warm it up first or start out easy ?

[MotoSook]

Originally posted by randywebb
Only let it idle -- even for a minute -- if it is likely to stall. Drive it easy -- not too high on rpm and not too low -- as soon as you can. On 911's the maximal stress on the cam train is at idle. You can read more about this from Bruce Anderson.

Here is the above Randy...what can you offer to support the above? How is there maximum stress on the cam train at idle? Because BA said so?

Yes, it's stated in the Manual...but what I continue to see posted is still the same old stuff posted time and time again.

A 911 engine can build temps to over 210 at idle....I've done it to test a t-stat and cooling system install...Oh my god! My car will blow up

Randy, the 210 number is approx. the temperature most engines were designed to run at...and it's also about the point where water in your oil starts to vaporize.

Again...just because it's stated in the manual...it does not mean doing otherwise will cause early failure! And a 911 engine does not have the best tolerance out there.

Someone tell me why and how a well oiled engine spinning at 1000 RPM is experiencing more wear and tear than it might at 4000 RPM.

[thabaer]

I have a theory to answer Souk's question:

WUR enrichment is pouring more fuel in and washing off just that little bit more lubrication until the car warms up. The theory part is that the mix is richer at idle than at revs while cold, if anybody has a wideband OXS hooked up they could check this, LM-1 maybe ? ( I beat Wayne to the punch! )

[MotoSook]

"A cold start is one of the worst things to do to an engine, esp. one w/o electronic fuel injection."


Not an entirely correct statement Randy. Cold starts are bad for an engine mainly becauses the engine doesn't have oil between all the bearing surfaces and ring to cylinder contacts...not until your oil pressure has built up. It doesn't matter what type of induction (fuel and air) is on the engine.

[anthony]

I let all my cars run in place for a minimum of 30 seconds to up to a few minutes depending on how cold it is, and how long it takes for the cars idle to smooth out. If I'm sitting in the car, I'll put my foot on the accelerator and bump it up a little. I feel the cars run better having had that 30 seconds to a minute of warm up.

[MotoSook]

Originally posted by thabaer
I have a theory to answer Souk's question:

WUR enrichment is pouring more fuel in and washing off just that little bit more lubrication until the car warms up. The theory part is that the mix is richer at idle than at revs while cold, if anybody has a wideband OXS hooked up they could check this, LM-1 maybe ? ( I beat Wayne to the punch! )

Charlie, I know the engine runs richer when cold. Now put that together with all the other stuff that has been stated.

[thabaer]

I meant to say the mixture might lean out a bit when off of idle, therefore more revs when cold are better than idling. i.e. idle when cold richer than 3000rpm at the same engine temp.

I kinda assumed you were already on top of that whole cold-start enrichment thing

As far as the rest of the posts, I think Kurt listed my approach right at the start of the thread. I get moving as soon as I feel like the oil has made it through the galleries and everything is up to pressure, probably no more than 30 seconds after the engine fires up on any typical morning.

[randywebb]

This will be my last post on this topic as it isn't really worht while to keep swatting at these "needs" for absolute proof.

Carbs dump more gas into the cylinders than does EFI, washing them down and reducing the lubrication. EFI is best at optimizing for cold starts.

210 oF is "about the point where water in your oil starts to vaporize."
- Completely wrong. Water "vaporizes" (or volatilizes) at any temperature above freezing (ice changes to vapor also, but the term is sublimes). Sit a pan of water out at 70 oF to demonstrate this to yourself. I'll anticipate a possible reply re the greatly increased rate of vaporization by simply directing you to phase change curves at std. pressures.

I'm sorry you don't want to rely on either the factory or on Bruce Anderson. I can't help you with that. If you are interested, you can look up his book and his articles. Or you can run your own experiments.

[KNS]

The owners manual for my '68 VW said to "drive off immediatley". John Muir (idiot's guide) swore by warming it up for a minute or so. In a recent Road & Track, a Volvo owner asked about the warm up in the technical correspondence column. The R & T "experts" concluded that 30 seconds to a minute was not a bad idea.

[banjomike]

My car runs a bit differently for the first 15-30 seconds. You can feel it change. If I get underway before then it is likely to stall or backfire. So I turn it on and wait for it idle to steady then I drive off. Until I get to the freeway (just a few nimutes) I shift between 3k and 3.5k. Once on the freeway I shift at no higher than 4k until I am across the bridge. By then the oil temp guage is usually around 180F and I have an opportunity when the new lane merges in on the left to pass lots of people and run it up to red in 3rd! That's my favorite moment of the commute.

I've always figured, what's the point of warming up the engine and not the tranny and other bits.

[MotoSook]

Randy,

You won't reply, but you'll read this.

My 210 ref. should have been better stated as boil off. I am very familiar with PVT charts. I deal with them on a professional basis. Yet, by your arguement, one can just open the oil cap in one's car, and let the water evaporate after it has contaminated the oil? Not likely to be effective. You are over simplifying principles that you and understand, and you should know better than to apply any one principle without applying the effects of all the parameters.

As a scientist, I would expect you to be a bit more skeptical, or at least have a desire to understand why, rather then take the word of BA or the factory manual w/o question. Aren't you a lab scientist too? I'm not saying that the two sources are entirely wrong, but we are talking about an event (idle) that is a bit more complicated than a yes-no answer might suffice.

I don't mean to offend, but I find that you (me too sometimes) are easily offended ......but! like I said I don't mean to offend you, I'm just trying to understand the "why." Don't you have discussions with your collegues that get drawn out? Oh well.....

Yet again, the "why" is still left out there. I think I'm going to go home tonight and idle my car to warm my sub-freezing garage!

[Steve87-911]

The solution is to always park in your garage, and to have a *real* Porsche that belches a cold start cloud. Then you will have no choice - you must drive off immediately before your garage becomes one big smoke house.

[1fastredsc]

Instead of asking why, think further with ideas to fill the void. For instance, besides wasting fuel, whats a nasty by-product of running rich? Carbon, it builds on your pistons and cylinder head, raising static compression. I remember when i used to clean and prep engine parts before/after the machine shop, that the ones with the worst build up of carbon where daintilly driven street cars. This is of course when i still lived in new jersey where traffic is quite typical, therefore prolonged idling in traffic was common. Anything that would take a good flocking from the owners like DE or track cars usually came out with some light surface carbon at best.

[fireant911]

Originally posted by randywebb

210 oF is "about the point where water in your oil starts to vaporize."
- Completely wrong. Water "vaporizes" (or volatilizes) at any temperature above freezing (ice changes to vapor also, but the term is sublimes). Sit a pan of water out at 70 oF to demonstrate this to yourself. I'll anticipate a possible reply re the greatly increased rate of vaporization by simply directing you to phase change curves at std. pressures.

I am quite glad to see this statement. So many times the magical number of 212° F is referenced here as the oil temperature to acheive to remove condensation/moisture from the oil. It just isn't so... Personally, I hope that my engine does not get up to that temperature - this is the exact reason I went to all the trouble to install an oil cooler.

Back to the original question... I always allow my car to idle for at least 30 seconds regardless of the ambient air temperature before driving off. My purpose is to allow the oil to get where it is needed before adding any additional stress to the engine. I keep the rpms's at a maximum of 2,800 rpm's until I see some movement in my temperature gauge. I do not go above 4,000 rpm's until I reach at least 170° F. I carefully monitor the A/F ratio meter during the warm up phase to see what is happening in regards to the CIS system and engine temps.

I also allow my lawn mower, garden tiller, and chain saw to warm up prior to placing a load on the cold engine which, in my opinion, is just a good practice. I even leave the drain valve open on my air compressor for the first 30 seconds of run time as to reduce the intial load on the engine when first starting. Am I going overboard??? These procedures have worked very, very well for me in years past and I am not about to change unless there is some definite proof delivered against these practices.

[MotoSook]

Originally posted by randywebb
210 oF is "about the point where water in your oil starts to vaporize."
- Completely wrong. Water "vaporizes" (or volatilizes) at any temperature above freezing (ice changes to vapor also, but the term is sublimes). Sit a pan of water out at 70 oF to demonstrate this to yourself. I'll anticipate a possible reply re the greatly increased rate of vaporization by simply directing you to phase change curves at std. pressures.

OK..one last post from the instigator and I'll let it die...but when I was in 4th grade (a bit young to be a nerd yet!) my science project was to make clouds inside a jar using water and ice...guess how that works...uhuh....

[nut11]

It becomes partially philosophical and engineering. I believe a legitimate 1 to 2 minutes of warm up b/f driving allows the DME to sort it self out and then the raw egg factor comes into play. Happy new year to all BTW!

Paul, 85 coupe

[Por_sha911]

Time to put things in perspective:

"Ours is not to question why.
Ours is but to drive like its stolen as soon as it is warmed up!"