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Thanks guys. Yes, I have the Fister cans, so the burble is more pronounced than with the stock mufflers. To think I was ready to, say, replace timing chain tensioners, etc, before figuring this out and having it confirmed. BTW, nwGTS, loved your "PCCB on all four corners or 1,500 cans of AA" response on the other thread. LMAO.
The reason you want to drive off during the enrichment phase occurring to warm the cats is because more fuel is being injected (that's why the mixture is richer) and this fuel, especially in the DFI engine, where it's being directly injected, can wash the cylinder walls with fuel, diluting the oil's protection properties. In the non DFI 997.1 cars, waiting the 30 seconds or so until the high idle drops down is OK as it lets things warm a little before placing any loads on the motor or parts. It also allows for a more gradual warm up in cold temperatures which may help to prevent bore scoring when the pistons expand faster than the cylinder walls.
The load on the IMS Bearing is actually the highest when the motor is at idle. When it's revving, the intermediate shaft is more self-centering, thus decreasing the load on the bearing. With the larger bearing, very high revs, like on a track, can actually cause the bearing surface speed to exceed it's design parameters, and this is why the smaller IMS bearing is better for track cars that see high revs repeatedly than the larger IMS bearing, but the larger bearing is better for street driven cars. Unfortunately, the smaller bearing cars are rarely only track cars, which is why it's best to replace the bearing on those with The IMS Solution. With larger bearing, street driven only cars, removing the bearing seal allowing for splash lubrication is all that's necessary to prolong it's life, and since it's not serviceable anyway, that's all us larger bearing 997.1 car owners can do anyway.
You'll get lots of technical and purist feedback. My recommendation is drive without redlining for 3-4 miles and as oil temp increases feel free to start driving. On street you're not redlining every gear. Don't let anyone scare you on engine damage from street driving. Main point is not high revs first 3-4 miles to lubricate everything and warm engine, eg 6-7k.
Then enjoy your p. It's a joy. Don't live scared trying to eliminate other people's fears. Oh that's right. Someone might want to buy your car and say oh, you exceeded 4K on tach with oil temp at 150. F'em. Chance of engine damage minuscule.
There is much wisdom rooted in waiting until oil temp rises before RPM increases > 4k and thats why Porsche gave you an Oil Temp Gage in addition to a Water Temp Gage in later cars.
Originally Posted by ManoTexas
You'll get lots of technical and purist feedback. My recommendation is drive without redlining for 3-4 miles and as oil temp increases feel free to start driving. On street you're not redlining every gear. Don't let anyone scare you on engine damage from street driving. Main point is not high revs first 3-4 miles to lubricate everything and warm engine, eg 6-7k.
Then enjoy your p. It's a joy. Don't live scared trying to eliminate other people's fears. Oh that's right. Someone might want to buy your car and say oh, you exceeded 4K on tach with oil temp at 150. F'em. Chance of engine damage minuscule.
My rule of thumb is 175. My car would never hit 200 if I didn't get on it. I could cruise for an hour and it wouldn't get over 190ish. I think I just have a really cool car.
I generally short-shift at 3K until the oil temp gauge shows an increase above the lowest measurement (usually about 5 minutes of normal driving). I'll shift at 4K after that point until the gauge shows 190-200 (usually another 5 minutes of normal driving). After the car reaches 190ish, I'm free to go to redline.
Interesting about start up. I will generally let my car idle for the 30-60 seconds it takes for the RPMs to settle in below 1000. Is this not good?
Double_J - I follow the exact same protocol as you with my 997.1 cars. You're good.
With a DFI 997.2, I would probably skip the stationary idle until the RPM drop and drive off sooner, so the engine is under some load, using more of that warm-up enrichment fuel being put into the cylinders, and pumping more oil to mix with it..
Originally Posted by Double_J
I generally short-shift at 3K until the oil temp gauge shows an increase above the lowest measurement (usually about 5 minutes of normal driving). I'll shift at 4K after that point until the gauge shows 190-200 (usually another 5 minutes of normal driving). After the car reaches 190ish, I'm free to go to redline.
Interesting about start up. I will generally let my car idle for the 30-60 seconds it takes for the RPMs to settle in below 1000. Is this not good?
There is much wisdom rooted in waiting until oil temp rises before RPM increases > 4k and thats why Porsche gave you an Oil Temp Gage in addition to a Water Temp Gage in later cars.
Agreed. However the manual ONLY states the car is to be driven moderately in relation to the water temp gauge. It says nothing about the oil temp gauge. That seems in stark contrast with what members here are doing. That was the basis for my question I guess.
I started driving during the air cooled days of Porsches where oil and alot of it was the only real thing that cooled the engine.
My 930 is air cooled and holds 11.5 qts of oil and that is what mainly cools it, so I guess at least in my case I carried this habit over from the air cooled days.
Originally Posted by sadcaper
Agreed. However the manual ONLY states the car is to be driven moderately in relation to the water temp gauge. It says nothing about the oil temp gauge. That seems in stark contrast with what members here are doing. That was the basis for my question I guess.
Related to what Wayne (Smith) posted: I have been waiting for the motor to idle down on cold starts before driving. I take it by doing so I may be inappropriately delaying warm-up of the cats? And here's another semi-related question: during the "run-rich" period I here a burbling sound out of the exhaust that goes away once the motor idles down to the normal 650 RPMs or so. Is that normal and related to the motor running rich? (Porsche neophyte here.) I previously attributed that sound to a possible mechanical issue, but now think it might be related to the motor running rich upon start up. Thanks in advance for the any answers.
Now so much in my Boxster but my 996 Turbo emits an exhaust burble and I hear faint backfires at cold start. This is normal as the engine is running rich, extra fuel is being injected to mix with the air supplied by the secondary air injection pump. While the intent is that this extra fuel and injected air burn ahead of or in the converters to warm them up not all of this fuel burns there and the fuel that doesn't burns in the exhaust system and this is the source of the faint backfires.
Concurrent with the idle speed dropping the air injection pump is turned off and the DME switches to closed loop mode.
It does this because the O2 sensors and converters are up to operating temperature and it can rely upon the sensors to help it maintain proper fueling.
Based on my admittedly non-scientific observation whether I let my car idle until the cold idle RPMs drop or drive the car the secondary air injection pump runs about the same amount of time.
The reason behind the drive off immediately recommendation in the manual is for emisssions/fuel economy testing. If there was any call for a "warm up" then the test would include this and this would hurt Porsche's numbers.
For warming up the converters and getting some heat into the engine idling is best, in my opinion.
Consider this: At idle the air flow is very consistent. The amount of fuel injected is very consistent. Since at idle the combustion heat is the least it can be and the engine still running this results in the gentlest warm up of the engine with the least severe temperature gradients.
The extra fuel is injected after combustion into the exhaust gases which carry the fuel along until the fuel encounters the extra air being supplied by the secondary air injection system. There is very little risk to the fuel washing the oil from the cylinders or contaminating the oil. Then the fuel combusts and it is this heat that helps warm up the converters.
As for warm up neither of my cars have an oil temp gage. The Turbo does have an oil pressure gage. From observing the oil pressure I know that oil takes longer to warm up so even though the temp gage needle is at the "180" hash mark it has to be there for some time before based on the oil pressure gage I have reasonable confidence the the engine (and its coolant and oil) is fully up to temperature.
Until in my opinion (based on direct observation by either observing the in-dash temp gage and in the Turbo the oil pressure gage or by monitoring the coolant temperature using an OBD2 code reader/data viewer) the engine has run long enough for the coolant (and oil) to be fully up to temperature I keep the engine RPMs down, below 4K, and avoid subjecting the engine to high loads such as full throttle acceleration even though RPMs do not exceed 4K.
What are we doing here guys.. it's a car, not a rocketship witch some strict operational instructions. It's kind of ridiculous how OCD and specific this has become.
Just treat like any other car and you will be fine. Start the car, drive it.. dont beat the **** out of it until warmed up.
I guess I'm a rebel in my level of driving aggression. Here's a picture of the oil temperature gauge in my 997.2. This is what it looks like on a cold start - the needle is just below the 150F mark. If you were to imagine the needle on the high side of 150 by about the same amount as it is below it in this picture, that's normally the point I'll wait until my self-induced redline starts to move upwards. This normally takes about 5 minutes.
If I were to drive in self-imposed granny mode until the needle is north of 175 I may as well just get a Prius as a large percentage of my trips are under 10 miles, including my commute. The oil temperature may never even get that high. Before the purists crucify me I will state for the record that I drive my Toyota 4Runner to work more often than not such that this alleged devastating short-trip cold start damage on my 997.2 is minimized. The unicorn semen additive I include with oil changes can only do so much
Double_J - I follow the exact same protocol as you with my 997.1 cars. You're good.
With a DFI 997.2, I would probably skip the stationary idle until the RPM drop and drive off sooner, so the engine is under some load, using more of that warm-up enrichment fuel being put into the cylinders, and pumping more oil to mix with it..
Agreed. It is an almost universal truth that idling to warm up the car is NOT the preferred method. Almost all sources of car information, from the manual, to popular mechanics, to Click and Clack, etc., say that a car warms up faster, more efficiently, and with less wear to the engine when it is warmed up by driving at moderate speeds and at moderate RPM.
I don't know if this is just as important or MORE important on a DFI engine, but I certainly know that DFI or not, the universal advice that you not idle to warm up still holds true.
10-24-2016, 09:11 PM
