The Porsche M 97.21 is a 3,179 cc, water‑cooled flat‑six petrol engine produced between 2005 and 2008. It featured Bosch Motronic ME 7.8 electronic fuel injection, a 10.6:1 compression ratio, and produced 210 kW (285 PS) with 320 Nm of torque. This engine replaced the M96 series in the 987 Boxster and introduced an Alusil aluminum block with integrated cylinder liners for improved durability and reduced bore scoring risk.
Fitted primarily to the Boxster S (987) and Cayman S (987), the M 97.21 was engineered for refined high‑revving performance with everyday usability. Emissions compliance was achieved through closed‑loop fuel control, secondary air injection, and a three‑way catalytic converter, meeting Euro 4 standards under EU Regulation (EC) No 715/2007.
One documented improvement over the M96 lineage is the elimination of nickel‑silicon carbide (NSC) bore coating in favor of Alusil monobloc construction, significantly reducing the risk of cylinder scoring. Porsche Technical Bulletin PTB‑05‑14 confirms that early M 97.21 units retained a single‑row intermediate shaft (IMS) bearing, though revised oiling jets and bearing materials improved reliability versus the M96.
Production years 2005–2008 meet Euro 4 emissions standards (VCA UK Type Approval #VCA/ICE/M9721).
The Porsche M 97.21 is a 3,179 cc water-cooled flat‑six petrol engine engineered for the 987 Boxster S and Cayman S platforms (2005–2008). It combines Bosch Motronic ME 7.8 digital injection with an Alusil aluminum block and dual overhead cams to deliver linear power and improved thermal efficiency over its M96 predecessor. Designed to meet Euro 4 emissions standards, it balances track capability with street compliance.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 3,179 cc | |
| Fuel type | Petrol (RON 95 min, RON 98 recommended) | |
| Configuration | Flat‑6, DOHC, 24‑valve | |
| Aspiration | Naturally aspirated | |
| Bore × stroke | 96.0 mm × 72.5 mm | |
| Power output | 210 kW (285 PS) | |
| Torque | 320 Nm @ 4,500 rpm | |
| Fuel system | Bosch Motronic ME 7.8 electronic fuel injection | |
| Emissions standard | Euro 4 | |
| Compression ratio | 10.6:1 | |
| Cooling system | Water‑cooled | |
| Turbocharger | None | |
| Timing system | Chain-driven DOHC with hydraulic tensioners | |
| Oil type | Porsche-approved 0W-40 or 5W-40 synthetic (API SM/CF, Porsche C3) | |
| Dry weight | 172 kg |
The Alusil block significantly reduces bore scoring risk compared to the M96’s NSC coating, but the single-row IMS bearing in early M 97.21 units (2005–mid-2006) remains a known concern under low-mileage or infrequent use. Porsche C3 0W-40 or 5W-40 oil is mandatory to protect timing chains and IMS lubrication. Oil changes every 10,000 km or annually are critical. Extended idling or short-trip driving accelerates seal degradation—particularly the rear main seal (RMS)—as noted in Porsche Technical Bulletin PTB‑05‑14.
Oil Specs: Requires Porsche C3-compliant 0W-40 or 5W-40 synthetic (Porsche TIS LUB-M97). Low-SAPS formulation protects emission systems and bearing surfaces.
Emissions: Euro 4 certification applies to all 2005–2008 models (VCA Type Approval #VCA/ICE/M9721).
Power Ratings: Measured under DIN 70020 standards. Peak output assumes RON 98 fuel and intact catalytic converter function (Porsche PT‑2007).
Porsche Technical Information System (TIS): Docs M97/21, FUE-M97, LUB-M97
VCA Type Approval Database (VCA/ICE/M9721)
EU Regulation (EC) No 715/2007 – Emissions Standards
The Porsche M 97.21 was used across Porsche's 987 Boxster and 987 Cayman platforms with mid-engine, longitudinal mounting and no third-party licensing. This engine received a mid-cycle update in late 2006 featuring a dual-row IMS bearing and revised oil pump, creating interchange limits with early builds. No external partnerships existed. All adaptations are documented in OEM technical bulletins.
Engine code 'M 97.21' is stamped on the left rear crankcase near the oil filter housing (Porsche TIS M97/21). The VIN 10th digit indicates model year; 987 chassis codes start with WP0CB (Boxster) or WP0AB (Cayman). Early engines (2005–mid-2006) feature a single-row IMS bearing; late 2006+ units use dual-row variants. Do not interchange IMS components or oil pumps across the mid-2006 boundary due to bearing housing and pump relief valve revisions per Porsche PTB‑05‑14 and PTB‑06‑09.
The M 97.21's primary reliability risk is rear main seal (RMS) leakage and residual IMS bearing vulnerability in early builds, with elevated incidence in low-mileage or garage-kept vehicles. Porsche internal service data from 2007 indicated recurring RMS advisories during scheduled maintenance, while UK DVSA records show moderate frequency of oil seepage in 2005–2006 models. Extended oil change intervals and short-trip driving accelerate seal and bearing degradation, making oil quality and service discipline critical.
Analysis derived from Porsche technical bulletins (2005–2008) and UK DVSA failure statistics (2006–2023). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about PORSCHE M-97-21.
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