Turbo lag sucks big time. I know it when I feel it. One onethousand...two onethousand....whoosh!!! Not very satisfying. Most times when you floor the throttle you need power NOW not in just a bit. My guess is that BMW/MINI have worked very hard to remove as much lag as possible. I'm waiting for a test drive before I pass judgment.

 

We just returned a leased 2003 Saab 9-3. Too late to look in the manual now, but I'm certain it didn't mention anything in there. The 9-3 did have a fan that would kick in about 1 minute after turn off and would run at high speed for 5 to 15 minutes.

 

it's a twin turbo six, and they said they felt NO lag. Other interesting tidbits: Common rail direct injection with a 2600 PSI line pressure, and peizo electric injectors pressed into the head. They run 10.2:1 compression and relatively lean, stratified charge, and have some funky new blade alloy smaller turbos and the reviewer loved it. So the technology is marching along, and turbo lag will be lessoned, if not eliminated. Rember, in our Ss, you don't really build good power until 3000+ RPM or so, so while there is direct drive of the SC, if you're in the wrong gear you're toast. Once the turbo'ed car is running at those RPMs the impellors will already have good speed, just need to feed them the air and it's off you go!

Too bad it's just south of $50k....

But the lag will always be worse with larger turbos used for max power, as the rotors have much more mass....... But for a good street car, lag has been severly reduced.

Matt

 

I agree with you Matt turbo's are improving. I also agree that the sweet spot starts around 3,000 on a Cooper S. The 15% pulley fattened the sweet spot up nicely. It seems that the trend of late has been smaller low pressure turbos. Great stuff is always just around the corner.

 

This makes me laugh.

Its not the thousands of rpms, but the thousands of degrees the turbo sees under a high load. Take the load off (let it idle, let off the gas) the exhaust temp decreases SIGNIFICANTLY. Lower temps = no cooked oil clogging the turbo's lines = increased longevity of your turbo, and your bearings/bushings.

When you turn off a turbo engine, the impeller slows very quickly. There is no longer any air moving through the engine to turn the compressor and there is no where for the boost charge to go. The charge wants to escape back the way it came in and there is nothing driving the compressor to keep it from doing so. When the engine stops, the oil stops, and since the turbo is still a thousand degrees (*depending on the load), it cooks the oil. * One could essentially drive "lighter," and cool the exhaust temps too.

The timer just allows the engine to idle for a preset amount of time after the ignition key is removed to allow the exhaust temp to come down to a safer level, basically, relieving the driver of "remembering every time." Timers may take into account peak boost levels, number of boosts, avg. speeds, and amount of time the engine was running to determine a safe idle down time.

Theres two custom turbo builds and one stock turbo in the family. I hear it every time we get together. And then again when I visit my diesel truck-pulling friends.

 

Interesting thread. After owning two turbo's -- Audi 1.8T (160k mi) and Audi 2.7T (118k mi) -- common sense in proper warm-up and cool down will take care of 99% of any concerns in turbo longevity. BTW - turbos would be extinct in mass production cars if they were that fragile (just my opinion).

 

Exactly.

Timers really become helpful when tuning has been done to the turbo and injectors.

Stock, it should last, atleast in theory, forever on todays motors.

 

Glad this makes you laugh, but it is no less accurate. I didn't make this up, it was shared by me by the mechanic who maintained my Turbo Esprit, and who current owns and maintains the X180R LotusSport Esprit race cars, and vintage races them. He also maintains a number of very high end sports cars, including turbo charged street and race cars.

Interestingly enough, when you sit there idling the engine temperature is NOT going down, at least not significantly, as you suggest. Why do car temps go up while you're idling at a light? Coolant is being pumped through the radiator more slowly. There is no air going through the intercooler. There is no air circulating through the engine compartment when at rest. Even though the rpms are lower at idle, it is not significantly lower to offset the reduced cooling capacity of nil air flow over the engine/turbo/manifold surfaces, or through the various cooling (radiator/intercooler) devices.

And you are incorrect re the spin down time needed. True, there is no air pushing the impellor, and you imply a braking effect from back pressure, but in most turbos the result is NOT a rapidly slowing impellor, sorry. The impellors are designed with advanced bearings and lubrication to spin with as low a friction as mechanically possible. Again, use some common sense. Turn off your box window fan from its highest speed and see how long it takes to wind down. It spins at a fraction of the rpm a turbo impellor does, it has far inferior lubrication and bearings, yet takes a measureable amount of time to spin down, EVEN though it would have greater resistance due to a exponentially larger swept area of it's blades versus those of a relatively smaller turbo impellor.

There is a very nominal effect, if any, in letting a car idle for 30 to 60 seconds in terms of cooling anything down. Again, your own observation and common sense will tell you this. Take the radiator cap off your car after letting it idle for 60 seconds, and see if it is significantly cooler. At your own risk.

You say the exhaust temp decreases significantly when the load is reduced, true. But that does nothing, in the brief idle times suggested, to reduce the stored heat in the oil and metail components of the engine, manifold, turbo, or impellor. Again, the fact is you're still adding heat.

The best are the systems with a separate, electric oil pump that does NOT rely on the engine still running, which is still adding heat. The separate pump on time will address both issues: Supply needed lubrication to a rapidly spinning impellor, which will spin for quite some time, and continue to circulate the oil helping its temperature drop somewhat, at least below the coking danger point.

So again, laugh all you want. You'll forgive me if I believe the word of someone who actually works on these things.

 

Make no mistake, I agree that heat is dangerous, I'm saying and still know that the idle time is not to reduce heat by simply letting things cool, but to avoid additional heat and damage to bearings by providing lubrication (and avoiding friction and therefore more heat) for a longer period of time to the impellor bearings. Spending more time on this than I should, laugh away...

From the Industrial Diesel Products website:"[FONT=Helvetica][SIZE=5]Oil Starvation Is The Largest Single Cause Of Turbocharger Failure & Premature Wear."[/SIZE][/FONT]

[FONT=Helvetica]And the following citations from that website.[/FONT]
[FONT=Helvetica][/FONT]
[FONT=Helvetica]If the turbo isn't given that cooling-off period, oil around the bearing stops flowing immediately after the engine is stopped. It vaporizes and forms abrasive deposits -- called "coking" -- that can result in failure of the close-tolerance turbo wheel. That exhaust-driven wheel driving a compressor, has to spin at 100,000-250,000 rpm to achieve the performance boost.[/FONT]
[FONT=Helvetica]Courtesy Wards Auto World[/FONT]
[FONT=Helvetica][/FONT]
[FONT=Helvetica]In the case of turbocharging, the problem is more the effect of the turbocharger turbine rotating at high speed for up to two minutes after the engine has been shut off. The problem here is twofold. First, at shutdown, the turbine spins in an unrenewed oil supply. Hot, and no longer under pressure, the oil is forced off the turbine bearings, leaving these closely machined tolerances to run in a diminishing oil film. In short order, the turbo bearings wear themselves out, the turbine no longer fits its housing properly, and things begin to deteriorate rapidly.[/FONT]
[FONT=Helvetica]Herein lies the reason most automotive manufacturers request that the engine be run at idle for two to three minutes before being shut down in an effort to help slow and cool the turbine and its bearings. The hidden enemy here is heat soaked oil, which develops a condition referred to as "coking." Basically, coking is the effect of the oil burning, not unlike burnt pudding; it forms a sticky film that is scorched to the surface. And, though small in total volume, this oil's lubricating qualities are destroyed; then it mixes with the engine's principal oil supply, slowly contaminating it, resulting in the destruction of the engine's lubrication protection.[/FONT]
[FONT=Helvetica]Courtesy Lubrication Research[/FONT]
[FONT=Helvetica][/FONT]
[FONT=Helvetica]Turbocharged engines should be idled for several minutes after starting and before shutdown to prevent "oil lag" failures to turbocharger bearings. This is particularly important during cold weather or when the equipment has not been in use for extended periods.[/FONT]
[FONT=Helvetica]Courtesy Arrow Engine Company[/FONT]
[FONT=Helvetica][/FONT]
[FONT=Helvetica]Causes of failure by type and corrective measures:[/FONT]
[FONT=Helvetica]A. Lack of lubrication and/or oil lag.[/FONT]
[FONT=Helvetica]1. This type of failure occurs when the oil pressure and flow is insufficient to:[/FONT]
[FONT=Helvetica]a. Lubricate the journal and thrust bearings.[/FONT]
[FONT=Helvetica]b. Stabilize the shaft and journal bearings.[/FONT]
[FONT=Helvetica]c. Reach bearings before unit is accelerated to high speeds.[/FONT]
[FONT=Helvetica]2. The turbocharger bearing's need for oil increases as the turbocharger speed and engine[/FONT]
[FONT=Helvetica]load increases. Insufficient oil to the turbocharger bearings for period as short as a few[/FONT]
[FONT=Helvetica]seconds during a heavy load cycle when shaft speed is high will cause bearing failure.[/FONT]
[FONT=Helvetica]Courtesy Betan Turbochargers Specialists[/FONT]
[FONT=Helvetica][/FONT]
[FONT=Helvetica]The most common failure of automotive turbos is due to hot shutdown. This occurs when the vehicle has been running at a constant speed for a period of time and the vehicle is shut off before the turbo has had time to slow down. A turbo can spin at speeds exceeding 100,000 rpm, the faster the vehicle goes or the harder it works, the faster the turbo will spin. If a vehicle is shutoff suddenly the turbo will continue to spin without oil. Each time this occurs, the life of the turbo is shortened because of wear occurring from no lubrication. Eventually there will be enough wear to allow one of the wheels on the turbo to contact its housing. This causes the wheel to be out of balance. This causes even more contact and the turbo is usually destroyed. [/FONT]
[FONT=Helvetica]Courtesy 01 Motors[/FONT]
[FONT=Helvetica][/FONT]
[FONT=Helvetica]Many turbocharger failures are due to oil supply problems. Heat soak after hot shutdown can cause the engine oil in the turbocharger and oil lines to "coke.''[/FONT]
[FONT=Helvetica]Courtesy Auto Zone[/FONT]
[FONT=Helvetica][/FONT]
[FONT=Helvetica][/FONT]

 

Note Bolded from your own research. Refer back to my post.

You should understand the differences in load at idle, and load under boost. At idle, a turbo makes zero boost, low rpms. It still spins, but not at the high rpms it does under a heavy load (boost). This is where exhaust temps are crucial. Under a heavy load, one can glow their header hot orange with heat (in extreme circumstances, just to show a point that load creates heat and excessive load creates excessive heat). If the car was immediatly shut down, problems will show, just as your research indicated. Heat and moving parts do not co-exist well, we all know that. Kindly, your research also indicates that letting the car "cool down" before shut off will help extend the life of the turbo. At idle, the exhaust temp is not going to be anywhere close to the heat it produces under load. A "couple" minutes of cool down lowers the temps and turbo rpms (I did't originally state turbo rpms would lower, assuming you realized that the turbo has already begun to slow, being off boost at idle) to a safer level for shut down, again, as your research indicates and as supported by my earlier post.

So once more, I laugh.

 

So, the basic gist of this whole thread is that a turbo timer is not needed, and that the electric water pump and a proper cooldown will do the trick. Am I right, or am I missing something?

 

The electric aux water pump is essentially a built-in turbo timer. After you drive the car, just shut down the car and walk away; no need for you to worry about it, the car does it all itself.

 

please realize you resurrected a 6 month dead thread. This stuff was posted before we knew anything about the new MINI. As Ryephile said, all the stuff in this thread is N/A to the new MINI's turbo.