vh41de vs vh45de

[mak3]

just wondering if anybody could please tell me if the vh41 came before or after the 45 i have vh41 for a transplant and have been told that some have vvt and im not sure how exactly to tell this.

[JimmyMethod]

VH45 was first.Then 41. Both were in the Q45.http://en.wikipedia.org/wiki/Nissan_VH_engine

[mak3]

thanx..you.ve answered aquestion iv ben wondering for a while.so im guessing the 41 isan evolution of the 45

[Q45tech]

Evolution might be the wrong word- Devolution in that the 4.1 was a lighter duty downsized version to increase fuel economy in the downsized Q.

Obviously this was the wrong way to go as the engine only lasted 5 years [97-01] before being upsized on the light duty block back to 4.5

[maxnix]

VH41DE was already in the inventory in many guises, and Nissan thought the gas guzzler tax was killing G50 sales, so they brought in the FY33 as a LS400 price leader beater. US market didn't really want it.

Still a damn nice car, and great for an everyday driver.

[elwesso]

I would guess that the VH41 was out around the same time give or take a few years as the VH45

THe VH41 was offered in many other cars too, nissan cima and J-ferie come to mind.... It is often hard to tell the difference because early VH41s came with the spider intake like the VH45!

The VH41 is still a nice engine, just made for lighter and lower class cars...

[Mettler]

The VH45DE has siamesed exhaust ports (bad for flow), whereas the VH41DE has significantly higher flowing heads.

In base trim, the power difference is around 11HP, but for modification, the VH41DE is the more desirable platform due to its significantly better heads, and smaller physical size.

[elwesso]

THe exhaust ports were not siamesed, just hte intake ports... Also, the 94+ VH45 did not have those ports.

[Fred D.]

Has any one ever replaced the spider intake, seems their might be some advantage to a lower profile intake, for low rpms. I have done research that shows high rise intake manifolds only improve ab0ve 3-4000rpms.

[Q45tech]

THe runner length [from valve midlift point to entrance to plenum] is what primarily tunes the rpm at which the torque peak occurs. [assuming 2nd mode]

To get a lower torque peak rpm you need longer runners.The plenum voume primarily sets the rpm HP peak rpm along with the runner taper [diameter at top vs diameter at last round portion past injectors.

The volume of the runner must be larger than the cylinder volume [562cc] to get the extra boost [in volume] as the reflected wave from the sudden enlargement of the column at it reflects of the air mass of plenum.

The plenum volume must contain enough air to feed the runners without going dry at max rpm [or max flow] usually just above the HP peak rpm.

Anyway the exotic Q design was necessary to boost torque at 1500, 2000, 4000, and 4500 rpm then to provide a tiny increase at 5500 and 6,000 rpm................very complex design to squeeze the max out.

Obviously the harmonic frequency of tune [2nd, 3rd, or 4th] results in different runner lengths but the 2nd harmonic [reflection] creates the most ram effect and this declines as you go to higher orders [modes].http://mgcgti.clarkeandclarke.co.uk/Page28.html

http://www.mne.psu.edu/me415/f....html

http://www.eng.ed.ac.uk/~jchic...7.htm

[maxnix]

And there was a spider intake plenum on the JDM VH41DE in the Leopard J Ferie like on the VH45DE rather than the US Log type intake plenum on the US VH41DE in the Cima based 1997-2001 Q45.

One of those spider plenum with the Impul headers might be interesting, but illegal on road.
Modified by maxnix at 8:57 AM 2/2/2006

[Q45tech]

You cannot study the runner and plenum in isolation as the Helmholtz neck from plenum thru throttle body and the plastic tube all the way thru MAF including the air box flow stack are tuned as is the air filter and all the acoustic piping to the final ram horn in front of radiater.

Probably the most expensivea and complex intake system ever used on a car............just to smooth out the peaky nature of a detuned 32 valve racing engine.

Exact rpm tuning varies with air temperature. and barometric pressure.

From 32F to 120F the speed of sound changes 8.5% so th rpm tune would changes that much say +-4% from 60F. Not that the torque peak rpm would necessarily change just the additive amount from the tuning would rise and fall at a specific rpm.

The 8% density improvement over the temperature range would be in addition to the 8% tuning changes.

Why important to understand that the absolute peak torque amount will vary with temperature of intake air and all engine are speced at 60F thus the designed of plenum will be at 60F.

[Q45tech]

As to the differences in lower runner and its mating to head........oval vs 2 almost round ports.

If you look you will see even the oval port is divided into a dual path inside the head.............in effect the oval is just extended by 1.3" from south of injector thru head interface..........as I understand it these changes were made to decrease sudden richness [emissions] when the throttle was suddenly closed [lift off] at high rpms.

Doubt that this change had much torque effect since the length from half open valve to plenum is the critical parameter.......the loss of metal volume [the dividers] probably increased runner volume by a % at most.

Same thing happened to G20 2 liter in 1994 went to oval port..

One much consider reversion at low rpms when the intake valve is still open as the piston moves up and in the exhaust cycle when the first part of in charge is used to blow out last bits of used charge.

1500-4600 rpm -20 IVO vs +8 EVC........28 degrees overlap.

Only the designer knows for sure what he was accomplishing. Generally these things are changed for emissions not to create more dirty power........as it wasn't until 1998-2000 that the Q competitors exceeded the 90-95 power outputs for the 4.0-4.5 engine range.

[Q45tech]

See the length of the cross ram runners to try to boost low rpm torque and members think our 18" inchers are long.

[Q45tech]

Above picture..............."Now THIS is the crowd stopper. An engineering miracle in its own right, I am amazed this thing actually runs as well as it does for a 4300 lb car. The 413 inch wedge motor with its 30 inch long ram-induction intake manifolds with twin Carter 4bbl carbs, produce 375 hp and 495 ft lbs torque. More than enough to launch this beast from 0-60 in 7 seconds flat (if you can keep the wheelspin under control) and propel it down the quarter mile in 15.5 sec @ 92 mph"

See the difference in old GROSS HP and Torque compared to a newish Q.

Gee a Q can equal this brute's 375 HP/495 lb/ft at least in accelerating the same weight. with 280/300 real power vs inflated gross power.

413 cubic inches vs 274?

Better picture so you can fully appreciate the runners

[maxnix]

Noticed on my 2K FSM GI-40 showing where the serial number plate on the engine is located, the intake manifold is the spider. Oooops!