RWD SR FAQ Version 2.0

For the RWD SR20DET cars! Sponsored by Wiring Specialties.
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RWD SR FAQ Version 2.0

Postby Hijacker » Fri Jan 18, 2008 5:42 am

Welcome to the RWD SR20DET forum. This FAQ is designed to help introduce you to the basics of the SR20DET and learn some common upgrade paths as well as answer some of your nagging questions.


The SR20DET is a 2.0 litre, rear wheel drive (RWD) 4 cylinder motor found in the Nissan Silvia and Nissan 180SX starting in 1991 and leaving production in 2002 in varying forms over the years. It is a common engine replacement for the US 240SX as it is a direct bolt in replacement. Only minor wiring needs to be done to make the motor work.

The motor went through minor updates throughout the years when Nissan would release a new Silvia chassis. These are commonly referred to as the Redtop, Blacktop, S14 Blacktop, and S15 Blacktop

The S14/S15 Blacktops received upgraded turbos and Variable Valve Timing (VVT) for the intake cam. The S15 also received a different Mass AirFlow Meter (MAF) and 444CC injectors. Both received Garrett T-28 turbos, but the S15’s T-28 was further upgraded from the S14’s.

Basic specs:
1998 CC (499.5 CCs per cylinder)
Dual Over Head Camshaft (DOHC) 16 Valve
Intake Valve Stem Diameter 6mm
Sodium Filled Exhaust Valve Stem Diameter 7mm
86mm Bore
86mm Stroke
136.3mm Rod Length measured from center of both bearing races
8.5:1 C/R
1.1mm Headgasket Thickness

Power Output and Generation Specific Differences
This chart was copied from Sport Compact Car's website

List of Turbo Changes Between Generations
S13 Redtop and Blacktop:
Bushed bearing Center Housing
T-25 Compressor. 60 Trim 56mm BCI-1
T-25 Turbine. 62 Trim 53.8mm 0.64 A/R

The second generation received an upgraded compressor housing and a ball bearing housing

T-28 Compressor. 60 trim 60mm BCI-1 compressor wheel inside a T04B Housing
T-25 Turbine. 62 trim 53.8mm 0.64 A/R
This turbo is now referred to by Garrett as the GT2560R to follow with their current identification system.

The third generation received a more refined T-28 turbo. The compressor was the same BCI-1 wheel put inside a T04B housing, but the turbine received an upgraded inconel wheel and had a cast divider wall in the wastegate discharge path to help aid spool characteristics.

This turbo is now referred to by Garrett as the upgraded GT2560R to follow with their current identification system.

An inconel wheel is a Titanium Aluminum (TiAl) alloy turbine wheel that is used as a replacement for lightweight Nickel based turbine wheels. Traditional metal wheels tend to fail in high temperature exhaust gasses, but with the introduction of the TiAl turbine wheel, it is possible to have a lightweight wheel that can withstand higher exhaust temperatures.
Referrenced from ScienceDirect

One thing to note about Garrett turbos is that they now all share the GT nomenclature, where as before GT was thought to refer to ball bearing turbos. Breaking down the S15 T28 code of GT2560R follows like this:
GT25 - refers to the turbine wheel frame (which for this frame size is 53.0mm)
60 - refers to compressor wheel exducer diameter (big end), which is 60.0mm in this case
R - denotes a ball bearing center cartridge. You will sometimes see an S after the R, which denotes further upgrades that require additional designation.

Differences Between FWD and RWD
FWD NA motors have 9.5:1 C/R
Physical dimensions are different
Distributor is ran off the rear of the exhaust cam
Intake collects from the opposite direction of the RWD intake
Clutch is of smaller diameter (215mm 18spline)

Basic Maintenance Items
-Spark Plugs: NGK Iridium BKR6EIX Gapped to .036” for stock performance. Commonly gapped down to .032” for higher boost applications
-Oil Filter: Any that fit a Sentra SE-R with an SR20DE.

The SR20DET holds about 3.5 quarts of oil. Upgraded oil pans will sometimes add an extra quart to that capacity.

Below is the recommended oil weight chart. This chart bases oil weight on the ambient temperature.

Typically, 15w50 is recommended by some mechanics for summer and 10w30 for winter.

Synthetic oils are the best type for turbo motors, as they resist thermal breakdown longer and better than conventional oil. On turbo motors, the oil sees extra heat transfer from lubricating the turbo's center shaft.

Parts Compatability
-Motor Oil Seals: Identical to Sentra SE-R SR20DE (P/N front: 15020-79E00 /rear: 12279-1N510)
-Valve Stem Seals: Intakes are identical to Sentra SE-R SR20DE. Exhausts are 1mm bigger and will have to be ordered specifically.
-Water pump is a JDM item. The FWD SR20DE is not compatible. You can order pumps at various vendors. Courtesy Nissan should be your first stop to buying one
-The timing chain kit is identical to the FWD SR20DE.
-The Idle Air Control Valve (IACV) is a RWD SR20DET item only.
-Water temperature sensors for both ECU and dash cluster are identical to KA24DE. Make sure to get the same sensor as your year chassis.
-Knock sensor is identical to KA24DE, although the sub-harness is SR specific
-Motor mounts are identical between KA24E, KA24DE and RWD SR20DET
-Motor mount brackets are a RWD SR20DET item only.
-Fuel injectors are identical to NA 300ZX (Z32)
-Fuel Pressure Regulator is a RWD SR20DET item only
-Alternator Belt P/N K050370 (Gates P/N)
-Power Steering Belt P/N K040345 (Gates P/N)

Clutch Facts
-Stock RWD SR20 clutches utilize a 240mm diameter, 24 spline clutch disc with a 25.6mm diameter sprung hub.
-Maximas equipped with the VG30 utilize the same clutch, but many importers today keep RWD SR20 clutches in stock.
-Dave Coleman successfully mated a 350Z sport clutch and pressure plate to an SR20 flywheel by redrilling the flywheel to accept the Z's pressure plate bolt pattern

For a more detailed parts list, click this link

The S13 and S14 SR transmissions are identical to the American counterpart mated to the KA24E/DE. The primary differences are the bellhousing bolt pattern and 5th gear.

S13 SR20DET Transmission Gear Ratio
1st - 3.321
2nd - 1.902
3rd - 1.308
4th - 1.000
5th - 0.838
Final - 4.083

S13/S14 Transmission information copied from S14 EUDM Service Manual.

The S15 SR20DET is mated to a 6 speed gearbox. The primary differences on this gear box are still the bellhousing bolt pattern as well as the lack of a speed sensor. The speed sensor for these transmissions were located on the differential housing.

S15 SR20DET Transmission Gear Ratio
1st - 3.626
2nd - 2.200
3rd - 1.541
4th - 1.213
5th - 1.000
6th - 0.767
Final - 3.692

S15 Transmission information copied from

NISMO released an updated version of the 6 speed gearbox that uses reinforced gears and has the hole for the speed sensor as well.

Fuel Pressure Regulators (FPR) are to be set to 43.5 psi with the vacuum source hose unplugged from it. With the hose plugged in, the regulator should read 36 psi. Aftermarket fuel pumps tend to force an old, tired regulator to run higher pressure. A Walbro 255 lph fuel pump has been shown to consistently run stock FPRs at 43 psi with their vacuum sources plugged in. This will result in a slightly rich condition, which doesn’t affect drivability or performance. It does seem to adversely affect injector life, however.

Swap Basics
Swapping an S13 SR into an S13 chassis is about as simple as it gets. The motor is a direct bolt in, the motormounts are identical between the KA24 and SR20, and the driveshafts are interchangable.

Wiring wise, all that is needed to be done is to repin the big plug next to the battery that connects the EFI harness to the chassis, extend the O2 and MAF signal wires, and rewire a few wires for the ECU to dash plug. Be sure to check FRSport's Wiring FAQ for a detailed guide to wiring the motor in properly.

When using the US driveshaft, you will need to remove the dust cover from the end of the transmission, but the US driveshaft is the proper length and spline count. Just be sure to use a 5 speed driveshaft if your SR is a manual.

Be sure to remove the heatshield from the turbo and the AIV tube as both tend to make contact with the US steering column. Also, an SR downpipe will be needed but it will bolt to the US catalytic converter.

S14 chassis basics to be added later

Safe limits of the T-25 Turbo
The T-25 turbo shouldn't be ran above a 13 psi setting if using an aftermarket boost controller. While, 14 psi is attainable, it is barely within the compressor effeciency range of the turbo and will decrease the life expectancy. 15 psi puts the compressor outside of its effeciency range and you risk severe damage to the turbo.

Taking an old rule of 1 psi of boost is equal to about 8 horse power, at 13 psi, the T-25 should be producing a ballpark figure of 253 horse power.

To get that number, simply take the boost setting, minus the stock boost setting (13-7) to get the difference (6). Multiply 6 by the rule of thumb 8 (48) and add it to the stock crank horse power rating given by Nissan (205) to get 253.

Again, that is a ballpark estimate as all turbos and motors are different. Also, this should show you that at 13 psi, the entire fuel management system is maxed and going beyond 13 psi could seriously damage the motor as well as the turbo.

Safe Limits of Stock SR20DET
Many people ask what power levels a stock block SR20 can handle. The internals have been known to support 400 whp reliably. However, that is dependent on your fuel management. Proper supporting mods must be done to the fuel system to support this number, or you will melt pistons. The pistons are the first part of the motor to fail internally. They tend to overheat and either burn holes through them, or their ringlands crack and fall apart.

Reports of rod failure have been practically non-existant for 2 reasons. Most people upgrade their rods when they rebuild, so it's rare to find someone stress testing rods with an aftermarket piston. The other reason is that SR rods are beefy, and short. Shorter rods don't have the same leverage of force placed on them as a longer rod, and are less likely to bend. The rod bolts Nissan uses, are of good quality, and have yet to show fatigue at high RPM leading to spun bearings.

The crank has yet to be proven as a weak point, and it's rare to see someone crack or snap one due to power output.

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RWD SR Links

Postby PyR0NiAk » Fri May 28, 2010 1:57 pm

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