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Thread: 4CW vs 8CW vibes

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Posts: 1-10 of 32
2009-06-26 21:59:07
#1
4CW vs 8CW vibes
with all the talk in the other thread here about light weight crank pulley VS oem with rubber dampner this made me think....

when i was a DE (8cw crank of course) driver i vividly recall not only the sound of the engine @ 7500-7800 rpm, but more importantly the feel. a very distinct pounding as it approached fuel-cut. it felt as though it was ready to give up the farm if i didn't shift very soon.
now the VE (with its 4cw crank) is a completely different animal altogether.
its almost rotary engine smooth up high in comparison. really freaky if you've never driven one and you just climbed out of a good running de.
so, the question is this...is it a function of the 4cw crank throwing less weight around that makes the ve smoother or what? does putting a 8cw de crank in a ve bring back those bad vibes/pounding at high revs? inquiring minds wanna know

thanks guys,
2009-06-26 23:43:31
#2
high mileage cranks have been known to bend slightly over time. Not sure if the SR crank has that issue with time...

I have a VE with an 8cw and it is very smooth up high. Sounds great. About the only vibrations I feel are from the stiff motor mounts. Other than that it is really quite smooth.
2009-06-27 01:05:26
#3
My VE/DE mutt feels ok at 8k. But my brothers VVL feels smoother up top though.
2009-06-27 02:12:34
#4
i thought it was better to have a 4cw in a boosted car then a 8cw
2009-06-27 14:22:59
#5
the 4cw crank only makes sense in a cvt transmission. It will not be smoother in high rpms. I actually feel that the 4cw crank with an 8.8lb flywheel is too light and hurts the first to second shift. The a 8cw crank with a lightweight flywheel feels alot smoother and seems to keep better momentum between shifts. I will have an sr16 trans on my car soon so the gearing will help out the issue keeping momentum from the 1st to 2nd shift.
2009-06-29 08:23:56
#6
Originally Posted by bj200sx
i thought it was better to have a 4cw in a boosted car then a 8cw


why do you say that??
2009-06-29 15:24:05
#7
Originally Posted by crackerjack
why do you say that??


just what i was reading, maybe i got my facts crossed, but i thought i remember reading a lot of guys where switching cranks when they started boosting their ve.
2009-06-29 15:48:45
#8
Think about this. The first gen SR20VEs had the 4cw crank. Why would Nissan go back to an 8cw crank on the SR20VE 20V motor. What you feel as "smoothness" is you getting up in the high RPMs much faster than a DE. Ive driven a VE and took it up to 8K RPM. Sat in my modded DE and took it up to 7.5K RPM. I felt no weird vibration or such. The only difference I felt was the extra power when the cams switched over and that it got to 8K RPM quicker than my DE.

This is a quote from Dre.

Originally Posted by Andreas

This is my opinion.

Even Nissan made the change back to the 8 CWC in the newer motors.

Here is a look at SR20 motor that dont rev past 7000 RPMs, they all have 4 CWC

SR20VE P11
SR20DE Roller Rocker B15, P11 and U14

Here is a look at SR20 motors that rev above 7000 PRMs, they all have 8 CWC
SR20VE 20V P12
SR20DE B13, B14, P10
SR20DET RNN14, U12, U13, W10, W11


Lets take a look at SR16VE motors

The early ones come 4 CWC. After the first 2 years Nissan changed back to the 8 CWC, makes you wonder why.

The only thing the 4 CWC has on the 8 CWC is weight. The 4 CWC is about 7 pounds lighter which is alot of weight. So that being said a 4 CWC should rev up way faster than an 8 CWC. This is a major advatage.
2009-06-30 07:13:21
#9
this is a really good thread, cant wait to find out some results..
2009-07-01 00:04:27
#10
It is worth mentioning that K20s come with both cranks as well. The 160hp version of the K20(A3) is a 4cw and revs to 7K rpm. The Fun K20 (The A1, A2, Z3 etc) rev to 8 and 9K and have 8cw cranks.
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