consume when starting the engine

.....................Modern EFI systems can restart an engine very efficiently with very little waste of fuel, especially if the engine is still hot. Once the sensors get cold, there is a cold start injector and an enriched mixture but even then only for a brief period depending on how much latent heat is still left over from running before. ACVWs with the solex carburetor rely upon an electrical choke and accelerator pump which together can cause a lot of wasted gas. Electrical chokes don't sense whether the engine is still hot and will work as if it was the first startup of the day after only a few minutes of shutdown.

I've always heard that starting the engine is one of the most gas consuming operations in a car, and if you are going to be stopped for a couple of minutes, it is better to live the engine running idle. Now, what I would like to know is how much time at idle matches the engine starting in consume for a stock 1600. Just to have an intuitive idea of this extra consume at start.

thanks Ant

Still is less than 2-5 minutes idle.

I think the real issue has gotten screwed up somewhere down the line of urban legend and other crap. The start\let idle issue has more to do with wear on the engine than economy, if I remember right.

Sneaks

..................It's well known that start up is when a lot of friction and wear is occurring without adequate lubrication until the oil gets flowing. This is an advantage of synthetic motor oil, especially in cold weather. It flows a lot better than mineral oil when it's cold.

The usual figure I've seen puts the break even point at about

20 to 30 seconds, not a couple of minutes. I have no idea exactly how VW engines rate but they aren't going to be too far off from that. I suspect that since smaller engines require less energy to get them spinning that a VW would tend to do better than the average.

-- Mark Sokos Electrical Engineer, Computer Geek (er, programmer), and no talent bum musician

Gas is not THAT expensive!NEVER leave an air cooled engine idling.If air isn't moving over the motor,it gets very hot-very fast.Steve

...................I'm not trying to disagree with you all of the time Steve, but my head temp. & oil temp. gauges tell me that idling is one of the times when an ACVW engine is running its coolest. The only other time that I've seen when it runs as cool is during prolonged downhill stretches of road when the workload must be nothing at all. The more work an engine is doing, the more heat is produced. At idle, there's not much work going on and the fan's output is more than enough to bring down the temperature after running hard and 'under load' while driving. The heads in particular start cooling down quite rapidly when you're idling at a stop light for instance.

Yahhhhhh!

Mine doesn't consume much gas at all if I don't start the engine !!??

(Acceleration kinda sucks, though!)

Well... your gauges show perfectly that idling an aircooled engine is the worst way to warm it up. You want the engine to warm up very quickly. The best way is to drive it. Idling the engine will warm up the heads and pistons fast, but the rest of the engine will take a long time. Driving creates more heat, so gets the engine up to speed faster, and warms the engine up much for evenly. Idling an engine to warm it up is not good for it. Thats why the hand book for every well designed car says not to leave the engine idling to warm it up. 30 seconds is eaily sufficient. as long as the oil is flowing the engine can be used. Just take it gently for the first

10 minutes or so. No full throttle, and keep it under 3500 where possible.

Allan :-)

If your gauges say it's cool Tim,so be it.My own experience is basicly from the first car I had that had a oil temp gauge,a'67 912.The oil temp would climb at idle.And just on general principle,it makes me uncomfortable.We shouldn't even discuss remote starters.Steve

..............hmmm............Maybe there's some specific characteristic of the 912 that caused your oil temp. to rise but I'm not familiar with that car. Being a similar aircooled four cylinder, I'm surprised that it happened. My oil temp. sender is poorly located in the same location as the oil pressure sending unit so it only changes temp. very slowly and doesn't reflect what you'd call 'real time' readings. I'm hoping to relocate my sending unit this winter when I pull my engine for some head work. I'd like to put it at the in-flow side of the oil cooler but I haven't figured out how I'm going to do it yet. Another half-assed idea that I've thought about is to fabricate a tiny shunt line from that dual sending unit brass block to the fuel pump block off plate. It would only flow enough (a trickle?) to bring the hot oil in the oil gallery in direct contact with the sending unit. I do know that head temps drop right away when a hot engine is idling and that indicates to me that the engine is cooling down........I think.

\...what about just doing something like what eric did here...

...its in the oil path.

...Gareth

................Well........I'm hoping to leave the case intact and I'm too much of a woosy to drill & tap into a case and hope that there aren't any filings left inside. I know that some have done it using heavy grease on the drill & tap but like I said.......I'm afraid.......

................I'm not in disagreement with you but here's another reason to not let a cold engine idle for too long that was posted recently here by Bob Hoover:

Bob's post copied & pasted:

-----------------------------------------------

Muir is sharing his wealth of Model A experience.

All air cooled engines warm up fairly fast, so long as their cooling system has not been disabled (ie, air vanes, thermostat, etc).

The VW instructions have more to do with the TRANNY rather than the engine. The tranny gets only splash-lubrication. The INPUT shaft is located ABOVE the output shaft. On a cold morning the main shaft won't get any oil until the output shaft starts spinning... and that won't happen until you put the thing in gear and start to move.

The clue to this came from an German guy, slightly older than God, who used to work for Hermann Cook VW in Encinetas, California, just down the road from me. Talking about Volkswagens in the snow up near Ramona, he told a young lady it wasn't good to let her bus warm up less she stayed inside the bus. Took us a while to winkle it out of him but he meant for her to stay IN the bus so she could keep the CLUTCH depressed. 'Not good' warming it up in neutral. 'Iss in de book' meaning the owners manual. Except the ENGLISH version of the owner's manual does not give you any options, simply start it up and take off. Or, sit there with the clutch depressed until you feel some heat THEN take off.

Truth is, I've always let my VW's warm up for a minute or two. Force of habit rather than anything technical. Based on 40 years of experience my trannies seem to last about as long as everyone elses. But I've never let the thing sit there idling for thirty minutes at a time... and I know some folks who do. And they DO seem to have a higher incidence of tranny problems.

For what it's worth. (There really aren't enough VW's left to matter HOW you warm the things up :-)

-Bob Hoover

What I know, the vast fuel consumption when starting is true only when starting a _cold_ engine. Choke will be fully closed, gas not vaporising properly, etc. During winter time here, the=20 engine will suck gas like hell during the first kilometers. When starting a warm engine that you turned off just few minutes ago, it wont take much gas at all. Surely less than idling the engine for minutes.

The grease idea makes me nervous too. I prefer using airflow to keep the chips out of the engine.

Max

If the engine's warm, then the restart is a fairly efficient operation. I would think the break even point would be less than a minute.

If you're talking about an engine that you just got started in -30F weather then that's an entirely different question, and the answer might be more like 5 minutes. It could also depend heavily on the question of whether you have managed to recharge your battery after the earlier -30 start.

-

----------------------------------------------- Jim Adney snipped-for-privacy@vwtype3.org Madison, WI 53711 USA

-----------------------------------------------

"Tim Rogers" wrote in news:bnpg70$14d2ib$ snipped-for-privacy@ID-46866.news.uni-berlin.de:

Not only that...you could drive along in 1st gear all day w/o overheating, provided you don't exceed the proper amount of revs. Try that in your

35 year old water-cooled...