Subaru turbo

Getting a new car, seriously considering Subaru Forrester or Outback. Forrester has turbo version I really like, but my last experience with Turbo was my dad’s 199X Mazda RX7 which required you to – at the end of every trip – park the car and leave it in idle for 2 mins to avoid damaging the turbo. My friend had same issue with 199X Nissan 300ZX.

Has turbo technology improved? Or if I get this car can I expect years of sitting in an idling car to avoid killing the turbo?

Oh one more question – the Outback has CVT… so no gears, just continual variable transmissions… can you tell I know next to nothing about cars? Anyway, is that any good? If it is, why don’t most cars have it? If it isn’t, why are they using it here?

I never had an issue with the turbo on my Forester. Of course, if you’re in the habit of driving like a maniac, maybe waiting a few minutes before getting out of the car might be a good idea :smiley:

Yeahhhhhh… unless they’ve done some major modifications to those cars, they’re either misinformed and/or just want to call more attention to the fact that they’ve got turbo-ed cars. If you pull right off the freeway and immediately park, it’s a good idea to let the engine cool off for maybe 15-20 seconds, but with most actual driving scenarios no cool down is required (or, to put it another way, just turning onto your street and pulling into your driveway is usually all the cool down it needs).

Subarus are actually a rare situation where the turbo engine has proven to be more reliable than the non-turbo 4-cylinders, which have been plagued by head gasket problems (supposedly fixed now). It’s a pretty reliable motor, and I certainly wouldn’t hesitate to get a subie with one.

As for the CVT, try driving one. Some people really don’t like how they drive and would discount them simply for that reason. A lot of people are suspicious of them as well because Subaru’s introduction of the CVT in the Justy in the 1980’s didn’t go very well. But as far as I’ve heard, the modern batch of CVT’s have been pretty reliable. Of course, they may not be old enough yet to pass final judgment, so it really depends on what your threshold for early adopterhood is.

CVTs are a wonderful device that people tend not to like if they like driving. Basically they let the engine run at a constant speed which is most efficient, in terms of economy or power output, whilst altering the gear ratio to change the speed. This means that acceleration is very nearly linear, rather than the swell, dip, swell, dip of a standard gearbox, allowing for faster acceleration whilst being no less economical than the equivalent manual version.
Another major plus point is the removal of a lot of moving parts, interlocking gear teeth, synchro hubs, linkages to move everything around etc. There are (AFAIK) two broad types of CVT that are commonly used, the variable pulley style, and the toroidal style, although cone, ratcheting, and hydrostatic are among other types available.
It’s well worth checking the wiki page Continuously variable transmission - Wikipedia for more info, although note that in the disadvantages section it mentions that they are not as capable of handling torque as other transmission systems without a citation. If this were the case I think it fairly unlikely that Fendt, John Deere and JCB would have made them available in their most powerful tractors, it’s certainly not something to put you off buying a car fitted with one.
The major downside that puts off many drivers is that we are used to the engine revving up and down as we accelerate, it gives us a feeling of progress somehow as we go through the gears. With a CVT the engine just runs at the speed you set and the gear ratios alter to make the car’s speed change; lots of people find this offputting or just generally don’t like it, despite all the advantages of the system. You would have to try one and see if it suits you or not. In a tractor it is fantastic but I’ve never driven a CVT car so can’t give my opinion on that.
While I’m here I’ll second Jack’s point that unless you have been driving hard, running high boost pressure (and therefore temperature) then there is no need to let the car idle any longer than normal after coming to a halt.
What many people fail to understand is that even with a naturally aspirated engine, it is not advisable to switch off the engine immediately as you stop, especially if you’ve just come off a long hard jag, say, into a motorway service station for a break. It doesn’t need long, I normally give about 1/2 to 1 minute, but it just helps if the engine can have a little bit of a run down without going straight from high revs to slowing down to off. As soon as the key is turned back, the cooling system is no longer pumping and so the heat in the engine block can only dissipate through the block, which nowadays is not at all well ventilated in most cases.
Worth noting is that a drive down your road (if it takes 30 seconds or more) at low engine speeds is probably enough to bring the temps down enough, but if you are one of these drivers that races all the way home (or to your destination) then turns the ignition off, it’s probably not doing any good.

Great, thanks!!

PS forgot to mention, it was my dad’s Mazda, and he’s the kind of guy who buys a sports car and then drives 2 miles under the speed limit (and car was 100% stock, no mods at all). That particular RX7 he had was a total lemon, major problems all around, and no matter how much time he waited before turning it off, the turbo had major issues until he finally sold it in disgust.

My friend with the Nissan fared better, but he had a “turbo saver”… anytime he’d park the car and remove the key, get out, lock it, etc, the car would keep running for 2 mins and then turn itself off.

Which is why I started the thread in the first place. Paranoid due to previous experience. =)

Going off on a tangent, a helicopter like the Robinson R22 takes about five minutes to shut down. Per the checklist, set idle to 70% to 80% for approximately four minutes until the cylinder head temperature drops. After that you can close the throttle and disengage the clutch, and then you wait 30 seconds for the clutch to disengage. Pull the mixture to idle cut-off and then wait 30 seconds before applying the rotor brake. (Shut of the magnetos and master switch in the meantime.)

With a fixed-wing like a Cessna 172, you just go to your parking place and pull off the mixture and shut off the mags and master (after turning off the electrical items, of course). Similar to the last bit I quoted, the low-speed taxi from the runway to parking allows the engine sufficient time to cool.

Yeah I figure driving home in my neighborhood, easy for engine to cool there. Going to work, I’ll try the 30 sec thing as needed.

Speaking only for my STi, and getting a little more technical than the OP probably wants, the Coolant is routed in such a way that it flows downhill to the turbo when the motor is turned off. This coolant flashes to steam, allowing more coolant to flow down and cool the turbo. It’s a closed system and the coolant re-condenses.


Nothing to do with Subarus, but I recently took a supercharged Jaguar out on a racing circuit. We were told to leave the cars running when we came into the pits. I think it’s fair to say that we were pushing the cars just a little harder than six pack Joe on the daily commute :smiley:

I just wanted to share this image. I think this guy needs to idle for a while.

CVT boxes are less efficient than manual gearboxes, because the mechanical losses are higher. For the same reason, performance is compromised to some degree.

In my car, the 0-60 time is 9.3 sec for the manual and 11.1 for the CVT, while the fuel economy is 34 mpg vs 33 mpg. I expect there are more efficient CVT boxes than that one out there, but I’ve never seen one where the figures match the manual. Looking at the CVT in the most recent Audi A4, the performance difference is negligable, but the fuel economy is 3 or 4 mpg less.

Not necessarily so, depending on the vintage of the car. Older turbos were oil only cooled devices and after running it particularly hard (which is entiely possible of owned by a lead foot), can generate quite a bit of heat. In those oil only situations, the oil could coke, eventually destroying the turbo’s bearings early.

My 89 RX-7’s turbo was water cooled (it was a near new feature then), but they still recommended some cooldown time…mostly because you couldn’t run synthetic oil in the rotary engine, and the temperatures involved were closer to the limits of non-synthetic. I had that turbo glowing dark cherry-red on more than one occasion.

My Subaru was owned by a racer before I purchased it and he swapped in a stock exhaust system before sale. He did not replace the heatshield for the turbo as that’s something the riceboys tend to remove/overlook/not worry about. After getting the system good and hot, a non-contact thermometer was showing a good 750 degrees F.

My point? There’s a LOT of heat generated there. If the factory service manual recommends some cool down time, you oughta cool it down some. Luckily for stock engines, there’s a much larger pool of used OEM turbos as a lot of the kiddies like to upgrade. What used to be a $3000 repair (to have a mechanic swap a turbo on my 89 RX-7) is now about $140 to swap the turbo myself with someone else’s take off part.

This is what I came in to say. Cooldown is less necessary on water-cooled turbos.

Also, the Forrester/Outback are not really sports cars and have smaller turbos that aren’t pushed as hard as those on the sporty RX7 / 300ZX.

Unless you have been doing a lot of hard acceleration before stopping, you shouldn’t need to worry about the turbo temperature at all. Driving at a constant speed (e.g., interstate) doesn’t engage the turbo much so you don’t need to worry about cooldown in that situation either.

I would only worry about it if you are into autocross or some other sort of amateur racing hobby.

I’ve noticed at least one of the turbos I’ve driven, an 80s SAAB–not mine, so I don’t know the specifics–had a something (fan? pump?) that ran automatically for some time after shutdown, a feature I’ve never noticed in a non-turbo. If I’m following this, such a set up would be a substitute for cooling in idle.

A long time ago, I owned a Mazda MX-6 GT, with a 2.2L intercooled turbo. On the way to a party I chased a guy in a '70’s era Porsche 911 up the hill to Big Bear Lake in California as the sun was setting. When I arrived at the cabin I got out of the car, opened the hood and was shocked to see the turbocharger glowing BRIGHT orange. That big chunk of cast iron and steel was producing visible light. Lots of BTUs there!

Allow for a cooldown period if you drive the car hard. Modern turbocharged cars are reliable and long lived. Having owned both supercharged and turbocharged cars, I learned that the tuning potential of turbos can’t be beat. There are some crazy fast Scoobies out there, and they are not all STi WRXs.

The newest direct injected, variable valve timing, turbocharged/ intercooled engines that BMW, Audi, and Ford are producing are potent and fuel efficient. Turbos are The Way.

I currently own one of everything (well, I don’t own a hybrid), but I’ve got a NA 383, a Supercharged LS1, a BB Caddy, and the Subie.

Turbos are a way. :wink: They all have pros and cons. Superchargers (at least the roots hybrid in my Magnuson) heat soak. Turbos get hot and lag. Normally Aspirated is an exercise in making the whole system flow air efficiently, and Big Blocks are FAR from fuel efficient…

…and Teslas have a tiny range, especially when driven hard.

I have a turbo Mazda, and the best advice I’ve heard it just to keep out out of turbo boost in the last few miles you drive. So that’s what I do.

Just get a Turbo Timer.

This is what your friend has - after removing the key, it will keep the engine running to give the turbo a chance to cool down.

After market timers are available, I would be surprised if it cost much more than a few hundred dollars to have one installed.

Doesn’t it depend on the TC design?
Wait… Strike that. It does, entirely. Turbo chargers are driven off of the gases from the exhaust manifold, so yah, they would heat up a lot in driving hard, and would need a cooldown if driven hard. Then again, newer ones should have better material sciences behind them, no?

Super-chargers are actually driven by the engine, and shouldn’t fall victim to the same thermal stresses as a rapid cooldown of a turbocharger does, but for the most part both normally fail in the compression pumps, don’t they?

I’m really out of my normal water here, so am looking for opinions.