A Nissan Sentra Forum banner

1 - 10 of 10 Posts

·
Registered
Joined
·
2,028 Posts
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, tapered skirts, and a box type perimeter support.


(bottom view of piston showing perimeter box frame and asymmetrical skirts)

The minor thrust side of the piston, the exhaust side, has a smaller area than the intake side. The intake side is the major thrust side and has more surface area because it is more stressed with side loads, and the decrease in the surface area of both skirts 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 right, 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 protected].

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
 

·
Registered
Joined
·
7,399 Posts
good info, when does the testing begin? what are the compression ratio when using those selected pistons on a qr25
 

·
Registered
Joined
·
2,028 Posts
Discussion Starter #3
good info, when does the testing begin? what are the compression ratio when using those selected pistons on a qr25
Not sure yet, because the face of the piston isn't flat I can't measure the dish and make a calculation on CR. Assuming the new heads have a combustion chamber volume of 55cc, then they would be the same, but until I can find some data, or measure a 2007 head, i have no real way of knowing. I'll keep updating the writeup as I find out new info. Probably be doing an NA build around February-March so keep on the look out for that.
 

·
Registered
Joined
·
2,028 Posts
Discussion Starter #7
new stuff

Technical said:
Well, the Frontier piston is in my hands…………. I can’t find any evidence of a superceded part number, so I’m disappointed I didn’t take a look at this piston earlier. I’ll look into this some more, but the 2005 Frontier FSM shows an illustration of the piston face that shows the same face design.

The 2005 Frontier piston has the same squish/quench inducing protrusions on the face as the Gen II pistons but the skirt structure and shape of Gen I piston. The dish is extremely deep and oval shaped. To compensate for the depth, the protrusions are larger than the Rouge and Spec V pistons. You can clearly see in the pictures below as the dish gets deeper the squish areas get larger. I wish I knew in more detail how the differences affected flame front propagation and detonation resistance.


(2009 Altima piston on left, Frontier piston on right)


(Frontier piston on left, Spec V piston on right)

The flip side of the pistons clearly illustrates the difference in skirt design. The Frontier piston is mostly Gen I from this end, with the exception of the bottom oiling hole missing from the pin boss, and the addition of cutouts to the lower side of oil control ring boss to facilitate oil drain back toward the side of the pistons. No clue if those features were an evolution of the Gen I design before the clear change to the Gen II stuff. Defiantly not features on the pistons of motors I’ve torn down.







The Frontier piston has full profile symmetrical skirts that are about 2-3mm longer than Gen II pistons.



When you start to take a look at the ring pack and ring lands things start to get more interesting. The total height from the top of the Gen II piston to the bottom of the ring pack is noticeably shorter than the Frontier and Gen I pistons. The area between the 1st and 2nd compressions rings is much wider, the width of the oil grove is about 1mm wider, and the top ring land is about 1mm thicker than the Rouge or Altima pistons. It’s the same thickness as the 2007 Spec V piston. The compression ring grooves look to be the same. It’s hard to capture in a picture but with a pin between two pistons the frontier piston has an ever so slightly higher compression height.


(2007 Spec V piston on left, Frontier on right, top ring land is same thickness as Spec V piston)


(this picture makes the difference in height look larger than it is)

Now that the motor has a quench and squish area it adds another dimension to tuning and engine building. Once you start milling the deck and head you’re closing the clearance between the squish areas and roof of the combustion chamber. Go too far and you’ll have piston to head contact, get it just right, and you’ll pick up some power. Nissan probably left a good bit of room (as far as small clearances go) to play with. There isn’t a minimum clearance established so play with these clearances at your own risk.

For an NA build the best choice is looking like the 2007 Spec V piston hands down, when you turn making a choice for a boosted or heavy nitrous application the choice gets more difficult. The one choice that is obvious is anyone of these pistons is better than the original flat top design.

Oh, and once again the pistons are made by Hitachi, well, one of their subsidies, UNISIA





Options are good,

TwoFiveTuning.com.com
 

·
Registered
Joined
·
9 Posts
Just in case anyone likes to order by numbers...

The parts list for the newER Spec-V QR guts into an old QR is:
12201-ET80A Crankshaft (8-weight) 1 req'd
12100-ET80B Rod Compl (the beefier ones) 4 req'd
12314-JA00A Plate-Signal (i haven't confirmed personally, but if trav says so...) 1 req'd
12315-EN200 Bolt-Signal (i don't recall if you need 3 or 4. they're cheap, tho) 4 req'd
A2010-ET82A Piston, W/Pin (these are the funky semi-domed Spec-V ones... apparently the highest compression stock... THIS NUMBER IS *STD. GR. 3* the largest std available, if you're only gonna have your std bore block honed up a bit... *0.020 O.S. is A DIFFERENT NUMBER.*) 4 req'd
12033-ET80B Ring Set-Piston (THESE ARE *STD* BORE. if you're gonna go *0.020 O.S. it's a DIFFERENT NUMBER*) 1 req'd

Please note, these numbers are subject to supersession... they may get new part numbers eventually as design changes come out.

You'll need to order the correct rod and main bearings after the crank arrives and you check the numbers vs the bearing grade chart.

There's also a pin that holds the signal ring in alignment... I don't know the number for it. I simply had my machine shop install a roll pin to hold the alignment.

The pistons I received were 1.5 grams out of balance, and the rods were WAY out of balance (almost 5 grams total), so plan on having the assy balanced.

It's a bit pricey for a N/A build, but my spec ate the pre-cat, and I'd like to have it back together, and just a bit tougher than stock. When I get to bolting it together, I'll check the head and piston volume for all you confuzzled people.

I'll also weigh everything if I get the chance. I've got all the new stuff, when I tear down my (s)crap engine, I'll weigh it before I toss it.
 

·
Registered
Joined
·
1,720 Posts
So I must ask, I read all this and still don't know for sure. Is the frontier piston better for turbocharged application? also what would it's compression ratio be in an 04 spec v?
 

·
Registered
Joined
·
1,059 Posts
So I must ask, I read all this and still don't know for sure. Is the frontier piston better for turbocharged application? also what would it's compression ratio be in an 04 spec v?
Anyone got any info for that yet? I was wondering too for turbocharged applications
 
1 - 10 of 10 Posts
Top