Rear mounted turbos

[Stiff]

Can anyone explain this? I cannot understand the benefits of fitting turbos way back there? The car shown is an E60 BMW M5 (It was the best picture of the setup I could find).



I can only see it being incredibly laggy and whistley? That's a lot of tube to keep pressure up in.

[matrix MG]

maybe that's the whole point, for the turbo whistle. you know how chavs are, doesn't matter how it actually goes as long as it looks and sounds the part.

[p_b82]

a turbo acts as an excellent silencer, so it will not sound all that different...

the main reason it is done, is because there is just not the space for a turbo setup under the bonnet....

with an engine to drive enough exhuast gas through two seperate chanels like that the lag will not actually be as bad as you think....they may even be the 3rd or 4th turbo in the system....

I seriously considered it for my derv, but the cost was prohibative - tho with hindsight could have saved me money from my HG rebuilds!

[1955diesel]

I worked on turbo installation for Ford and the rule was that the turbo should be positioned as close to the engine as possible. Any link pipes required from manifold to turbo were double skinned and insulated.

The turbo uses exhaust energy (heat and pressure) to pump the inlet air. The further away from the engine you get, the more of that energy will have already been dissipated in its journey down the pipes.

With the turbos mounted at the rear, I would think that a scavenge pump would be required to clear the oil, but the main problems of heat and packaging would be greatly simplified.

[rpaterson]

There was something in Practical Performance Car (?) aaaaages ago where someone had fitted the turbo from a diesel to the rear of their Pug 205.

I didn't buy it, I was just in ASDA wiaitng for the chickens to come off the rotisserie thing.

[Stiff]

Originally Posted by 1955diesel

The turbo uses exhaust energy (heat and pressure) to pump the inlet air. The further away from the engine you get, the more of that energy will have already been dissipated in its journey down the pipes.

This was our thought. That's a lot of compressed air that needs to be managed and kept up to pressure!

Originally Posted by 1955diesel

With the turbos mounted at the rear, I would think that a scavenge pump would be required to clear the oil, but the main problems of heat and packaging would be greatly simplified.

I saw one site that said because the turbo is away from the engine it doesn't need an oil supply.

[Road_Rally_Rob]

Originally Posted by rpaterson

There was something in Practical Performance Car (?) aaaaages ago where someone had fitted the turbo from a diesel to the rear of their Pug 205.

I didn't buy it, I was just in ASDA wiaitng for the chickens to come off the rotisserie thing.

Yeah, it was balance motorsport if i remember right.

One of the benefits was said to be the extra cooling of it being mounted under the car.

They did explain all of the theories, but it was some time ago and other useless info has replaced that now.

As already said, it can be done as there is no space left in the engine bay. But there is so much lost in pressure and exhaust speed to spool up the turbo, and then there must be lots of forced induction pressure lost on the return trip to the engine.

It all works fine until you go over a bump / rock and rip off the oil feed....

[E_T_V]

Rear mounted turbos are only really worth considering as a last resort (unless you have a rear or mid mounted engine of course!).

Turbos to be efficient need hot exhaust gas. Between the engine and a rear mounted turbo you could easily lose a couple of hundred degrees C. This will make the turbo a lot less efficient and therefore give less gains than it would have done mounted to the engine in a close configuration as is normally the case.

[Roverdose]

could use a vnt though! dont normally work on petrol cars as the exhaust gas is too hot!

Drew

[phoenix3dfx225]

The lack of heat to have efficent turbos is still better than running with two less turbos. its a great idea and also remember reading it in PPC magazine. The big issue with adding turbos is space under the bonnet, this is a great work around. As for lag, ive ran an intercooler at the front of the car on a rear engined motor and the amount of air a car can shift is massive so it doesnt really cause a delay.

So whos going to be first to do it on a mg or rover?

[E_T_V]

No-one as there is plenty of room in there for a proper mounted turbo.

[Russ220]

wait til the p i k e y s realise the turbo is mounted there! if they're willing to steal the Catalyst, those two turbos must be easier money

[E_T_V]

Not easier money no. Cats can be weighed in. Turbos aren't and they'd need to make the effort to sell them to someone which isn't quite as easy.

Also as turbos have a serial number they are easier to trace and so carry a higher risk.