D Car — July 2004
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About this issue
246 available scans from D Car — July 2004, in right-to-left reading order. Japanese OCR and English translation drafts are available throughout. Drafts have not received exhaustive image proofreading; unreadable source remains recorded in the archival data.
Page 179 — English draft translation
Intake and exhaust systems Exhaust gas spins the turbine, so this is important: if exhaust flows more smoothly, the turbine can spin faster. Simply replacing the muffler with a more efficient one can increase power. Exhaust efficiency matters for naturally aspirated cars, too, but the effect is greater on a turbo because the turbine is involved. The intake side works the same way: better-flowing parts help the turbine work more smoothly.
Computer The finishing touch for a tune is the computer! The final step is the ECU, which mainly adjusts fuel mixture and ignition timing. This applies to naturally aspirated and turbo engines alike. An engine runs poorly if the mixture is too rich or too lean. A stock setup is fine as-is, but replacing the air cleaner or muffler changes the air/fuel ratio. The ECU is changed so the tuned engine can run at the correct ratio.
Captions and page details
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Now that you have a rough idea of what a turbo does, let’s look at its detailed construction. A turbo cannot do the job by itself; it relies on supporting components, too.
Controls actuator pressure
Compresses the air
A turbo is made up of three main parts. Look at the cutaway photo: the central section is the center housing, which supports the turbine with bearings. The round housing on the left is the exhaust housing; exhaust gas passes through it and spins the turbine. Opposite it is the compressor housing, which compresses the air.
From right to left: compressor housing, center housing, and exhaust housing. The turbine rotates inside.
…housing
…spins at high speed.
Compressor…
This is the HKS GT-SS turbo, recommended for its turbine size, which suits cars in the Silvia class.
This is the T04Z, a larger “big-turbine” model. It moves more air and can make more power…
Comfortable…
Most ordinary turbos have this part. When pressure gets too high, a valve opens and pulls a rod, opening a flap in the exhaust housing to release pressure.
The basic principle is the same as the actuator, but this device can control higher pressure. It is installed in a different place—on top of the exhaust manifold—so a dedicated manifold is required.
Actuator
Releases excess exhaust gas to control boost pressure The actuator opens when the turbo’s boost gets too high, bleeding off gas until pressure returns to a suitable level.
Conversely, making it harder to open keeps pressure from escaping and raises boost. That is important. A wastegate is a reinforced version; it is separate from the turbine and branches off the exhaust manifold.
SPF
A low-restriction muffler improves exhaust flow, and the turbine spins faster in proportion. It keeps turning faster and faster…
Intercooler Cools the hot air compressed by the turbo An intercooler does not cool the engine or the turbo itself. It cools the air compressed by the turbo. Why? Pressure raises a substance’s temperature. Compressed air gets very hot, so it is cooled. Cooler air packs more efficiently, allowing more air into the engine—and more power!
An intercooler is fitted to almost every turbo car. Compression heats the air…
One ECU fully replaces stock control; another keeps the stock ECU and adds control over selected adjustments…
…controller.
Air does not flow down the center of a pipe; it tends to follow the walls. That is why a stock corrugated intake pipe creates significant resistance. Replacing it along with the air cleaner is effective…
…is significant.
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