Nissan QR25DE Engine

1. Specifications
2. Overview, problems
3. Performance tuning

Nissan QR25 engine specs

Nissan QR25DE engine reliability, problems and repair

This engine was developed in 2001 and substituted KA24DE. It is the same as QR20DE, but new crankshaft with piston stroke 100 mm was installed into cylinder block. Deck height remained the same, 225 mm. Also the engine has 143 mm connections rods and pistons with dish, their compression height is 32 mm. All that let increasing engine displacement to 2.5L. Cylinder block remained the same.
Cylinder head is also the same as on QR20DE. It is DOHC with 4 valves per cylinder and continuous variable valve timing system CVTC. This engine does not use hydraulic tappets, so every 60,000 miles of mileage (90,000 km) you should regulate the valves to avoid appearing of irritable ticking noise.
Also QR25DE uses individual ignition coils and electronic throttle body. As it is peculiar to many large 4-cylinder engines, QR25 also has two balancer shafts, which let the engine working smoothly and diminish vibration.
In 2007 QR25DE was upgraded. Intake manifold and pistons were modified, connecting rods were reinforced, balancer shafts were somewhat moved. Also camshafts were somewhat updated, redline was raised and some more insignificant novelties happened yet.
Specially for JDM Nissan Primera, QR25DD with direct injection system was created. Its compression ratio was increased to 10.7.
Supercharged QR25DER engine has been produced since 2014. It uses new pistons and compression ratio is reduced to 9.1. Besides, 20 HP electro motor was installed on that engine. All this has made the engine quite powerful, 250 HP at 5,600 RPM and torque 329 Nm at 3,600 RPM.

Nissan QR25DE engine problems and malfunctions

1. Idle problems, jerking. More likely your QR25DE timing chain has stretched. It often happens on the very first generation of the engines. You need to change timing chain and usually it solves the problem completely.
2. Oil leak. Usually valve cover gasket is leaking. Upon changing it, everything will be all right.
3. High oil consumption. If your oil consumption exceeds 1 qt. per 1500 miles (0,5L per 1000 km), then more likely your piston rings have got out of order. It may need overhaul.
4. Misfire. Fuel injectors and throttle body require cleaning.
5. QR25DE vibration. It mainly happens because of lame soft ECU, it must be changed. Yet the spark plugs may be the reason, perhaps they have expired.
Besides, QR25DE engine does not start at the temperature below -20 C. Anyway, it is hard doing it. If the engine was produced till 2004, catalytic converter may fail often. It happens because of lame soft ECU also. It gave a lot of fuel, and burning down in catalytic converter, it promoted its quick destruction. Also thermostat on QR25DE does not have long lifetime, and when it fails, the engine may overheat.
Service life of QR25DE is about 120,000 miles of mileage (200,000 km) at general exploitation by common person. However, thanks to the regular service and high quality motor oil, its service life may increase to 180,000+ miles of mileage (250,000 km).
Is QR25DE a good engine? Having compared it with KA24DE, it is evident that QR25 has become more modern and producible, but along with this, it has many shortcomings. While old KA24DE is not that perfect, but thanks to its simplicity, it is rather reliable and durable.

QR25DE engine number location

It is on cylinder block on the tablet to the right.

Nissan QR25DE engine tuning

N/A build

The engine was developed for low end torque, what is evident from proportion rod length/piston stroke. Anyway, if you have decided to increase the power of your engine, you will need to purchase some performance parts. They are balancer shaft removal kit, cold air intake, Nissan Sentra SE-R Spec V cams, 4-2-1 header and aftermarket exhaust system. On Sentra SE-R Spec V camshafts are more aggressive and let raising redline to 7,000 RPM. When you install everything, it is necessary to adjust ECU. These upgrades let gaining 200-210 horsepower, nice sound and quite good dynamics.
If you purchase QR20DE pistons, compression ratio will increase to 11.5, and as the result, the power will rise to 210-215 horsepower. It is the reasonable limit, it would be rather expensive to exceed it.

QR25DE Turbo. QR25DET

How to turbo QR25DE? It is not all that simple about it. Stock engine is not suitable for the boost at all, and also connecting rods are quite weak, and pistons may burn through easily. Therefore you will need forged internals. Buy connecting rods Crower 148.2 mm, forged pistons JWT with 5 mm piston ring offset and compression ratio 8.5. It would also have a sense to install oil nozzles for cooling pistons. You should buy MLS head gasket, ARP head studs, Garrett GT28 (or other) turbocharger, turbo manifold, thermal insulation, boost controller, wastegate, intercooler, 3” pipes, clamps, downpipe, blow off valve, MAF, oil feed line, oil return line, fuel injectors 630 cc, Walbro 255 lph fuel pump, 3” exhaust system and APEXI SAFC. Or you may buy QR25DE turbo kit at once, it may be easier.
Thanks to all this about 280-300 horsepower (15 psi /1 bar) will be gained.

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