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| Turbo How To E-Book Guides $7.95 Each - Learn how to turbo your car. Download PDF E-Book after purchasing. |

This informative EBook guide teaches you everything that you need to know about building your own turbo kit. It covers the hot and cold sides, turbo sizing, wastegates, BOVs, tuning and more. (57 pages, lots of photos and diagrams) Only $7.95 Download after purchase.
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After reading this guide, you will be able to build your own LS1 (LSx) turbo kit. The guide covers all aspects of turbo charging the LS1 including heads, manifolds, cams, pistons, truck headers, tuning and more. (62 pages, lots of photos and diagrams) $7.95 Download after purchase.
|  FBody Rear Turbo Guide Learn how to build your own rear mount turbo. This guide teaches you everything that you need to know about rear mount turbos. Covers the GM FBody, but there is a lot of good information that can be used on any car or truck. (42 pages, lots of photos and diagrams) $7.95 Download after purchase.
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Learn how to build a turbo system for your 5.0 Mustang. You will learn about the correct turbo(s) to use, how to route tubing, engine internals (pistons, cams, crank), headers, manifolds, tuning and much more. (56 pages with lots of photos and diagrams) $7.95 Download after purchase. |
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Turbocharger Area Ratio
A/R
The other consideration is the A/R. It determines when the turbine starts to
spool. The turbine housing A/R is the cross sectional area of the turbine
housing divided by the distance from the center of that cross section to the
center of the wheel. This makes sense if you look at the graphic.

If you take for example, the area in A1 and divide it by R1, you will have
found the A/R for this turbine housing. Each cross section and radius have the
same proportions so the A/R will be found by using any cross section/radius.
Common turbine housing A/R's are .58, .69, .81, .84, .96 and 1.00. The turbine
will start to spool sooner with a .58 A/R, and later with a 1.00 A/R. Lag will
be a problem if the A/R is too large, but if it's too small, the turbo will run
out of steam and be nothing more than a restriction.
Trim
Trim for a compressor or turbine wheel is the squared ratio of the smaller
diameter divided by the larger diameter, multiplied by 100. Turbocharger wheels
have a large and small diameter. On the compressor, the small diameter is the
inducer and the large diameter is the exducer. This is the reverse for the
turbine wheel.
Compressor trim = inducer2 x 100
exducer2
Turbine trim = exducer2 x 100
inducer2
For
compressor wheels, given a constant exducer size, the larger the trim, the
better the wheel flows. It also means the wheel has slightly lower efficiency.
For turbine wheels, given a constant inducer, a larger trim means the turbine
has better flow with less back pressure. It also means that less energy is
recovered from the engine's exhaust slowing spool time.
Remote
Turbocharging Considerations
Special
considerations in A/R need to be taken into account for remote mount turbo
systems. Since heat, acoustic pulses and
exhaust gas pressure supply the energy to spin the turbine, and these pressures
are reduced as the distance increases from the source, adjustments in A/R need
to be made.
Keeping the
turbine A/R at .84 or smaller will keep the turbine spool time to a
minimum. Anything larger than that will
not spool quickly, and the infamous turbo-lag will be very apparent.
Garrett
offers ball-bearing cartridges that help keep friction to a minimum. This helps the turbo to spool much
quicker. These turbos tend to be a bit
pricey, but may be worth it if you are not on a budget. Look at the Garrett GT series with the ball
bearing cartridge.
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