Hi.
I am new to this forum.
I want to buy Infinty FX 2010-2014. FX37 Seems better in terms of performance.
But i have 3 Concerns.
1. Are those engines same in terms of reliability ? Is there any new technology implemented on VQ3.7 that may make it even slightly less reliable?
2. Compression Ratio. Due to the country i live in, there is another problem. Fuel quality. I will use Premium Fuel anyway, but our Premium Fuel does not have as high octane level as the advertised. VQ37 has 11:1 Compression ratio as opposed to 10.6:1 ( VQ35) . Is this difference is high enough to lead to more strict premium fuel requirement? (I know that if there is a detonation, ECU will retart the timing to adapt the fuel quality. But retarded timing may not be good in the long run and lower Compression Ratio may be a better solution)

3. Spare Parts Availability.
Again, Since my country is small, High quality spare parts are not always easy to find. From my past experience i see that, if a car has as an engine which is common with other models, its engine parts are easier to find.
So, Any idea, VQ3.5 or VQ3.7 is more commonly used engine in Nissan-produced cars ?

Any help is appreciated

 

Welcome- the first item you should plan for is that the VQ37VHR is a generation ahead of the VQ35HR. As such, the newer engine is more sophisticated in terms of the sheer number of sensors and overall electronic architecture. Both engines will dial back ignition advance and power with substandard fuel. To be honest, I'm not sure either the VHR or HR will do well with less than premium unleaded. As far as parts availability, it's hard to say which engine has more plentiful parts. Here in the USA, HR parts are drying up quickly, as that engine was sold in smaller numbers than the VHR.

Tradeoffs are difficult to evaluate in a different country. I'd suggest looking at the overall condition of any car you purchase, whether its a FX35 or FX37. Check with Nissan specialists in your country to see what they are seeing as far as parts availability and overall reliability.

 

On the other hand, I'd be surprised if Nissan did NOT take into account the local markets. I would think that the tune/compression/VVT, etc would be tuned for the country the car was originally sold in. I mean, if you took the USDM version and shipped it in (or was sold as such by Nissan), I'd think that there might be problems (slim chance though). But taking into account fuel quality, elevation (if that applied), and all other environmental factors, I really doubt there'll be any performance issues.

Parts availability is another thing altogether. With Covid still rearing its ugly head around the world, parts availability is already sketchy. But even in the best of times, you might want to check with both local and other market suppliers to gauge how this will affect the maintenance of your Nissan.

 

The VHR will be a plenty reliable engine and has better technology than the HR.

both the HR and VHR are very similar in architecture with one major difference that the VHR has variable valve lift along with variable cam timing on both intake and exhaust(found on both).

both engine will be difficult to repair if you need to replace anything unique (depending on your mechanical abilities).

the earlier model VHR (like anything before 2013 I think) have paper gallery gaskets and you’ll want to change this out and/or keep an eye on oil pressure.

the VHR is used in so many models that it’s widely available and less expensive than the DE or HR.

I wouldn’t worry about low / lower octane fuel. The engine and ecu monitor the knock sensor signal and will retard timing of you get into knock due to bad fuel or low quality fuel.

I believe both the HR and VHR have dual knock sensors where the DE has a single.

further, the VQ engines are MBT limited (not knock limited) and it actually takes them quite a bit of ignition timing to knock.

 

Hi Friends.
Thanks all for very much for detailed answers

Can you please elaborate on this? i Made some Google search about 'MBT Limited vs Knock Limited' but the results was too technical to understand.
Does it mean that MBT limited engines are specially designed, so that they see MBT likely before knock. So in brief, they are less likely to knock than other types of engines ?
Regards.

 

Its a relatively complicated topic but I would suggest you research further as it’s the basis on how and why engines make power and how/why tuning an engine can make more power.

Here’s a free set of basic tuning courses from HPA
https://www.hpacademy.com/courses/ba...ng-fuel-tuning

essentially an engine is going make a peak amount of torque at a given RPM. (Lets focus on torque here and horsepower last). How an engine makes torque is from harnessing mechanical leverage on the crank shaft from the reciprecating motion of the piston powered by the combustion event of air & fuel. And its not an explosion that drives the piston, it’s the combustion pressure from the explosion (think of the foot of atomic bombs back in the 1950s / 1960s - it wasnt the explosion of the bomb that did damage, it was the shock-wave the exposion created that wiped cities down).

So there is an optimal amount of torque that an engine will produce … you find this by starting at a safe ignition timing value (for a given RPM & load) and gradually increase timing until one of two things happen.

1. As you increase timing you will find a peak torque point…you increase timing and torque rises, and rises, and rises and then starts to fall off as you continue to increase timing. This is called MBT timing (among other things). Maximum Brake Torque. This is also know as MBT Limited…meaning the engine isnt knocking as you increase timing and doesnt knock past the point of peak torque - so you set your timing here and that’s the highest output.

2. As you increase timing you start to encounter knock. In this scenario, the air:fuel is ignited by the spark plug too soon (too much timing) and causes the engine to ‘knock’ and you’re igniting the air:fuel mixture prior to the piston reaching the top of cylinder and you are essentially pushing the piston and rod in the opposite direction.

Knock is different than pre-detonation/pre-ignition where pre-detonation and pre-ignition are combustion events that are caused by something other than the spark plug and usually before the spark plug fires - excessively hot cylinders, excessive cylinder pressure, hot carbon deposits on the head, hot spark plugs, etc.

So when an engine is knock-limited it means that as you increase timing you reach a point where you experience knock and need to back timing down even though you have not reach peak torque. You’re limited based on the knock you experienced.

The VQ engines are mostly MBT limited and once you get into turbo/superchargers you start finding that you become knock limited.

There are many factors that go into why an non-turbo’d / non-supercharged engine is/isnt MBT limited - bore:stroke ratio, rod length:stroke ratio, compression ratio, fuel choice, spark plug choice…I’m sure there are more attributes.

From above - torque is a good measure of how efficient you engine is identifies the RPM at which your engine operates at it’s peak efficiency. Horsepower is mostly a function of how fast you can spin the engine. Torque will rise and peak and then fall. The peak is where the engine is most efficient. Horsepower (typically) will climb proportionally to your engine speed. The faster you can move air:fuel in and out of the engine will dictate how much horsepower it can make. Find an engine with a 10k rpm redline and it’ll make plenty of horsepower, but at 10k rpms the torque has fallen off drastically.

 

Thanks very much for another great explanation.

As far as i understood, the terms 'MBT Limited' and 'Knock Limited' are about ignition timing rather than Engine specification. Right ?
If engine is running and advancing the ignition will provide no more torque increase, or even reduce it, so it is running at MBT. And, If advancing the ignition timing can raise the torque, but cause knock too, then it is Knock Limited.
So if it is all about Ignition Timing, and there can be many factors why timing is MBT limited or Knock limited, such as Engine compression ratio, Engine load, Combustion chamber design, Fuel octane and so on. why should we call VQ engines MBT limited.
Is it because those engines are designed in a way, so that when using recommended quality fuel, they are running at MBT, and still have some room till it becomes Knock limited? So that they are not too sensitive to variations in fuel octane?
Sorry if i misunderstood the whole point
Regards.

 

MBT Limit and Knock limit are all application specific. No two engines will ever be the same. It doesn't matter if you are running a DE, HR, VHR no two engines will have the same limits. Each generation will be similar but not the same. Yes it is timing that will more often than not causes knock but, many many things will help or hurt when knock occurs. Air Temp, Air Density, Engine Load, Fuel Quality, Combustion Chamber Temp all play a role in how much timing you can run.

On a N/A motor you 'should' reach MBT long before you ever see knock. If you are seeing knock before MBT then you need to evaluate the things above and figure out what you can make better.

The one thing you have to understand is, the is head is where ALL power is made. You can only make 'X' amount of power when you have 'A' amount of Fuel, 'B' amount of Air (Oxygen) and 'C' amount of timing. 'A', 'C', can be changed quite simply with stroke of a key, but 'B' can not changed like that. It will be a constant value based on Compression Ratio, Valve Size, Combustion Chamber Size, Cam Specs (The Heads). So, when you have a static (yes it will change slightly based on RPMs) flow of oxygen into the combustion chamber that oxygen can only make and explosion so big. Regardless of how much Fuel you input or or when you ignite that fuel in the combustion chamber. If you ignite it to soon or too late you will not make the optimal explosion decreasing power. If ignite to soo you have a good chance of causing knock damaging the engine.

This is why we reach MBT, before he hit knock limitations on a N/A application. When you are running boost/NO2 you are introducing extra oxygen which allows for a bigger explosion to be possible. Thus resulting in the possibility of higher combustion chamber pressures which can cause the fuel to explode on its own (knock).

Sorry if this makes no sense.

 

It really makes sense
Thanks a lot

 

Hi, i decided to by VHR 3.7, but your this comment made me concerned.
So the 3.7 Before 2013 has poor Gasket design ? In later models only new gasket was made to solve issue or some engine parts redesigned along with the gasket ?
i should by cars 2013 onward ? Any exact date possible ? For example late 2012 models or early 2013 models are affected ?
Or just buying any early models of 3.7 would be fine if i replace those gaskets with newer gasket types ?
Is it head gasket or other gaskets too ?
Sorry if i could not understand the point
Regards.