3.1 Conversion to a 2.9 vr

[Chris VR6nos 0]

This is it and if you get an intercooler you'll have to get the charger to work so hard that you get into belt slip areas and the outlet charged air temps are way up high too so making it false to have the c/r too low too.

H8RRA's is 9.8:1 so just under the 10:1 std and it works so well indeed and it has a git big daft Skyline FMIC on aswell.

 

 

 

Chris

[rixy 0]

right o, this defo sounds like the best way to go then?

 

so is it best to stay maybe a 3.0L and go for slightly lower c/r, or go with the pistons vince has got, which are slightly lower c/r 3.1 jobbies? i suppose if im going to do it, id rather go 3.1 jobs, what sort of difference will offsetting the crank do? and what companies can do this work? as if im going to do it, i may aswel do it all in one hit eh?

 

what other things do i need to think about?

[Rob_B 0]

dont bother with the vr, buy my engine!

[Chris VR6nos 0]

Rob_B, what do you mean, buy a 4cly engine?

 

Rixy, a good machine shop specialising in engine work will do the offset thing but you need to tell them critically what you want and i can't explain as much as i want on here cos text doesn't carry enough explanation.

The offset thing is much more complicated and might be more trouble to you than it's worth.

You need to find out the cloarence volume of the piston, this is critical then you can work out the C/R you need from there Pi x r2 x h gives you the swept volume then add the clearence volume and divide the clearence volume+swept volume be the clearence volume, this will give you the static C/R and you can work out from there what you need to do.

I did a thread, was it this one some time back explaining it much more in depth!

 

 

Chris

[Chris VR6nos 0]

rixy, i meant to say, click on the CC calc in my sig and you can play around with some sizes and it will give you the total cc of the engine in any configuration, i might modify it to work out C/R too, that'll be handy i think for projects such as yours.

 

 

 

Chris

[Rob_B 0]

Rob_B, what do you mean, buy a 4cly engine?

 

Chris

 

sounded like u said that with some disgust!

[rixy 0]

well, who would want an inferior engine hey rob, he he, hows ya car going now anyway, is she painted yet?

[rixy 0]

chris, i cant use the cc calc as i dont have the program i need to run it, what prog is it, i'll download it now?

 

prob wont bothrer with the offset thing then, as it sounds well above my head, lol, just get the crank knife edged and balanced,a nd get the flywheel balanced and lightened?

[double-6s 0]

microsoft excel mate.

[rixy 0]

cheers double 6's, now getting it m8

[double-6s 0]

:)

[Rob_B 0]

well, who would want an inferior engine hey rob, he he, hows ya car going now anyway, is she painted yet?

 

[Chris VR6nos 0]

But Rob, there is huge work to convert it to a 4cyl engine and a STD VR is 200bhp so even a modded G60 isn't much against that, and torque wise the VR has 6cyls to help it spin, poor argument but i know where you are coming from :wink:

I'm a great follower of modding engine bits for more power or advantage, however you will see less that the usual benefits knifing the VR crank as it doesn't really impact upon the oil in the sump as some engines do but as long as it's well ballanced ans tuftrided and straightened it will be a benefit

 

 

Chris

[double-6s 0]

Whats this knife edge crank thing Chris??

[Kevin Bacon 5]

:-)

 

Basically the big cam lobes are 'filed down' for want of a better expression.

 

As Chris touched on above, some cranks slap into the oil which can slow it down at high revs, so I think the idea behind knife edging the big crank counter weights is to aid a smoother path through the oil or some such flannel.....it'll be a lighter crank too, which is also gives faster spin up times.

[double-6s 0]

Aye than kew :)

[rixy 0]

yeah, thats what im thinking of doing, it may not do much on a vr, but if its better balanced,as you say, it'll defo help?

[Henny 0]

the main problem with knife edging is that you're removing a LOT of the inherent strength from the crank by removing that much material... Fine for a race engine that's gonna get stripped regularly and checked over after each race, but for a regular use road car, simply mildly lightening and then dynamically balancing the whole bottom end will yield some very nice results without compromising strength too much... 8)

[Chris VR6nos 0]

No one's saying make it look like a spiders web and anyone capable of carrying out such work would do it to a safe specification i woul d have thought.

Kev, what the hel is that heap of crank out of? a cement mixer?

 

 

Chris

[steve_16v 0]

what the hel is that heap of crank out of? a cement mixer?

 

I was wondering the same thing yesterday and had a look, it's part of a motorbike crank

[Chris VR6nos 0]

That's not a knife edged crank, it's a lightened crank, this is a knife edged crank!

 

 

Chris

[Rob_B 0]

yep, thats what a knife edged crank looks like as thats what the lobes of mine look like! its a work of art!

[Chris VR6nos 0]

Surely you have pics of yours then?

As we won't believe you unless you post them!

 

 

 

Chris

[Rob_B 0]

this could be a picture from anywhere so how will you believe me?!

[Chris VR6nos 0]

Just a matter of trust but i'm pleased you have one, is it running and if so what's the noticable result?

I like things like this and wonder what the differences would be if it was done to a VR crank!

Let us know how it goes.

 

 

Chris