BMW M52 / S52 Turbo Build Reference Guide

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1. Power Potential (M52 / S52 w/ M3 Cams)

• Stock compression: ~400 WHP

• Low compression (cut ring + spacer): ~500 WHP

• E85 (any compression): 600+ WHP

• Note: 328 cams remove ~40 WHP compared to M3 cams.

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2. Turbo Options & Output

Precision

• 6266 (DBB best, journal works): Baseline turbo.

  • Next Gen version: +50 WHP (~700–850 WHP capable).

• 6466: Adds ~50 WHP compared to 6266.

Garrett

• G35-900: Comparable to 6262. Similar to 6266, but 6266 has a better power curve.

• GTX3582R: Makes similar numbers, but weaker power curve.

BorgWarner

• SXE362: Matches 6266 in peak power, but spools later and loses boost on shifts.

Smaller Options

• 6062 (~600 WHP turbo):

  • Makes less power per pound of boost.

  • Limited on pump fuel (expect ~50 WHP less vs. 6266).

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3. Engine: Stock vs. Built

• A built engine adds zero HP by itself.

• Benefit = durability when mistakes happen (lean condition, overboost, etc.).

• Real-world examples:

  • Many stock engines survive 600+ WHP for years.

  • Others fail at 350 WHP due to install errors (vacuum lines wrong, bad fuel pump install, etc.).

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4. Manifolds

• Top Mount:

  • Best: Otis / Good & Tight (E36, proven 900+ WHP, ~$600).

  • Other solid options: Jon Vigil Viengineered, 88 Lab.

  • CX Racing: manifold cracks; charge pipe must be fully redone.

  • American-made options: good fabrication quality, but expect long lead times. Do not follow their “tuning suggestions.”

• Bottom Mount:

  • SPA T4: caps out ~700 WHP (can push ~900, but backpressure extreme).

  • Corey Misko: strong bottom-mount option.

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5. Exhaust & Turbine Housing

• Use large housings (1.0+ A/R) for these engines.

• 3.5” exhaust helps reduce backpressure and raise safe WHP.

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6. Intercoolers

• TR1035:

  • Fits with A/C.

  • Excellent cooling for most builds.

• TR1045: Better option if it fits.

• Rule: Keep IAT low, especially on pump gas.

  • High IAT + high backpressure = knock limit.

• With big housing + 3.5” exhaust, some unopened S52/M52s can push ~500 WHP on pump gas.

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7. Fuel & Octane Guidelines

• All WHP numbers are on 93 E10.

• Subtract ~50 WHP for:

  • 91 E10

  • 94 E10 (Canada)

• E85:

  • Higher octane + cooling effect.

  • Some think it’s a “bandaid,” but it’s actually a huge help in keeping engines alive.

  • Works at 35+ PSI on any compression.

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8. Fuel System

• Over 255 lph pump → aftermarket FPR required:

  • AER13129 fuel pressure regulator

  • TS-0402-1110 –6 ORB to 8mm barb fittings (to OEM line)

  • TS-0402-2023 gauge

  • 8mm E85-safe fuel line (PN: 27340 / 42196039)

• Radium PTFE in-tank lines only.

  • Do not use pump-supplied or OEM lines.

  • Radium PTFE will outlast the car.

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9. Spark Plugs

• NGK 4091 (up to 700 WHP):

  • .024 gap → 350–450 WHP

  • .022 gap → 450–550 WHP

  • .018 gap → 550–700 WHP

• NGK 4554 (750+ WHP):

  • .018 gap → 750–800 WHP

  • .016 gap → 850+ WHP

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10. Boost & Tuning Practices

• Always boost leak + smoke test.

  • Even professionals find leaks.

  • Charge pipe popping off is not the most common failure—small leaks matter more.

  • PMAS/VMP MAF housings: they always leak slightly through the connector.

    • Fix: apply silicone to the modification plate (email for images).

• Run no boost controller first, then add it in (fewer variables).

• Manual controller: use yours (others are bleed style = slower spool).

• Electric controllers: most are fine. AEM = hard to read.

• CX Racing turbo kits → guaranteed boost creep, risk of motor damage.

  • Start with 5 PSI spring.

  • If high-RPM boost exceeds 10 PSI (stock compression) or 15 PSI (low compression), fix manifold/wastegate flange.

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11. Intake & MAF Setup

• MAF must be in straight 3” aluminum pipe (not aftermarket housings).

• Reducers (3" → 2.75"), even 10” away, = turbulence → drivability issues.

• BOV must be fully closed at idle/light throttle.

  • If it stays cracked open, use stiffer spring.

  • Even small leaks 10” away from MAF cause surging.

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12. Hoses, Couplers & Lines

• Reinforced silicone couplers only for charge pipes.

• Pressure hoses: snug, with clamps + zip ties.

• Vacuum hoses: silicone, very tight fit (Vibrant packs recommended).

• Wastegate lines: reinforced silicone or AN.

• Valve cover vent: vent to atmosphere.

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13. E36-Specific Notes

• ICV fitting: clean + epoxy in place OR buy aftermarket.

• ICV hoses: must be silicone (OEM fall apart/leak).

• Do not use ICV hose kits going to a CCV separator → will pressurize crankcase.

• O2 sensor: plug closest to firewall.

• M50 manifold on OBD2: requires OBD2 IAT (thread to M12x1.5 or buy adapter).

• Up pipe: idle may sound like a small misfire.

• SAP valve: no need to plug in fuel rail harness connection.

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14. Fuel Octane & Boost Limits

• Stock compression / 91 octane: 7–9 PSI

• Low compression / 91 octane: 13–17 PSI

• Stock compression / 93 octane: 7–12 PSI

• Low compression / 93 octane: 13–20 PSI

• Any compression / E85: 35+ PSI

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15. Support Guidelines

• For support, always include:

  • Screenshot of codes (using supplied software).

  • Datalog (single gear pull, 100% throttle).

  • Photos: vacuum routing, ICV hoses, FPR line routing, MAF + charge pipe routing.

• Do not send logs with multiple gear pulls unless specifically requested.

• All logs must be full throttle.

  • If traction issues: log in a higher gear.