TURBO8

iTrader: (9)

I was just wondering how hot the exhaust side of the turbine gets front mount vs rear mount. I am sure it is alot hoter on the front mount. Has any body tested the temps after a hard pull on there set up, front or rear mount?

Mort

This is what STS says:
"Approximately 500F lower turbo temperatures. Eliminates the need for a turbo-timer, which allows the engine to run after the car is shut off in order to cool down the turbo and prevent oil and bearing damage."

"Don't turbos have to be really hot to work properly?
Putting a torch to your turbo and getting it hot doesn't produce boost. What produces boost is airflow across the turbine which causes the turbine to spin. If turbochargers required very high temperatures to produce boost, Diesel trucks and Methanol Race cars wouldn't be able to run turbos. However, each of these "Low Exhaust Temperature" vehicles work very well with turbochargers when, like any turbo application, the turbocharger is sized correctly.

In a conventional, exhaust manifold mounted turbocharger system, the extra heat causes the air molecules to separate and the gas becomes "thinner" because of the extra space between the molecules. This extra space increases the volume of air but doesn't increase the mass of the air. Because the volume is higher, the velocity of the gas has to be higher to get it out in the same amount of time.

By mounting the turbo further downstream, the gasses do lose heat energy and velocity, however, there is just as much mass (the amount of air) coming out of the tailpipe as there is coming out of the heads. So you are driving the turbine with a "denser" gas charge. The same number of molecules per second are striking the turbine and flowing across the turbine at 1200F as there is at 1700F.

Front mounted turbos typically run an A/R ratio turbine housing about 2 sizes larger because the velocity is already in the gasses and the volume is so big that the turbine housing must be larger to not cause a major restriction in the exhaust system which would cause more backpressure. With the remote mounted turbo, the gasses have condensed and the volume is less, so a smaller A/R ratio turbine housing can be used which increases the velocity of the gasses while not causing any extra backpressure because the gas volume is smaller and denser.

Sizing is everything with turbos. There is more to sizing a turbo for an application than cubic inches, Volumetric Efficiency, and RPM ranges. A turbo must also be sized for the exhaust temperatures. A turbine housing sized for 1700F gasses would have lag if the gasses were 1200F. This is why turbo cars have lag when they are cold and not warmed up yet. Both systems work well if sized correctly."

So the front mount turbo will be about 1700*F and the rear mount about 1200*F.

TchargedLS1TA

iTrader: (9)

At 1600*F, you start changing the characteristics of the metal inside the turbo- i.e. things start to melt. You probably wont melt anything right away, but your starting to.. When I had my TTi kit, my EGTs were 1500*F at worst (with a 10.9:1 afr). If you start getting hotter than that, you've got to worry about other things, like melting pistons..

TURBO8

iTrader: (9)

Man, you really broke it down. That was way more info than I was expecting.. Thanks

03sierraslt

iTrader: (22)

Well Put man....

MikeGyver

iTrader: (5)

Was the temperature that high because of fuel burning in the exhaust, or was it that high just because?

TchargedLS1TA

iTrader: (9)

It was that high because of how lean I was running.. EGTs are another way to tell what you AFR is. Too lean= Hot, Too Rich= Cold