Some may have seen my questions on TDP. Well, I figure I won't get much reply over there and we have several very knowledgable folks on here as well as Guy himself. So...
Let's talk about it.
C-ya
Let's talk about it.
C-ya
Duramax Stroker Questions...
- Thread starter SmokeShow
- Start date
Initially this is my simpleton take. How would it be done in a Duramax?
De-stroking moves the powerband up in the RPM range, the piston doesn't remain near TDC as long, requiring more RPM to do the same work, Fairly easy as i remember, shorter rotating assembly or change the crank.
Stroking is a dif story depending on the block... stroking generally makes torque and moves it down in the RPM range. But in order to stroke it you have to increase the diameter of the crankshafts rotation... new crank or off set grind the stocker (i see this as ruining a perfectly good nodular crank, 800 hp on an offset crank
),will this increased diameter still fit within the physical limitations of the block? Or will the rods hit the block... then you have to clearance the block...whats between the rod and the rail? Oil passages? Coolant? Depending on how it's done this could be a great mod or a BIG dollar/low return mod.
I'm not a pro by any stretch! But i have to wonder, why add cubic inches when we have cubic inch adder in the form of a turbo??? Perhaps to add more time for fuel burn relative to crankshaft rotation...working fuel time on the piston.
I may be way off and usually am, I look forward to a pro's response. How about Turbotug? Isn't he a machinist?
De-stroking moves the powerband up in the RPM range, the piston doesn't remain near TDC as long, requiring more RPM to do the same work, Fairly easy as i remember, shorter rotating assembly or change the crank.
Stroking is a dif story depending on the block... stroking generally makes torque and moves it down in the RPM range. But in order to stroke it you have to increase the diameter of the crankshafts rotation... new crank or off set grind the stocker (i see this as ruining a perfectly good nodular crank, 800 hp on an offset crank
),will this increased diameter still fit within the physical limitations of the block? Or will the rods hit the block... then you have to clearance the block...whats between the rod and the rail? Oil passages? Coolant? Depending on how it's done this could be a great mod or a BIG dollar/low return mod.I'm not a pro by any stretch! But i have to wonder, why add cubic inches when we have cubic inch adder in the form of a turbo??? Perhaps to add more time for fuel burn relative to crankshaft rotation...working fuel time on the piston.
I may be way off and usually am, I look forward to a pro's response. How about Turbotug? Isn't he a machinist?
http://www.rpmmachine.com/shop/html/Subcategory-54-0.html
http://www.rpmmachine.com/shop/html...Stroker-Kit-up-to-800HP---6.385-Long-Rod.html
I spose if we could stroke it and get the same bene's realized as a BBC that would be cool... Look at this rotating assembly for $2,000 w/ a 6.3 rod.
http://www.rpmmachine.com/shop/html...Stroker-Kit-up-to-800HP---6.385-Long-Rod.html
I spose if we could stroke it and get the same bene's realized as a BBC that would be cool... Look at this rotating assembly for $2,000 w/ a 6.3 rod.
THIS is where this conversation is derived from.
I'm trying to see the reason for doing it. Is it as simple as the statement "no replacement for displacement"???
Ohhh! well yea, initially no replacement for displacment. But jeeez if the cost of Duramax billet rods is double or more of BBC billets (roughly same dimension) than that's a $3000 crank, now the rods are special, the pistons are special and we gotta bore +20. No we have a 30k motor with no off the shelf parts.
Cool!? I spose we gotta ask ourselves how fast we wanna go...is 10sec HP enough.
IMO, yes...As long as you've got the parts (cyl. heads, cam, turbo) that support
the extra inches, on paper it "should" make more power...
anyone care to enlighten me on the benefit of the increased torque at lower RPMs from a stroker being the thing we want to be doing when I thought we were aiming to reduce torque through RPMs.
This just seems like the opposite of what we had been talking about needing to do - rev higher to make more power and less torque.
I'm all cornfused.
I understand the benefit of increased displacement and how more torque helps in our application IF our parts (rods, pistons, who-knows-what-may-be-next) can take the extra torque and thats what I thought we were at a limit of, ability to handle the torque. Perhaps an explanation of how the longer stroker increases torque will help me. Is it not by increasing cyl. pressure as is the case right now???
This just seems like the opposite of what we had been talking about needing to do - rev higher to make more power and less torque.
I'm all cornfused.
I understand the benefit of increased displacement and how more torque helps in our application IF our parts (rods, pistons, who-knows-what-may-be-next) can take the extra torque and thats what I thought we were at a limit of, ability to handle the torque. Perhaps an explanation of how the longer stroker increases torque will help me. Is it not by increasing cyl. pressure as is the case right now???
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I see what you are chasing... sorry i stayed at Best Western last night!
I think one of 3 people would know, new_2_LB7, Mcrat or Johnboy. Tuner, Racer and Machinist.
Yeah, I'm hoping all three will chime in, as well as Guy when he get's back. I'm not trying to incenuate that this is a bad thing, just trying to see how it's plays into the advancement of the Duramax.
Perhaps forged pistons and rods CAN take the extra pressure (if that is, in fact, how a stroker engine makes more torque) and they are ready to push them closer to their capacity and therfore make more power by doing so with this stroker kit.
Just trying to learn and understand something new. I'm a nerd that likes the details, the in's and out's, the how's and why's of the way things work. Just like knowing all that science-y stuff.
C-ya
Perhaps forged pistons and rods CAN take the extra pressure (if that is, in fact, how a stroker engine makes more torque) and they are ready to push them closer to their capacity and therfore make more power by doing so with this stroker kit.
Just trying to learn and understand something new. I'm a nerd that likes the details, the in's and out's, the how's and why's of the way things work. Just like knowing all that science-y stuff.
C-ya
Ok
Stroke: The distance the piston travels in the bore. The distance from Top dead Center (TDC) to Bottom Dead Center (BDC).
Stock stroke is 3.898"
To increase the stroke the crank must either be altered or replaced. Trippin is replacing the crank. His new crank has a larger swing. Swing is the distance from the center of the main journal to the center of the rod journal on the crank. Basicly swing eqauls half the the stroke. I say basicly because things like offset bore centerlines and offset wrist pins actually can have effect on the stroke of the piston vs the stroke of the crank. But that is another dicussion.
To make things easy lets just go with this. Stock stroke is 3.898" Stock crank swing is 1.949". What Trippin has done is make a new crank that has a swing that is larger by .125. Which equals 2.047" That means a stroke of 4.148". So the piston is now traveling .25" further per crank revolution.
That increases dispacement. Displacement is the max total volume of one cylinder times the total number of cylinders. Max displacement is measured with the piston at Bottom Dead Center.
Make sense?
Now you can not simply bolt in a new crank to increase stroke. Why? The large swing of the crank will cause interference issues with the pistons. At BTC a skirt of the stock piston is very close to the bob weight of the stock crank. So to really pull off the increase in stroke you need a custom crank. You also need rods and pistons made to work with this crank. Trippin has done this and I gather he is going to selling them in a Kit form.
Advantages of the longer stroke.
1:More displacement means more air in which means more fuel can be burnt. Which equals more power!
2: Incearsed torque because of increased leverage. The same cylinder pressure now has more leverage of the crank so the same pressure equals more force(ie. torque).
There is more to it than just this. There are disadvantages to increased stroke also. But I have to get back to work!:rofl:
Stroke: The distance the piston travels in the bore. The distance from Top dead Center (TDC) to Bottom Dead Center (BDC).
Stock stroke is 3.898"
To increase the stroke the crank must either be altered or replaced. Trippin is replacing the crank. His new crank has a larger swing. Swing is the distance from the center of the main journal to the center of the rod journal on the crank. Basicly swing eqauls half the the stroke. I say basicly because things like offset bore centerlines and offset wrist pins actually can have effect on the stroke of the piston vs the stroke of the crank. But that is another dicussion.
To make things easy lets just go with this. Stock stroke is 3.898" Stock crank swing is 1.949". What Trippin has done is make a new crank that has a swing that is larger by .125. Which equals 2.047" That means a stroke of 4.148". So the piston is now traveling .25" further per crank revolution.
That increases dispacement. Displacement is the max total volume of one cylinder times the total number of cylinders. Max displacement is measured with the piston at Bottom Dead Center.
Make sense?
Now you can not simply bolt in a new crank to increase stroke. Why? The large swing of the crank will cause interference issues with the pistons. At BTC a skirt of the stock piston is very close to the bob weight of the stock crank. So to really pull off the increase in stroke you need a custom crank. You also need rods and pistons made to work with this crank. Trippin has done this and I gather he is going to selling them in a Kit form.
Advantages of the longer stroke.
1:More displacement means more air in which means more fuel can be burnt. Which equals more power!
2: Incearsed torque because of increased leverage. The same cylinder pressure now has more leverage of the crank so the same pressure equals more force(ie. torque).
There is more to it than just this. There are disadvantages to increased stroke also. But I have to get back to work!:rofl:
Stroke
With a longer stroke shorter rod(less rod ratio) you will help the rod bending problem. When I build a pump gas or nitrous motor I will run less rod ratio so the piston spends less time at TDC. It will have faster piston speed which will get the piston away from TDC quicker. Everyone thinks loger rods and normaly I will disagree. There is advantages to each.
With a longer stroke shorter rod(less rod ratio) you will help the rod bending problem. When I build a pump gas or nitrous motor I will run less rod ratio so the piston spends less time at TDC. It will have faster piston speed which will get the piston away from TDC quicker. Everyone thinks loger rods and normaly I will disagree. There is advantages to each.
Ok
Stroke: The distance the piston travels in the bore. The distance from Top dead Center (TDC) to Bottom Dead Center (BDC).
Stock stroke is 3.898"
To increase the stroke the crank must either be altered or replaced. Trippin is replacing the crank. His new crank has a larger swing. Swing is the distance from the center of the main journal to the center of the rod journal on the crank. Basicly swing eqauls half the the stroke. I say basicly because things like offset bore centerlines and offset wrist pins actually can have effect on the stroke of the piston vs the stroke of the crank. But that is another dicussion.
To make things easy lets just go with this. Stock stroke is 3.898" Stock crank swing is 1.949". What Trippin has done is make a new crank that has a swing that is larger by .125. Which equals 2.047" That means a stroke of 4.148". So the piston is now traveling .25" further per crank revolution.
That increases dispacement. Displacement is the max total volume of one cylinder times the total number of cylinders. Max displacement is measured with the piston at Bottom Dead Center.
Make sense?
Now you can not simply bolt in a new crank to increase stroke. Why? The large swing of the crank will cause interference issues with the pistons. At BTC a skirt of the stock piston is very close to the bob weight of the stock crank. So to really pull off the increase in stroke you need a custom crank. You also need rods and pistons made to work with this crank. Trippin has done this and I gather he is going to selling them in a Kit form.
Advantages of the longer stroke.
1:More displacement means more air in which means more fuel can be burnt. Which equals more power!
2: Incearsed torque because of increased leverage. The same cylinder pressure now has more leverage of the crank so the same pressure equals more force(ie. torque).
There is more to it than just this. There are disadvantages to increased stroke also. But I have to get back to work!:rofl:
SHAZZZAAAAM Thanks Dude.
As John posted, adding cubic inches adds air space. There is only a slight friction amount created with the added cylinder diameter ( cylinder bore ) and piston travel distance ( stroke ). The added cubic inches will effect both dynamic and static compression.
We are charging our dmax's to higher boost levels, doing this, we are effectively increasing the cubic inches ( relative to baro ). Using boost as cubic inch "replacement" or "adder", is said to have a larger impact with adding power. But, then again, increasing a 700 inch engines atmosphere by one effectively doubles the cubic inch to 1400 inches without adding to friction.
Larger pistons and longer strokes increases mass, more room for trouble with load and rpm. Shorter rods increase piston speed, added wear to the skirt and cylinder wall and therefore friction. Longer rods add weight, but slow the piston for better timing control as well as a longer duration for cylinder pressure ( longer time at desired pressure for crank angle ).
Increased torque is what we are after, wins the races. By managing the amount of cylinder pressure over a longer period of time, we increase torque.
Boost, as well as increased cubic inch, require mechanical reinforcement ( head studs, main studs and so on. Adding to stroke, adds a bit more time for managed cylinder pressure. I'm thinking a lower timing number will be required with the added dynamic cylinder pressure ( boost or cubic inch ).
Will it be cheaper to adapt a stock cubic inch engine for more boost, or will the stroker kit be the cheaper power adder? Adding air/fuel adds power, boost and cubic will do this. Will the stroker kit allow for the same boost level as a none stroked engine? Time will tell, hopefully Guy will give an insight to this.
So, "no replacement for displacement" is dead on. But, what is the best way to achieve displacement?
In John's post I would like to add to this statement. " 2: Incearsed torque because of increased leverage. The same cylinder pressure now has more leverage of the crank so the same pressure equals more force(ie. torque). "
The same cylinder pressure will have an impact, the .020 larger diameter will be the only advantage ( surface area ). Well, maybe not the only advantage, there is the advantage to having the rod journal .125 inches further away from the main journal center line if the stroke is .25 inches longer. But, the .020 cylinder bore diameter adds a touch of cylinder pressure in the absence of the added stroke.
The stroker kit advantage will be the stroke. On a rebuild, we can install .020 larger pistons and increase boost to compensate for the added displacement of a stroker kit. Or, if we keep our same turbo, a stroker kit will be an advantage. Wonder if I'm babbling on?
Hypothetically, if we make 1000 cubic inches with a 400 inch engine at sea level, 14.5 baro x 2.5 = 36.5 pounds of boost. The same engine that is 430 cubic inches only needs about 33.75 pounds of boost for 1000 cubic inches. The thing is, nothing is free, even boost.
We are charging our dmax's to higher boost levels, doing this, we are effectively increasing the cubic inches ( relative to baro ). Using boost as cubic inch "replacement" or "adder", is said to have a larger impact with adding power. But, then again, increasing a 700 inch engines atmosphere by one effectively doubles the cubic inch to 1400 inches without adding to friction.
Larger pistons and longer strokes increases mass, more room for trouble with load and rpm. Shorter rods increase piston speed, added wear to the skirt and cylinder wall and therefore friction. Longer rods add weight, but slow the piston for better timing control as well as a longer duration for cylinder pressure ( longer time at desired pressure for crank angle ).
Increased torque is what we are after, wins the races. By managing the amount of cylinder pressure over a longer period of time, we increase torque.
Boost, as well as increased cubic inch, require mechanical reinforcement ( head studs, main studs and so on. Adding to stroke, adds a bit more time for managed cylinder pressure. I'm thinking a lower timing number will be required with the added dynamic cylinder pressure ( boost or cubic inch ).
Will it be cheaper to adapt a stock cubic inch engine for more boost, or will the stroker kit be the cheaper power adder? Adding air/fuel adds power, boost and cubic will do this. Will the stroker kit allow for the same boost level as a none stroked engine? Time will tell, hopefully Guy will give an insight to this.
So, "no replacement for displacement" is dead on. But, what is the best way to achieve displacement?
In John's post I would like to add to this statement. " 2: Incearsed torque because of increased leverage. The same cylinder pressure now has more leverage of the crank so the same pressure equals more force(ie. torque). "
The same cylinder pressure will have an impact, the .020 larger diameter will be the only advantage ( surface area ). Well, maybe not the only advantage, there is the advantage to having the rod journal .125 inches further away from the main journal center line if the stroke is .25 inches longer. But, the .020 cylinder bore diameter adds a touch of cylinder pressure in the absence of the added stroke.
The stroker kit advantage will be the stroke. On a rebuild, we can install .020 larger pistons and increase boost to compensate for the added displacement of a stroker kit. Or, if we keep our same turbo, a stroker kit will be an advantage. Wonder if I'm babbling on?
Hypothetically, if we make 1000 cubic inches with a 400 inch engine at sea level, 14.5 baro x 2.5 = 36.5 pounds of boost. The same engine that is 430 cubic inches only needs about 33.75 pounds of boost for 1000 cubic inches. The thing is, nothing is free, even boost.
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Like I said there is far more to it then what I listed or what I even claim to know. I claim to know very little by the way.My example of the added torque was made assuming all things like the bore stayed the same. Just the stroke was increased. Honestly I think the stroker kit is neat. But not for me. IMHO enlarging the bore is a better option. We already can make enough torque to hurt hard parts. We have better Rods. Pistons we really dont know yet. One week spot no one has talked about lately is the bearings. Many that hurt pistons have hurt bearings also. I can think of more than a few that had bearing issues.
To me money better spent would be on better valvetrain that right know only really exists on several engines and is not purchasable buy the average Dmax owner. Bearings are right next to valvetrain on the list. Better bearings like some of the supposedly new bearings from King would be a great thing.
Another problem is the increase stroke means the wrist pin must be closer to the top of the piston or the rod must get shorter. I like Sting think that shorter rod would actually be a good thing in our case. Even with a stock stroke. Why? Several reasons. One there is not a lot of room between the top of the wrist pin and the bottom of the bowl. New pistons with shallower but wider bowls would be great, but still leaves us problem number two. Two the ring pack is to close to the top of the piston for my liking. Look at performance Cummins pistons like the Cummins Marine piston or the Peirs piston. They moved the rings further down for good reasons. Dmax rings are closer then even a stock Cummins piston to the top.
I disagree on the torque wins races or pulls. Horsepower tells the tale IMHO. I know Horsepower is a function of torque. I know the math well. I also know that when racing or pulling you never run near your peak torque. You are far closer to peak HP then the peak torque. Torque is force. How much work can be done. Horsepower is how fast you can do the work. If you want to go faster or pull farther you need more HP. Which can mean you need more torque. But not always. I have sure I can make enough torque to hurt my engine. I really would rather not. I am hoping to go a whole pulling and racing season before tearing down. But I still want big horsepower. More than most.
So I need to use my only freind left. RPM.Your right nothing is free! And it is not cheap! At least for a Dmax!:rofl:
absolutely excellent posts John and new2lb7 (is it Mike? sorry I forgot your name -_- ). That helps a bunch.
Sounds like what I was thinking, the stroker kit may be harder on our parts due to the increased torque, has some merit in deciding if this is a viable option right now. I don't think it will be a bad mod, certainly not for most though. It will also likely tell the tale on those bearings John mentioned or the next weak spot in the Dmax that is yet to be determined.
Pretty cool stuff. Thanks guys.
Sounds like what I was thinking, the stroker kit may be harder on our parts due to the increased torque, has some merit in deciding if this is a viable option right now. I don't think it will be a bad mod, certainly not for most though. It will also likely tell the tale on those bearings John mentioned or the next weak spot in the Dmax that is yet to be determined.
Pretty cool stuff. Thanks guys.
Good posts men, that really explains it all! :book::thankyou: It explains it exactly, and without fighting between steve and someone else :rofl:
I totally agree :angel::rofl::rofl:
I totally agree :angel::rofl::rofl:
My example of the added torque was made assuming all things like the bore stayed the same. Just the stroke was increased. Honestly I think the stroker kit is neat. But not for me. IMHO enlarging the bore is a better option. We already can make enough torque to hurt hard parts. We have better Rods. Pistons we really dont know yet. One week spot no one has talked about lately is the bearings. Many that hurt pistons have hurt bearings also. I can think of more than a few that had bearing issues.
To me money better spent would be on better valvetrain that right know only really exists on several engines and is not purchasable buy the average Dmax owner. Bearings are right next to valvetrain on the list. Better bearings like some of the supposedly new bearings from King would be a great thing.
Another problem is the increase stroke means the wrist pin must be closer to the top of the piston or the rod must get shorter. I like Sting think that shorter rod would actually be a good thing in our case. Even with a stock stroke. Why? Several reasons. One there is not a lot of room between the top of the wrist pin and the bottom of the bowl. New pistons with shallower but wider bowls would be great, but still leaves us problem number two. Two the ring pack is to close to the top of the piston for my liking. Look at performance Cummins pistons like the Cummins Marine piston or the Peirs piston. They moved the rings further down for good reasons. Dmax rings are closer then even a stock Cummins piston to the top.
I disagree on the torque wins races or pulls. Horsepower tells the tale IMHO. I know Horsepower is a function of torque. I know the math well. I also know that when racing or pulling you never run near your peak torque. You are far closer to peak HP then the peak torque. Torque is force. How much work can be done. Horsepower is how fast you can do the work. If you want to go faster or pull farther you need more HP. Which can mean you need more torque. But not always. I have sure I can make enough torque to hurt my engine. I really would rather not. I am hoping to go a whole pulling and racing season before tearing down. But I still want big horsepower. More than most.
Your right nothing is free! And it is not cheap! At least for a Dmax!:rofl:
John, thank you for the constructive criticism, if I can say that without causing a problem.
" Repeat after me. "It is better to make torque at high rpm than at low rpm, because you can take advantage of *gearing*."
Thanks for your time.
Bruce "
This is a quote by a fellow " Bruce ".
After doing some research on the subject of hp vs torque, by me, at various sites, I have still gotta interpret torque as being the winner. This link, http://vettenet.org/torquehp.html , is one interpretation for my Torque vs horsepower mindset. I am open to a correct interpretation if so proven.
Torque is created by the twisting force of the engine. We take advantage of the torque, at a specific rpm,( work over time) which calculates to horsepower.
Zero horsepower without torque, but 1 pound feet of torque will give you a small work amount ( horsepower ) by an engine or motor for that matter.
A horse makes horsepower, but 0 torque unless something mechanical is connected to the horse.
Hello Mitch
Mike is fine unless Simon, Larry or Mick have a say so.
:rofl::cool2:Hmmm... might have left a few names out.....
John, thank you for the constructive criticism, if I can say that without causing a problem.
" Repeat after me. "It is better to make torque at high rpm than at low rpm, because you can take advantage of *gearing*."
Thanks for your time.
Bruce "
This is a quote by a fellow " Bruce ".
After doing some research on the subject of hp vs torque, by me, at various sites, I have still gotta interpret torque as being the winner. This link, http://vettenet.org/torquehp.html , is one interpretation for my Torque vs horsepower mindset. I am open to a correct interpretation if so proven.
Torque is created by the twisting force of the engine. We take advantage of the torque, at a specific rpm,( work over time) which calculates to horsepower.
Zero horsepower without torque, but 1 pound feet of torque will give you a small work amount ( horsepower ) by an engine or motor for that matter.
A horse makes horsepower, but 0 torque unless something mechanical is connected to the horse.
Where all good Mike!
TQ vs HP is like which came first the chicken or the egg.
Good link.
Where all good Mike!
TQ vs HP is like which came first the chicken or the egg.
Good link.
Well, gotta guess on the chicken or the egg.... I say hmm... well..... what about the belly button we have?
Good luck to you aey. Happy Scary Night to ya John and the rest of you folks as well. Be safe and look out for them little peoples... :angel:
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