New to Turbo's

[Dougmac]

I have just got my first turbo powered Rover 620. At what speed or reves does the turbo cut in, and is there any indication that it has??

[KebabMeister]

A turbo is powered by exhaust gases leaving the engine which power a turbine.  The turbine is connected to an Impellor which then sucks in air and 'rams' it into the engine.  This means that more air, and thus more fuel, can be drawn into the engine and burnt = more power.

Anyway, this means that the higher the engine revs go the more then turbine spins.  However it isn't quite as simple as there are a few other factors involved that I won't go into just now.  You would notice, and hear, a turbo cutting in at around 2,000 RPM on a 620 (is it a Ti or a diesel?).  The more acceleration you give you'll notice more noticeable reaction from the turbo charger.

Please note that because the turbo is always spinning (up to 150,000 RPM) let the engine idle for up to 30 - 45 seconds before switching the engine off.  This is because if you switch the engine off there will be no oil pressure and the turbo will continue to spin 'dry', or in other words without oil = premature wear and could cause the turbo to fail.

[KebabMeister]

Doh, replace impellor with 'compressor' (the turbine exhaust bit is the impellor whereas the other end of the shaft is the compressor). 

[Dougmac]

KebabMeister,

Thank you for the explaination. I can't say I have noticed any difference in noise or acceleration, Could that mean the turbo is not working, and is there anyway to test this. By the way it is a 620ti on an M reg 140000 miles on the clock. Any Ideas please.

[tigga]

I believe you would surely notice the turbo working if it was, especially if you are new to them - i had the larger (and heavier) 820 vitesse tubo and it went like sh** off a chrome shovel so yours should be quicker again.

[Dougmac]

tigga,

Thanks. I have not noticed any difference from my 620sli so assume there must be a problem with the turbo.

[KebabMeister]

620Ti and 820 Vitesse Turbo had the same engine (late spec), though I think the 620 had traction control.  I preferred the 827 Vitesse, V6 normally aspirated.

[jake-the-peg]

You may not hear the turbo if you're not attuned to listening for them and the insulation's good.

What happens when you put your foot down from a standing start?

Most turbos have a slow start for a second or two (bit scary at roundabouts) which is the turbo lag, and then shoot off as enough exhaust gasses start to spin the turbo.