ironhorse,

I believe I may be able to help you out here. Although I'm not a wiz when it comes to turbos and superchargers, I have had alot of exposure to jet engines. In principle they all operate the same way. Exhaust drives a compressor stage which accelerates air through a series of rotors and stators(stages) and compresses it. This air is then mixed with fuel and ingnited in a combustion chamber. The resuly is high velocity gasses escaping through an exhaust port which powers a turbine and the process is repeated. Well a supercharger or turbo charger is no different, well with the exception of the fact that unlike the jet engine the turbo itself is not the powerplant. What it does is it uses exhaust gasses to power a turbine which accelerates air and compresses it prior to it going into the engine. This air is relatively dense and when mixed with fuel and ignited, it produces more power. It also maintains a higher manifold pressure relative to a non turbocharged car at higher altitudes.

Now let me actually answer your question......

There needs to be a way to lubricate the shaft which connects the turbine with the compressor (all of these systems are essentially one moving part). This lubrication is thicker than what you would find in a typical motor oil, so for it to work properly, it needs to be warmed up so that its fluid properties can be maximized. Conversely, when shutting down, these systems require a cool down period. The reason for this is as you know, when you shut off an engine, it actually gets slightly hotter before it starts to cool down. Well, with the shaft no longer moving, the lubrication no longer "circulates" and sits in its current location. This lube can actually bake on to the shaft and form a hardened residue which can do a number of things to the performance of the unit. This hardening is called "coking". Hoepfully this answers your question. I tried to keep it short, but I failed miserably.

Dave

 

An uncle used to have a turbo LeBaron and he said the same thing about letting them cool down before shutting it off. I think his reasoning was in his mind it would cut down on the heat stress.

Sounds hoaky to me...

 

Bottom line.......If you are looking to prolong the life of the turbo, let the engine warm up to operating temperature before putting a "load" on the turbo (you will notice that you dont get a boost in manifold pressure unless the engine is under a load), and let the engine idle for a few minutes in neutral or park before shutting the engine down. This is the technique that is recommended.

Dave

 

They do sell oil rotating kits to eliminate that problem.

 

True Bismarck,

But that would have been the simple one sentince answer to his question. And that would have been WAY too easy /emoticons/emotion-1.gif.

Dave

 

It's called a Turbo Timer..i have a friend that had a Calloway turboed Rabbit that had one....when you shut the car off and take the key out the motor continued to idle for a specified amount of time letting it cool down. I think it was a Blitz or a Greedy turbo timer.

 

Turning off the engine before its cooled down after a hard thrash means you suddenly cut the oil flow to the turbo when its really hot and this ultimately will cause an untimely demise of the turbo. I guess the reverse applies to warm up. Those things spin at like 100,000rpm or something mad. I think these days that the turbos are more robust with things like fans that carry on once the engine has switched off. I am on my third turbo car, with the first one I did the really excessive warm up and cool down, I've since got bored with it and just switch off straight away: it hasn't blown up yet and I've done 130k miles so far!

 

oly,

They spin at about 25000RPM at most. The turbo chargers on my SUV have liquid cooling and also an electric pump that keeps the coolant rotating until the temp sensor sends a signal that its OK. But also keep in mind the synthetic oils these days help a looooot. The unit uses engine's coolant and engine oil. They have come a long way. With synthetic, you really do not run into those situations anymore that you had organic oils. I rarely ever see the oil pump work for more than just a little bit.

 

Another approach was to allow the liquid coolant and oil to drain back through the turbo unit thus ensuring cooling and lubrication during spindown. I think Chrysler was doing this in some of their 4cyl turbo fwd cars(I think the 'Charger' and maybe the 'Omni'). Of course not much of this applies for the air cooled Warrior. I would think by now with the advances in metalurgy and lubricants(like Bismarck says) that most of these issues would be addressed.

 

quote:Originally posted by WolfLand

.... I would think by now with the advances in metalurgy and lubricants(like Bismarck says) that most of these issues would be addressed.

Yes and no. If you have a turbo timer you don't have to worry about it at all. If the last few minutes of driving are at low sppeds/rpms you can safely shu it down. If you have been driving hard right up to the time you stop you should let it idle for a while to cool it down. Even with synthetic oil bad nasty things can happen if the turbo isn't properly cooled.

 

I'm getting the feeling that many of us have 'top tips to look after your turbo' that are out of date and not really worth worrying about these days (unless you have an old turbo). I suppose the other important thing is that the price of turbos has significantly dropped in the last 10 years, so who cares!

 

I know that alot of companies also offer essentially "disposable" turbos. When the Buick Regal Grand National was a big draw in the mid- to late 80's, their turbo would "die" all the time (well the fact that the car just begged to be savaged). They were only a few hundered dollars to replace.

 

We are probably looking at a steep price for the turbo for the warrior, so I want to be able to drive and stop drive and stop whenever I want without having to worry about my expensive turbo dieing.

PR can this be done with your system?

OE when will you announce yours?

Check back in tomorrow.

Mike

 

Rob in another thread you were saying that the turbo is more streetable than the supercharger. When I looked at the dynos I saw a steeper increase in boost with the turbo and a more gradual increase with the supercharger.

Is a quick boost of power and then steady delivery of increased power the reason for superior streetability?

Or could a more gentle supercharger power curve with high end power be a better ride?

These are my guesses. Could you explain why you believe that turbos are more streetable than superchargers?

Thanks

Mike

 

ironhorse, it would be a good idea to let it warm up, and cool down. It will increase the life of the turbo unit by doing this. Basically, I usually start my bike up, then put on my gear. When I reach home, I usually let it idle while I'm taking off my gear. I know that doesn't sound like a lot of time, but it's much better than shutting it down and rolling into the garage.

 

I don't know about the turbo on the PR kit but I used an Aerodyne turbo on my Harley. It had its own lubrication system. The turbo ran roller bearings and had a wick lubrication system with a special synhtetic lube. After 5 years I never had a problem with the turbo. I would fire it up and start driving. I would let the engine warm up before I got on it hard simply because it would run a little lean and if it did the lean backfire through the intake it would blow out the diaphram in the Kein CV carb. There was no reason to let it idle before shutdown because there was no pressurized lubrication system. Idling would just make everything very hot. As a side note the turbos do approach and sometimes exceed 100,000 rpm, it is not uncommon on todays turbos.

 

If you just shut off after the turbo has been spinning at XXXXXXrpm the lubrication is usually cut at the same time and that thing is **** hot, this will reduce the turbos life but with modern turbos you are probably reducing life from 10 years to 8 years which doesn't really matter.

 

xharley had a similar turbo kit. We have the same type of turbo system on some of our Harley motors, the only problem those guys tend to have is going through back tires. That's what happens when you can lay a 250 wide tire mark about 50 yards long.

 

On My Busa all i do start my bike , then put on my helmet and gear and take easy out the lane till the temp gauge clicks a notch or two. Shut down i just let it idle a bit , thats all it take, and so far on my old Busa i have 15 thousand miles with no turbo problems,

 

Thats the sort of careful treatment that will extend the life quite nicely.

 

I would always go the conservative route when it comes to engines. Truth be told, it can only help the engine by letting it warm up before riding and letting it cool for a few minutes before shutting it off. At least with jet engines, you actually have to idle them for two to five minutes before shutting them down due to heat. I know there is a big difference between a jet engine and a turbo, but like I said earlier the concept is exactly the same.

Dave