|VH POWER Parts Technical Info VH FORUM Contact Info|
Projects are currently being populated
Crash Course of the VH. Basically, there are 3 types of VH. They are
The VH45DE is the “king”, and was used in the Infiniti Q45 90-96, and the Nissan President 89-01. The VH41DE was used in Japan only in the 90’s in cars such as the Y32 Cima, JPY32 J.Ferie (Basically an infiniti J30) and so forth.
The VH41DE used in the 97-01 Q45 was very different. It is not as strong as the VH45DE or JDM VH41DE, had log type intake and exhaust manifolds, and the internals were not as strong. The crankshaft bearing girdle was lost, as well as many other of the features we love about the VH’s.
The major difference between the VH45DE and JDM VH41DE is the stroke is simply shorter. Rods and pistons are the same, difference is in the crankshaft. VH45 internals can be swapped into a VH41. The VH41 have slightly better heads due to a duplex timing chain setup, but the heads are otherwise nearly identical. Heads can flow nearly 500HP.
The VH45 uses 370cc injectors, identical to the ones used in the VG30DETT and SR20DET. The VH41 uses 270cc injectors which are identical to the KA24 and VG30DE injectors. With that being said, it is possible to use 555cc or 740cc NISMO side feed injectors on a stock VH45 fuel rail. Obviously, tuning would be required.
Currently, VH Power is researching the ability to use VQ30DET pistons as decompression pistons for boost. They have the same bore and wrist pin measurements, and very similar compression height, and have a dished design.
VH Power is also currently researching the use of valve springs from other motors for use in the VH. The stock VH valve springs are very weak at a measly 120lb, sufficient for a stock Q45 but not for a race motor with 15lbs of boost!
How far can I take a VH?
One of the best things about the VH is how far they can be taken with little to no modification. The stock pistons, which are of a flat top design with recesses for the valves are not very prone to detonation, which means they can be boosted very safely with no internal modification. Of course, we all are familiar with the legendary internals that Nissan gave us back in its prime, and the VH is no slouch. It seems that other things break easier than the insides of a VH.
In New Zealand, many of the Super Stock racecars use JDM VH41’s. They run those things to about 9000 RPM and 500HP on basically stock motors. Modifications include mostly things like headers, intake and cams/valve springs (note stock hydraulic adjusters are retained).
VH Power has not been made aware of anyone boosting a VH past its stock injector HP rating, which is around 450HP, so its hard to say right now how much boost one could run with larger injectors and a really good tune. It seems everyone who blows up boosted VH’s loses them to tuning, because on a high compression motor detonation will kill it very quick. Properly tuned vehicles have been known to see lots of boost and a lot of HP, but the line where adding more fuel does nothing to prevent detonation is not yet known.
Even HIGH MILES motors can take a beating if they were properly maintained. If the oil was changed regularly, a motor with 200k could be about as good as a motor with 120k. They simply don’t wear out that fast. However, if the motor was overheated or looks really dirty inside then avoid it because it will probably need redone. Clean examples can be imported from Japan very often, so its usually not cost effective to rebuild but rather find a clean, complete motor.
Quirks/Problems with the VH
The VH45DE was the motor used in the Infiniti Q45 luxury vehicle. Since this was Nissan’s first attempt at a luxury vehicle, and stiff competition from Toyota and Honda, as well as the Germans, they had to be sure to do it right. Most of the problems with VH’s are all age related. Hoses get brittle, knock sensors go bad, and so forth, all of which can be replaced with factory parts fairly easy.
It must be stated that all 90-93 VH45’s need to check the timing chain guides. Like the KA motor, the chain guides were made of plastic and when they break they can throw the chain off the camshaft and destroy the motor.
The major problem with VH45’s is the injectors, mainly due to the higher ethanol content in today’s gasoline. In areas of where this is not a problem you see much less injector related issues. Most Q45 injector issues occur in California, Arizona and New York, as their gasoline has higher concentrations of ethanol.
The MAF on the VH45 can also be somewhat troublesome, causing really weird driveability issues. Generally, VH45 MAF’s cannot be rebuilt or saved, you must replace with a working used or new. Knock sensors also fail with age, they can be easily tested and the harness should also be replaced anytime the sensors are being replaced. One can easily inspect the knock sensors and if there are cracks anywhere on them, they are probably bad. Also, if the knock sensors look like they have melted, the engine has been overheated severely and further action should be taken before the motor is damaged further.
- Forged steel crankshaft.
Some Measurements and Pictures
Here are some measurements from various components in the VH45. Thanks to “defrag010” on the forum for providing these.
* all measurements are +/- .005"
Intake valve head size = 1.501" / 38.15mm (no
oversize possible w/o shrouding)
Valve stem seals (SBI part numbers, viton, metal
I also took measurements of the cam cap bolts so that I can have some made that are low profile 5-point heads vs. the crappy 1/4" torx. I twisted off two different snapon torx bits getting these caps undone, so I think some 5-point head bolts will be nice to have incase you break one off and have to drill the head off of the torx bolt like I did.
-height = 1.56"
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