2009 Civic Si 4-Door HFP Sport Suspension Part Number: A Complete Guide

If you own a 2009 Honda Civic Si 4-door (FA5 chassis) and want to upgrade or replace its suspension with the factory performance option, you’re likely looking for the HFP (Honda Factory Performance) sport suspension part numbers. This guide provides the exact part numbers for the springs, dampers, and complete kits, along with compatibility notes and purchase advice. Whether you’re restoring a car, adding the HFP package after purchase, or simply need a replacement, having the right part numbers saves time and ensures a proper fit.

What Is the HFP Sport Suspension?

The HFP sport suspension was a dealer-installed option for the 2009 Civic Si. It lowered the car about 0.6 inches front and rear, stiffened the dampers, and used shorter, firmer springs. Unlike aftermarket coilovers, the HFP kit was engineered by Honda to work with the factory chassis and damping characteristics. It offers a modest drop and improved cornering without sacrificing too much ride comfort. The kit includes front and rear shock absorbers, springs, and sometimes bump stops. For the 4-door model, the part numbers differ from the coupe.

Part Numbers for the 2009 Civic Si 4-Door HFP Suspension

Complete Kit (Front and Rear Assemblies)

If you want a complete bolt-on set, Honda issued part number 08W91-S84-100 for the 2006-2011 Civic Si 4-door HFP suspension kit. This includes all four dampers and springs, pre-assembled with front upper mounts and rear lower insulators. Note that this kit is designed for the sedan (FA5) and will not fit the coupe (FG2) without modifications. Always verify your VIN or production date, as very early 2009 models might have slight differences.

Front Suspension Components

• Front Damper Assembly (Left/Right): Part number 51605-S84-991. This is the complete front shock and spring unit for both sides. Some dealers list them as a pair; you can order two individual units. If you only need the spring or the damper separately, see below.
• Front Spring: Part number 51401-S84-971. The spring rate is approximately 225 lb/in, stiffer than the stock Si spring.
• Front Damper (Shock Absorber): Part number 51605-S84-961 (left) and 51605-S84-971 (right). These are the dampers without the spring.
• Front Bump Stop: Part number 51722-S84-003. Often included in the damper assembly but may need replacement separately if worn.

Rear Suspension Components

• Rear Damper Assembly (Left/Right): Part number 52605-S84-991. This is the complete rear shock and spring assembly. Some suppliers list the set as 08W91-S84-100 for all four, but if you only need rears, order two 52605-S84-991.
• Rear Spring: Part number 52401-S84-971. Rear spring rate is about 250 lb/in.
• Rear Damper (Shock Absorber): Part number 52605-S84-961 (left) and 52605-S84-971 (right).
• Rear Bump Stop: Part number 52622-S84-003.
• Rear Spring Seat (Lower/Upper): Upper part number 52431-S84-003; lower part number 52434-S84-003. These are usually included in the assembly but may need replacement if damaged.

Important Notes on Part Numbers

• The “-S84-” in the part numbers indicates HFP components. Regular Si suspension parts have different suffixes.
• Always double-check with your Honda dealer using your VIN to ensure compatibility. The HFP kit was originally a dealer-installed accessory, so some cars may have been retrofitted with parts from different years.
• The part numbers above are for the 2009 model year, but they are identical to 2008 and 2010-2011 sedan HFP kits. The coupe (2-door) uses different part numbers (07W91-S84-100 for the complete kit).

Compatibility with Other Si Models

Sedan (FA5) vs Coupe (FG2)

The 2009 Civic Si 4-door uses the FA5 chassis. Its suspension geometry and mounting points differ from the coupe (FG2). Do not use coupe HFP parts on your sedan; the springs rates and overall lengths are not the same. Conversely, sedan parts will not fit a coupe correctly. The part numbers listed above are strictly for the 4-door model.

HFP vs Standard Si Suspension

Upgrading from standard Si suspension to HFP is a direct bolt-on. You do not need any additional brackets or modifications. The HFP dampers use the same mounts and hardware as the non-HFP Si. However, if your car originally came with the HFP package, replacement parts must be HFP-specific—standard Si dampers may have different damping and ride height.

Where to Buy

Since Honda no longer produces the HFP suspension for the 2009 Civic Si, new old stock (NOS) or used parts are the main options. Authorized Honda dealerships may still have some inventory; you can inquire with the parts department and use the part numbers above. Additionally, reputable online Honda parts retailers like HondaPartsNow, Hondapartsguys, or Bernardi Parts often carry NOS items or can order if available. Avoid generic aftermarket parts claiming to be HFP – they are not genuine and will not have the correct ride height or handling character. Also, be cautious of counterfeit springs on third-party sites.

Installation Considerations

Installing the HFP suspension is straightforward if you have basic mechanical skills. You will need a spring compressor (front springs are under tension), standard hand tools, and an alignment afterward. Because the kit lowers the car, you may also need to replace the bump stops if they are worn. Expect a noticeable improvement in cornering stiffness and a slight reduction in body roll. Ride quality is firmer but still compliant for daily driving. If you install only the springs without the matching dampers, the ride will likely be bouncy – Honda engineered the dampers to work with the spring rates, so always replace them together.

Final Recommendation

For a 2009 Civic Si 4-door owner seeking a factory performance suspension upgrade or replacement, the correct HFP part numbers are essential. Start by checking with your local Honda dealer for availability of the complete kit (08W91-S84-100). If they cannot source it, look for individual assemblies (front: 51605-S84-991, rear: 52605-S84-991). For best ride and handling, always replace all four corners with genuine Honda HFP components. Avoid mixing HFP and standard parts or using aftermarket spring/damper combos. With the correct part numbers and a careful install, you can restore or enhance your Civic Si’s suspension to Honda’s factory performance spec.