Cool down required?

[joema]

Do any of the commonly-used e46 superchargers (AA, ASA, VF, etc) require a cool down period -- idling the engine a minute after hard use?

What about after average (non-hard) use? What is the common practice?

[faded67]

Do any of the commonly-used e46 superchargers (AA, ASA, VF, etc) require a cool down period -- idling the engine a minute after hard use?

What about after average (non-hard) use? What is the common practice?

I'm not sure of the others, but the ASA's are clutched and don't spin when at idle.

[joema]

If clutched (non-spinning) does that stop oil flow to the compressor? The issue is high heat build up in the compressor causing oil "coking" if engine is immediately shut down after hard use. That's why "turbo timers" are often used on turbocharged engines -- to idle the car for a preset period after key removal, which keeps oil flowing to the turbo and allows cool down before engine stop.

A centrifugal supercharger is essentially a mechanically-driver turbocharger, and would seem to have the same problem.

Is there any manufacturer feedback on this? Does anybody use a cool down period for their supercharged e46s?

[russ330]

Interesting question, I've thought about this myself from time to time.

[Dirtboy]

A centrifugal supercharger is essentially a mechanically-driver turbocharger, and would seem to have the same problem.



Except that with a belt driven supercharger, there isn't any heat from exhaust like on a turbo...

I think that a supercharger would have less heat issues than a turbo, so you may not need to cool down as much as a turbo... :dunno:

[redronin]

^^^ good point

i dont believe any of the centri chargers use a cool down period, i imagine they are ALL clutched.

[crovax]

hrmmm i wonder if the vortec blower VF uses is clutched.

[joema]

I think only ASA is clutched. However I don't think the clutch hugely affects the heat issue. The heat comes from the heat of adiabatic compression, plus possibly some bearing heat. The compression heat is highest at high rpm, so hard use at high rpm generates much more heat. That makes the entire assembly very hot, especially internally. An immediate shut down stops oil flow. On a turbo the trapped heat can fry the oil, turning it to sludge.

True there's less heat than a turbo, so maybe that's the difference.

I guess if it was an issue the mfgs would provide warnings, just curious what other people did.

[Juha 323Ci]

I think only ASA is clutched. However I don't think the clutch hugely affects the heat issue. The heat comes from the heat of adiabatic compression, plus possibly some bearing heat. The compression heat is highest at high rpm, so hard use at high rpm generates much more heat. That makes the entire assembly very hot, especially internally. An immediate shut down stops oil flow. On a turbo the trapped heat can fry the oil, turning it to sludge.

True there's less heat than a turbo, so maybe that's the difference.

I guess if it was an issue the mfgs would provide warnings, just curious what other people did.

Very valid points!
A turbo will easily heat up to temperatures in excess of 600-700 fahrenheit and even higher whereas the supercharger will never get anywhere close to those temperatures. (You can easily touch a supercharger after hard driving and not burn your hands.)
One thing about turbos is also that the very high temperatures make the impeller axle "soft" and suddenly stopping it down without cooling it properly may bend it...

The fact that ASA blowers are clutched also proves that no coolinf down is needed as the oil will not circulate when the blower is not spinning.

[Ervin87]

I agree.
On my 337, just warming the car up for 2 minutes in the morning gets the turbo HOT. I always slow down 5 min before I reach home for the turbo to cool down and let it idle for a min or so and then turn off the engine. I need a turbo timer lol.

[zolti@technik]

To clarify some things...

1) There is <u>always</u> oil moving through the compressor, whether at idle (clutched) or on-throttle. This is because the compressor shares the oil supply with the engine, which is pressurized.

2) While a turbo-timer is helpful, it isn't as critical as when used in a turbo application. A good rule of thumb with an SC is to simply let it cooldown for 30-60 seconds by a) idling the car before shutdown or b) doing a low-RPM cooldown "lap" before parking the vehicle. This is only necessary when coming off a hard/extended run.

[Juha 323Ci]

To clarify some things...

1) There is <u>always</u> oil moving through the compressor, whether at idle (clutched) or on-throttle. This is because the compressor shares the oil supply with the engine, which is pressurized.



Oops, that's correct. I didn't even remember that, even though I've once owned a ASA blown E46... slap me for that...lol!

[Jojo@DPE]

To clarify some things...

1) There is <u>always</u> oil moving through the compressor, whether at idle (clutched) or on-throttle. This is because the compressor shares the oil supply with the engine, which is pressurized.

2) While a turbo-timer is helpful, it isn't as critical as when used in a turbo application. A good rule of thumb with an SC is to simply let it cooldown for 30-60 seconds by a) idling the car before shutdown or b) doing a low-RPM cooldown "lap" before parking the vehicle. This is only necessary when coming off a hard/extended run.



sorry to go off topic, but welcome aboard zolti! :bow: