Welcome to the SR20 Community Forum - The Dash.
Register
SR20 forum logo
Forum
The Dash Manifesto
The Dash Gallery
Chat
New Posts
Private Messages
FAQ
Calendar
Community ▾
Forum Actions ▾
Quick Links ▾
Forum Rules
Advanced Search
→
SR20 Community
→
VVL
→
VE 4CW crankshaft max load

Thread: VE 4CW crankshaft max load

+ Reply To Thread
Posts: 11-20 of 80
Search Thread
2010-03-31 01:27:45
#11
Originally Posted by Andreas
The WHP load is the same as the 8 CWC. The RPM limit is much lower than the 8 CWC as far bearing life goes.

Please note that all NISSANs SR cranks that go over 7000 RPMS are 8 CWC and all cranks under 7000 RPMs are 4 CWC.


Originally Posted by Andreas
why does thing havre to so black and white with you guys.

Building a street motor to do some 1.4 mile racing run the 4 CWC

Building a race motor to go around a track run an 8CWC

Going to pullthe motor down every few races build an 8 CWC



Sorry mate - im in disagreement here for you.

Have you got any actual factual data/nissan data/physical data to prove this? I have to say otherwise!
Reply Reply With Quote  
2010-03-31 01:33:16
#12
if you have a 4cw crank run it. no one yet has posted info saying there motor went pop because of the 4cw. this is all just hear say and hype. thats how i see it anyways..

stratton.
Reply Reply With Quote  
2010-03-31 01:58:26
#13
Originally Posted by Autech
Sorry mate - im in disagreement here for you.

Have you got any actual factual data/nissan data/physical data to prove this? I have to say otherwise!


Crankshaft
Reply Reply With Quote  
2010-03-31 04:04:58
#14
Originally Posted by Andreas
Crankshaft


Thats just marketing crap = with some truth - but hardly a valid reason.

Your balance half comes from the timing and firing of the cylinders.

If all pistons and rods are balanced - you will never have any issues.

Our cranks run a 5 main cap system obviosuly. In between each cylinder the crank is tied down. We dont suffer issues of crank flex because of this. Our blocks will twist yes - but this has nothing to do with our cranks.

The extra weight of the 8cw actually puts MORE stress onto the bearing shells as there is effectively 4 times the weight of a 4cw crank. This is apart of newtons second law of physics.

T = R x F. We calculate the torque needed to rotate the crank. I wont go into the maths layout - but having a heavier crankshaft means there is more toque needed to rotate a heavier force.

During a crankshaft rotation for 45degrees either side of of the down stroke and 45 degrees either side of the upstroke there is hard load directly onto the bearing shell as the pistons velocity is either towards the head or towards the sump.

If you also use the the angular load formula - and substitute values - you will find the force on the pivot point (ie crank bearings) is higher with an 8cw crank than a 4cw. Simply because of the less weight.
Reply Reply With Quote  
2010-03-31 04:24:39
#15
oh ****, here we go

There are many things to argue about but the fact is that a 4cw I4 crank shaft puts more stress on the motor than an 8cw crank.

That second order harmonics that has been proven many times over even outside of nissan specific applications.
Reply Reply With Quote  
2010-03-31 05:05:36
#16
Originally Posted by donttazmebro
oh ****, here we go

There are many things to argue about but the fact is that a 4cw I4 crank shaft puts more stress on the motor than an 8cw crank.

That second order harmonics that has been proven many times over even outside of nissan specific applications.


exactly its got nothing to do with balance, its to do with harmonics. And as said its far from a nissan sepecific thing its a 4 cyl thing.

In short what miko said, if its a road car that you thrash everywhere you'll probably never have an issue. If you want to race the thing or spending hours abusing the limiter (eg track day) then a 8cw would be a good investment.
Reply Reply With Quote  
2010-03-31 10:43:38
#17
AUTECH, you just like argue to damn much, I could have brought a paper writen by Albert E and would have still came up with crap. I showed you that NISSAN changed their motors back to 8 from 4 CW and yoy still came up with ****. NISSAN had some big issues with bearing failure on their QR25DE SPEC V SER motors and they switched back to 8 CWC and made the bearings wider. You would figure they could have just left it 4 CWC and made the bearings wider.

Any way,I am done so keep arguing with yourself
Reply Reply With Quote  
2010-03-31 13:49:43
#18
Youve all got your heads in the sand.
Reply Reply With Quote  
2010-03-31 16:13:29
#19
Originally Posted by bigtoe
Folks,
From what I have seen the Bearing Beam (Girdle) holds the crank in the plane parallel to the main bearing centerline. Because the Block is a deep skirt design there is no need for a Girdle (by definition: main caps part of the assembly).
It is proven that the combination of deep skirt, registered main caps, a bearing beam and a torsional "external mass" damper gives the best overall control of crank vibration.
This is the method Nissan used on the SR20 for noise and vibration control, by extension it gave rise to a rock solid bottom end.

The discussion on 4 vs 8 CTW is a nice one. From what I have seen with my motors and others;
The 4 CTW tends to "vibrate" the NO.4 Main Cap and bearing.
The effect of this is seen on the NO.3 Rod Bearing.
I have not seen evidence of the same on the 8CTW.
I have felt the 4CTW come through a distinct harmonic for a very brief period in the rev range (solid mounted motor and solid all welded chassis).
There is also another thing that happens on an inline 4 motor and that is the fact that on this engine combination two cylinder fire right next to each other (3 and 4). What happens here is that by extension from the leverage forces of the rod journal, the Main journal between the two is twisted at a very high frequency from the unloading of one (exhaust stroke) to the re-loading of the same (power stroke on the other). It typically manifests itself on main bearing NO.4. This is something that every V configuration motor has to take into account in their crank designs (like Porsche got wrong on the first generations of the 928 V8 Motors). There is a lot more to this discussion because the only time it is evident is when the motor is "fired" and live under load, and not static for an imperical calculation on balance of individual components.

My recommendation would be for an 8 CTW for a car that will be pulling through a fairly wide rev range.

Now SUMITUMO under financing of various japanese OEMS studied the dynamics of 4 vs 8 CTW cranks and actually came up with the 4 CTW being better for any specific 4 cylinder motor. HOWEVER, the counter weigts are not egual mass in their design. SUMITOMO was chosen because they make the bulk of the Japanese crankshafts.

Again from my own experience: The Bearing Beam takes power away due to windage in the crank case and obstruction of the attomised oil around the crank. I have not seen this on my Dry Sumped negative pressure sump motor.

Later tonight I will post the two SAE Paper numbers for the crank design and for the vibration analysis on four cylinder engines for any one interested.


/thread
Reply Reply With Quote  
2010-03-31 16:35:02
#20
Originally Posted by donttazmebro
/thread


uh uh, oh no he didn't
Reply Reply With Quote  
+ Reply To Thread
  • [Type to search users.]
    • Quick Reply
    Thread Information
    There are currently ? users browsing this thread. (? members & ? guests)
    StubUserName

    Back to top
    Contact Us
    SR20 Community Forum
    Archive
    Privacy Statement
    Terms of Service
    Top
    Powered by ForkBoard™ Version 1.6.8
    Copyright © 2017-2024 Fork Computing. All rights reserved.
    All times are GMT -?. The time now is ??:?? ?M.