i know you're suppose to let the car idle for a little bit before turning it off so the turbo can be cooled. i let it idle for a minute and turn it off, the turbos are still spinning for another few minutes. is this normal?

 

Perhaps you are hearing the electric fans spinning and not the turbos?

 

perhaps u are right (don't know much about fds and turbos). something was spinning for several minutes.

 

Correct, the turbos stop spinning all together about 20 secs after you shut off the car. and they are spinning soooooo slow at idle what does it matter right? just look in the engine bay after you shut the car off.

Nick

 

I am going to agree, the fans are still spinning. The turbos at idle do not make enough noise to the point where you can really hear them well. I don't even hear mine until I get on the boost and I have an open intake.

 

thanks guys, sounds right. the sound i was hearing was more of a fan sound. man, i have a lot to learn...

 

We all need/have learned what we know... just never act like you know something you don't and the members of the RX7Club.com community will help you threw anything. Welcome to the club!

Nick

 

Turbos, when they're going full blast, spin at an extremely high rate of speed. I forget how high they go on the FD, but it's something on the order of 100,000 RPMS or higher. So, if you've had your engine going at high revs shortly before you're ready to turn it off, those turbos are still spinning down. It takes a while to come down from 100,000+ RPM. If the turbos are still spinning at a high rate of speed when you turn your engine off, the spinning can generate heat and end up turning the oil in the bearings into a hard substance known as coke. This can ruin your turbo bearings. It's always wise to let the engine idle for a minute or two before turning it off. Hope you're enjoying your car.

 

I for awhile I wondered how fast some turbos really get going and I heard on most lambo's (cars with high end turbos) they get over (doc. Evil voice) 1 MILLON RPM'S. pretty crazy huh? concidering anything over 1000 rpms to the human eye is just a blurr.

Nick

 

Only partially true. Yes the turbos do spin on the order of 100,000rpm. No they don't spin that fast for long if the throttle isn't open. Think about it, they don't have much mass and they are pumps, if they have no input power (lot of hot exhaust) then they aren't going to have any output power. Shut the throttle and the turbos back down from the 100K rpm nearly instantly.

On shutdown the turbos won't spin for much more than 1 sec. 20 sec is WAY out of the range.

Doubt me? Start your car up with the airbox and inlet to the front turbo off and have a buddy shut it off, you can watch this whole thing happen.

Jeff

 

The FSM says the primary spins at 20,000-30,000 rpm @ idle (turbo idle ie No Boost ) and runs up to 100,000rpm prior to transition. The secondary overspeeds to aprox 140,000rpm during the PRESPOOL phase of the transition
ie it accelerates from 30krpm to 140krpm in about 0.5 sec!

 

I'll Chime in. a few years ago I managed a car stereo store. We took the intake pipe off a customers turbo diesel dodge truck (hee hee, customer dropped it off) and reved it. Wow that turbo got moving. Then we reved it up to redline (like 3000 RPM's) and shut it off. The turbo spun for more than 30 seconds. We only did it once because I was afraid something would fly into the turbo and that would be a little hard to explain to the customer. Even from idle the turbo spun for like 10 seconds. So it is very possible that a smaller turbo like on an FD could spin for a few seconds after shutdown. Hopefully you are not shutting it off after boosting!!