Stroker Builds: Basic Concepts
Last Updated: 02.18.11
Over the years, increasing the displacement of our engines has become more and more commonplace. That also means questions on it, are becoming more and more common, but answers are not. This article intends to just introduce you to the concept, it is by no means a guide to use for the final planning of your motor build.
Once you understand the concepts presented here, the research lies on you. Hopefully this helps you know what to search for and guide you to the right path.
What is a stroker?
An engine that has a greater than stock displacement due to an increase in the factory crank throw. An increase in crank throw increases stroke.
Stroke:
Stroke is the difference between the piston's top dead center and bottom dead center.
What are my stroker options?
For all intents and purposes, we will be considering a 4G64 bottom end a stroker in this tech article. You may feel free to disagree, but the science is the same, so in the interest of moving on, leave it be.
The 2.1 Stroker:
This build utilizes the 4G64 block combined with the 4G63 crankshaft and head. The head is not relevant in this particular article.
In order to complete this build you will need to seek out longer rods to make up for the extra 6 millimeters of block height. You will also need to plug several oil drains with freeze plugs before mating the 4G63 head to the 4G64 block.
The 2.3 Stroker:
This build utilizes the 4G63 block and head combined with the 4G64 crankshaft.
In order to complete this build you will need to seek out "stroker" pistons to account for the loss of 6 millimeters of block height.
The 2.4 Stroker:
This build utilizes the 4G64 block and crank combined with the 4G63 head.
You will need to plug several oil drains with freeze plugs before mating the 4G63 head to the 4G64 block.
The 2.1L and 2.4L build will require some fabrication to make the timing belt work. The information on methods to do this can be found on this site. I offer no preference.
Some other things to remember when planning your build. The 4G63 and 4G64 blocks use the exact same rods from factory, same length and forging process. The cranks are different, the 4G63 has an 88 millimeter stroke and the 4G64 has a 100 millimeter stroke, the pistons are also different, the 4G64 uses a wider bore piston, because the block is a wider bore.
Why would I want to build a stroker?
A stroker engine increases the displacement of your motor, and the more displacement the more leverage which equates to more torque.
Displacement:
Is measured in cubic inches. The formula to derive this is simple and listed below:
Cubic Inches = Bore² x Stroke x .7854 x # of Cylinders
I have been kind enough to do the math for you for the above listed builds as well as strock figures. In this instance, the # of cylinders on each motor is 4, but of course you knew that.
This math obviously cannot be done by inputting the metric numbers, since cubic inches is an imperial number.
So...
1 inch = 25.4 millimeters
Dividing the metic measurements of our stroke and bore by 25.4 will yield you the inches value.
Of course, if you know the cubic centimeters of the motors (or cc rating) you could have saved yourself a lot of time with this equation:
1 Cubic Inches = 16.387064 Cubic Centimeters
So what are all these numbers? That's probably the question in your head right now. It's simple Liters, Cubic Inches, Cubic Centimeters, they are all the same thing and that is the volume of air and fuel the collective cylinders hold. So, if you read my turbo article, you know that the more air and fuel you can have, the more power you make.
In my opinion, bigger is better...moving on.
As our knowledge expands and more people are aware of the facts, and as stroker kits, budget or not, are more readily available, this becomes a great alternative to increasing power, especially torque.
Benefits:
There are many benefits that actually just compound onto other aspects to create more benefits. Let's take a look.
Torque
Torque is also known as moment of force, which is the tendency of a force to rotate an object about an axis, fulcrum, or pivot. Just as a force is a push or a pull, a torque can be thought of as a twist.
Because you have more displacement, you already are cramming more air and fuel into the engine, which means it is creating more power, and more power gets your vehicle moving quicker and faster.
Because you are already creating more base power, that means you immediately create more exhaust flow that sees the turbine of your turbocharger.
Faster Spool
As discussed in my turbo article, the amount and pressure and heat of your exhaust is what is powering your turbocharger, the exhaust spins the turbine, which in effect spins, your compressor. The faster your compressor spins the quicker you get into and build boost.
You have a natural advantage over every smaller engine, you will get into boost faster. And boost is more power.
Downfalls:
Increasing the stroke of your crankshaft does have some negative factors as well. Especially in many instances with our cars where we do not usually increase the rod length or increase it drastically. This causes what is known as our rod ratio to be smaller and that in turn means we cannot see the same RPMs as we could with our 2.0L build.
Rod Ratio:
Rod ratio is also known as rod to stroke ratio. It is very simple to calculate. The mathematical equation for it is as follows:
Rod Ratio = Rod Length / Stroke
The greater this ratio, the less the rod angularity is and the lower this ratio, the more rod angularity there is. You want less rod angularity (higher rod ratio) to decrease friction on the rotating assembly. Otherwise you have a greater chance of accelerated wear to the cylinders, pistons and rings, as well as a greater chance at bending or snapping a rod.
We can attempt to remedy this by lengthening the rod as we increase the stroke, but by lengthening the rod, we have to shorten the piston. In the end, we can only shorten the piston so much before the piston pin intersects with the oil ring groove, which is potential for increased oil consumption. Some companies have engineered their pistons to counteract this (known as "stroker pistons") with tighter ring packs (grooves) and bridge rings, but you are still limited in the end. Consider this when building your engine, stroker or not, because it's dependality could be compromised.
In the end, the general agreement among manufacturers is that the absolute lowest ratio of 1.50 is what makes an engine acceptable for a street motor and all options fall into this range. The ideal number is 1.65 to 1.80.
So how high can I rev my motor?
That's a hard question to answer, it all depends on your rod ratio, the manufacturing of your internals and how comfortable you feel with a certain RPM range.
Magnus engine internals are claimed to be good for upto 11,000 RPMs. However, even in his data sheet on his engines, he sets certain strokers to certain levels as a recommendation. I would suggest using it as a guide. You can read it by clicking here.
You have plenty of options, in fact you have two more options that I haven't covered yet. It is possible to create a 2.2L stroker build. You accomplish this with a 4G63 block and head and a custom crankshaft, as well as increasing the bore to 86 millimeters.
I'll let you do the math to get more comfortable with the information I threw at you.
Wait...what's rod angularity?
Yes, I seem to forgot to have explained that. So I will leave you with the definition.
Rod Angularity:
This is basically the most drastic angle that the rod is at during it's travel, it occurs right before the rod changes direction between up and down.
Credits: Thanks to member jnf63, for proof-reading and suggestion grammatical changes to make the article better flow.
Last Updated: 02.18.11
Over the years, increasing the displacement of our engines has become more and more commonplace. That also means questions on it, are becoming more and more common, but answers are not. This article intends to just introduce you to the concept, it is by no means a guide to use for the final planning of your motor build.
Once you understand the concepts presented here, the research lies on you. Hopefully this helps you know what to search for and guide you to the right path.
What is a stroker?
An engine that has a greater than stock displacement due to an increase in the factory crank throw. An increase in crank throw increases stroke.
Stroke:
Stroke is the difference between the piston's top dead center and bottom dead center.
What are my stroker options?
For all intents and purposes, we will be considering a 4G64 bottom end a stroker in this tech article. You may feel free to disagree, but the science is the same, so in the interest of moving on, leave it be.
The 2.1 Stroker:
This build utilizes the 4G64 block combined with the 4G63 crankshaft and head. The head is not relevant in this particular article.
In order to complete this build you will need to seek out longer rods to make up for the extra 6 millimeters of block height. You will also need to plug several oil drains with freeze plugs before mating the 4G63 head to the 4G64 block.
The 2.3 Stroker:
This build utilizes the 4G63 block and head combined with the 4G64 crankshaft.
In order to complete this build you will need to seek out "stroker" pistons to account for the loss of 6 millimeters of block height.
The 2.4 Stroker:
This build utilizes the 4G64 block and crank combined with the 4G63 head.
You will need to plug several oil drains with freeze plugs before mating the 4G63 head to the 4G64 block.
The 2.1L and 2.4L build will require some fabrication to make the timing belt work. The information on methods to do this can be found on this site. I offer no preference.
Some other things to remember when planning your build. The 4G63 and 4G64 blocks use the exact same rods from factory, same length and forging process. The cranks are different, the 4G63 has an 88 millimeter stroke and the 4G64 has a 100 millimeter stroke, the pistons are also different, the 4G64 uses a wider bore piston, because the block is a wider bore.
Why would I want to build a stroker?
A stroker engine increases the displacement of your motor, and the more displacement the more leverage which equates to more torque.
Displacement:
Is measured in cubic inches. The formula to derive this is simple and listed below:
Cubic Inches = Bore² x Stroke x .7854 x # of Cylinders
I have been kind enough to do the math for you for the above listed builds as well as strock figures. In this instance, the # of cylinders on each motor is 4, but of course you knew that.
This math obviously cannot be done by inputting the metric numbers, since cubic inches is an imperial number.
So...
1 inch = 25.4 millimeters
Dividing the metic measurements of our stroke and bore by 25.4 will yield you the inches value.
Optional Math said:4G63: (1997CC - 2.0L)
Bore: 85 millimeters = 3.346456692913386 inches (3.346 will suffice)
Stroke: 88 millimeters = 3.464566929133858 inches (3.465 will suffice)
Cubic Inches = 121.872578701104 (122 will suffice)
4G64: (2351CC - 2.4L)
Bore: 86.5 millimeters = 3.405511811023622 inches (3.406 will suffice)
Stroke: 100 millimeters = 3.937007874015748 inches (3.937 will suffice)
Cubic Inches = 143.4846987686112 (143 will suffice)
2.1L Hybrid: (2065CC)
Bore: 86.5 millimeters = 3.406 (As we know from our previous math)
Stroke: 88 millimeters = 3.465 (As we know from our previous math)
Cubic Inches = 126.282570798384 (126 will suffice)
2.3L Hybrid: (2261CC)
Bore: 85 millimeters = 3.346 (As we know from our previous math)
Stroke: 100 millimeters = 3.937 (As we know from our previous math)
Cubic Inches = 138.4739804751072 (138 will suffice)
2.4L Hybrid: (2351CC)
I already mentioned above that the head doesn't matter for this article. The numbers are the same as your normal SOHC 4G64 or later model DOHC versions.
Of course, if you know the cubic centimeters of the motors (or cc rating) you could have saved yourself a lot of time with this equation:
1 Cubic Inches = 16.387064 Cubic Centimeters
FAQ said:I thought that the metric system was all even and divisble by increments of 10's?
It's true, engine manufacturers round up when determining the liters or their motor. For more accurate calculations further down the line, you should utilize the cubic centimeters number over the rounded liter number, or adjust liters properly.
4G63 = 1.997 Liters
4G64 = 2.351 Liters
2.1L Hybrid = 2.065 Liters
2.3L Hybrid = 2.261 Liters
2.4L Hybrid = If you haven't got it by now, the same as the standard 4G64 numbers.
So what are all these numbers? That's probably the question in your head right now. It's simple Liters, Cubic Inches, Cubic Centimeters, they are all the same thing and that is the volume of air and fuel the collective cylinders hold. So, if you read my turbo article, you know that the more air and fuel you can have, the more power you make.
In my opinion, bigger is better...moving on.
As our knowledge expands and more people are aware of the facts, and as stroker kits, budget or not, are more readily available, this becomes a great alternative to increasing power, especially torque.
Benefits:
There are many benefits that actually just compound onto other aspects to create more benefits. Let's take a look.
Torque
Torque is also known as moment of force, which is the tendency of a force to rotate an object about an axis, fulcrum, or pivot. Just as a force is a push or a pull, a torque can be thought of as a twist.
Because you have more displacement, you already are cramming more air and fuel into the engine, which means it is creating more power, and more power gets your vehicle moving quicker and faster.
Because you are already creating more base power, that means you immediately create more exhaust flow that sees the turbine of your turbocharger.
Faster Spool
As discussed in my turbo article, the amount and pressure and heat of your exhaust is what is powering your turbocharger, the exhaust spins the turbine, which in effect spins, your compressor. The faster your compressor spins the quicker you get into and build boost.
You have a natural advantage over every smaller engine, you will get into boost faster. And boost is more power.
Advanced Concept said:Written by FordMuscle.com:
Piston Dwell Time and Piston Speed:
An often overlooked factor that contributes to the advantage of a stroker motor has to do with piston dwell time, the amount of time the piston remains at the top and bottom of the stroke. The increased stroke and rod length of a stroker motor yields a longer piston dwell time. Longer dwell time allows for better flow of combustion and exhaust gases since the piston accelerates slower in the transition between "up" and "down" strokes. Intake gases have a longer time to enter the cylinder while exhaust gases are given more time to escape. This translates into more natural torque over a longer range of rpm. Power and torque can also be enhanced with valve event timing and cam profile.
Even though the piston accelerates slower in transition, the piston ultimately reaches higher speeds to cover the additional stroke. This increase in piston speed means greater component strain. Another factor to consider before simply going with the kit or components that give you largest stroke increase.
Downfalls:
Increasing the stroke of your crankshaft does have some negative factors as well. Especially in many instances with our cars where we do not usually increase the rod length or increase it drastically. This causes what is known as our rod ratio to be smaller and that in turn means we cannot see the same RPMs as we could with our 2.0L build.
Rod Ratio:
Rod ratio is also known as rod to stroke ratio. It is very simple to calculate. The mathematical equation for it is as follows:
Rod Ratio = Rod Length / Stroke
The greater this ratio, the less the rod angularity is and the lower this ratio, the more rod angularity there is. You want less rod angularity (higher rod ratio) to decrease friction on the rotating assembly. Otherwise you have a greater chance of accelerated wear to the cylinders, pistons and rings, as well as a greater chance at bending or snapping a rod.
Optional Math said:4G63 Rod Ratio:
Rod Length: 150 millimeters
Stroke: 88 millimeters
Rod Ratio: 1.7045
4G64 Rod Ratio:
Rod Length: 150 millimeters
Stroke: 100 millimeters
Rod Ratio: 1.5000
2.1L Hybrid Rod Ratio:
Rod Length: 156 millimeters
Stroke: 88 millimeters
Rod Ratio: 1.7727
2.3L Hybrid Rod Ratio:
Rod Length: 150 millimeters
Stroke: 100 millimeters
Rod Ratio: 1.500 millimeters
As you can see there is a reason why the 2.1L hybrid is known for being an RPM whore, it offers the least angularity, but has the benefit of slightly more displacement. Another thing you should note is that the ratio is the same on the 2.3L and 2.4L, there really is no reason not to just go with the full swap, other than having to be slightly creative with the timing belt.
There are also long rod kits sold that change these numbers a bit. We will cover that shortly.
We can attempt to remedy this by lengthening the rod as we increase the stroke, but by lengthening the rod, we have to shorten the piston. In the end, we can only shorten the piston so much before the piston pin intersects with the oil ring groove, which is potential for increased oil consumption. Some companies have engineered their pistons to counteract this (known as "stroker pistons") with tighter ring packs (grooves) and bridge rings, but you are still limited in the end. Consider this when building your engine, stroker or not, because it's dependality could be compromised.
In the end, the general agreement among manufacturers is that the absolute lowest ratio of 1.50 is what makes an engine acceptable for a street motor and all options fall into this range. The ideal number is 1.65 to 1.80.
So how high can I rev my motor?
That's a hard question to answer, it all depends on your rod ratio, the manufacturing of your internals and how comfortable you feel with a certain RPM range.
Magnus engine internals are claimed to be good for upto 11,000 RPMs. However, even in his data sheet on his engines, he sets certain strokers to certain levels as a recommendation. I would suggest using it as a guide. You can read it by clicking here.
FAQ said:You mentioned long rod setups for increasing the RPMs you can safely see, what are they?
Keep in mind, that these are all accomplished through the same method. You are going to decrease the piston height to increase the rod height to increase you rod ratio (decrease the angularity).
2.0L Long Rod:
Rod Length: 156 millimeters (was 150)
Stroke: 88 millimeters
Rod Ratio: 1.7727
2.1L Long Rod:
Rod Length: 162 millimeters (was 156)
Stroke: 88 millimeters
Rod Ratio: 1.8409 (Holy RPMs.)
2.4L Long Rod:
Rod Length: 156 millimeters (was 150)
Stroke: 100 millimeters
Rod Ratio: 1.560
You have plenty of options, in fact you have two more options that I haven't covered yet. It is possible to create a 2.2L stroker build. You accomplish this with a 4G63 block and head and a custom crankshaft, as well as increasing the bore to 86 millimeters.
I'll let you do the math to get more comfortable with the information I threw at you.
Wait...what's rod angularity?
Yes, I seem to forgot to have explained that. So I will leave you with the definition.
Rod Angularity:
This is basically the most drastic angle that the rod is at during it's travel, it occurs right before the rod changes direction between up and down.
Credits: Thanks to member jnf63, for proof-reading and suggestion grammatical changes to make the article better flow.
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