG for enjoyment.
You guys should be ashamed of yourselves.
I would just say, that the manual says don't warm up. Start and drive right away. I checked the German, it reads the same. So, I will follow the builders advice, myself.
I've a 997, but based on the same general theory that a really low engine speeds aren't great for the IMS, I try to keep the car at a minimum of 2000 rpm in 2-5th gears, which I think is a good compromise of keeping the engine spinning at a good clip, being just a jab of throttle away from real performance, and not being so loud that the neighbors call the cops on you. 3000-3500 rpm on my car is way too loud for everyday, around town driving. I rarely get to 6th in town since that's about 55-60mph at 2000rpm so most cruising around 45-55mph in town is in 5th.
Hoe is it that the oil with the fuel in it is making its way into the combustion chamber?
You think perhaps its boiling off when the oil warms up to roughly 200 degrees and stays there for 30 min or whatever instead?
Like i said, rev it at 5000rpm all day long if thats what does it for you, but all youre doing is creating extra wear, burning gas, and making you look like a complete jackass to bystanders. if you are so desparate to hear the noise from the pathetic m96 while cruising, then have at it.
I don�t think you mean � don�t warm up,� but rather, �warm up by driving it, being careful not to use prodigious amounts of throttle and RPMs during warmup.�
Everyone warms up their car�s engines, except those who do not ever start them. How you warm up is the difference.
What RPM do you drive at?...........The title should be "At what RPM do you drive?" Never end a sentence with a preposition.
There.........a useful contribution to the thread.
I'm not even sure we can agree on what is "high" and what is "low".
Personally I would consider 4000-5000 "medium/moderate" rpms. 3000 or less "low" rpms, and above 6000 "high" rpms but I get the feeling there would be a lot of disagreement around here. ( once again on my M96 987S with MT) I don't know where I got those numbers. never analyzed anything. Just my driving "feel" regarding the car.
Still too long warm up IMO. Start, wait for RPM's to drop and go while maintaining lower (3K) revs until operating temp reached.
How does Mobile 1 protect M96 cylinders in cold start? Don't all oils drain into the pan after shutdown? Isn't the correct viscosity for the season what will protect the cylinders at cold start?
How long does it take for your RPMs to drop? My Mk1 starts up and revs immediately to 2k within the first 1-2 seconds and then stays at 1000-1100 for at least 1-3 minutes. I do not wait longer than 5 seconds to start driving. I see no reason to wait for the secondary air injection to stop and for engine to ultimately settle down to 675, which is where my car idles when hot without the AC on (800 with the AC on).
Yes, but some oils stick to surfaces better than others. I don�t know about Mobil 1.
For folks driving their cars regularly, like every day, there is hardly any metal to metal contact on startup due to oil sticking to surfaces from the day before. Those driving their cars once a month will suffer more wear from each cold start because much of the oil would have made its way off the surfaces.
There's nothing controversial in what you post, since every conscientious owner "warms up" his engine as you suggest. The question however is whether it is advisable to let the engine idle for a few minutes after start-up. No one recommends that any longer. When carburetors were used in cars, it was necessary to idle the engine for a couple of minutes on cold mornings to facilitate a smooth running engine. Ole timers like me even remember when we had to pull the choke **** at start-up.
About 10 seconds, then I'm ready to go with due respect for all the other moving parts that are not loosened up/ up to temp like suspension/ transmission.Then when temps rise to about 180-200 anything goes.
Pretty much what I was getting at, does M1 have any cold start cylinder wear protection that any other oil wouldn't possess?
I use a proprietary blend of the top 10 oils to counter the inevitable argumentative-ing around the subject. I also add a bit of DT40 into the coolant to add viscosity.
Perhaps some kind, patient and knowledgeable soul can�t straighten me out here on a couple fronts:
As for the warm up, I�ve always thought the reason a car starts with a high idle and then simmers down is that this is the designed warm up period, so honor it. You say get in, start up and drive gingerly until the engine is up to temp so your not dumping unburnt gas into the cylinders� wouldn�t driving it gingerly just dump more unburnt gas into the cylinders than at idle? It�s not like the AFM would be wildly different on or off idle??
As for crushing rpm, what little research I�ve done has told me the variocam solenoids activate around 3100 rpm, yet you guys state to keep it at/around/above 3k � wouldn�t this constantly exercise the solenoids and cause undo wear and tear? Seems 2500 or 3500 makes more sense.
The idea of driving off shortly after starting the car (say 30-60 seconds) is that the motor heats up quicker, thus making the Air/Fuel Ratio (AFR) leaner faster. When the motor is cold the AFR is low which means unburned fuel is washing the oil of the cylinder liners. In short, i believe that yes you driving off shortly after starting the car would dump more fuel into the cylinder, but the you are also a) warming the car up faster than idling, and b) have higher oil pressure (due to higher RPMS) going to the oil squirters that is replenishing the oil on the cylinder walls.
The AFR is (dramatically ?)different at cold idle than when cruising/light load. I am pretty sure the 996 M96 motor uses narrow band O2 sensors which are not terribly accurate like the wide band O2 sensors are.
https://goo.gl/2Sekuh
Also, the faster you can get the DME into closed loop mode, the better the AFR will be. I relatively sure that the DME disregards the o2 sensors until they reach operating temperature (420 degrees) and go into closed loop mode. Until then I assume the DME uses a simple fuel table that always errors on the rich side.
https://goo.gl/oZGorC
The higher idle is just to get away with dumping more AIR, not necessarily fuel, to accelerate warmup for those who idle their car, accelerate warmup at stop signs and stoplights, etc.
There is no significant excess fuel being dumped into the engine in any stage of warmup. This fuel dumping issue was for carbureted engines and only when the choke was on and only required to make the engine run with black clouds of smoke exiting the exhaust. New engines today don�t have this problem, as fuel metering is able to deliver fuel in the proper ratio for combustion.
So you can wait, but if you drive off, rest assured, the computer systems will deliver the right amount of air and fuel, and since the load will be higher when driving, the air and fuel will generate more heat to get the cats up to temp faster, thus helping the environment as well as reducing engine wear.
Do you have any data for this claim? I'd love to learn something new. Its my understanding that the high cold idle speed is governed by extra fuel and thus extra air (from an idle air control valve, or egas throttle plate) to get the o2 sensors (and cats) heated up quickly.
Do you have any data for this claim? I'd love to learn something new on this as well. Its my understanding that when the motor is cold and in open loop that the motor cannot read the o2 sensors b/c they have not gotten up to operating temperature (~420 degrees) and the DME uses preset fuel amounts (based on throttle position, Barometric pressure from the map, calcd engine loading, etc) since measurement of combustion efficiency cannot be read until the o2 sensors heat up and the DME goes into closed loop fuel trims.
If you could post some links or site your claims, that would be great. I posted some in my previous post for reference. I was thinking it may be worth grabbing some data logs of AFR at cold start to see how the cards fall on this topic.
Well, OK, I should have said this differently. Yes, during cold start, additional fuel as well as air, are being allowed into the combustion chamber for many reasons:
- A cold engine has very low efficiency (can be below 10%), versus a hot engine (that can be 30-45% efficient)
- A cold engine uses a lot more fuel/air at cold temps because the fluids are a lot more viscous, and it�s a lot harder to move the engine components to keep them running
So fuel efficiency is quite low. But it�s not as if the fuel/air mixture isn�t being burned quite properly, resulting in wet (dumped) fuel down the cylinder walls, through the valve guide, etc. If that were the case, the engine would run quite rough, you would smell a lot of fuel and see a lot of smoke. It�s not as if the preset air/fuel mixtures are going to be 5:1 or 8:1 with these modern engines.
Remeber, too, that stoichiometric AFRs being 14.7:1 for �ideal� are not always used to develop maximum power. For maximum power, AFRs would be below that, even if the result is less than ideal combustion. Yet, we aren�t too concerned about excess fuel under full power conditions either.
In summary, the big reason for driving to warmup your car vs idling it is not going to be fuel contamination in the oil.
Here is a link: https://www.sciencedirect.com/science/article/pii/S0196890414001939
Another link: http://www.autotap.com/articles/Diagnosing%20Fuel%20Delivery%20Problems_0106ta.pdf
https://cartreatments.com/air-fuel-ratio-at-starting-warming-up-accelerating-cruising-heavy-loads-and-decelerating/
Also, if you see lower AFRs that some folks are reporting, it�s likely an older engine technology. The two main reasons for low AFRs on cold starts are:
- difficult to ignite fuel-air mixture (carbureted engine or old-style fuel injection systems
- condensing of fuel due to poor atomization of fuel-air mixture on intake manifolds, or intake ports of the head or pistons
Both of these conditions are greatly reduced with newer engine systems that have modern fuel injection, kit to mention direct injection systems.
https://www.physicsforums.com/threads/ratio-of-air-and-fuel-in-si.398511/
Around town cruising, I shift around 3,500 -4,000. The more spirited i get, the higher rpms I shift, but just getting from point A-to-B, I shift 3,590-4000. On the highway, if I am cruising, at constant speed, I drive in 6th gear. If I am passing, I drop my gear and let the fun begin. I drive in fun mode about 25% of the drive on my commute to work.
My other car is a Honda Accord. I care about fuel economy, but I also like fun-mode. I do not live in fun mode in my morning commute. I have a tunnel I drive through, and that always mandate fun-mode, pulls in 3rd gear.
No no everyone has to live in fun mode all the time.
i do not to see see people who judge others based on how that person choose to live their lives. My job is dependent on me not having a criminal record, so fun mode has to approached with caution.
Driviving at constant speed on the highway is the best thing you can do for your engine. I hope to keep my 911 for another 70-100k Miles, bringing me to 200k Miles. I care about keeping my car healthy until I can afford a turbo. If I am going to get my Turbo, and my bigger house, I need to be frugal so that I can achieve my goals while having fun in my 911.
Got it, thanks. Oh, i know all about open and closed loop based on an e30 i built. Without a lot of equipment, it's best to leave it to the manufacturers to dip out of their parts bins. It's a bit of a mut, but it will run circles around a stock e30.
So basically it makes no difference. Sit and wait or not. Yes driving off is more efficient, i get that, but ultimately this is about fuel economy. The manual states that a prolonged warm up wastes gas not potentially harms your engine. Same reason smaller turbos are everywhere these days, it's all about playing the horsepower game with the EPA in mind.
The only reason the engine-harm narrative has gained traction around here is because an m96 builder that shall remain nameless has said over and over and over again that it *compromises the already weak cylinder design by increasing the exposure of cylinder liners to unspent fuel*. If you know more than him, great. If not, maybe just accept the builder's opinion for what it is & discount the fact that maybe your theory is based on less experience & data. I don't care if I'm right or wrong, the important thing for me is to discern between high & low quality information.
Sure, but by how much? When I said lower, I should have said �significantly lower.� Folks online complaining about rough engine problems and smoke at cold start are seeing ARFs like 8 or 9:1. Some are having trouble starting at all when it�s near 7:1 (flood condition). Others have posted AFRs in the 12-14:1 range during cold start on YouTube.
As someone already suggested in this thread, perhaps since we don�t know what the AFR for cold start is on this M96 engine, we can look for someone who has collected actual data.
EDIT: Durametric can probably do this
I really doubt you're gonna see a/f on a torque app with the narrow band sensors on these cars. At best you'll see voltage, but its gonna be bouncing all around which makes it difficult to get useful info. A wideband sensor is really the only way to pull this off with any legitimacy
I thought conventional wisdom stated that holding constant revs creates cam wear in one area where varying revs spreads the wear across the cam.
Not sure how Variocam effects this.
There won�t be cam wear on a fully warmed up engine.
Also, VarioCam kick in at around 1300-1400 RPM, and stays there until 5500 RPM on the mk1 engines.
VarioCam Plus on the mk2 engines is different.
This is a source reference. Confirm exact model applicability in the original material.
