With the price of used 350Zs, 370Zs, G35s, and G37s, there’s a lot of growing interest in the VQ platform. While it might not be as special as something like the RB26, the VQ family of engines has decent potential for a mild streetcar. Recently we created a video covering the VQ35DE and VQ35HR and it was pretty clear that the HR is a far superior engine.
The VQ Family
As we found in the DE vs HR article, all VQ engines appear pretty similar from the outside looking in, but Nissan made significant changes from one engine to the next to make them better. It’s the same case with the VQ35HR and the VQ37VHR. The engines appear to be pretty much the same, but in actuality, the differences between them are pretty significant.
When Nissan was developing the HR aimed to improve every aspect of it compared to the DE, and they did the same thing when developing the VHR. They wanted more power, more efficiency, and better emissions. Just so we’re clear because I have seen some people on forums asking about this, there is no VQ37HR, the VHR is an evolution of the HR and the only VQ37 Nissan has produced is the VQ37VHR.
Starting from the top down, we have different intake manifolds. They share the same dual throttle body design, however, the VHR intake manifold has short intake runners compared to the HR manifold. Depending on the engine you’re looking at, shorter runners generally result in more high-RPM power compared to long intake runners.
In the case of the VH37, any potential loss in the low-end torque from using shorter intake runners is offset by the increased displacement and some of the other cool features we’ll talk about just a little bit later. Also, for whatever reason, Nissan slightly changed the bolt pattern on the intake manifold compared to the HR intake, which means you can’t simply put a VHR intake manifold on an HR engine.
Moving down to the cylinder heads, there are some significant changes and technologies that Nissan used which they previously hadn’t used on any other engine. The most notable changes in the cylinder heads revolve around each engine’s unique variable valve timing system.
On the HR, you’ll find a Dual VVT system that uses hydraulically actuated continuously variable valve timing for the intake cams and an electromagnetically actuated cam phaser on the exhaust side, the system offers a high degree of flexibility in setting valve timing to improve combustion efficiency over a wide engine speed range.
On the VHR, you’ll find Nissan’s VVEL system on the intake side. This system is unique from typical variable timing and lift system because the lift of the camshaft is continuously variable and the timing is continuously variable. The huge benefit to having continuously variable lift is the ability to effectively use the intake valves to control airflow into the engine instead of the throttle bodies.
You might be wondering, why bother with that when the VQ37VHR already has two throttle bodies? Well, if you were to have your throttle body opened less than – let’s say – 50%, your engine will experience a pumping loss. What I mean by this, is the throttle body created a lot of negative pressure in the intake manifold.
By using the intake valves to control the airflow at low throttle amounts, you can pretty much eliminate this pumping loss which simply means more efficiency, at least in theory. Another interesting benefit to this type of system is reduced camshaft wear since intake valve lift can be kept pretty small when the throttle is opened small amounts.
On top of all that, the VVEL system also improves throttle response and massive improves the power curve of the VQ37VHR. VVEL doesn’t increase peak power all that much, but it does provide more low-end and mid-range torque and flattens the torque curve to make it more linear and predictable.
To help minimize friction on both the HR and VHR engines, Nissan used a hydrogen-free diamond-like carbon coating for the valve lifters. To put it simply, the DLC coating, results in a 40% reduction in friction. Another notable difference on the heads is that the VHR has better exhaust ports and flows more air on the exhaust side.
Engine Internals and Blocks
Moving down to the bottom end, one of the big and rather obvious differences between these two engines is displacement. The VQ35HR is a 3.5L and the VQ37VHR is a 3.7L, which if you didn’t know is that the 35 and 37 stands for in their names.
Interestingly enough, the cylinder blocks between the HR and VHR are the same, despite the difference in displacement. They increased displacement by increasing stroke from 81.4mm to 86mm and leaving the bore the same since the blocks are the same.
Of course, increasing the throw of the crankshaft also means the connecting rods have to shorter if Nissan wanted to retain the same deck height, so the connecting rods on the VHR are 2.28mm shorter than the rods on the HR. From the info I was able to find, the VHR rods are also just slightly stronger than HR rods and capable of handling more power, other people have found they’re equally as strong.
The pistons are noticeably different and the VHR uses a higher 11:1 compression ratio compared to the HR’s 10.6:1 compression ratio. There are some other very small differences between the HR and VHR, however, we covered all the major and important differences.
Which One is Better?
The important takeaways from all this info, is that the HR and VHR are very similar. According to Nissan’s press release from 2007, 35% of the parts on the VHR are different from the HR. The most notable changes are the addition of VVEL on the intake side, shorter intake runners on the VHR, supposedly improved exhaust ports on the VHR, displacement increased from 3.5 liters to 3.7 liters, and use of the same block.
Both engines are really great and far superior from the VQ35DE. Nissan didn’t add anything that made either engine worse, both the HR and VHR are better than the engines which came before them, but in this case, I think it’s clear that the VHR is the better engine.