PDA

View Full Version : Knife edging cranks...



H8PVMNT
02-12-2009, 01:22 AM
What do you guys think of knife edging crankshafts?

Worth it or not?

Shadowlife25
02-12-2009, 03:50 AM
There was a fella here a while back that offered this along with oil pan baffles.


http://www.crank-scrapers.com/Toyota.html

afief
02-17-2009, 02:04 AM
its worth it but you might want to upgrade your valve spring and retainers could cause valve float

MrWOT
02-17-2009, 02:14 AM
its worth it but you might want to upgrade your valve spring and retainers could cause valve float

Wat?

Shadowlife25
02-17-2009, 02:48 AM
Wat?

x2

How exactly does using a crank-scraper cause valve float? :confused:

pitcelica
02-17-2009, 03:19 AM
and in what way knife edging is linked with crank scraper...

This is knife edging a crank :

http://www.turbomagazine.com/tech/0610turp_castillo_crankshaft_service/photo_02.html

KoreanJoey
02-17-2009, 04:46 AM
He's saying the guy that sold crank scrapers also offered knife edging.

Great for a quick rev built motor.

Horrible for a street car.

Roundy
02-17-2009, 09:46 AM
He's saying the guy that sold crank scrapers also offered knife edging.

Great for a quick rev built motor.

Horrible for a street car.

I'm sorry, how is it horrible for a street car?

KoreanJoey
02-17-2009, 02:12 PM
Generally reducing the rotational mass at engine speed will create massive loss of low end.

It's like adding a lightweight flywheel but with greater effect *depending on amount removed from crank*

If you're doing with a higher angle without much material removed I'm sure you probably won't notice too much as far as loss of driveability but you also won't see as much in gains either.

Also, I'm pretty sure the factory computer will only allow the engine to rev so fast in order to prevent you from blowing out the cat.

Roundy
02-18-2009, 12:08 AM
Generally reducing the rotational mass at engine speed will create massive loss of low end.

It's like adding a lightweight flywheel but with greater effect *depending on amount removed from crank*

If you're doing with a higher angle without much material removed I'm sure you probably won't notice too much as far as loss of driveability but you also won't see as much in gains either.

Also, I'm pretty sure the factory computer will only allow the engine to rev so fast in order to prevent you from blowing out the cat.

I disagree, entirely.

Is a lightweight flywheel bad? NO

Makes it a touch harder to take off, but once you get used to it there is no problem, and it makes the car FASTER

With the crank, you will be removing less weight from closer to the rotating centre, so the effect is less than that of a flywheel.

The loss of bottom end is a total and utter myth. The lightweight flywheel on my car made it accelerate better pretty much everywhere, it is only right when taking off that there is a (very little) problem, just need to give it a few more revs.

By extension of your ideas, lightweight pistons and rods are bad too?

Factory computer limiting the rev build up to prevent blowing out the cat?! :lolhittin

how the hell did you come to that conclusion?!

Sit there and free rev the engine, the revs can and will build very quickly (ok so there is SFA load, but the ECU lets it go) or for another example, give it the beans on a very slippery bit of road in first, the revs will skyrocket with no drama.

The main advantage of knife edging the crank is the reduction of drag due to air and oil.

Is it worth it? I don't know, it is more from the 'old days' where cranks used to actually go through the sump oil during their rotation.

KoreanJoey
02-18-2009, 12:37 AM
Um, yes many of the modern ECUs will limit RPM climb.

It's a conclusion made by the simple fact that it's true.

Lots of the racers will convert to smaller and lighter clutch/flywheel combinations but some have found a failsafe to limit by EPA regs for NOX output.

Probably not a problem in earlier models cars.

And it depends on how much you take off the crank. And how does taking the weight off closer to the center of rotation make it less?

Bad, no, bad for driveability, yes. You keep losing out on low end and the car does become more difficult to drive. Turbo cars, probably not a problem as boost can offset that. NA cars become an issue. Believe me trying to drive a built 4AG with no power or torque below 6K is NOT a good street car.

grayscale
02-18-2009, 02:16 AM
I disagree, entirely.

Is a lightweight flywheel bad? NO

Makes it a touch harder to take off, but once you get used to it there is no problem, and it makes the car FASTER

With the crank, you will be removing less weight from closer to the rotating centre, so the effect is less than that of a flywheel.

The loss of bottom end is a total and utter myth. The lightweight flywheel on my car made it accelerate better pretty much everywhere, it is only right when taking off that there is a (very little) problem, just need to give it a few more revs.

By extension of your ideas, lightweight pistons and rods are bad too?

Factory computer limiting the rev build up to prevent blowing out the cat?! :lolhittin

how the hell did you come to that conclusion?!

Sit there and free rev the engine, the revs can and will build very quickly (ok so there is SFA load, but the ECU lets it go) or for another example, give it the beans on a very slippery bit of road in first, the revs will skyrocket with no drama.

The main advantage of knife edging the crank is the reduction of drag due to air and oil.

Is it worth it? I don't know, it is more from the 'old days' where cranks used to actually go through the sump oil during their rotation.
First off you're comparing apples to oranges. You drive a 3sge whilst the op is driving a 5sfe. You don't have quite as much to lose on the bottom end as he does and your car happily revs a bit higher than his and as Joey pointed out, epa regs affect us here whereas they may not concern you downunder.

Second of all, please try to use a bit more tact when disagreeing with comments made.

Continue.

Roundy
02-18-2009, 09:29 AM
I have never hit anything trying to limit the RPM climb on my ECU, lightweight flywheel, larger turbo, more power, even on a wet track where i got all 4 wheels spinning in first gear, quick gain in revs and nothing.

How would a quick revving engine affect the cat?

Removing it closer to the centre reduces the loss of INERTIA which is what helps keep the engine turning (and why i need more revs to take off than with the standard flywheel, less inertia) so the crank will affect it a LOT less than a light flywheel.

I didn't explain that well in my previous post.

Didn't realise it was a 5s, but the physics is the same.

In no way will it reduce the torque output of the engine, it may make it FEEL like it has less torque off the line, but that is due to a loss of inertia.

In gear acceleration will be improved, noticeably.

Even cruising around off boost i could notice crisper acceleration after changing my flywheel.

MrWOT
02-18-2009, 04:39 PM
Roundy is correct. And if there was a rev speed limiter, it would be to keep the O2 sensor working correctly if anything ;)

joe's gt
02-18-2009, 10:10 PM
Based on what I've read here and from google, knife edging won't do much compared to a lightened flywheel. I don't see much advantage in this in any street driven car. Lightened flywheel, yes, but going as far to knife edge the crank, (which if reducing inertia is the main purpose) a big no in terms of work, cost, and performance gains for street applications.

It seems the cost outweighs the gains IMO.

Roundy
02-18-2009, 10:38 PM
Roundy is correct. And if there was a rev speed limiter, it would be to keep the O2 sensor working correctly if anything ;)

Not sure on the 5S, but if your revs are building quickly you would be in open loop mode no?

The O2 sensor would be rather useless at 13:1 AFRs

Joe's GT

I guess it depends on what the OP's idea of value is.

If you had the engine out getting rebuilt, the cost of knife edging would seem quite small.

But to pull the whole engine out just to knife edge the crank, yes that is a bit silly.

KoreanJoey
02-20-2009, 08:53 AM
Apparently it's not a problem with the old school OBD-0 systems. I know it's a factor with some of the newer cars (CSP Mazda MX-5s encounter that problem).

And yes, quick revving will eat cats. Even stock vehicles are capable of frying cats with rapid revs and no load. Try it yourself. When you start smelling bad eggs, stop.

I guess it's a matter of how much material you remove from the counterbalances.

My idea of knife edging might be a little more on the extreme side (only way I'd be able to justify doing it in the first place)...

In fact, essentially cutting OFF the counter balances on a 22RE is about the only way to make that tractor motor rev with any sort of real speed.

And as you've mentioned, you'll have to rev higher before engaging your clutch, not a big deal for someone highly performance driven, but definitely adds to the effect of "less" streetable. You can live with it, I can live with it. But I can live with a lot for a "street" car.

*Gen 3 3SGE, 11lbs TODA flywheel, Centerforce 6-puck unsprung HD clutch kit, kirkosaurus motor mounts, 450in/lbs springs/fr, 350in/lbs springs/rr (On a 2600lbs FWD celica, not a 3300lbs GT-4*

Now, I can street it, and live with it. Is it pleasant? Not so much...

Roundy
02-20-2009, 10:46 PM
But is it fun? Hell yes! And that is what we all do this sorta stuff for :D

I'm still a bit confused about the Cat. Why does it burn it out?

KoreanJoey
02-21-2009, 01:31 AM
It just overloads the cat with hydrocarbons. Cat gets to hot.

Roundy
02-21-2009, 10:45 AM
From what exactly?

Ok yes excess hydro carbons, but what is the reason for them?

My understanding of cats is they need the constant switching between slightly rich and slightly lean of stoich to work properly.

So excessively rich will kill a cat, but under load most engines run richer than stoich anyway which will kill a cat.

It will kill it, but i am failing to see how knife edging the crank will make it noticeably worse, which is what you are implying.

KoreanJoey
02-21-2009, 04:21 PM
My understanding of cats is they need the constant switching between slightly rich and slightly lean of stoich to work properly.

Yes, this is what will create the heat that cats need to burn off the hydrocarbons.

It's the rapid load and unload from a fast revving motor that can kill cats.

It's know knife edging in and of itself, it's rapid revs. Again one of those, my thought of knife edging is more on the extreme side, sort of deals.

H8PVMNT
02-25-2009, 11:51 PM
Dropped off my crank at the machine shop to get turned and inquired about the cost/benefit if knife edging...

The guy said if I was extremely concearned about saving 1/10 of a second at the drags and I didn't mind spending about $1,000 more than the standard machine work then go for it, if it was for a daily driver it would probably be a waste of money.

He said you would see more of a noticable difference using an aluminum flywheel than knife edging the crank.

In this case the engine is a 3RZ for a swap in my Toyota 4x4, so I think it would be a waste... But it sounds like it would not be worth it on a 5S either unless you were building a balls out 5SFTE.

Anyway thanks for all the input guys. :bigthumbu

Roundy
02-26-2009, 10:59 AM
1k?! farken hell that is expensive!!

H8PVMNT
02-26-2009, 06:04 PM
Those were almost my words exactly!