A few questions about modern diesel cars. (cold weather and performance)

I am considering a diesel for my next car (specifically a Volkswagen Golf) and had a few questions. I understand modern diesel cars are much better now but still have issues in cold weather. In my area we typically get to single digit temperatures and on rare occasions temps below zero. (Fahrenheit) Do modern diesels start reliable at these temperatures? How long does it take to get heat to the passenger cabin as compared to gas engines? I understand a block heater will help but since I live in an apartment that is impractical. Can you install a remote starter on a diesel car?

Is there any reason to think the cost of diesel will rise drastically in the next few years? (as compared to the price of gas)

On the performance side, there are companies that sell aftermarket ECUs (IE chips) that claim gains of 15-30 Horsepower (depending on the specific engine). From what I have read on the Volkswagen forums people seem to think this is legitimate. Is it? And why would Volkswagen leave this much potential performance unused?

For those unfamiliar with after market ECU upgrades they typically give less than 10hp on their own and sometimes help other upgrades work better.

One aftermarket chip company

I have a 2009 Jetta TDI, and had a pretty cold winter for DC: overnight temperatures were often in the 20s.

Noting that those temps are quite a bit warmer than yours, it takes all of about half a second for the glow plugs to heat up, and the car is ready to start. In terms of cabin heat, it is my experience that it takes somewhat longer for the car to heat up, yes, but the seat warmers work quite fast and are quite effective.

As far as diesel prices, who knows? From my own point of view, diesel seems to consistently cost about 10-20% more than gas, but the mileage is about 40% better than the same gasoline-powered car. I call that a win. Over the last 18 months, the cost of diesel in my area has fluctuated from being a few cents more than the cost of 87 octane, to right about the cost of premium.

15-30 HP in a diesel is meaningless. A diesel’s bread ‘n’ butter is low-end torque, and lots of it where you need it (low RPM) and when you need it (decent range of RPM).

Adding HP is easy. You advance timing, or change some fuel/air/whatever settings and the dyno the engine and find out that at 4000 RPMs she read 15 more HP! YAY! Right? Yes, but if you take a very good power curve, and you move the power up in the curve, you actually hurt ‘drive-ability’. 10-15 HP means virtually NOTHING in terms of performance. It is as close to zero as you can get, likely hurts the power curve and MIGHT shorten the life of some components.

It’d mean hardly anything is a gas engine that lives on HP. For a diesel, I wouldn’t dare touch it.

I’ve been around car hot rodders and boat hot rodders for a long long time. Gas… Diesel… all of it. It is incredibly common to find an engine has more PEAK horsepower but is slower to accelerate. It’s called ‘screwing up the power curve’, and while it is a problem is gas engines, it’s 2-3 times worse in diesel engines.

Even old diesels would start reliably in cold weather if they had good compression, the valves were properly adjusted, the battery was good and the glow plugs worked right. I had an old '80 240D Benz that would start just fine in subzero temps with no block heater or anything-- I think the lowest I ever started it at was about -20.

Since newer diesels are all around less maintenance intensive, it’s a lot easier to keep them in the sweet spot of startage goodness. So I wouldn’t let cold weather stop you from getting a diesel. Once they’re started they (more or less) warm up just as fast as a gas engine.

If your car is under warranty, do not mess with the ECU. Supposedly some of those performance chips don’t cause any harm, but if something goes wrong (even if it’s not the chip’s fault) it makes it very difficult to make a warranty claim. Newer turbodiesels are plenty fast for just tooling around town, but if you want a fast car get a GTi.

I’ve driven many VW TDIs in Europe [friend’s and rentals] and cold starting is not a problem, though as mentioned take an extra second or so. Diesels have been around in Europe for decades and are pretty much ironed out for most climates. Heck, my 1984 Toyota Camry TD started reliably in northern Iowa/Illinois down to -20F; staying running while driving was a problem until I routed a duct from the exhaust manifold area to the fuel filter/water separator:).

Performance; you may be wasting your time/money on a chip. The latest electronic systems are tough to hack and will screw up your warentee. Most gain is usually from allowing a higher boost before blow-off. Check the torque increase on a TDI; forget any HP claims. IMHO, best option is to get a set of summer high performance tires on a lighter set of wheels [tirerack has the specs posted]. Change back to the factory all-season tires/wheels for the New England winter. The lighter tires/wheels will help acceleration, braking, and handling. Summer HP tires are great. Speed enforcement really curtails the high speed stuff but tearing up the curvy sections and off-on ramps is a blast. If you do a track day with a VW club, you’ll find the TDIs do well - lots of torque throughout the rev range means less shifting and more oomph out of the corners. Turbo lag is non-existant at any rpm above idle. Great fun.

Anachronism, if you haven’t done so already, head over to TDIClub.com & read the appropriate forums there. It’s where all the TDI experts (and those of us who want to become experts) hang out. Having had an Audi A3 TDI (basically an upscale version of the Jetta SportsWagen) for about 7 months now, I can take a stab at some of the VW/Audi-specific questions.

I can’t address the cold starting questions directly – I live in Atlanta, and my car is garaged, so it’s never gotten below freezing. I’ve read at TDIClub that even without a block heater, a well-maintained TDI engine with properly winterized fuel can start at below-zero Fahrenheit temps without difficulty. The gas stations take care of winterizing the fuel for you, so that shouldn’t be a problem unless you’ve got some old fuel in the tank.

Block heaters are available and do work, I’m told; my A3 came with one standard, but I’ve never had to use it. Remote start may be a bit tricky, as VW/Audi have an immobilizer system that uses a chip in the key to allow the engine to start. If your key is with you when you try to trigger the remote start, that might be a problem. There’s probably a way to work around that, however.

My Audi has an electric auxiliary heater for the passenger compartment, as well as electrically-heated front seats. The former is presumably to account for the time it takes the engine to heat the coolant sufficiently for the conventional heater core to do its thing – whether it’s longer or shorter than the comparable time in a gasser, I don’t know.

As for the chips, I’ve seen that they can add substantial power to gasoline engines, so I have no reason to believe they wouldn’t, if done properly, have the same effect on TDI engines. However, these chips usually trade off power for emissions, so your car might fail its next smog check, assuming you have such things in your part of the world. Also, running at higher power may shorten the life of your engine – not a big problem with TDIs, as they’re built quite a bit stronger than gassers, in order to accommodate the higher compression of the diesel cycle. There are many accounts over at TDIClub of drivers racking up 300K+ miles on their TDIs, so I wouldn’t have too many worries about engine longevity.

Modern high-pressure systems start far more reliably than the older indirect- injection systems.

I’d be more concerned with VW’s mediocre reliability, honestly.

Starting with HDis is as simple as petrol. Mine just starts until -5°C when the glow plug light shows briefly.

They are more efficient and do take longer to warm up, however, mine is fitted with a supplementary heater in the cooling system so is warm within two miles.

I drive a 2003 Citroen Xsara Picasso, so not something you will have ever seen in the US, but it has a 2.0 litre HDi engine and it springs to life in any temperature I have ever experienced. I live in the UK so we don’t get down to negative F figures - the coldest I have seen here has been about -12C (10F) and at that temperature the glowplugs come on briefly, usually for about a second or so, and then the engine starts as normal. It is a high pressure common rail engine (Peugeot and Citroen’s branding for this is HDi) so I would expect that.

In cruise (55mph, flat road) I can get 80mpg out of it, but my real world average across all driving styles is 50mpg (including urban traffic) - the other posters are right. Horsepower really doesn’t mean anything for a diesel; your heavy lifting is all in the torque and the power band. My Xsara has only 92 bhp, but it will haul minivan-sized loads at 80mph without breaking sweat, and get 50mpg while doing it. She is a little slow off the line, but she was built for economy, not speed!

VW’s TDi engines tend to be tuned more for a gasoline-feel though - the 150 bhp 2 litre TDi on the Touran (same engine that is in the Jetta and Golf) is a portable rocketship. Get it in the turbo band and it takes off. It also gets a very respectable 50mpg. My father drives one and loves it, and I have taken it out a few times myself.