Turned Crank Theory..Controled Test
Aug 23, 2010, 05:14 PM
#31
You are absolutely correct. The crankshaft is not nitrided from the factory.
The factory crankshafts are induction hardened. This is not the same thing as nitriding. Yes, turning a factory crank removes the induction hardening, which is at least one reason why Mitsubishi recommends replacement. Of course, Mitsubishi doesn't expect anyone to have the crank nitrided.
Another reason why Mitsubishi recommends replacement is probably because turning the journals will reduce/remove the pronounced fillet at each edge, which could affect how oil is channeled away from the bearings. How this can affect things in the real world, I won't try to predict.
The factory crankshafts are induction hardened. This is not the same thing as nitriding. Yes, turning a factory crank removes the induction hardening, which is at least one reason why Mitsubishi recommends replacement. Of course, Mitsubishi doesn't expect anyone to have the crank nitrided.
Another reason why Mitsubishi recommends replacement is probably because turning the journals will reduce/remove the pronounced fillet at each edge, which could affect how oil is channeled away from the bearings. How this can affect things in the real world, I won't try to predict.
Jan 18, 2011, 11:35 PM
#33
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42psi must feel pretty good 
I never heard of the "don't use a cut crank" thing but I'm new to these engines and am used to my stang's ford 302/351 motors and I recently rebuilt a 98 vette LS1 engine and the kid spun 2 rod bearings, the mains were cut .010 and the rods were cut .040. Car is easily making 400rwhp all motor and spinning over 7k rpm with quite alot of miles on it by now and no problems even with .040 journals even though I wouldnt want it that thin on my car. But it seems like 75% of the v8's that are rebuilt whether n/a, boosted or spraying nitrous have cut cranks, I don't see the difference in these crank and an evo crank? Sure an evo has a faster crank journal speed because of the smaller journals but IF all your tolerances are correct and keep Good oil Fresh I don't see the worry. The bearing DOES NOT touch the crank journal IF you use good oil and needs to be the proper weight and FRESH so it's not broken down. So wether the crank lost it's "hardness" or not I don't see what's going to happen unless the rotating assembly wasn't balanced or the engine was detonating theenn it will help destroy it. Is the oil radius thing the only concern?
Anyone with more info please fill me in. In the meantime I don't see anything wrong with the OP's combo as long as the tune/maintenance stays good
I never heard of the "don't use a cut crank" thing but I'm new to these engines and am used to my stang's ford 302/351 motors and I recently rebuilt a 98 vette LS1 engine and the kid spun 2 rod bearings, the mains were cut .010 and the rods were cut .040. Car is easily making 400rwhp all motor and spinning over 7k rpm with quite alot of miles on it by now and no problems even with .040 journals even though I wouldnt want it that thin on my car. But it seems like 75% of the v8's that are rebuilt whether n/a, boosted or spraying nitrous have cut cranks, I don't see the difference in these crank and an evo crank? Sure an evo has a faster crank journal speed because of the smaller journals but IF all your tolerances are correct and keep Good oil Fresh I don't see the worry. The bearing DOES NOT touch the crank journal IF you use good oil and needs to be the proper weight and FRESH so it's not broken down. So wether the crank lost it's "hardness" or not I don't see what's going to happen unless the rotating assembly wasn't balanced or the engine was detonating theenn it will help destroy it. Is the oil radius thing the only concern?
Anyone with more info please fill me in. In the meantime I don't see anything wrong with the OP's combo as long as the tune/maintenance stays good
Jan 19, 2011, 03:39 AM
#34
Evolving Member
We did grind a crank down all the way to determine the deep of the hardening.
The hardening is not nitrite, its inductive hardening ( thats the reason why you can polish the crank.
It was an used Evo8 crank with an rod bearing failure on cyl.1, which was trash anyway due to the failure
We started to grind the number 2 Rod surface.
ALL dimensions in metric (mm) here. Hardness is not an absolute value in our case, its relative measurement!!
Initial : 47.993mm Fillet depth: 0.49mm Hardness: 88
1st grind : 47.893mm Fillet depth: 0.39mm Hardness: 88
2st grind : 47.743mm Fillet depth: 0.24mm Hardness: 88
3st grind : 47.493mm Fillet depth: none Hardness: 86
4st grind : 47.243mm Fillet depth: none Hardness: 84
5st grind : 46.993mm Fillet depth: none Hardness: 68 hardness drops fast
So , in conclusion, you can grind the Crank Rod pin ( only rod testet ) down.
so, 0.25 mm is possible when the fillets should be there and 0.50 mm if fillet doesnt matter or can be refreshed.
Any more does not make it because fillets gone and also hardening drops ( extreme loss after the -0.75 grind )
Also, the grinding should be done in an really smooth way, so it should not be done like an V8 crank. There should be removed only a small amount of material, with cool down times in between. The hardening can change extreme if to much heat is transfered into the crank. ( tried that at Rod position 3, more material in one grind, hardening changes 5 more point than rod 2 )
But, there is an other problem you will run into.
All Bearing manufacturers doesn't make the right bearings for the turbo application.
The max grind to get Turbo bearings is -0.25mm. smaller to get bearings from them.The bigger OS will be only for the N/A 4g63 / 4G64.
This was approved from King bearings, the materials and coats used will be different than and they do not advise to use in high HP applications.
Same Information from Clevite, ACL and Glyco.
Also, Mitsubishi has different bearings ( but same dimensions ) for the 4g63T and 4g63 n/a Engines.
It may be possible that someone has get Bearings as an custom order, but not "off the shelf".
For my self: For an almost stock Evo ( stock turbo ) i would use an g rinded crank (-0.25) when an new one is not in the price range..
In any high HP application ( 500++) i would never used an grind crank.
Get an new or good used one. Better safe then sorry.
here in Germany, its easier and cheaper to use an new crank all time, because the grinding is expensive. Grinding all 4 rod sections is about 500$.
In the states, i assume, it will be much cheaper because you have more Engine shops then here in Europe.
my 2 cents
The hardening is not nitrite, its inductive hardening ( thats the reason why you can polish the crank.
It was an used Evo8 crank with an rod bearing failure on cyl.1, which was trash anyway due to the failure
We started to grind the number 2 Rod surface.
ALL dimensions in metric (mm) here. Hardness is not an absolute value in our case, its relative measurement!!
Initial : 47.993mm Fillet depth: 0.49mm Hardness: 88
1st grind : 47.893mm Fillet depth: 0.39mm Hardness: 88
2st grind : 47.743mm Fillet depth: 0.24mm Hardness: 88
3st grind : 47.493mm Fillet depth: none Hardness: 86
4st grind : 47.243mm Fillet depth: none Hardness: 84
5st grind : 46.993mm Fillet depth: none Hardness: 68 hardness drops fast
So , in conclusion, you can grind the Crank Rod pin ( only rod testet ) down.
so, 0.25 mm is possible when the fillets should be there and 0.50 mm if fillet doesnt matter or can be refreshed.
Any more does not make it because fillets gone and also hardening drops ( extreme loss after the -0.75 grind )
Also, the grinding should be done in an really smooth way, so it should not be done like an V8 crank. There should be removed only a small amount of material, with cool down times in between. The hardening can change extreme if to much heat is transfered into the crank. ( tried that at Rod position 3, more material in one grind, hardening changes 5 more point than rod 2 )
But, there is an other problem you will run into.
All Bearing manufacturers doesn't make the right bearings for the turbo application.
The max grind to get Turbo bearings is -0.25mm. smaller to get bearings from them.The bigger OS will be only for the N/A 4g63 / 4G64.
This was approved from King bearings, the materials and coats used will be different than and they do not advise to use in high HP applications.
Same Information from Clevite, ACL and Glyco.
Also, Mitsubishi has different bearings ( but same dimensions ) for the 4g63T and 4g63 n/a Engines.
It may be possible that someone has get Bearings as an custom order, but not "off the shelf".
For my self: For an almost stock Evo ( stock turbo ) i would use an g rinded crank (-0.25) when an new one is not in the price range..
In any high HP application ( 500++) i would never used an grind crank.
Get an new or good used one. Better safe then sorry.
here in Germany, its easier and cheaper to use an new crank all time, because the grinding is expensive. Grinding all 4 rod sections is about 500$.
In the states, i assume, it will be much cheaper because you have more Engine shops then here in Europe.
my 2 cents
Last edited by german_evoVII; Jan 24, 2011 at 03:34 PM.
Jan 24, 2011, 03:02 PM
#35
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I'm very glad to see this. I've been building/racing DSM's for 10 years and have ALWAYS heard you should never use a cut crank. I'm glad it's working out for you! As far as break in procedure my motto is drive it around the block and spray the **** out of it. It's worked great on my 2.4 Eclipse so far LOL.
Last edited by Mattsubishi; Feb 1, 2011 at 09:53 AM.
Jan 28, 2011, 01:26 PM
#36
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We did grind a crank down all the way to determine the deep of the hardening.
The hardening is not nitrite, its inductive hardening ( thats the reason why you can polish the crank.
It was an used Evo8 crank with an rod bearing failure on cyl.1, which was trash anyway due to the failure
We started to grind the number 2 Rod surface.
ALL dimensions in metric (mm) here. Hardness is not an absolute value in our case, its relative measurement!!
Initial : 47.993mm Fillet depth: 0.49mm Hardness: 88
1st grind : 47.893mm Fillet depth: 0.39mm Hardness: 88
2st grind : 47.743mm Fillet depth: 0.24mm Hardness: 88
3st grind : 47.493mm Fillet depth: none Hardness: 86
4st grind : 47.243mm Fillet depth: none Hardness: 84
5st grind : 46.993mm Fillet depth: none Hardness: 68 hardness drops fast
So , in conclusion, you can grind the Crank Rod pin ( only rod testet ) down.
so, 0.25 mm is possible when the fillets should be there and 0.50 mm if fillet doesnt matter or can be refreshed.
Any more does not make it because fillets gone and also hardening drops ( extreme loss after the -0.75 grind )
Also, the grinding should be done in an really smooth way, so it should not be done like an V8 crank. There should be removed only a small amount of material, with cool down times in between. The hardening can change extreme if to much heat is transfered into the crank. ( tried that at Rod position 3, more material in one grind, hardening changes 5 more point than rod 2 )
But, there is an other problem you will run into.
All Bearing manufacturers doesn't make the right bearings for the turbo application.
The max grind to get Turbo bearings is -0.25mm. smaller to get bearings from them.The bigger OS will be only for the N/A 4g63 / 4G64.
This was approved from King bearings, the materials and coats used will be different than and they do not advise to use in high HP applications.
Same Information from Clevite, ACL and Glyco.
Also, Mitsubishi has different bearings ( but same dimensions ) for the 4g63T and 4g63 n/a Engines.
It may be possible that someone has get Bearings as an custom order, but not "off the shelf".
For my self: For an almost stock Evo ( stock turbo ) i would use an g rinded crank (-0.25) when an new one is not in the price range..
In any high HP application ( 500++) i would never used an grind crank.
Get an new or good used one. Better safe then sorry.
here in Germany, its easier and cheaper to use an new crank all time, because the grinding is expensive. Grinding all 4 rod sections is about 500$.
In the states, i assume, it will be much cheaper because you have more Engine shops then here in Europe.
my 2 cents
The hardening is not nitrite, its inductive hardening ( thats the reason why you can polish the crank.
It was an used Evo8 crank with an rod bearing failure on cyl.1, which was trash anyway due to the failure
We started to grind the number 2 Rod surface.
ALL dimensions in metric (mm) here. Hardness is not an absolute value in our case, its relative measurement!!
Initial : 47.993mm Fillet depth: 0.49mm Hardness: 88
1st grind : 47.893mm Fillet depth: 0.39mm Hardness: 88
2st grind : 47.743mm Fillet depth: 0.24mm Hardness: 88
3st grind : 47.493mm Fillet depth: none Hardness: 86
4st grind : 47.243mm Fillet depth: none Hardness: 84
5st grind : 46.993mm Fillet depth: none Hardness: 68 hardness drops fast
So , in conclusion, you can grind the Crank Rod pin ( only rod testet ) down.
so, 0.25 mm is possible when the fillets should be there and 0.50 mm if fillet doesnt matter or can be refreshed.
Any more does not make it because fillets gone and also hardening drops ( extreme loss after the -0.75 grind )
Also, the grinding should be done in an really smooth way, so it should not be done like an V8 crank. There should be removed only a small amount of material, with cool down times in between. The hardening can change extreme if to much heat is transfered into the crank. ( tried that at Rod position 3, more material in one grind, hardening changes 5 more point than rod 2 )
But, there is an other problem you will run into.
All Bearing manufacturers doesn't make the right bearings for the turbo application.
The max grind to get Turbo bearings is -0.25mm. smaller to get bearings from them.The bigger OS will be only for the N/A 4g63 / 4G64.
This was approved from King bearings, the materials and coats used will be different than and they do not advise to use in high HP applications.
Same Information from Clevite, ACL and Glyco.
Also, Mitsubishi has different bearings ( but same dimensions ) for the 4g63T and 4g63 n/a Engines.
It may be possible that someone has get Bearings as an custom order, but not "off the shelf".
For my self: For an almost stock Evo ( stock turbo ) i would use an g rinded crank (-0.25) when an new one is not in the price range..
In any high HP application ( 500++) i would never used an grind crank.
Get an new or good used one. Better safe then sorry.
here in Germany, its easier and cheaper to use an new crank all time, because the grinding is expensive. Grinding all 4 rod sections is about 500$.
In the states, i assume, it will be much cheaper because you have more Engine shops then here in Europe.
my 2 cents
It is always been a big debate that DSM/EVO cranks are not to be cut..V8 is a completely different story
-Mike
Jan 28, 2011, 02:54 PM
#37
I think the debate so to speak was specifically concerning factory cranks, not aftermarket cranks. Sure a nitrided aftermarket crank can be turned without a hitch. I don't think anyone ever really questioned that. The question pertained to what happens if we do this with a factory crank.
What german-evoVII did above was illustrate that unlike a nitriding, induction hardening is strictly a surface treatment. Cut into that and what you encounter is an unhardened surface. But of course, removing 1mm (0.040") is quite a lot of material. Traditionally, we'd toss a V8 crank if we had to turn it >0.5mm (0.020"). And of course, there is always the potential concern of the radius fillets disappearing with the 4G63 crank.
Can a factory 4G63 be turned down, retreated, etc.? Of course. It's just that most find that the cost of a new crank is reasonable enough such that trying to salvage a damaged one isn't worth the effort and expense.
What german-evoVII did above was illustrate that unlike a nitriding, induction hardening is strictly a surface treatment. Cut into that and what you encounter is an unhardened surface. But of course, removing 1mm (0.040") is quite a lot of material. Traditionally, we'd toss a V8 crank if we had to turn it >0.5mm (0.020"). And of course, there is always the potential concern of the radius fillets disappearing with the 4G63 crank.
Can a factory 4G63 be turned down, retreated, etc.? Of course. It's just that most find that the cost of a new crank is reasonable enough such that trying to salvage a damaged one isn't worth the effort and expense.
Jan 28, 2011, 03:15 PM
#38
Evolving Member
I agree.
The reason we did this test was that the customer was running the Bad crank ( with one totally failed / then missing Rod bearing) a good 20miles more. Unbelievable.....
That was really loud knocking, i could here it with the mobile phone when he called me from the highway..
The rod itself started to melt in some places @ big end.
So we would try to grind the crank, the min he have to do was around 0.75mm, so the crank was anyway done....
Then we started the test.
What is really unbelievable that the crank did not broke during that abuse ( also the rod, Oliver i-Beam.)
The reason we did this test was that the customer was running the Bad crank ( with one totally failed / then missing Rod bearing) a good 20miles more. Unbelievable.....
That was really loud knocking, i could here it with the mobile phone when he called me from the highway..
The rod itself started to melt in some places @ big end.
So we would try to grind the crank, the min he have to do was around 0.75mm, so the crank was anyway done....
Then we started the test.
What is really unbelievable that the crank did not broke during that abuse ( also the rod, Oliver i-Beam.)
Feb 1, 2011, 02:29 PM
#39
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I think the debate so to speak was specifically concerning factory cranks, not aftermarket cranks. Sure a nitrided aftermarket crank can be turned without a hitch. I don't think anyone ever really questioned that. The question pertained to what happens if we do this with a factory crank.
What german-evoVII did above was illustrate that unlike a nitriding, induction hardening is strictly a surface treatment. Cut into that and what you encounter is an unhardened surface. But of course, removing 1mm (0.040") is quite a lot of material. Traditionally, we'd toss a V8 crank if we had to turn it >0.5mm (0.020"). And of course, there is always the potential concern of the radius fillets disappearing with the 4G63 crank.
Can a factory 4G63 be turned down, retreated, etc.? Of course. It's just that most find that the cost of a new crank is reasonable enough such that trying to salvage a damaged one isn't worth the effort and expense.
What german-evoVII did above was illustrate that unlike a nitriding, induction hardening is strictly a surface treatment. Cut into that and what you encounter is an unhardened surface. But of course, removing 1mm (0.040") is quite a lot of material. Traditionally, we'd toss a V8 crank if we had to turn it >0.5mm (0.020"). And of course, there is always the potential concern of the radius fillets disappearing with the 4G63 crank.
Can a factory 4G63 be turned down, retreated, etc.? Of course. It's just that most find that the cost of a new crank is reasonable enough such that trying to salvage a damaged one isn't worth the effort and expense.
True..It is worth just buying a new crank..however, many people will just turn a 4g63 crank all day..why do they do it..
Turning a crank: $150.00
Nitride Coating: $150.00
Total: $300.00 Vs Cost of a NEW AFTERMARKET approx. $500..
IMO..I would just buy a new crank for the extra money & mostly peace of mind..However, the debate for cutting ANY 4g63 not just aftermarket has ALWAYS been a huge one. People say don't cut one yada yada..It can be done if done correctly..
1. One must know how to cut it..Like you mentioned Ted, fillets are a huge concern
2.Nitride coat it..if you dont..Well, soft material + 40psi = Possible spun bearing
3. Not have an ordinary V8 guy cut your crank..
Also, factory cranks do get cut or turned all the time and work fine.. AS LONG AS YOU RE NITRIDE COAT THEM..Buschur does it all the time..take a look
https://secure.buschurracing.com/cat...a5334cedfdf83d
..Bottom line.. Can it be done..YES, if done properly..
As Ted B stated..is it worth it..IMO I would purchase a new one..However, I did the test to prove it will work fine..Even after people read this I bet they will continue to cut their cranks..What can you do though!?
-Mike
Feb 25, 2011, 01:48 PM
#40
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I've heard this debate for quite some time now, yet on an evo 8. I worked on the customer decided he wanted to turn his crank to save on the cost. Bear in mind, this took place in 04 and the crank cost more then. He also did not have it coated.
End result, his car ran perfect till the day the next owner wrecked it, and that car was extremely well beaten on by both owners.
Now was he running 40 psi? Absolutely not. That car saw 28 psi max and was in the 400whp territory. As well, the shop that turned it actually specialized in v8's. They never saw an import come into their shop, but they had level heads when it came to the machine work. I'm not sure on what it means to be a "regular" v8 guy as it's truly is the same for turning ANY crank, and that is not to go overboard on how much material is removed. Like German evo VII illustrated, the key is absolutely in how much material is taken off before it loses strength.
What I think the reason is as to why most of the DSMers have stayed on the rant of "machined cranks are bad" is because most of the DSMers out there, much like today's Honda kids, are inherently cheap. Because of this, they seek out the cheapest guy to do their machining rather than find a quality shop to do the work and like to gripe about the aftermath.
There are unfortunately far too many "hack" machine shops out there that don't know what they are doing UNLESS you tell them exactly what is needed. Otherwise, they guess, and not well. Your average kid or garage tuner will probably not know how much they need removed and will be relying on the machine shop to help them figure it out and advise. This is where the problem lies.
End result, his car ran perfect till the day the next owner wrecked it, and that car was extremely well beaten on by both owners.
Now was he running 40 psi? Absolutely not. That car saw 28 psi max and was in the 400whp territory. As well, the shop that turned it actually specialized in v8's. They never saw an import come into their shop, but they had level heads when it came to the machine work. I'm not sure on what it means to be a "regular" v8 guy as it's truly is the same for turning ANY crank, and that is not to go overboard on how much material is removed. Like German evo VII illustrated, the key is absolutely in how much material is taken off before it loses strength.
What I think the reason is as to why most of the DSMers have stayed on the rant of "machined cranks are bad" is because most of the DSMers out there, much like today's Honda kids, are inherently cheap. Because of this, they seek out the cheapest guy to do their machining rather than find a quality shop to do the work and like to gripe about the aftermath.
There are unfortunately far too many "hack" machine shops out there that don't know what they are doing UNLESS you tell them exactly what is needed. Otherwise, they guess, and not well. Your average kid or garage tuner will probably not know how much they need removed and will be relying on the machine shop to help them figure it out and advise. This is where the problem lies.
Mar 8, 2011, 05:28 PM
#41
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Out of interest...
How do you guys feel about a 0.020" cut on the big ends?
I've got a crank here with 0.010" cut on mains and 0.020" on Big Ends.
It's been Tuftrided after the cut.
Was going to run it in my new big build running 600WHP.
Now not so sure...
How do you guys feel about a 0.020" cut on the big ends?
I've got a crank here with 0.010" cut on mains and 0.020" on Big Ends.
It's been Tuftrided after the cut.
Was going to run it in my new big build running 600WHP.
Now not so sure...
Aug 9, 2011, 06:28 AM
#45
True..It is worth just buying a new crank..however, many people will just turn a 4g63 crank all day..why do they do it..
Turning a crank: $150.00
Nitride Coating: $150.00
Total: $300.00 Vs Cost of a NEW AFTERMARKET approx. $500..
IMO..I would just buy a new crank for the extra money & mostly peace of mind..However, the debate for cutting ANY 4g63 not just aftermarket has ALWAYS been a huge one. People say don't cut one yada yada..It can be done if done correctly..
1. One must know how to cut it..Like you mentioned Ted, fillets are a huge concern
2.Nitride coat it..if you dont..Well, soft material + 40psi = Possible spun bearing
3. Not have an ordinary V8 guy cut your crank..
Also, factory cranks do get cut or turned all the time and work fine.. AS LONG AS YOU RE NITRIDE COAT THEM..Buschur does it all the time..take a look
https://secure.buschurracing.com/cat...a5334cedfdf83d
..Bottom line.. Can it be done..YES, if done properly..
As Ted B stated..is it worth it..IMO I would purchase a new one..However, I did the test to prove it will work fine..Even after people read this I bet they will continue to cut their cranks..What can you do though!?
-Mike
Turning a crank: $150.00
Nitride Coating: $150.00
Total: $300.00 Vs Cost of a NEW AFTERMARKET approx. $500..
IMO..I would just buy a new crank for the extra money & mostly peace of mind..However, the debate for cutting ANY 4g63 not just aftermarket has ALWAYS been a huge one. People say don't cut one yada yada..It can be done if done correctly..
1. One must know how to cut it..Like you mentioned Ted, fillets are a huge concern
2.Nitride coat it..if you dont..Well, soft material + 40psi = Possible spun bearing
3. Not have an ordinary V8 guy cut your crank..
Also, factory cranks do get cut or turned all the time and work fine.. AS LONG AS YOU RE NITRIDE COAT THEM..Buschur does it all the time..take a look
https://secure.buschurracing.com/cat...a5334cedfdf83d
..Bottom line.. Can it be done..YES, if done properly..
As Ted B stated..is it worth it..IMO I would purchase a new one..However, I did the test to prove it will work fine..Even after people read this I bet they will continue to cut their cranks..What can you do though!?
-Mike
I am glad that things have worked out for you thus far. I just hope that it doesn't decide to give out on you. The 200 you could have spent, most likely would have kept your motor together. Just my .02
Mikey