taken from our cousins over at Maxima.org (courtesy of SilverMax_04)

I have an Acrobat Reader File of a 2000 engineering paper (SAE Technical Paper) titled “Second Generation of High-Response V6 Engine Series (3.0 and 3.5 Liters)” by Nissan Engineers Arai, Yajima, Murata, and Hibino (written in English). Because it’s on Acrobat Reader, it’s not easy to copy the complete paper here. It has a number of graphs, some that are hard to read, even when printed out from the Reader version.

I’ve decided to quote what I think are the significant sections of this 5-page technical paper (no graphs), and mainly those that apply to the Maxima engine (3.5L) {with my comments in these brackets}:

Abstract:
Since the VQ engine series of lightweight, compact, low friction and high response engines was released in 1994, they have been rated highly both at home and abroad. Two new 3.0-liter and 3.5-liter V6 engines have been developed as the second generation of the VQ engine and introduced into the North American market. Continuing the characteristics of the first generation, this new VQ engine series achieves a performance figure of 98Nm/L as a result of adopting part shapes defined with a three-dimensional analysis method. . . . The new VQ35DE engine adopts a continuously variable valve timing control system and a long branch intake manifold with an inertial induction system. It also incorporates a new concept piston and a hot coined connecting rod to reduce its reciprocating inertial mass. These features enable it to continue the advantages of the VQ engine such as lightweight, high response and excellent fuel economy despite the increased displacement {Versus the first generation 3.3L}. Consequently, the pin diameter of the crankshaft per liter has been reduced to one of the thinnest in use. High productivity {automated engine assembly} has also been achieved, maintaining the rate of automatic assembly at 70% on a line for 2.0, 2.5, 3.0 and 3.5-liter engines due to the unification of parts and specifications.

Development Objectives:
The following main objectives were set for the development of this second-generation V6 engine series:
1. Reduction of weight and friction to maintain high response.
2. Improvement of quietness.
3. Improvement of volumetric efficiency to achieve one of the largest torque-per-liter figures in the world.
4. Improvement of thermal efficiency and reduction of friction to improve fuel economy.

Engine Specifications:
Major specifications of the V6 engine series {VQ35DE only}:
Number of Cylinders = 6
V-angle (degrees) = 60
Displacement (ccm) = 3498
Bore x Stroke (mm) = 95.5 x 81.4
Compression Ration = 10.0:1
Valvetrain = DOHC 24 valves
Fuel Supply System = Nissan EGI
Fuel = Premium
Max Power (kW/rpm) = 179/600
Max Torque (Nm/rpm) = 357/3200

{Note the compression ratio, which was confirmed by a tech at my local dealer. Some on this site have quoted this compression ratio as 10.3:1, which is not correct.}

Reduction of Weight and Friction:
PISTONS – The ADAMS analysis package was used for the VQ35DE to analyze the influence of the excitation forces, stiffness, behavior and offset of the pistons. The results indicated that slap noise could be controlled by reducing the stiffness of the piston skirt while decreasing the friction by reducing the piston offset. This would achieve both lower friction and reduced slap noise.

The specific measures taken to reduce the stiffness of the lower part of the piston skirt were to abolish the lower piston rib and to provide a back rib around the pin center. Accordingly, the transfer distance of the load center is shortened when combustion pressure is applied to the piston crown and piston movement becomes smoother, thereby reducing the impact pressure on the bore wall and suppressing piston slap noise.

Because the lower part of the thrust side acts as a slipper, the skirt length can be shortened without affecting the suppression of slap noise, making it possible to reduce friction and weight even more. Further, friction is reduced further and durability against scuffing is improved because the load applied to the piston skirt is reduced by this stiffness reduction. Shortening the piston pin length by tapering the piston pin boss shape has the effect of reducing the bending moment, so the compression height can be lowered to reduce the piston weight. As a result, the piston weight was substantially reduced. . . .

CONNECTING RODS – Connecting rods are usually cold coined to correct the deformation induced in the I-section by the heat treatment process. However, the VQ35DE connecting rods are made of vanadium steel, making the heat treatment process unnecessary. I-section deformation is corrected by hot coining to prevent deterioration of fatigue strength due to the residual stress and deterioration of buckling strength due to dislocations. This improvement of I-section strength allows the sectional area of the connecting rod to be reduced for a weight saving.

The small end shape has been tapered to reduce friction and weight without increasing pressure on the pin bushing when combustion pressure is applied. The way of fastening the connecting rods was changed from bolts and nuts to bolts only to reduce overall weight. Consequently, their reciprocating inertial mass was considerably reduced. . . .

CRANKSHAFT – The VQ35DE crankshaft pin diameter was thickened to accommodate the increased displacement. But the increase in the diameter was kept to a minimum through the aforementioned weight reduction of the pistons and connecting rods. As a result, the diameter of the crankshaft pin per liter is one of the smallest in the world, making it possible to reduce the inertial mass and friction of all reciprocating parts considerably. . . .

Through the foregoing improvement of reciprocating parts, the friction of the whole engine was reduced to maintain the high response characteristic of the VQ engine.

Improvement of Volumetric Efficiency:
REDUCTION OF INTAKE RESISTANCE – Intake resistance has been reduced . . . . in the VQ35DE through the selection of a suitable diameter of intake port molding sand without increasing the engine cost. Intake resistance of the VQ35DE has also been reduced by using three-dimensional analysis to define the detailed shapes of the intake manifold. . . . .

CONTINUOUSLY VARIABLE VALVE TIMING CONTROL SYSTEM (CVTC) – The VQ35DE adopts a continuously variable valve timing control system that allows suitable valve timing control relative to the engine speed and intake manifold length for improved volumetric efficiency. . . . This improvement has greatly improved volumetric efficiency over that of the previous engine. {The graph shows CVTC provides the biggest improvement in volumetric efficiency between 1K and 3K rpm. The new engine’s volumetric efficiency is highest between about 2,400 and 4,200 rpm; peaking at about 3,200 rpm – which is about peak engine torque.}

Improvement of Thermal Efficiency:
IMPROVEMENT OF EXHAUST PORT SHAPE – Knock resistance of the VQ35DE has been improved by reducing the temperature around the combustion chamber as a result of improving exhaust gas flow by adopting an improved exhaust port shape. . . . . Consequently, the engine achieves one of the worlds highest compression ratios to bore diameter. {The graph shows improvement over the previous engine in these approximate valve lift ranges: 1.8 to 3.5 mm and 6 to 7.5 mm. The graph flattens at about 6 mm of valve lift, with little increase in air flow mass above that opening up to a maximum of 9 mm of lift.}

IMPROVEMENT OF WATER FLOW BY LONG REACH SPARK PLUG – Cooling performance of the VQ35DE has been improved by expanding the water jacket around the spark plug as a result of increasing the spark plug screw length. Consequently, knock resistance has been improved. . . . {The graph shows the expanded water jacket results in improvement in ignition timing advance over the base water jacket design across the range from 1.5K to 6.5K rpm with the largest improvements of between about 2 to 4 degrees additional ignition timing advance between about 2K and 4.5K rpm and again from about 6K to 6.5K rpm.}

TWO-WAY COOLING SYSTEM – Generally, reducing the temperature at which the thermostat valve opens is one way to improve knock resistance. However, this approach reduces the bore temperature more than necessary and consequently may cause friction to increase. To manage both temperatures suitably, a two-way cooling system has been adopted in . . . the VQ35DE that switches by means of a thermostat. . . . . These measures have improved fuel economy over the level of the previous engine. {The graph shows the biggest reduction in fuel consumption for the driving sequence known as "LA4CH" and very little reduction for "Hwy" (highway) driving.}

Reduction of Noise and Vibration:
Crankshaft stiffness of the VQ35DE has been improved by increasing the crankshaft pin diameter. Furthermore, main journal clearance of the . . . VQ35DE was reduced by subdividing the grade of the journal and bearing diameter. Consequently, noise and vibration have been reduced. . . . {The graph shows a reduction in Noise Level (dB) versus engine load (Nm) of about 1.5 dB for engine loads from 310 to 340 Nm.}. . . .

 

CONTINUED..


Summary:
Through the improvements described here, this second-generation V6 engine series further improves the excellent performance and high response characteristics of the previous generation. Consequently, the power performance of vehicles fitted with these engines ranks among the highest in the world of passenger cars and SUVs. Figure 11 shows the engine performance curves for the New VQ35DE. {These curves were apparently done at the engine flywheel. The horsepower graph does not start until the engine has reached 4K rpm, and peaks at 180 kW at about 6K rpm. The torque graph goes from 1.2K to 6.5K rpm, peaks at about 355 Nm at 3.2K rpm, is relatively flat (between 300 and 355 Nm) from 1.4K to about 5K rpm, and still is about 255 Nm at 6.5K rpm.}

 

MORE:

I just received another Acrobat Reader File of a 2002 SAE Engineering Technical Paper titled: “Third Generation of High-Response and High-Output 3.5L V-6 Engine” presented March 4-7, 2002 in Detroit by Nissan Engineers Michi****a, Nakada, Yamagiwa and Murata (written in English). Because it’s on Acrobat Reader, there’s no easy way to copy the complete paper here. This paper also runs 5 pages, but it has many more pictures, tables, graphs, and diagrams than the 2nd Generation Paper. With fewer written words, this paper will be harder to describe only in words for this site, but I’ll try {with my comments in these brackets}:

Abstract:
The VQ engine was developed as a lightweight, compact, low-friction and high-response engine in 1995. In 2002, a new 3.5-liter third-generation version will be introduced in the North American market. The major development aims set for the new-generation VQ35 engine were to improve output and to reduce noise and vibration, while maintaining the VQ’s original features. This paper describes the technical approaches taken to achieve power output, noise and vibration improvements. In the process, CAE modeling and virtual simulations were used in performing a cylinder-block stiffness analysis and an airflow efficiency calculation.

Development Objectives:
The following objectives were set for the development of the third-generation VQ engine series.
1. To increase output and response for use on a sporty vehicle {read Maxima and 350Z}.
2. To improve not only engine stiffness but also that of the powertrain.
3. To reduce unpleasant noise and vibration during acceleration.

Engine Specifications:
The major specifications of the new V6 engine series are shown in Table 1 in comparison with those of the second-generation VQ35.
______________________________ New V-6 _______________ Previous V-6
Number of Cylinders _________________ 6 _______________________ 6
V-angle (deg) ______________________ 60 ______________________ 60
Displacement (ccm) _______________ 3496 ____________________ 3496
Bore x Stroke (mm) _____________ 95.5 x 81.4 _______________ 95.5 x 81.4
Compression Ratio _______________ 10.3:1 ____________________ 10.0:1
Valvetrain __________________ DOHC 24 valves ___________ DOHC 24 valves
Fuel Supply System ____________ Nissan EGI ________________ Nissan EGI
Fuel __________________________ Premium _________________ Premium
Max Power (SAE Net)(KW/rpm) ___ 216/6000 ________________ 179/6000
Max Torque (SAE Net)(Nm/rpm) ___ 362/4800 ________________ 357/3200
Valve Lift (mm) ___________________ 9.2 _____________________ 8.8
Valve Timing (deg CA):
______________ IVO _______ 5 ATDC - 30 BTDC ______ 3 BTDC - 27 BTDC
______________ IVC ______ 65 ABDC - 30 ABDC _____ 53 ABDC - 29 ABDC
______________ EVO _________ 52 BBDC _________________ 48 BBDC
______________ EVC __________ 8 ATDC __________________ 4 ATDC

Increased Output and Response:
Figure 1 shows the torque curve of the new VQ35 engine compared with that of the previous VQ 35 used in a sport-utility vehicle (SUV). {It also shows the HP curve from 4.8K rpm (peak torque) to 6.4K rpm (near redline), with no discussion of this measurement in the paper.} Torque output has been improved especially in the high-speed range {above 3.8 K rpm}. This improvement has resulted from better intake airflow efficiency, a higher compression ratio and a wide-range variable valve timing control system. {The torque curve for the previous engine dropped off fairly sharply after peaking at 3.2K rpm, such that the torque at 6.4 K rpm was about equal to the torque at 1.0K rpm. The 3rd Gen engine’s torque starts higher (275 Nm at 0.8K rpm) and except for a few small rpm ranges (where the previous engine has slightly higher torque) it remains above the previous engine to the end of the graph at 6.4K rpm. The increase in torque is particularly noticeable above 3.8K rpm, where the torque is substantially higher for the new versus the previous engine. The new engine’s torque curve is fairly flat (between 340 and 362 Nm) between 2.2K and 6.2K rpm.}{The HP graph starts at about 180 KW at 4.8K rpm, increases in a straight line to 216 KW at 6.0K rpm and falls to about 210 KW at 6.4K rpm. The new engine has from 30 to 35 KW more HP than the previous engine in this rpm range.}

INTAKE AIRFLOW EFFICIENCY – To improve intake airflow efficiency, the intake duct, intake manifold and intake port of the cylinder heads were redesigned. A straight intake duct was adopted as shown in Fig 2 {small, hard-to-see picture}. This straight duct improves airflow efficiency by 20% as shown in Fig 3 {graph}. As a result, intake boost is reduced at wide open throttle (Fig 4){graph}, resulting in increased power output. This indicates that the straight duct design works to reduce airflow resistance.

The intake manifold and intake collector were designed on the basis of CAE modeling and an airflow analysis. Two kinds of collectors were analyzed, one with a double surge tank and the other with a single surge tank (Fig 5) {small, hard-to-see picture}. According to the results of the airflow analysis, the double tank type showed a lower airflow rate than the single tank type in the high-speed range. The reason is that a double tank experiences a stronger air resonance effect than a single tank, as can be seen in Fig 6 {graph with wide pressure swings for the double tank at 6K rpm}which shows the results of measurement of pulsation at the intake collector. And Fig 7 {graph} shows a result of air-flow coefficient analysis comparing the two type intake collectors. Based on this analysis, the intake collector of the new engine has been designed such that two surge tanks are used in the middle-speed range, whereas both tanks are connected to form one large surge tank for overcoming the resonance effect in the high-speed range.

Other specifications that play an important role in improving airflow include the cylinder head port. On the new V-6 engine the cylinder head port has a larger port angle than that of the previous generation (Fig 8) {cut-away diagram}. This modification, together with a valve lift increase from 8.3 to 9.3 mm, improves the airflow rate by 6% as shown in Fig 9 {graph showing most of the improvement occurring when the valve lift is over about 6 mm.} Generally, a high flow port produces low tumble flow and leads to inefficient combustion. To avoid that conflict, the compression ratio has been raised from 10.0:1 to 10.3:1 to increase combustion speed under a lower tumble condition as indicated in Fig 10 {graph}, which shows the ignition timing characteristics compared with those of the previous engine.

VOLUMETRIC EFFICIENCY – Wide-range (35 CA deg.) continuously variable valve timing control (C-VTC) is a key technology for the high flow intake system. The intake system pulsation characteristics as shown in Fig 11 {series of 3 small graphs at 2.4K, 4.8K and 6.2K rpm} in relation to engine speed. It is clear that each engine speed requires a different intake valve timing. Because the valve timing is optimized by the C-VTC system, the new engine can achieve high volumetric efficiency, such as 105% at 5,600 rpm (Fig 12), without any decline in the lower speed range. {Graph showing volumetric efficiency versus engine speed with little difference in efficiency between generations up to about 4K rpm. Above that engine speed, the previous engine’s efficiency falls off above 4.4K rpm to about 90%, while the new engine’s efficiency continues to remain at or above 100% up to 6.4K rpm.}

COMBUSTION EFFICIENCY – As noted earlier, to increase the combustion speed, the compression ratio was raised to 10.3:1. Coolant flow through the cylinder heads was therefore modified to avoid knocking. Using CAE modeling and a water flow analysis, the configuration of the water jackets was defined so as to improve flow between the exhaust ports and also the velocity distribution (Figs 13 and 14). {Small pictures of “Defined water jacket core” and “Defined water jacket-Cylinder head section.”}

Stiffness Improvement and Noise Reduction:
CYLINDER BLOCK COUPLED WITH DRIVETRAIN – A front-engine rear-drive vehicle naturally has a long drivetrain and a potential for lower stiffness. It is well known that insufficient bending stiffness is one cause of rumbling noise during acceleration. Figure 15 shows the bending vibration level of the modified VQ powerplant compared with that of the previous generation. {Graph of “Noise and vibration level on acceleration” which shows the new engine with reduced high-frequency noise level: the same up to 5 kHz, down over 6 dB at 6.3 kHz, and down over 12 dB at 10 kHz.} According to a finite element analysis (FEA), the addition of several ribs to the oil-pan surface to increase its stiffness is effective in reducing bending stress compared with a pan without ribs (Fig 16). {Two small blurry pictures and a graph of engine speed versus vibration level which shows the new pan with reduced vibration level from 4.5K to 5.5K rpm with the maximum reduction of about 6 dB at 5K rpm.}

CYLINDER HEADS – reducing tappet noise is one effective measure for lowering the mechanical noise level. A CAE analysis revealed that mechanical noise could be reduced by increasing the stiffness of the tappet chests so as to lessen their movement while the engine is running. A bridge structure was therefore added between each of the tappet chests to restrict their movement (Fig 17). {Small blurry picture of “Cylinder head stiffness improvement” with an area labeled “Bridge.”} The bridge structure is effective as shown in Fig 18. {Graph of “Improvement of vibration level” which shows the most reduction in vibration level occurred in frequencies from just above 2 kHz to just below 4 kHz and also above about 7 kHz. The peak improvement was about 5 dB.}

 

MORE continued..


TIMING CHAIN – A super silent timing chain has been adopted to reduce timing chain noise. This super silent chain has a ramp profile between the sprockets to reduce impact energy produced by the chain contact with the sprockets (Fig 19). {Diagrams of the two chains and a graph showing a reduction in impact energy of over 0.04 J at 1.5 K rpm.}

NOISE REDUCTION EFFECT – The noise level of the new V-6 engine is compared with that of the other engines in Fig 20. {Graph of 10*Log (torque) versus SPL that shows an improvement over the previous engine of about 1.25 dB. The new 3.5 engine is also quieter than three V-6 engines from 3.0 to 3.2 L and an L-6 engine of 2.8L.}

Creation of Pleasing Acceleration Sound:
INTAKE MANIFOLD COLLECTOR – This factor is known to cause intake air rumbling noise during acceleration. The new V-6 engine has been redesigned with an equal distance between the throttle chamber and each intake port to attain high output. Figure 21 shows the results of an FFT analysis of air intake noise. The results indicate that the new intake collector reduces the 0.5 harmonic order, as well as reducing rumbling to provide a clear acceleration sound. {Two small graphs labeled “Intake air noise analysis result.” They are hard to read and interpret.}

Summary:
As a result of incorporating the improvements described here, the new 3.5-liter V-6 engine can achieve higher output than the previous generation while reducing unpleasant noise and vibration. The modified intake system and optimized intake valve timing enable the engine to attain volumetric efficiency of 105% at 5600 rpm. The compression ratio has been raised to 10.3:1 to prevent a decline in combustion speed due to lower tumble flow, and coolant flow through the cylinder heads has been improved to avoid the occurrence of knocking. As a result, power output of 216 kW is achieved. In spite of the increased output, noise and vibration have been reduced by increasing the stiffness of the engine proper, adopting a super silent timing chain and modifying the intake and exhaust manifolds.

 

even more...


For those of you (like me) who don’t relate well to metric measurements or an engine’s horsepower expressed in terms of KiloWatts (KW), I have some added information – I have converted all of the power and torque measurements provided in the technical paper on the 3rd generation VQ engine to terms we better understand (Horse Power and Ft-Lbs). I’ve also compared the results of the engine described in this paper with the advertised power and torque for the 04 Maxima 3.5 L engine. From that, it is clear that the test engine is not exactly the Maxima engine – NOR is it exactly the VQ engine in the 350 Z. (see the table below for comparisons)

Remember, the Maxima and Z results are what Nissan is advertising for each engine.

Measurement ______ 3rd Gen Test Engine __ 04 Maxima _____ 350 Z

Power (KW/rpm) _______ 216/6000
Horsepower (HP/rpm) ___ 290/6000 ________ 265/5800 ____ 287/6200

Torque (Nm/rpm) ______ 362/4800
Torque (Ft-Lbs/rpm) ___ 267/4800 _________ 255/4400 ____ 274/4800


For anyone who wants (or will need at some time in the future) to make these conversions, I recommend the following site for conversion factors:

http://www.processassociates.com/pro...ert/cf_all.htm

 

???

under summary:
"The compression ratio has been raised to 10.3:1"

and under engine specs:
"Note the compression ratio, which was confirmed by a tech at my local dealer. Some on this site have quoted this compression ratio as 10.3:1, which is not correct."

Which is correct?

 

10.3:1 ..

well. according to the dates of the SAE papers.


there also seems to be more than 3 versions of the VQ35

 

Excellent article, thanks. In your first post, you mention that some on this site refer to engine compression incorrectly at 10.3:1, where you claim it should be 10.0:1. But if i understand the article correctly, that is for the older 2nd generation VQ35. Then I am lead to believe that the newer 3rd gen VQ35 is bumped up to 10.3:1. Am I clear on this?

 

yea.. BL--

our version VQ (presumably the third version) is 10.3:1...

the earlier version 3.5s were 10.0:1..

all of this was taken from maxima.org's posts..

 

can you email me that article at joshua.l.bass@lmco.com or utaengineer@yahoo.com

 

Excellent find Cheston.

 

im trying to get that article from that 6thgen maxima owner..

its an Society of Automotive Engineers (SAE) report....

 

105% volumetric efficancy in NA motors was unheard of in production car motors & its not that long ago that Cosworth achieived it in race motors.

 

Cheston

Great find on the SAE papers. Could you please email them both to me at dr_gallup@yahoo.com Thanks in advance. The maxima.org is a nice site too.

 

Cheston:

Thanks for posting what you had available.

I searched the SAE site and found the following:

1. 2000-01-0668 : Second Generation of High-Response V6 Engine Series (3.0 and 3.5 Liters) 03-06-2000 Paper

2. 2002-01-0450 : Third Generation of High-Response and High-Output 3.5l V-6 Engine 03-04-2002 Paper

You posted from paper #1; paper #2 from 2002 is probably the one that describes the Z's engine.

The papers are for sale and download from the SAE site for $12 each:

http://www.sae.org/servlets/productD...D=2000-01-0668


and

http://www.sae.org/servlets/productD...D=2002-01-0450

Thanks again,
Dave

 

again, wonderful post. made my day (from bad to good)...

 

those who requested the files.. i have sent them out.. it is roughyl 1.5mb.. if you cant get that big of an email.. let me know..

 

Cheston....Brad4rdHay@aol.com

 

can someone forward the files to me also, please...

robert@rcreations_no_spam.com (remove the "_no_spam" part)

thanks,
rob

 

interesting..

i found a few more papers on SAE.org.... this is cool.. but i dont have it. :P

Document Number: 1-110-10-97
Title: Nissan 350z
The company's FM platform blitz accelerates with the new sports car. AUTHOR(S):Jack Yamaguchi - Society of Automotive Engineers