Forum threads throw around EA837, CREC, hot-V, ET45 and "just do the valley" like everyone was born knowing them. This Audi performance parts glossary translates the jargon into plain English so you can shop, ask questions and talk to your shop without nodding along. Every definition is written for real Audi owners on B8, B8.5, B9, C7, C8, D5 and 4M platforms, and where it helps we link the part or guide that goes deeper. Start with the one term every supercharged 3.0T owner eventually meets: the OE Ultimate under supercharger kit for B8.5 and C7 3.0T.
How to Use This Audi Performance Parts Glossary
Most fitment questions come down to two codes: the platform (chassis generation, like B8.5 or C7) and the engine code (like EA837). Get both right and half of your shopping headaches disappear. For the big-picture build order, pair this page with our Audi performance upgrades guide and the Audi S4 mods roadmap. Here is how the three engine families we focus on compare:
| Engine code | Layout and boost | Where you find it | Common upgrades |
|---|---|---|---|
| EA837 3.0T (incl. Gen 2 CREC) | V6, Eaton R1320 supercharger with air-to-water intercoolers in the valley | B8/B8.5 S4, S5, Q5, SQ5; C6 and C7 A6, A7; 4L and 4M Q7 | Pulleys, ported supercharger, under supercharger kit, heat exchanger, headers, high flow cats |
| EA839 3.0T | V6, single turbo inside the V (hot-V) | B9/B9.5 S4, S5, SQ5 | Ignition coils, 4 bar MAP sensors, tuning |
| EA825 4.0T | V8, twin turbos inside the V (hot-V) | C8 RS6, RS7; 4M SQ7, SQ8, RSQ8; D5 A8, S8 | High-flow catted or catless downpipes, tuning |
Not sure which you have? Check the engine code on the sticker in your service book or spare tire well, or send us your VIN and we will confirm before you order a B8.5 and C7 under supercharger kit or anything else.
Shop the OE Ultimate Under Supercharger Kit, $649.99
✅ OE-supplier Graf, Hengst and Elring parts plus billet upgrades ✅ Fitment help from real 3.0T and 4.0T owners ✅ Fast US shipping
A to B: Aluminum to Bolt Pattern
6061 Aluminum
A heat-treatable aluminum alloy with a great strength-to-weight ratio. Most forged wheels, including our forged VF-01 rotor-style wheels, start as a 6061 billet before forging and machining.
AFLAS
A fluoroelastomer seal material that shrugs off heat, coolant and oil far better than basic rubber. It is why our TruSeal AFLAS coolant gasket upgrade outlasts the O-rings that weep on so many 3.0T thermostats.
Audi Tax
Our affectionate name for the premium you pay for dealer parts and dealer labor. Same car, same bolts, bigger invoice.
Ball Seat (Radius Seat)
The rounded seat Audi uses on its lug bolts. Conical-seat lugs from other brands will not seat correctly and can loosen. Our titanium ball seat wheel lug kit keeps the correct Audi seat.
Big Brake Kit (BBK)
Larger rotors and multi-piston calipers that add thermal capacity and pedal consistency once you add power. See the Anker Track front big brake kit for B8, B8.5 and C7.
Billet
A part machined from a solid block of metal instead of cast or molded. Billet parts replace failure-prone plastic, like our billet thermostat housing for Gen 1 EA837.
Boost Creep
Boost that keeps rising past target because the wastegate cannot bypass enough exhaust. Our 46mm wastegate guide explains why size is only part of the fix.
Bolt Pattern (PCD)
The number of lug holes and the circle they sit on. Most modern Audis use 5x112, but always confirm with your hub before ordering wheels.
C: Catless to CREC
Catted vs Catless
Whether an exhaust section keeps a catalytic converter. Catted parts keep emissions hardware; catless parts are for off-road and competition use. Our catless vs catted downpipe guide covers the trade-offs.
Check Valve
A one-way valve in the vacuum and PCV plumbing. When one sticks, you get idle faults and lean codes. Replace them as a 3.0T oil check valve set.
Coilover
A combined spring and damper, usually with adjustable ride height and damping, such as the RS TwinTrac coilovers for B8 and B8.5 A4 and S4.
Crank Pulley
The pulley on the crankshaft that drives the belt. On the supercharged 3.0T, a larger crank pulley spins the blower faster for more boost, which requires a matching tune. See the TruDrive 3.0T crank pulley upgrade in 179, 187, 193 and 207mm sizes.
CREC
The engine code for the later (Gen 2) EA837 3.0T. Many service parts differ from Gen 1, so CREC owners should always choose CREC-specific listings.
D to E: Downpipe to EA839
Downpipe
On a turbo car, the pipe bolted to the turbine outlet, the first and most restrictive part of the exhaust. On the 4.0T V8, a high-flow catted downpipe for EA825 RS6, RS7, A8 and S8 keeps cats while freeing flow.
DL501
The seven-speed S tronic dual-clutch gearbox in B8 and B8.5 S4 and S5 models. The plastic filter cap is a common upgrade: our billet DSG oil filter cap kit for DL501 replaces it.
EA825
The 4.0T twin-turbo V8 in C8 RS6 and RS7, 4M SQ7, SQ8 and RSQ8, and D5 A8 and S8.
EA837
The supercharged 3.0T V6 in B8 and B8.5 S4, S5, Q5 and SQ5, C6 and C7 A6 and A7, and 4L and 4M Q7. Our Audi V6 supercharged guide covers the engine in depth.
EA839
The turbocharged 3.0T V6 in B9 and B9.5 S4, S5 and SQ5, with the turbo inside the V. Common first mods include a Zeus ignition coil upgrade kit for EA839.
ECU Clone
Copying the full engine computer contents to a replacement unit so it works without dealer coding. See our ECU clone service.
F to H: Forged to Hot-V
Forged Wheel
A wheel pressed from a solid aluminum billet under enormous force, then machined. Stronger and lighter than cast. Our forged vs cast wheels guide explains the difference.
Headers
Replacement exhaust manifolds with tuned-length tubes that improve exhaust flow, like the HEH Headers V2 for supercharged 3.0T.
Heat Exchanger
The front-mounted radiator that cools the intercooler coolant loop on supercharged Audis. A bigger core such as the GP Ice heat exchanger v2 fights heat soak.
Heat Soak
When the intercooler system gets so hot it stops cooling, so intake temps climb and the ECU pulls timing. Watch it with an intake air temperature gauge.
High-Flow Cat
A catalytic converter with fewer cells per square inch so it flows more while keeping a catalyst in place. See our high flow cats for 3.0T S4, S5, Q5 and SQ5.
Hot-V
An engine layout that puts the turbos inside the V between the cylinder heads for short exhaust paths and quick spool. EA839 and EA825 both use it.
I to O: IAT to Oil Filter Housing
IAT (Intake Air Temperature)
The temperature of air entering the engine after the supercharger or turbo and intercooler. Lower and more stable IATs mean more consistent power.
Intercooler Brick
The air-to-water cores sitting inside the EA837 supercharger housing. Our supercharger intercooler brick upgrade story explains how they are improved.
MAP Sensor
Reads manifold absolute pressure. Tuned cars can exceed the factory sensor range, so B9 owners fit 4 bar MAP sensors for B9 EA839.
O2 Spacer
A small adapter that moves an oxygen sensor slightly out of the exhaust stream, sometimes used after cat changes. A pair of Euro 6 O2 spacers is inexpensive, but a proper tune is the real fix.
Offset (ET)
The distance in millimeters from the wheel centerline to its mounting face. Higher ET tucks the wheel in. Learn to check it in our how to measure wheel offset guide.
Oil Filter Housing
The assembly that holds the oil filter and routes oil to the cooler. The factory 3.0T unit is a known leaker; our EA837 oil filter housing conversion is the permanent answer.
P to S: PCV to Supercharger
PCV (Positive Crankcase Ventilation)
The system that vents crankcase gases back into the intake. When its diaphragm tears, you get whistles, lean codes and oil consumption. The OE-supplier Hengst PCV valve 06E103547AC is the go-to replacement.
Ported Supercharger
A blower with reworked inlet and outlet ports so it moves air more efficiently. Our Artus-Sturm ported supercharger service for the Eaton R1320 is how 3.0T owners do it.
Stage 1 / Stage 2
Tuning shorthand. Stage 1 is software on stock hardware. Stage 2 adds supporting parts, usually exhaust, intake or pulleys, with a tune written for them. Definitions vary by tuner, so ask what each stage assumes.
Subframe Inserts
Billet pieces that fill the voids in rubber subframe bushings to cut slop. See our billet subframe inserts for B8 and B8.5.
Supercharger
A belt-driven compressor. The EA837 uses an Eaton R1320 roots-type unit sitting in the valley of the V6, with the intercooler bricks built in.
T to Z: Test Pipe to ZF 8HP
Test Pipe
A straight pipe that replaces a catalytic converter. For off-road and competition use only, since removing cats on a road vehicle breaks federal emissions law. See our 3.0T supercharged test pipes V2 and test pipes vs high flow cats guide.
Throttle Body
The electronically controlled valve that meters airflow into the supercharger. An 84mm Luft-Strom throttle body upgrade kit is a popular 3.0T mod.
Torsen vs Haldex
Two very different all-wheel-drive designs. Our Torsen vs Haldex guide explains which Audis use what.
Transmission Mount
The mount that locates the gearbox. Soft factory mounts cause wheel hop and clunky shifts; the TruShift transmission upgrade mount firms them up.
Under Supercharger Kit
Everything you should replace while the supercharger is off: thermostat and housing, water pump, PCV valve, heater pipe and gaskets. One labor bill instead of four. See our under supercharger kit for B8.5 and C7, the B8, C6 and 4L version and the Gen 2 CREC kit.
Unsprung Weight
Mass not carried by the springs: wheels, tires, brakes and hubs. Cutting it helps the suspension keep tires on the road.
V-Band
A clamp and flange style that joins exhaust parts without bolts or gaskets. Common on turbos, downpipes and external wastegates.
Wastegate
A valve that bypasses exhaust around a turbine to control boost. Sizing matters: see our 38mm wastegate guide and 46mm wastegate guide.
Water Accelerator (Auxiliary Coolant Pump)
An electric pump that circulates the intercooler coolant loop. Upgrading to a Pierburg CWA-100 or VWA-100 coolant pump upgrade moves more coolant through the heat exchanger.
ZF 8HP
The ZF eight-speed automatic used in many 3.0T Audis. Adding an external cooler is easier with our ZF8HP55 transmission oil cooler adapter.
Audi Performance Parts Glossary FAQ
What does EA837 mean on an Audi?
EA837 is the engine family code for the supercharged 3.0T V6 found in B8 and B8.5 S4, S5, Q5 and SQ5, C6 and C7 A6 and A7, and 4L and 4M Q7. CREC is the later Gen 2 version.
What is the difference between Stage 1 and Stage 2?
Stage 1 is a tune on stock hardware. Stage 2 is a tune written for supporting hardware such as exhaust, intake or pulley upgrades. Each tuner defines stages a little differently.
Is a test pipe the same as a downpipe?
No. A test pipe replaces a catalytic converter with a straight pipe and is for off-road use only. A downpipe is the whole first section of exhaust after the turbo and can be catted or catless.
What is an under supercharger kit?
It is a bundle of the wear parts buried under the 3.0T supercharger, such as the thermostat and housing, water pump, PCV valve, heater pipe and gaskets, so you replace them all during one supercharger removal.
Where can I find more terms from this Audi performance parts glossary explained in depth?
Most entries in this Audi performance parts glossary link to a full guide or product page. Our blog also covers downpipes, test pipes, heat exchangers, wheel offset and more.
Bottom Line on This Audi Performance Parts Glossary
Bookmark this Audi performance parts glossary and you will never again smile politely while someone says "just do the valley on your CREC." Know your platform and engine code, pick parts built for them, and skip the Audi Tax. If your 3.0T is due for the big job, start with the OE Ultimate under supercharger kit for B8.5 and C7 and browse the full under supercharger kits collection.
Shop the OE Ultimate Under Supercharger Kit, $649.99
Drive the difference. Drive Vorsprung.
Prices checked September 25, 2026 and subject to change.
