Knife edged crank?

[sideways danny]

hehe

well it would be the 421 cams i would be using i expect, bit more mainstream than the hillpower ones...

should do ok with 421s. wont do 240 though!!!. think the high comp engine we mapped (didn't build it) with 421s did 221bhp, cams were holding it back IMO.

 

[sideways danny]

did you not set the date right either?

does it matter?

 

[Dangerous_dave]

should do ok with 421s. wont do 240 though!!!. think the high comp engine we mapped (didn't build it) with 421s did 221bhp, cams were holding it back IMO.

what would you recommend? cams wise

 

[Fred@BTM]

does it matter?

not really, are you "on" at the moment? this thread started so well, we agreed on something! LOL

 

[sideways danny]

what would you recommend? cams wise

I'd personally use 422s. Better suited to a high comp engine, and peak power.
Investigating other options but dont have another recomendation at the moment

 

[sideways danny]

not really, are you "on" at the moment? this thread started so well, we agreed on something! LOL

it was just a quick reference graph i kept on my laptop, not supplied to a customer. the original is on here somewhere, all correctly titled etc etc. just giving a quick example of what to expect from a 240bhp engine

 

[Fred@BTM]

i know, just confusing to others seeing 0.6bar boost when talking about n/a engines

 

[Dangerous_dave]

Spec -

Bits i already have
F4R engine re-bored
Wossner Forged Pistons (12.8:1) 83 or 84mm cant remember exactly
Hillpower / Catcam 421 Cams - could sell both to buy more aggressive.
Uprated Valve Springs
Jenvey Throttle Bodies
Jenvey 90mm Trumpets
Lightened Billet Flywheel
Helix Paddle Clutch
Full Samco Hose Set
Pro Alloy custom short rad and uprated fan

Bits i still need
Will get bottom end balanced.
uprated ARP Bolts - to be purchased
main/thrust bearings - TBC not sure what to do
big end bearings - TBC not sure what to do

Aftermarket management & loom etc - To be purchased!

 

[Dangerous_dave]

what about 423's?

newman cams do anything worth looking into?

also baffled sumps? worth considering for aggresive driving?

 

[sideways danny]

423s will peak over 8k I think (not tried, but an educated guess) newman are pricey, never really looked at them

 

[Dangerous_dave]

423s will peak over 8k I think (not tried, but an educated guess) newman are pricey, never really looked at them

I didnt think they were too pricey - F7r stuff is £350+vat

no price for f4r cams though so will email them see what they say

what about C&B / Shrick

 

[stan*]

For the OP...no point in knife endging a crankshafts leading edge.

Read any basic sources on aerodynamics, you will quickly find the most aero-dynamic shape is a tear-drop, so it follows that making a knife edge isnt going to reduce drag.
Knife-edging the trailing-edge would theoretically be better, but i cant really see any quantifiable gain.

As for dynamic balancing--each to their own...its not something which has solid theory behind it either.

 

[Dangerous_dave]

For the OP...no point in knife endging a crankshafts leading edge.

Read any basic sources on aerodynamics, you will quickly find the most aero-dynamic shape is a tear-drop, so it follows that making a knife edge isnt going to reduce drag.
Knife-edging the trailing-edge would theoretically be better, but i cant really see any quantifiable gain.

As for dynamic balancing--each to their own...its not something which has solid theory behind it either.

Cheers for advice stan, are you doing Bazzon's build?

 

[Mike_182]

Having looked at the work to get 800bhp+ out of an I5, knife-edging seemed to cause more problems than the gains were worth. Taking material out of anything inherently causes changes in where the stress points are, and unless someone is very well acquainted with the engine then it's entirely possible to ruin it.

As the argumentative pair have said, balancing is more than adequate for 99.999% of circumstances.

 

[Dangerous_dave]

Having looked at the work to get 800bhp+ out of an I5, knife-edging seemed to cause more problems than the gains were worth. Taking material out of anything inherently causes changes in where the stress points are, and unless someone is very well acquainted with the engine then it's entirely possible to ruin it.

As the argumentative pair have said, balancing is more than adequate for 99.999% of circumstances.

i am pretty set on getting the balancing done - and also seeking advice on the knife edge side of things from a few people in the know.

 

[Jonny1*2]

dry sump for the 1*2. didnt realise you could get one. Would be nice though. Good for track work.

 

[Barron]

Cheers for advice stan, are you doing Bazzon's build?

Barron ;-) and yes he is

 

[Dangerous_dave]

Barron ;-) and yes he is

ooops sorry matey

 

[stan*]

I can have cranks dynamically balanced, if you want to send the crank/pulleys/clutch cover down to me. Its £125.
I do it on 90% of my engine builds for customers, but its more out of matter of course...i.e. whilst the crank is being ground may aswell do it, as I tend not to charge for it.
But as said, the actual theory behind what you are trying to achieve makes it pretty pointless. Each to their own though...lots of people do it for whatever reasons they have.

"knife-edging" i really wouldnt even bother with...ive never done it and never would.
As someone above has said, you could easily make a detrimental effect on the engines harmonics, as you could definately get the balance between reciprocating mass and counter-weight mass way off.

 

[_WILL_]

"knife-edging" i really wouldnt even bother with...ive never done it and never would.
As someone above has said, you could easily make a detrimental effect on the engines harmonics, as you could definately get the balance between reciprocating mass and counter-weight mass way off.

I have never heard of this "knife-edging" but from what i have read on here, wouldn't/couldn't it lead to a massive increase in vibrations? Surely the counter weights have a very important job and removing them or modifying them could cause a lot of damage and reduce reliability?

When you say "balancing" does that just mean the whole existing shaft is re-balanced more accurately than it would be standard? If so how? adding counter weights or removing material? Sorry for the questions, just learning?

 

[Dangerous_dave]

I have never heard of this "knife-edging" but from what i have read on here, wouldn't/couldn't it lead to a massive increase in vibrations? Surely the counter weights have a very important job and removing them or modifying them could cause a lot of damage and reduce reliability?

When you say "balancing" does that just mean the whole existing shaft is re-balanced more accurately than it would be standard? If so how? adding counter weights or removing material? Sorry for the questions, just learning?

same here,

google it , quite a lot of detail to read and understand...rather than someone retype 6 pages on here.

 

[_WILL_]

google it , quite a lot of detail to read and understand...rather than someone retype 6 pages on here.

im so lazy, googling now!

 

[stan*]

I have never heard of this "knife-edging" but from what i have read on here, wouldn't/couldn't it lead to a massive increase in vibrations? Surely the counter weights have a very important job and removing them or modifying them could cause a lot of damage and reduce reliability?

When you say "balancing" does that just mean the whole existing shaft is re-balanced more accurately than it would be standard? If so how? adding counter weights or removing material? Sorry for the questions, just learning?

Pretty much, its a case of balancing primary forces on all planes so that there is reduced vibration...this si done by typically drilling/grinding areas to achieve the desired effect.

However is doesnt take into account secondary forces, crank flex/whip, heat distortion etc.
I.e its fine balancing a cold non stressed crankshaft on a machine in a workshop, but when you put it in a running engine, where there are tons of force exerted on the pins, it twists and distorts etc so now all of a sudden its out of balance again.

 

[_WILL_]

Pretty much, its a case of balancing primary forces on all planes so that there is reduced vibration...this si done by typically drilling/grinding areas to achieve the desired effect.

However is doesnt take into account secondary forces, crank flex/whip, heat distortion etc.
I.e its fine balancing a cold non stressed crankshaft on a machine in a workshop, but when you put it in a running engine, where there are tons of force exerted on the pins, it twists and distorts etc so now all of a sudden its out of balance again.

This all sounds very interesting, im guessing to get it really well balanced you have to replicate all the forces when the engine is running? Surely the oe one is pretty good as the R&D department must have to and are able to spend a lot getting this right? I which i could do my final uni product on something like this!!!

 

[stan*]

As with most mass produced components, cost versus output is most important, so there is usually a massive compromise. The standard renault cranks arent that bad for steady state primary balance, and thats "good enough" as far as the R&D team would be concerned.

Why cant you do your final year project on it? Model a crank in IDEAS etc, simulate a running engine in WAVE to obtain cylinder pressure data, calculate crankshaft forces, apply them to an FEA...hey presto a working simulation of dynamic forces

 

[_WILL_]

Why cant you do your final year project on it? Model a crank in IDEAS etc, simulate a running engine in WAVE to obtain cylinder pressure data, calculate crankshaft forces, apply them to an FEA...hey presto a working simulation of dynamic forces

Have done some primary balance stuff before in some labs, but not to a very high standard. As for my final project, don't get me started. I am actually doing quite an interesting project, but its not something im personally interested in. and its not even close to this sort of thing. Plus its way to late to change my project now!!! (well thats what im told, i think it would be fine to change it)

 

[Mike_182]

What's key in all of this is that particularly for this engine (although many say it's true for all engines, there are some it provides questionable gains for) there is no tangible benefit it doing it, and certainly nothing to outweigh the risks of someone gettings it a little bit wrong.

From what I understand (not from experience!) it can take someone several attempts at getting the 'right' setup for a particular engine, and even then it's not guaranteed to do anything - potentially even give up the ghost entirely!

 

[Iceberg_172]

I was looking at this process for my MR2 engine. After splashing out 2.5k on the bottom end i decided it wasnt worth it.

It has its disadvantages aswell as its gains like the guy in the machine shop explained to me.

It may weaken parts of the crank ie, rod/bearing journals etc if it is not balanced correctly afterwards which for me personally i couldnt risk while running 1.75 bar of boost at 550hp.

When these forces are applied, again if its not balanced correctly or not run in correctly, Like mentioned above somewhere it will distort and heat up which could result in failure to the rest of the components, again which i didnt want to risk.

it is similar to lightening the flywheel, It doesnt help your torque figures at all and the slightest inclines on the road/track will soon take their toll on you.

This wasnt a great loss for me but on an engine without the help of a turbo etc this can have a big effect.

This is all what i was told personally for mines and that a good balance of the engine with the standard crank (which is the only part that is standard on my engine) is just as good as anything.

It might differ for your circumstances but all i can see it gaining is increased rev speed in the lower gears at the expense of the above

 

[Dangerous_dave]

This thread makes good reading!


i am not going to pursure the knife edged crank, just going to have the bottom end balanced and key parts renewed / upgraded so i know that it is all top stuff.

 

[Iceberg_172]

might be of no use but consider tufftride/thermal coating to some of the main components, I had the rods, pistons, crank and alot of other parts done on my engine.

Only as they were going through great heat and stress though not sure if this will be near the same on an n/a engine but it will help your intake temperatures aswell