[Amc-list] Rear mount turbos

[David Crooks <david.crooks@xxxxxxxxxxxx>]

>> ...but as the exhaust cools it looses velocity. The farther the turbo the
>> cooler/slower the exhaust right??


> the energy drops of really fast. The energy is in the heat that 
> makes the gas expand. 

A rear mount turbo can be made to work, but you've both hit the nail on the 
head.  The whole point of a turbo is to extract some of the wasted energy 
in the exhaust and make it do some useful work (by pressurizing the intake
air).  When the exhaust has cooled, it's lost a lot of it's useful energy.

A rear mount turbo is kind of like an old water wheel mill, you can't deny 
that it works, but the turbines at the base of the Hoover dam are much better
at producing power!  Yes the engineering challenges are greater, but the end
result is worth it.  

To work best, a rear mount turbo would have completely different turbine 
designs than a front mount type, to allow for the slower, and less 
energetic exhaust flow.  Simply bolting a normal front mount turbo to 
the end of your exhaust will have very poor efficiency.  I'm assuming
that the folks selling these kits have done their homework and are
sizing the turbines as best they can, given that the majority of "off
the shelf" components will be sub-optimal for their purpose.

The other problem that I see with a rear mount system, is the long lag
time that it will suffer, trying to pressurize the intake system volume.
Front mount systems all have some degree of lag, and with a rear mount,
you're adding 10+ feet of 2-3 inch piping volume into the equation.
That's a lot of volume to pressurize, and I suspect that these 
systems suffer a lot of lag....

of course, your mileage may vary!
Dave 

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