non sr20 but look at nissans new pistons
just found this forum the other day, the guys got some different nissan pistons like the NEW spec-v, rogue, frontier, etc and found some new designs and what not that Nissan is using now.
Piston Research
Here is a copy of the article....
All content is copyrighted and the property of TwoFiveTuning.com. Redistribution in part or whole is allowed, so long as the content is not; altered in a way to be presented or misrepresented as the effort or property of a person or entity other than TwoFiveTuning.com, or for personal gains. In simple terms, don't be a dick.
In the spirit of looking for a good solution in the OEM parts bin I picked up a few of the new pistons to do a little research, a 2008 Rogue, 2009 Altima, and a 2008 Spec V piston, which has a 10.5:1 compression ratio. I also ordered a 2005 Frontier piston hoping the truck motor chassis specific piston might have some unique and worthy features, but, they are on backorder without a release date, so no go for now. I’d also like to see a piston for a Canadian X-trail just for good measure. Before I started this research project I was fairly sure the new QR pistons would share a lot of the same features as the pistons in the VQ35HR and well as some carryover features from the old pistons. Very little made its way from the old pistons to the new pistons, just the anti-friction coating on the skirts and the hard anodizing on the first ring groove, other than that it’s a whole new design. It shares just about every feature of the VQ35HR piston, it’s a nice direction for Nissan and has a lot of features that were previously only found in race pistons.
One of the first things you’ll notice is an asymmetrical skirt design, a box type perimeter support, and racing type slipper skirts.
(bottom view of piston showing perimeter box frame and asymmetrical skirts)
The thrust side of the piston is the exhaust side and has a smaller area than the intake side. The overall decrease in the surface area results in a reduction of friction netting better overall efficiency. The direction of rotation of the crankshaft and the angle of the connecting rod pushes the piston into the cylinder wall as part of getting it to go up the bore. The greater the rod angle (like the QR) the greater the side loading force. The coating on the skirts is (most likely) a high quality molybdenum disulphide based epoxy. It greatly increases the wear life of the pistons and provides a lower coefficient of friction and higher efficiency overall, and combined with the skirt design, you get the idea. Nissan has been using low tension thin compression rings for a while now. One of the greatest areas of frictional losses in a motor is the rings. Nissan put together a winning package with the attention to detail given to the design of this piston.
(tapered skirts, smaller exhaust side (thrust side) on right, larger intake skirt on left, note anti-friction coatings, hard anodizing around first ringland, and oil jet notch on intake skirt)
The box type perimeter support is integrated into the pin boss for extra support of the pinboss, piston skirts, and piston head. The box runs squarely through the middle of the pinboss and uses gentle radii to avoid stress points and seamlessly merge together for a very ridged support structure.
(detail of boss and skirt structures)
The pin bosses themselves are a strut type with gentle outward sloping sides to widen the base, providing better support, and narrow as they near the pin to save weight. Contoured pin bosses for weight savings are an expensive option on custom aftermarket pistons. The Spec V specific piston has further contouring on the outboard side of the pin boss for additional weight savings. It’s probably a good time to mention the Spec V Gen II QR has a factory redline around 7000rpms, so weight savings is paramount. If I had money to throw away, I'd cut the pistons in half right through the face and take pictures to get a good look at the cross sections and thickness of the piston heads. A good cross section can tell you a lot about structure and the potential of a part to withstand abuse and heat. Maybe, just maybe, curiosity gets the better of me sometimes.
(pin boss detail showing Spec V specific piston profiling (on left) vs. Rogue piston (on right))
(note lack of profiling on aftermarket piston, piston on right is a Gen I QR piston)
Lacking from the pin bosses are the bottom oiling holes of the Gen I pistons.
(Gen I piston oiling bottom oiling holes)
My best guess is it would weaken the thin structure of the bosses, and with oil jets a feature on the new QRs, totally unnecessary for good pin oiling. Notice the subtle cut out to clear the oil jets.
(detail of oil jet (squirter) cutout in skirt)
The ring lands are an area of concern for turbocharged QRs. Nissan follows suit with most OEMs by pushing the top ring up high on the piston to reduce emissions and make more power. As the ring goes up, the ring land gets thinner. It just spells disaster if you run into detonation with a turbo charged QR. The ringland likes to fracture freeing up little sections which bounce around in the combustion chamber, and then bang their way though your turbo’s turbine on it’s way to piston heaven. I was hoping the Rogue piston, being for a truck and heavy duty use, would utilize a thicker top ring land, but that's just not the case. I do feel the alloy and casting quality adds considerable strength in the ringland area. The Spec V 10.5:1 piston's ringland is 1mm thicker than the Rogue or Altima piston. For the picture below I placed a wrist pin between the two pistons to line them up for a good comparison shot.
(ringland detail, Spec V piston on left, Rogue piston on right. Note 1mm thicker ring land on Spec V piston. Also note the very thin ring land for the oil control rings)
The FSM (Field Service Manual) shows the new QRs advancing the intake cam via the CVVT unit in the 40 degree range. The old CVVT sprockets will only do about 33* total, but in data logging I've never seen a value higher than about 23* of cam advance on Gen I motors. As you advance the intake cam the intake valve opens sooner and sooner, that puts it closer and closer to the piston in doing so. The intake valve reliefs on the new pistons are substantially deeper than on the Gen I pistons to allow for this.
(Gen II Spec V piston on left, Rogue on Right, valve relief depth is the same, the difference in the width of the outer rim and the taper angle into the dish of the piston creates the differing shapes of the cutout)
(Gen I piston for reference)
So now on to the most interesting feature of the new pistons.............. The new pistons have a unique face. There are protrusions above the face of the pistons that partially encircle the valves on the side closest to the cylinder wall. The exact reason for this feature is a mystery to me other than speculation, which I'll go into in a minute. Someone way smarter than me put this feature into the new design.
(yeah, I'll let you figure this one out)
(Ditto, refer to Gen I piston valve relief pic to compare Gen I and Gen II piston face.)
I am unable to measure the piston dish due to these protrusions, and subsequently unable to calculate a compression ratio of these pistons in a Gen I motor until I can CC the combustion chamber of a Gen II head. Once I get my hands on one I'll be making a mold of both the Gen I and Gen II combustion chambers for reference and comparison. The Spec V piston is 10.5:1 and has a shallower dish, because of this the overall size of the protrusions are smaller to compensate. If you look closely at the pictures you can see slight differences.
At first glance the protrusions look as though they would create valve shrouding at low lift near TDC. Part of the reason for that may be intentional, it is possible that at low lift the area between the valves creates turbulence that harms flow, and this was done to counter that, It is also possible they act as a small area of quench that intentionally creates turbulence on the compression stroke near TDC to aid in complete combustion. It is also possible it helps to more fully evacuate the cylinder on the exhaust stroke, or move the fuel air charge into an area it is more completely burned, or some combination of all the possibilities. If you have an idea or theory on the function of these, feel free to e-mail me at [email]youknowwho@twofivetuning.com[/email].
For a little advanced tinkering, taking either piston to a competent machine shop and having them mill the face of either piston flat might give you a compression ratio well suited to your needs. I may have the Altima piston cut flat to calculate a compression ratio. It would make a killer low comp piston modified like that, but I don't really recommend a comp ratio under 9:1 for a turbo QR motor, which still leaves a modified Spec V piston as a good option too.
On to another aspect all together: JDM vs. USDM, an age old battle. The design of the 2009 Altima piston and the Rogue piston are for all intents and purposes the same. Where they differ is where they are made, and cost. The retail on the Altima piston is $28 and is made in the USA, the Rogue piston is closer to $50 and made in Japan. What's the big difference? The casting quality of the Japan made Rogue piston is top notch as well as the machining and finish. Not to mention the alloy which could very well be different. There is nothing wrong with the US made Altima piston, but I like to nit pick the details. Examine the pictures below and you'll see some of what I'm talking about.
The Japanese pistons are made by Hitachi. It's not some top secret JDM tuner information, it cast right into the inside of the piston skirts.
("Don't they make TVs?" Actually, they make more stuff then you ever realized.)
I can't seem to find a stock piston floating around in my garage so it'll be a minute before I put out some side by side shots, weight comparisons, details about the wrist pins vs. the old stuff, and if I can get the hook up on some metallurgical testing, maybe even some alloy analysis, Rockwell data, etc. for the grown ups. Check back for updates as no research project is ever really done.
So, will the new pistons drop into the old motors? There are only a few ways to find out; dropping them in, taking careful measurements, getting your hands on a 2007 head, or bribing an engineer at Nissan. I'll weigh through those options and get back to you soon. Have fun, be safe, and make power.
Thanks for reading,
The TwoFiveTuning.com crew
Piston Research
Here is a copy of the article....
All content is copyrighted and the property of TwoFiveTuning.com. Redistribution in part or whole is allowed, so long as the content is not; altered in a way to be presented or misrepresented as the effort or property of a person or entity other than TwoFiveTuning.com, or for personal gains. In simple terms, don't be a dick.
In the spirit of looking for a good solution in the OEM parts bin I picked up a few of the new pistons to do a little research, a 2008 Rogue, 2009 Altima, and a 2008 Spec V piston, which has a 10.5:1 compression ratio. I also ordered a 2005 Frontier piston hoping the truck motor chassis specific piston might have some unique and worthy features, but, they are on backorder without a release date, so no go for now. I’d also like to see a piston for a Canadian X-trail just for good measure. Before I started this research project I was fairly sure the new QR pistons would share a lot of the same features as the pistons in the VQ35HR and well as some carryover features from the old pistons. Very little made its way from the old pistons to the new pistons, just the anti-friction coating on the skirts and the hard anodizing on the first ring groove, other than that it’s a whole new design. It shares just about every feature of the VQ35HR piston, it’s a nice direction for Nissan and has a lot of features that were previously only found in race pistons.
One of the first things you’ll notice is an asymmetrical skirt design, a box type perimeter support, and racing type slipper skirts.
(bottom view of piston showing perimeter box frame and asymmetrical skirts)
The thrust side of the piston is the exhaust side and has a smaller area than the intake side. The overall decrease in the surface area results in a reduction of friction netting better overall efficiency. The direction of rotation of the crankshaft and the angle of the connecting rod pushes the piston into the cylinder wall as part of getting it to go up the bore. The greater the rod angle (like the QR) the greater the side loading force. The coating on the skirts is (most likely) a high quality molybdenum disulphide based epoxy. It greatly increases the wear life of the pistons and provides a lower coefficient of friction and higher efficiency overall, and combined with the skirt design, you get the idea. Nissan has been using low tension thin compression rings for a while now. One of the greatest areas of frictional losses in a motor is the rings. Nissan put together a winning package with the attention to detail given to the design of this piston.
(tapered skirts, smaller exhaust side (thrust side) on right, larger intake skirt on left, note anti-friction coatings, hard anodizing around first ringland, and oil jet notch on intake skirt)
The box type perimeter support is integrated into the pin boss for extra support of the pinboss, piston skirts, and piston head. The box runs squarely through the middle of the pinboss and uses gentle radii to avoid stress points and seamlessly merge together for a very ridged support structure.
(detail of boss and skirt structures)
The pin bosses themselves are a strut type with gentle outward sloping sides to widen the base, providing better support, and narrow as they near the pin to save weight. Contoured pin bosses for weight savings are an expensive option on custom aftermarket pistons. The Spec V specific piston has further contouring on the outboard side of the pin boss for additional weight savings. It’s probably a good time to mention the Spec V Gen II QR has a factory redline around 7000rpms, so weight savings is paramount. If I had money to throw away, I'd cut the pistons in half right through the face and take pictures to get a good look at the cross sections and thickness of the piston heads. A good cross section can tell you a lot about structure and the potential of a part to withstand abuse and heat. Maybe, just maybe, curiosity gets the better of me sometimes.
(pin boss detail showing Spec V specific piston profiling (on left) vs. Rogue piston (on right))
(note lack of profiling on aftermarket piston, piston on right is a Gen I QR piston)
Lacking from the pin bosses are the bottom oiling holes of the Gen I pistons.
(Gen I piston oiling bottom oiling holes)
My best guess is it would weaken the thin structure of the bosses, and with oil jets a feature on the new QRs, totally unnecessary for good pin oiling. Notice the subtle cut out to clear the oil jets.
(detail of oil jet (squirter) cutout in skirt)
The ring lands are an area of concern for turbocharged QRs. Nissan follows suit with most OEMs by pushing the top ring up high on the piston to reduce emissions and make more power. As the ring goes up, the ring land gets thinner. It just spells disaster if you run into detonation with a turbo charged QR. The ringland likes to fracture freeing up little sections which bounce around in the combustion chamber, and then bang their way though your turbo’s turbine on it’s way to piston heaven. I was hoping the Rogue piston, being for a truck and heavy duty use, would utilize a thicker top ring land, but that's just not the case. I do feel the alloy and casting quality adds considerable strength in the ringland area. The Spec V 10.5:1 piston's ringland is 1mm thicker than the Rogue or Altima piston. For the picture below I placed a wrist pin between the two pistons to line them up for a good comparison shot.
(ringland detail, Spec V piston on left, Rogue piston on right. Note 1mm thicker ring land on Spec V piston. Also note the very thin ring land for the oil control rings)
The FSM (Field Service Manual) shows the new QRs advancing the intake cam via the CVVT unit in the 40 degree range. The old CVVT sprockets will only do about 33* total, but in data logging I've never seen a value higher than about 23* of cam advance on Gen I motors. As you advance the intake cam the intake valve opens sooner and sooner, that puts it closer and closer to the piston in doing so. The intake valve reliefs on the new pistons are substantially deeper than on the Gen I pistons to allow for this.
(Gen II Spec V piston on left, Rogue on Right, valve relief depth is the same, the difference in the width of the outer rim and the taper angle into the dish of the piston creates the differing shapes of the cutout)
(Gen I piston for reference)
So now on to the most interesting feature of the new pistons.............. The new pistons have a unique face. There are protrusions above the face of the pistons that partially encircle the valves on the side closest to the cylinder wall. The exact reason for this feature is a mystery to me other than speculation, which I'll go into in a minute. Someone way smarter than me put this feature into the new design.
(yeah, I'll let you figure this one out)
(Ditto, refer to Gen I piston valve relief pic to compare Gen I and Gen II piston face.)
I am unable to measure the piston dish due to these protrusions, and subsequently unable to calculate a compression ratio of these pistons in a Gen I motor until I can CC the combustion chamber of a Gen II head. Once I get my hands on one I'll be making a mold of both the Gen I and Gen II combustion chambers for reference and comparison. The Spec V piston is 10.5:1 and has a shallower dish, because of this the overall size of the protrusions are smaller to compensate. If you look closely at the pictures you can see slight differences.
At first glance the protrusions look as though they would create valve shrouding at low lift near TDC. Part of the reason for that may be intentional, it is possible that at low lift the area between the valves creates turbulence that harms flow, and this was done to counter that, It is also possible they act as a small area of quench that intentionally creates turbulence on the compression stroke near TDC to aid in complete combustion. It is also possible it helps to more fully evacuate the cylinder on the exhaust stroke, or move the fuel air charge into an area it is more completely burned, or some combination of all the possibilities. If you have an idea or theory on the function of these, feel free to e-mail me at [email]youknowwho@twofivetuning.com[/email].
For a little advanced tinkering, taking either piston to a competent machine shop and having them mill the face of either piston flat might give you a compression ratio well suited to your needs. I may have the Altima piston cut flat to calculate a compression ratio. It would make a killer low comp piston modified like that, but I don't really recommend a comp ratio under 9:1 for a turbo QR motor, which still leaves a modified Spec V piston as a good option too.
On to another aspect all together: JDM vs. USDM, an age old battle. The design of the 2009 Altima piston and the Rogue piston are for all intents and purposes the same. Where they differ is where they are made, and cost. The retail on the Altima piston is $28 and is made in the USA, the Rogue piston is closer to $50 and made in Japan. What's the big difference? The casting quality of the Japan made Rogue piston is top notch as well as the machining and finish. Not to mention the alloy which could very well be different. There is nothing wrong with the US made Altima piston, but I like to nit pick the details. Examine the pictures below and you'll see some of what I'm talking about.
The Japanese pistons are made by Hitachi. It's not some top secret JDM tuner information, it cast right into the inside of the piston skirts.
("Don't they make TVs?" Actually, they make more stuff then you ever realized.)
I can't seem to find a stock piston floating around in my garage so it'll be a minute before I put out some side by side shots, weight comparisons, details about the wrist pins vs. the old stuff, and if I can get the hook up on some metallurgical testing, maybe even some alloy analysis, Rockwell data, etc. for the grown ups. Check back for updates as no research project is ever really done.
So, will the new pistons drop into the old motors? There are only a few ways to find out; dropping them in, taking careful measurements, getting your hands on a 2007 head, or bribing an engineer at Nissan. I'll weigh through those options and get back to you soon. Have fun, be safe, and make power.
Thanks for reading,
The TwoFiveTuning.com crew
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