Extreme Engine Tech: Jim Wolf Technology’s Turbo Nissan QR25DE Powerhouse Part 1

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JWT Nissan QR25DE forged piston
A close up of the forged JWT piston is shown here in place, taken during the up fit up in the sectioned block.

The stock pistons are cast.  Cast pistons have good dimensional stability and can run close piston to wall clearances.  This reduces crevice volume and makes for a quieter engine.  Cast pistons are also brittle and weaker than forged.  These properties make the cast piston more susceptible to ring land damage and breakage of the pin boss.

JWT froged QR25DE piston with swain coating
JWT pistons feature full skirts because a strut type piston although lighter, may not have enough skirt contact area to avoid scuffing considering the side load of the long stroke, short rod engine.  The dome of the piston was coated with Swain Technologies Gold Coat thermo barrier coating and the skirts coated with PC9 anti friction coating.

JWT’s answer was to develop some strong forged pistons.  Forging work hardens and compacts the metal, refining the grain of the metal in an orientation that makes it stronger.  Metal like wood has a grain!  The forging process also makes the grain finer and removes voids that can cause areas of stress concentration that can be the nucleus of failure points.  Forged pistons are tougher and more ductile than cast. JWT’s pistons were designed to lower the compression from nearly 10:1 to 8.5:1 and move the piston pin as high as possible to make room for a longer rod.

JWT Forged QR25DE piston
The forged JWT piston has a dish to lower the compression ratio to a more turbo friendly 8.5:1

The JWT pistons were designed as a prototype for a possible street performance piston, JWT made them from a high silicon forging made of 4032 alloy. 4032 is more dimensionally stable than the tough 2618 low silicon forging alloy which is usually preferable for racing pistons. The 4032 can run a tighter piston to wall clearance but is more brittle although it is much tougher than cast pistons.  The pistons were sent to Swain Technologies to be coated with their Gold Coat thermo barrier coating on the dome and PC9 anti friction coating on the skirts.

JWT Forged QR25DE piston
Undercrown milling was used to lighten the piston as much as possible to reduce the stress on the rod and crank. The notch in the piston skirt is to clear the piston cooler nozzles that we are going to install later.

We have always had good luck with Swain coatings.  In testing at Nissan Motorsports for Nissan’s IRL program, Swain coatings were found to work the best and be the most durable.  Gold coat is a multi layer coating that has heat conductive and barrier layers.  The conductive layers helps insure an even temperature distribution across the dome of the pistons while the barrier layers protect the pistons from heat induced damage.  The even temperature helps reduce hot spots and chances of detonation as well as reduces the chances of temperature induced damage.  Holding heat in the combustion chamber instead of conducting it into the piston also makes for more power.

Swain’s PC9 skirt coating is unique in that it uses tungsten disulfide instead of molybdenum disulfide or Teflon.  This is a longer wearing, harder, low friction coating that conducts heat well.  Other coatings act like insulators and actually hold heat in pistons while Swain’s skirt coatings are heat conductive so the piston can shed heat to the cylinder walls better.  We have found PC9 to be the best wearing of all the skirt coatings we have sampled.

JWT Forged QR25DE piston
A pressure equalization groove is used between the compression rings to help them seal better under high piston speeds.  Dual pin oiler holes were also used to ensure good lubrication to the piston pin. 

Due to the high side loading of the QR’S poor stroke to rod length ratio, JWT opted to use a full skirt design to spread the load out over a larger area.  JWT also specified advanced design features such as a pressure equalization groove between the compression rings, dual piston pin oilers and under crown milling to minimize weight. A thick walled full length steel piston pin was specified to reduce deflection.  Thin, racing taper walled tool steel pins often flex in turbo motors and grab the connecting rod small end bushing which causes rod failure.  The pin is retained with dual spirolocks.

Turbo QR25DE mock assembly
Before the final assembly, a scrap QR25DE was cut apart to observe that clearances were correct with a longer rod and a different crank.

Before machining the block or any sort of assembly was initiated, the prototype parts were test fitted to ensure that there were proper clearances with the inside of the block. A damaged QR25 motor was cut apart to study the internal clearance with the new parts and the fits ruled as acceptable before anything else was done.  Follow us in the next installment of our project to see other tricks that Jim Wolf Technology used in the build up of our motor.

Sources

Jim Wolf Technology

Swain Tech Coatings

WPC

38 comments

    1. It is a pretty weak engine. It responds well to turbocharging making good power but its hard to make it reliable. The engine has a weak crank, small bearing area, long stroke and poor rod ratio combined with poor water jacketing and poor head sealing make thing problematic. For easy street use and occasional drag racing maybe on low boost but no track days, etc.

      1. I was thinking about starting with a 07+ block and replace the internals with forged parts. Doing something very similar like what you guys did with the QR25DE and probably push it close to 500 but using E85. I love my Nissan’s but I want professional advice before I start spending any more money.

      2. Also the build I want to start is for street use only not track. Daily driver and some drag racing once in a while.

  1. i have an sr20 engine and i am asking if i can do something to my qr20 xtrail.can l use also the rod and then look for the right pistons?
    do i change the compression with this things

  2. So… I have a 2018 Rogue.. Yes, Rogue, that I wanted to explore with performance upgrades. Long have I wanted to have a 500hp+ suv lol don’t judge me :p

    So, I thought about turbocharging it. Came across this article. It made me quite sad tbh 😂 I won’t be tracking it, or even drag racing it. I just want a sprinkle of power to play with while driving.

    Thoughts?

  3. I have a 2013 Altima with the qr25de and my goal for HP is 250HP. it’s completely stock at the moment. Could you give me some pointers as far as what mods to start with and where to go from there? Thanks.

    1. Possibly, a header, Intake, JWT cams, and a balance shaft delete kit. Then find someone that can tune it. I probably would not modify the engine beyond this.

  4. I really like my Altima coupe I just wish it came turbocharged from factory. It would have sold a lot better and it would stututu.
    So I have been looking at the pre-made “kits” for qr25de engines but they are all around $4900. So instead my question is, would I be able to make a t3/t4 universal turbo kit run safely on my qr25de? I am not looking to make anymore power than around 230-250hp I really do not care about the numbers as long as I can safely get the car to run a t3/t4 turbo. I want to pursue a career in which I work on cars so this wouldn’t be a situation where all I want is power, it would more be a test to see if I am be able to do it… I’ve already changed the stereo, wheels, brakes, exhaust and intake system with no help besides my phone and my tools that I borrow from my very nice neighbors. I don’t have access to a professional garage but I do have a lot of free time due to the pandemic.

  5. Even if I don’t end up turbo charging my Altima coupe I’ll be installing new headers, new cams and a tune. I’ll probably call it a day after that but I still wish from factory the Altima coupe was turbo charged. It definitely has the looks just not the love from Nissan.

  6. Hey y’all, I’m checking out a 2003 sentra SE-R Spec V through a private seller. I’m going to be meeting the owner to check it out, and then I have an appointment at a reliable mechanic shop for a pre-purchase inspection.

    I’ve been looking up the QR25DE and all of it’s faults, I don’t plan on boosting the engine, I just want a fun car with a 6-speed to row through gears during road trips. I don’t need a car to commute, so it’s a hobby vehicle. Seller says they have complete service history from Nissan starting from 2006, and that it has a Nissan factory remanufactured engine with only 36,000 km that was installed by Nissan. The body has a total of 275 km.

    My question is, what red flags should I be looking for?

    I am also looking for:
    Oil leaks from under the cylinder head cover
    Idle problems and/or jerking caused by stretched timing chain
    Random misfires
    High oil consumption (this may take time to ascertain)

    I know it’s not a race car and I know it won’t make 175 hp at the wheels.

    any advice would be greatly appreciated.

  7. So my 2003 se-r qr25de with 157,000 blew a piston today from just driving around. i am thinking of buying another qr25de what should i upgrade on the engine to prevent another piston mishap again? i just want it to be more reliable than the last one. the only issue i had was it burned a lot of oil and required 1 qt about every 2 weeks.

  8. I have an x-trail 2004 qr25de that has spit out the thrust bearing damaged the block and crank, $1000 to repair it has 100,000 k’s everything is good apart from crank, block and bearings. I have another engine it is from a 2009 Nissan Presage, it is a good runner with 325000 k’s I think it is a gen2 engine so I would like to use the block and crank, does this sound reasonable?

  9. Mr Kojima
    Has anyone done a 92mm sleeved post 08′ qr25de all motor to compete with 102mm stroked 2.6L K series hondas? At least the Nissan has a factory 100mm full counter stroke crank post 08 from what I hear. Trav using JW know how was playing with SR20DE cranks in the QR25DE back in 2004 which would make excellent SR20DE replacement motors with more displacement no need for sleeving an SR20DE and then stroking it.

    Finally is a turbo QR25DE with the right internals as heavy as an all motor VQ v6?

    1. There is no way a QR can even come close to competing with a K motor. This motor was never any good and its not worth sinking money into it.

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