pros and cons for a stroker
- Thread starter gnsrule
- Start date
- Joined
- May 26, 2001
Amazing, I have been around race cars for MANY years, and never heard that before?
The internet has spawned a new generation of "engine experts"!
It did sound silly to me too. I still need to decide if I'm going long rod stroker or just stock forged rotating assembly, either way going to 9.5:1 compression.Amazing, I have been around race cars for MANY years, and never heard that before?
The internet has spawned a new generation of "engine experts"!
20psiofevil
Active Member
- Joined
- Feb 10, 2013
I thought this was a good read. (copy and pasted from a reputable engine builder)
The decrease in side loading while an improvement in power and durability is only a minor part of the equation. Increasing the length of the connecting rod will improve the pumping characteristics of any engine and increase its combustion efficiency by extracting more power out of the same amount of fuel and air. The physics of this gets a little complicated, but much of it has to do with the position of the piston relative to the combustion chamber as the crankshaft rotates.
The longer the connecting rod, the longer it takes the piston to reverse directions at either end of its travels. The rod has a wider swing than with a shorter rod so during combustion the piston is higher with more pressure against it when the crank and rod are at a 90* angle to each other when power transfer is most efficient. This extended transition time translates into a greater latitude in ignition timing. You can reduce the timing advance and still be able to achieve complete burn because the piston is traveling slower at the top of the cylinder with the longer rod. Reduced timing generates less negative pressure against the piston before the crank has swung past TDC and started back down. Because of this improvement in piston speed geometry the charge generates it's maximum combustion pressure while the piston is higher, therefore applying it for a longer length of the stroke and generating more power from the same amount of air and fuel.
When combustion efficiency is improved, sensitivity to detonation is also reduced. The advantages above also allow a higher static compression ratio, in fact if you lengthen the rods enough you can increase compression ratio and reduce octane requirements at the same time. This will again increase engine efficiency and reduce timing advance needs allowing each to maximize the other.
At the other end of the stroke, BTC, the slower turn around happens again with more good effects. The piston hangs at the bottom of the cylinder for a longer time, allowing for a more complete cylinder filling on the intake stroke, and on the exhaust stroke it allows for more reduction in cylinder pressure before the piston starts back up which reduces pumping losses.
The more efficient piston movement due to longer rods will improve the flow of gases into and out of the cylinder and will dampen a cam with large amounts of overlap and duration as valve timing events are still happening at crank speed, not piston speed. This makes the engine less sensitive to valve timing and intake and exhaust systems. On the exhaust to intake stroke transition the slower piston forces more exhaust out and allows the exhaust valve to shut and the intake valve to be further open and more clear of shrouding before the piston picks up speed and pulls away. This reduces exhaust gas contamination of the intake charge greatly, especially with high amounts of overlap and exhaust system pressure. The increased piston speed at mid stroke coincides with the intake valve achieving it's maximum lift thereby generating a harder pull on the intake and better cylinder filling with less power used to do so. At the bottom of the stroke the piston slow down allows the intake valve to shut further before the piston reverses direction again, this traps more charge in the cylinder with less intake charge reversion.
Because longer connecting rods get more power out of the same displacement they increase overall efficiency by about 5 to 10 percent at the ground. They will generate more horsepower and torque than the same engine with shorter rods and produce a wider, less peaky, power band. This is how they work and why spare no expense professional racing motors will have the longest rod that can be fitted into its dimensions.
Is it worth it for you and me? I would say yes if you can swing it, but to achieve the greatest gain you need to know what it is you are doing and why, that way you can tune for them accordingly. The specifications that generated maximum power with your shorter rod combination will not carry over. You can and should run more cam and compression and less ignition timing.
The decrease in side loading while an improvement in power and durability is only a minor part of the equation. Increasing the length of the connecting rod will improve the pumping characteristics of any engine and increase its combustion efficiency by extracting more power out of the same amount of fuel and air. The physics of this gets a little complicated, but much of it has to do with the position of the piston relative to the combustion chamber as the crankshaft rotates.
The longer the connecting rod, the longer it takes the piston to reverse directions at either end of its travels. The rod has a wider swing than with a shorter rod so during combustion the piston is higher with more pressure against it when the crank and rod are at a 90* angle to each other when power transfer is most efficient. This extended transition time translates into a greater latitude in ignition timing. You can reduce the timing advance and still be able to achieve complete burn because the piston is traveling slower at the top of the cylinder with the longer rod. Reduced timing generates less negative pressure against the piston before the crank has swung past TDC and started back down. Because of this improvement in piston speed geometry the charge generates it's maximum combustion pressure while the piston is higher, therefore applying it for a longer length of the stroke and generating more power from the same amount of air and fuel.
When combustion efficiency is improved, sensitivity to detonation is also reduced. The advantages above also allow a higher static compression ratio, in fact if you lengthen the rods enough you can increase compression ratio and reduce octane requirements at the same time. This will again increase engine efficiency and reduce timing advance needs allowing each to maximize the other.
At the other end of the stroke, BTC, the slower turn around happens again with more good effects. The piston hangs at the bottom of the cylinder for a longer time, allowing for a more complete cylinder filling on the intake stroke, and on the exhaust stroke it allows for more reduction in cylinder pressure before the piston starts back up which reduces pumping losses.
The more efficient piston movement due to longer rods will improve the flow of gases into and out of the cylinder and will dampen a cam with large amounts of overlap and duration as valve timing events are still happening at crank speed, not piston speed. This makes the engine less sensitive to valve timing and intake and exhaust systems. On the exhaust to intake stroke transition the slower piston forces more exhaust out and allows the exhaust valve to shut and the intake valve to be further open and more clear of shrouding before the piston picks up speed and pulls away. This reduces exhaust gas contamination of the intake charge greatly, especially with high amounts of overlap and exhaust system pressure. The increased piston speed at mid stroke coincides with the intake valve achieving it's maximum lift thereby generating a harder pull on the intake and better cylinder filling with less power used to do so. At the bottom of the stroke the piston slow down allows the intake valve to shut further before the piston reverses direction again, this traps more charge in the cylinder with less intake charge reversion.
Because longer connecting rods get more power out of the same displacement they increase overall efficiency by about 5 to 10 percent at the ground. They will generate more horsepower and torque than the same engine with shorter rods and produce a wider, less peaky, power band. This is how they work and why spare no expense professional racing motors will have the longest rod that can be fitted into its dimensions.
Is it worth it for you and me? I would say yes if you can swing it, but to achieve the greatest gain you need to know what it is you are doing and why, that way you can tune for them accordingly. The specifications that generated maximum power with your shorter rod combination will not carry over. You can and should run more cam and compression and less ignition timing.
Yeah what he said. Big cube and lil cube V6's can make a ton of power.Wow that's very informative and I can actually understand it!
Not sure if it would be beneficial or not but if the crank could be stock stroke but have the longest rod possible would that be more efficient and produce more power than a stroker crank with the longest rod possible?
Everything else being the same.
I would imagine the regular stroke crankshaft would allow for a longer rod?
Can it be done?
Thx for the post!
good morning guys !
I currently i have a Alum headed stroker engine. This engine was built in 2010 by myself and Richard Clark . I tore back into it after BG in 2010 due to a spun main. The problem was with the Girdle and main cap line bore after the girdle was installed.. So after that problem i installed 2 steel main caps and put it back together....
So i just removed the engine to refresh it after 6 yrs of hard running! This engine has a crap load of track passes and street miles. it averages about 5k miles a yr. My best 1/4 has been 9.96 @ 133 @ 3680 weight. This car was also a test mules for various parts for bob bailey. The TR6 in its early days gave it a fit with sync issues .. SD2 setup baby XFI ..
The reason for pulling the engine was i literally wore the head gaskets out. Due to the expansion and contraction rate of the heads vs the block it wore the cometics down at the fire ring on all six holes. This happened on both sides of the gasket... This was causing me to have a pretty heathly oil leak at the pass side head.. Also under boost it would push water out the overflow!
When we tore into the bottom end! The rod bearings were pretty worn down ( i used the standard Cleavite77 ) on the top shell. The main bearing had some wear on them as well. The num3 bearing had the most wear. The timing chain was way loose ( the new one is a .05 under sized ).
I did a leak down on the engine before i took it apart.. The worse cylinder was No 6 @ 52 % (gasket was gone on that cylinder) The rest of the cylinders were between 20-36 % leak down...
I also had to replace the pistons due to a small cut at the top of the crown and below that it had a hair line crack.. There was zero damage to the piston elsewhere or to the cylinder...
The new pistons (JE ) i needed to have the bores opened up just a tad for the pistons to wall clearance... After all these yrs the cylinders didn't wear very much at all..
The new pistons are 25 k in the hole compared to the old ones at 5 k . So i had to have the block decked anyhow for the surface to be flat for the cometics so i had them take 10 k off...The pistons are now 15k in the hole.
The heads were decked as well due to the head gaskets wore on the heads and they were not flat where the fire rings rest. The heads were decked 5k
The engine build is eagle stroker crank, K1 rods (5.960) New pistons (JE) ...Old pistons ( Diamond) DLS roller cam 214/@214 Ta roller Timing chain TA alum heads (level 2 ported) roller rockers . Champion ported stock intake..
This has been my experiance with stroker motors and longevity...
here is the pics of the gaskets and the piston..
I currently i have a Alum headed stroker engine. This engine was built in 2010 by myself and Richard Clark . I tore back into it after BG in 2010 due to a spun main. The problem was with the Girdle and main cap line bore after the girdle was installed.. So after that problem i installed 2 steel main caps and put it back together....
So i just removed the engine to refresh it after 6 yrs of hard running! This engine has a crap load of track passes and street miles. it averages about 5k miles a yr. My best 1/4 has been 9.96 @ 133 @ 3680 weight. This car was also a test mules for various parts for bob bailey. The TR6 in its early days gave it a fit with sync issues .. SD2 setup baby XFI ..
The reason for pulling the engine was i literally wore the head gaskets out. Due to the expansion and contraction rate of the heads vs the block it wore the cometics down at the fire ring on all six holes. This happened on both sides of the gasket... This was causing me to have a pretty heathly oil leak at the pass side head.. Also under boost it would push water out the overflow!
When we tore into the bottom end! The rod bearings were pretty worn down ( i used the standard Cleavite77 ) on the top shell. The main bearing had some wear on them as well. The num3 bearing had the most wear. The timing chain was way loose ( the new one is a .05 under sized ).
I did a leak down on the engine before i took it apart.. The worse cylinder was No 6 @ 52 % (gasket was gone on that cylinder) The rest of the cylinders were between 20-36 % leak down...
I also had to replace the pistons due to a small cut at the top of the crown and below that it had a hair line crack.. There was zero damage to the piston elsewhere or to the cylinder...
The new pistons (JE ) i needed to have the bores opened up just a tad for the pistons to wall clearance... After all these yrs the cylinders didn't wear very much at all..
The new pistons are 25 k in the hole compared to the old ones at 5 k . So i had to have the block decked anyhow for the surface to be flat for the cometics so i had them take 10 k off...The pistons are now 15k in the hole.
The heads were decked as well due to the head gaskets wore on the heads and they were not flat where the fire rings rest. The heads were decked 5k
The engine build is eagle stroker crank, K1 rods (5.960) New pistons (JE) ...Old pistons ( Diamond) DLS roller cam 214/@214 Ta roller Timing chain TA alum heads (level 2 ported) roller rockers . Champion ported stock intake..
This has been my experiance with stroker motors and longevity...
here is the pics of the gaskets and the piston..
Perhaps we could form an investigative committee to figure out why.
achalmersman
Well-Known Member
- Joined
- May 28, 2012
Damn you must work for the same people I work for
No trees were harmed in the sending of this message, however, a significant number of electrons were terribly inconvenienced.
I'm for Stroker motors....... I just dropped it back in the car thurs and its running awesome!!!!!!! The biggest problem with the engine was the crack in the piston. But they lasted 6 yrs. Had i known the diamonds had a weakness of cracking i would have went with a different pistons from the start!
Runs Awesome...Glad to have it back !!!!!
the head gasket is what concerns me.i haven't had any issues with diamond Pistons and my stuff gets run hard,but I have thought long and hard about the al head on an iron block.some guys up here haven't had any issues though and some guys have.
I have had many stock stroke 109 which ran great however after going stroker i would not go back to stock. I drive on the streets alot and the torque and power is awesome with stroker, Cal tuned my stock stroke and it made 680 rwhp everything the same in parts but new stroker and i made 80rwhp more at 28psi. Cubes matter on the street, Richie has the fastest 109 but he is the exception the average guy will fine a difference with the stroker.
yes but the AVG guy can't harness that extra 80rwhp on the street .. so your just paying for bragging rights , as ultimately the car won't be any faster in the street.. actually it maybe slower.
Just got done with a SBF transition for a customer going back to a smaller motor so that he can apply the power to the street ... had to prove to him numbers as he didn't believe it ..
the smaller motors can have more USEABLE power .. but to each their own
Mickey T drag radials works for me also you don't need to be on kill just use the boost that suits your needs.
- Joined
- May 26, 2001
The information you posted contains lots of good information, but applies generally to large displacement V-8 engines, and our relatively small displacement turbo V-6 do not follows that theory of longer rods make more power.
Kenny Duttweiller has proven this with his many Buick V6 turbo engine builds up to almost 2000 HP. In one of his published articles a few years ago he stated, "it make no difference in HP in a turbo Buick engine whether it is a stock length rod or a longer one."
Conversations with other engine builders have stated the big-block V-8 race car see an additional 40-50 HP with a longer rod. Of course these engines also run 9000-10,000 RPM in competition where every additional HP counts!
dank GN
BlackArts Automotive (661)993-8277
- Joined
- Jan 11, 2009
The connecting rod bolt issue is with stage motors or the 109 as well when going stroker?
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