Would pre-heated air help cold start?

Harry · Post by **Harry** » Sat Sep 12, 2009 6:57 pm

Suppose ya rigged something like a hot-air hair dryer(or something?) to your air intake snorkle when cold start cranking, wonder if it would help?? Ideas along this line?

82vdub · Post by **82vdub** » Sat Sep 12, 2009 8:09 pm

I doubt this would do anything for cold starting. If you think about the temperature it takes to ignite atomized diesel fuel in a cylinder bank, then if you think you warmed the air before it got in the cylinder, I don't think it would make any difference. Plus, there's too much mass in the block to really make any effect. Warm cylinder walls will have more effect on it than the temp air coming in the intake.

Vincent Waldon · Post by **Vincent Waldon** » Sat Sep 12, 2009 9:15 pm

Good compression, good glow plugs, good battery, good starter, good connections, good oil... done.

JIM S · Post by **JIM S** » Sun Sep 13, 2009 8:09 am

Cummins heats the air going in.. no glow plugs..

Ziptar · Post by **Ziptar** » Sun Sep 13, 2009 8:10 am

Yes, a heated intake can help cold starts. Cummins B Series engines use an "Intake Air Heater" that kicks on below a certain temperature.

The B Series engines don't have glow plugs however and they are DI. For that matter with a fully charged battery and healthy starter a VW DI will light off with iffy / dead glow plugs at ~30Â°F fairly easily.

When it comes to an IDI you can heat the intake until the air box melts and it will do you no good I suspect. If you have weak batteries, bad glow plugs, bad starter, bad connections to the starter, low compression, or frozen oil, you've got trouble.

Harry · Post by **Harry** » Sun Sep 13, 2009 9:16 pm

Certainly do agree on the compression, GPs,battery,starter, connections/grounds, oil and other straightforward points, Vince, agreed. Nothing wrong with my '83 Quantum TD that about $3000 overhaul on engine and turbo wouldn't solve. Engine has something in excess of 325000miles, as when I got it it had 293000, from the PO, and then I had the odometer fixed, about 2 years ago. I know the compression is a bit down, how much not sure. The starter seems slow and kind of a dragging sound when it starts and I let off the key. Just had the Nam era pins and plates in my right thigh worked on by the VA(rather go to a Veternarian, they know more) and it will be a while before I can crawl under the beast. It was a landing somewhat short of our alternate destination, Tansanat. Naturally we are a bit cash strapped now, awaiting our "bail-out" check from our glorius leader, they say H*ll will freeze over this year. Ha.

Jim S and Ziptar, thanks for the info on the Cummins B engines, probably would take an awful lot of heat to help light an IDI.

Years ago guys used a certain small proportion of gasoline in the diesel fuel to aid in cold starting the VW diesels, so a friend of mine who did it for about 10 years told me. He doesn't remember the proportion. Does anybody know? He said it was actually published in the little Owners Manual. I don't have one of the manuals, so I'm sol there. To me adding gasoline to the fuel sounds pretty risky, maybe safer than ether starts though, I don't know. Anyway, does anybody know or do this? Seems like the mileage would not be so good. ????

Vincent Waldon · Post by **Vincent Waldon** » Sun Sep 13, 2009 10:52 pm

The original diesel Rabbits came out in a era where diesel fuel wasn't habitually winterized and was prone to gelling in some regions. The owner's manual mentions that in these areas up to 10% gasoline could be added to the fuel to prevent gelling.

I don't think it particularly helps cold starting, and in fact it decreases the luberosity of today's low-sulfur fuels.

Sounds like your engine is old enough to perhaps not have perfect compression, but it's probably still worth making sure your glowplugs are in good working order. Redoing your ground connections and the big positive lead from the battery to the starter is also a good step.

82vdub · Post by **82vdub** » Mon Sep 14, 2009 12:06 am

I think in my 82 owners manual it said that if winterized diesel wasn't available, you could mix 25% or 50% gas in the mix and run that. It was an ungodly high number from what I remember (it's late out and the glovebox is full). As mentioned, it will reduce the lubrication in the fuel, so I wouldn't necessarily do it unless you have to.

Harry · Post by **Harry** » Mon Sep 14, 2009 1:27 am

Well 10% might be ok, but 25-50% might provide more excitement than I would care to chance. Yeah, lubricity would be totally gone, especially now.

Checked all the connections, GP's, etc. considerable time ago. The fact is the compression is lower than spec. and the starter drags. Nothing left to check. Exept the checkbook which has less cash than the compression numbers.

However, ether releases, among other things, Oxygen which of course aids oxidation. Like it's necessary. Soooooo, I wonder what if ya have an oxygen bottle in the cockpit and a hose that goes to the intake manifold, in some manner or form, and after you have glowed and then start cranking crack the O2 valve and you have diesel fuel + very oxygen rich air entering high compression regime and maybe I will get a bang out of it, maybe not, maybe more bang than I ever planned on. One should probably not smoke while attempting such. But all you've added is oxygen, not the additional break down products of ether which themselves are an organic fuel, so as far as fuel supplied is concerned, all you have is the diesel injection system amount which should be about normal.

I suppose there's always an oil pan heater, once I can get under there again. Nobody here is willing to install a block heater and stand behind the installation.

MPalm · Post by **MPalm** » Mon Sep 14, 2009 6:17 am

Harry wrote: I suppose there's always an oil pan heater, once I can get under there again. Nobody here is willing to install a block heater and stand behind the installation.

Why?
Even a engine with good compression struggels to start at -25C without a block heater.
Do you have the kind of heaters that are mounted on the rad hose? They are pretty neat, very easy to install! I have one on my TDI.
http://wup.defa.com/en/wup_products_preheaters.html
you'll find a picture on the right if you scroll down a bit.

82vdub · Post by **82vdub** » Mon Sep 14, 2009 8:52 am

Confirmed my prior statement earlier: Page 91 of my 82 Rabbit owners manual states that you can mix up to 25% kerosene or gasoline with the fuel in winter months.

I am not sure why any repair shop would not be able to install an engine block heater. It's as simple as draining the cooling system, pounding out one freeze plug, intalling new block heater and turning bolt/screw until it's tight, fill cooling system, route electrical wire and it's done. All mechanics in your area of the world can't be that bad. The hardest part in that procedure is draining the cooling system and getting access to the freeze plug, which is a little difficult without a vehicle lift, but still do-able.

Harry · Post by **Harry** » Mon Sep 14, 2009 9:19 am

Thanks on the info on the gasoline adding, I think I will try to avoid this though. Yeah, our local guys probably could install the block heater, it is that they won't. Few options in this local area.

MPalm the hose heaters look like a good idea. There seems to be one model that would go into a radiator hose and another model that would connect to the heater hose(s)? On your TDI is it the one that goes into the radiator hose? And, does it go into the upper radiator hose, that would be a fairly easy installation, I am guessing?

82vdub · Post by **82vdub** » Mon Sep 14, 2009 9:29 am

Proper location for a hose heater would be the lower hose, unless the instructions say otherwise. Heat rises and thus the rising heat would heat the engine. Placing the heater in the upper hose would also allow it to be easily damaged, if your coolant level dropped enough to where the element was not submerged in coolant.

MPalm · Post by **MPalm** » Mon Sep 14, 2009 10:20 am

Harry wrote:Thanks on the info on the gasoline adding, I think I will try to avoid this though. Yeah, our local guys probably could install the block heater, it is that they won't. Few options in this local area.

MPalm the hose heaters look like a good idea. There seems to be one model that would go into a radiator hose and another model that would connect to the heater hose(s)? On your TDI is it the one that goes into the radiator hose? And, does it go into the upper radiator hose, that would be a fairly easy installation, I am guessing?

On the TDI the hose heater is attached to a smaller hose coming from the oil cooler.
There are a few different types and sizes of them, I put a hose heater on a M-B diesel I had a few years ago and it went into the lower rad hose. It was much bigger than the one on our TDI, probably had more wattage too.

As 82vdub said, the installation of a proper block heater is not that difficult, my dad put one on his Caddy and if I'm not mistaken it was mounted at cyl #3. It's a tight fit under the exhaust manifold but not difficult to do.

Harry · Post by **Harry** » Mon Sep 14, 2009 10:35 am

82vdub, yeah very important point on the convection and damaging aspects. I guess there would be enough space on the Quantum lower radiator hose to get such a heater in. I must admit that I don't quite understand VW's coolant circulation system but I guess the heated water would circulate to (and through) the block? It's the location of the thermostat that befuddles me, ain't like an ol' Ford or Chevy. Thing is I can probably get to the bottom hose ok with this leg surgery stuff I had with my ramp stand thingeys under the front wheels. Boy, a fixed leg and 3 grand, or so, would be peaches. Yeah and "if wishes were horses us ol' beggars would ride." I love this old Q it still gets 44-47 mpg, depending on my foot and the proximity of the minions of righteousness(police).

The coolant circulation thing? The heated coolant will get to the block and such? Of course will have to plug the heater in, put it on a timer would be good.