VWDiesel.net The IDI, TDI, and mTDI source.
General Information => Troubleshooting => Topic started by: Jettagli16v on January 19, 2009, 03:36:30 pm
-
I saw something months and months ago (tdiclub.com) before I even bought my TD,
and it said that warming up a diesel engine before driving is useless because the diesel engine does not build temperature at idle.
Certainly, you want to let it idle for at least 15 seconds to allow the oil to get everywhere.
My EGT (Pre-turbine, spruce/VDO) also does not seem to climb until I start loading the engine.
Any advice?
It feels so wrong to start a cold car and just go,
but I will do it if your sage wisdom supports it!
Thanks GTD!
-Brad
-
I'm going to go with let the turbo see oil and then go. So depending on how cold it is (the viscosity of the oil, if you're running synthetic i guess it doesn't matter...) would determine how long to wait. I would not start the car up, go inside, wait 10 minutes and then go because YES efficient engines take forever to get hot because they are burning so little fuel.
Diesels are renown for burning such a small amount of fuel on idle.
-
if the temp was -20C or below, idling for a minute or so will ensure that oil is getting to where its needed. using a synthetic you could probably just drive away normally with about 5-10 seconds.
the key here is that you do not want to load the engine while cold. sometimes you need to when going uphill, but try your best not to. thats how most damage occurs, and on TDI's extra sooty deposits will be going through the motor when the EGR is open...
-
I'm going to go with let the turbo see oil and then go. So depending on how cold it is (the viscosity of the oil, if you're running synthetic i guess it doesn't matter...) would determine how long to wait. I would not start the car up, go inside, wait 10 minutes and then go because YES efficient engines take forever to get hot because they are burning so little fuel.
Diesels are renown for burning such a small amount of fuel on idle.
Boy that's sure the truth, I just started my new 1/6 T//D on the hoist with a cooling system with about a quart and a half of fuel in a big coffee can to feed and return lines and after probably 12 minuets or so running it mostly idle and quick blips it looks like the can is just about where it was when I first started, my leaf blower uses more than that :lol:
-
I've read somewhere once (or twice) that at idle the average diesel engine is running at upwards of 100:1 air/fuel. Contrast that to a gasser 's stoichiometric 14.7:1, even at idle, and you start to understand one reason why they they sip so little fuel just turning over, and hence make very little heat.
Anyone remember "How To Keep Your Rabbit Alive" by Richard Sealey, with the fantastically detailed drawings? Way ahead of the "XXXX for Dummies" books, full of great advice, and with with the occasional dash of SoCal counterculture: Richard stated that the proper warm-up time for a cold VW engine is *exactly* as long as it takes to roll a new... er... cigarette.
Sorry, OP, I digress... yet again! :lol:
-
HAHAHAHA,
I should have given more info, as half of that is not relevant to my particular diesel!
1) I live in FLORIDA... -20C????
(Just kidding, this is good for the general discussion, just not me specifically!)
2) Going up hill?? (See #1!)
Anyways,
It seems like I was thinking straight.
I have not been on Full Synth on this car (burning a lot of oil, and can barely afford the Rotella she drinks) so I always wait for the oil light to go out (never more than 2-4 seconds after I am off the starter) and let her sit until the smoke decreases appreciably. Then I always run with light throttle and shift by 2000 - 2500 until up to regular temperature, then put my warm-up lever in, and ..... Boost away!
My EGT does not move from the bottom (250F) until I am driving... Idle will not move it.
Thanks!
-Brad
-
I'm going to go with let the turbo see oil and then go. So depending on how cold it is (the viscosity of the oil, if you're running synthetic i guess it doesn't matter...) would determine how long to wait. I would not start the car up, go inside, wait 10 minutes and then go because YES efficient engines take forever to get hot because they are burning so little fuel.
Diesels are renown for burning such a small amount of fuel on idle.
Boy that's sure the truth, I just started my new 1/6 T//D on the hoist with a cooling system with about a quart and a half of fuel in a big coffee can to feed and return lines and after probably 12 minuets or so running it mostly idle and quick blips it looks like the can is just about where it was when I first started, my leaf blower uses more than that :lol:
Your leaf blower prob gets 2 mpg.
-
I usually get into the car, start it, and then I fasten my seatbelt, turn on the radio, etc, etc.
That gives some time to the oil to get everywhere. After that (a minute or so) I just start driving gently till it gets to proper temperature.
-
I read in that add that they use a tablespoon an hour at idle
-
It's more than a tablespoon for sure. When I used that Moly lubo diesel purge stuff it took about 30 mins before it finished the can.
The can was probably half a litre. Can't remember.
-
well dang, I use a block heater but still let it idle for 5-10 min because I've got a 10 month old and want the car to be as warm as possible - but I noticed that it took for ever to warm up and wondered if it was worth it. Guess i'll quit wasting fuel and just go, warms up quicker that way anyway!
and i'm in Rexburg Idaho, 0-20 degrees for the past few months.
-
well dang, I use a block heater but still let it idle for 5-10 min because I've got a 10 month old and want the car to be as warm as possible - but I noticed that it took for ever to warm up and wondered if it was worth it. Guess i'll quit wasting fuel and just go, warms up quicker that way anyway!
and i'm in Rexburg Idaho, 0-20 degrees for the past few months.
best thing about VW/AUDI vehicles is that the temp gauge doesn't need to be anywhere near operating temp to actually get decent heat out of the vents. normally you can turn the heat on when the gauge just starts to move, and get lukewarm air.
-
It somewhat depends on whether you have to let it warm up before it will move to....
My VW will take off, with pretty good power, with only 30 seconds idling. It's good to give at least that much just to get the oil flowing everywhere.
My Mitsubishi has no power if cold started (especially at below freezing) till it's warmed up for a few minutes at least -- so you Can't drive it even if you wanted to -- letting the clutch out will just stall it.
I have no idea why the two of them behave so differently...
Z
-
It somewhat depends on whether you have to let it warm up before it will move to....
My VW will take off, with pretty good power, with only 30 seconds idling. It's good to give at least that much just to get the oil flowing everywhere.
My Mitsubishi has no power if cold started (especially at below freezing) till it's warmed up for a few minutes at least -- so you Can't drive it even if you wanted to -- letting the clutch out will just stall it.
I have no idea why the two of them behave so differently...
Z
could be the compression and or high CR of the vw/audi diesels.
detroit diesels are awesome. i don't know what they use for cold starting, but they will fire right up in the cold. could possibly be very advanced?
-
yeah that is wierd, our detroit always fires right up but it is a sorry excuse for a diesel! no power
-
yeah that is wierd, our detroit always fires right up but it is a sorry excuse for a diesel! no power
well too much advance = very low power...
-
Hi,
I seen Andrew's post about it being significantly worse to let the engine idle to normal operating temp. Could this be explained a bit more. For some reason I thought Idling for awhile (minutes) was better. I guess I was thinking it was less stressful to bring the components up to temp slower the better.
Thanks,
-JB
-
With 2/3's of my rad covered and a fast idle(hand throttle), my engine is up to at least 160 after 10 min of idling. I hate driving with the windshield freezing up on the inside, and have a poor defrost, so it idles every morning.
-
With 2/3's of my rad covered and a fast idle(hand throttle), my engine is up to at least 160 after 10 min of idling. I hate driving with the windshield freezing up on the inside, and have a poor defrost, so it idles every morning.
jimfoo how's the mTDI treating you? good cold starts?
-
You should wait for the oil light to go out before revving the engine and you should drive gently until it is up to normal operating temperature. It is significantly worse for the engine to idle it's way to normal operating temp than it is for it to be placed under gentle load to get there. BEST for any engine, gas or diesel, even in mild climates, is to install a block heater and use it pre-heat the engine year round to eliminate all cold starts.
Andrew
Thank you! I HATE idling, especially when cold, for the reasons you mentioned in your posts. Combustion is cold and sooty when cold, allowing deposits to form in the ring lands and on the valves. Plus its a waste of fuel, a valuable resource. The guys I work with who are all mechanics go out and start their vehicles when its cold and let them idle for 10, 20 minutes. Me, I start it, let it idle for 30 seconds-1 min, then drive off gently until it starts to warm up.
What really drives me nuts is truck drivers are always complaining about poor fuel economy, yet many of them let their engines idle for long periods unnecessarily.
-
Interesting discussion.
I don't see any comments on a cold engines oil pressure? I get a bit worried when I first set out about the oil pressure getting in the plus 100psi range & the effect on the seals in my turbo & elsewhere...
-
Top of the piston is .0001 - .0002 smaller than at the skirt (measured across at the lowest full-sized point). When the engine operates at a normal temp (160 - 180 F), the top of the piston enlarges (the hottest point) so that piston sides are parallel all the way down. This gives the correct support for your rings. Without being expanded the bore wears elliptically, oiled or not.
I farm. A diesel's made to be worked. It's not a machine to drive to the corner store and back. That's disrespectful. Had a Rabbit. 1 million miles before the engine tanked. Drove it hard.
-
I also agree that these diesels use very little fuel at idle whch should translate to a slow warm-up. But on the other hand, if they use less fuel at idle then why will the temps climb in the summer in stop and go traffic and the engine fan come on. You would think just the idling alone would bring it down but it doesn't work that way and this engine uses a 180 thermostat and never runs over 1/3 of the scale on the guage no matter how fast you go in the Summer. Block and head were cooked as well as the radiator and the rest of the cooling system works perfect as well and operates perfectly normal as far as I'm concerned. But since we started talking about less fuel at idle and all it's got me thinking now which sometimes is not the best thing for me to do :lol:
-
I also agree that these diesels use very little fuel at idle whch should translate to a slow warm-up. But on the other hand, if they use less fuel at idle then why will the temps climb in the summer in stop and go traffic and the engine fan come on. You would think just the idling alone would bring it down but it doesn't work that way and this engine uses a 180 thermostat and never runs over 1/3 of the scale on the guage no matter how fast you go in the Summer. Block and head were cooked as well as the radiator and the rest of the cooling system works perfect as well and operates perfectly normal as far as I'm concerned. But since we started talking about less fuel at idle and all it's got me thinking now which sometimes is not the best thing for me to do :lol:
I don't think that a diesel engine's lower fuel consumption has as much to do with not warming up as quickly as does its enormous appetite for air. A diesel goes through significantly more air than a gas engine due to a wide open intake system. When it's cold outside, the air coming into the engine is cold, which in turn cools the engine or prevents it from warming up as fast. A gasoline engine on the other hand has only a small opening in the intake at idle which limits the incoming quantity of cold air.
The engine heats up more at idle in the summer because the ambient air is hot. It will run hotter at idle than driving on say a flat road because there is no air flow across the radiator or engine. Another factor in seasonal engine temperature is the climate control of the cabin. Having the heater on takes heat away from the engine whereas having A/C on will place more strain on a cooling system.
Also as a point of interest, with all else being equal, for every 1 degree F increase in intake temp, the EGT will increase approx. 3 degrees.