Most Durable Rods & Pistons - Modded 2.5
03-30-2011, 12:58 PM
#1
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Most Durable Rods & Pistons - Modded 2.5
What rods & pistons are considered the most durable for a high HP modded 2.5 litre motor? I'm not so much interested in the lightest rods & pistons as I'm after power & torque in a similar RPM range to stock - perhaps a slightly higher max RPM. Durability - in respect of handling the compression loads & high temperatures of a modded motor are important.
03-30-2011, 05:11 PM
#3
Rennlist Member
Arrow rods out of the UK enjoy a very good reputation.
03-30-2011, 05:32 PM
#4
Rennlist Member
If you are after high compression you are going to want a forged rod. There are several out there I am using Carillo. You will also want to use high strength fasteners like ARP. And since you are asking these questions I would suggest a competent engine builder, as these engines have enough quirks in them to drive most sane peolpe mad. Which is one reason most 951 engine builders are carzy.
03-31-2011, 07:14 AM
#7
Rennlist Member
Arrow make good non Ti product as well. It would be interesting to see what you'd be charged for these in England?
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03-31-2011, 09:44 AM
#8
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The connecting rods are an interesting issue – and typically people don’t really address the need correctly. The original post is very telling and I will say the that Penguin established some very points in his post.
The ‘truth’ about 944 turbo connecting rods comes down to physics and math. If you don’t look at the physics then you are just blindly spending money. Most folks wrongly believe that the most stressful point of the cycle (for a connecting rod) is the power stroke. Nope. It’s the reverse in direction between the exhaust and intake stroke. At that point the piston has to change direction and the tensile loading of the rod is huge. To put it perspective – at 6k RPM the piston reaches a peak speed of approx. 250mph and in the space of .01 seconds it will have to stop, reverse directions and attain a speed of 250mph in the opposite direction. Massive G loads that increase exponentially with RPM.
The reason why it’s the exhaust to intake cycle and not the compression to power stroke is because the force of compression, ignition and power is actually pushing down on the top of the piston and helping to take the load induced by the change of direction off of the connecting rod. In fact the more power you make the less load on the rod during that change of direction (when was the last time that you heard that more power created less load?!).
So – the question is what pistons/ rods are the most durable – it depends on more on the RPM range you want to run that the power output. Penguin stated that he was going to operate fairly close to stock RPM range and for that range the stock forged rods are just fine – they will not fail. Even the stock pistons are quite capable and decent performers at those engine speeds. The only problem with both the stock rods and pistons is that they are very heavy compared to the various aftermarket parts available. If you want to up the RPM capabilities then the aftermarket parts become very attractive way to lessen the higher loads.
Weight examples –
Rods – Stock 837 grams
Carrillo – 720 grams
Pauter – 671 grams
Wossner / Arrow – 650 grams
Arrow Titanium – well under 500 grams(!)
Pistons – Wossner pistons are more than 100 grams lighter than stock.
The ‘truth’ about 944 turbo connecting rods comes down to physics and math. If you don’t look at the physics then you are just blindly spending money. Most folks wrongly believe that the most stressful point of the cycle (for a connecting rod) is the power stroke. Nope. It’s the reverse in direction between the exhaust and intake stroke. At that point the piston has to change direction and the tensile loading of the rod is huge. To put it perspective – at 6k RPM the piston reaches a peak speed of approx. 250mph and in the space of .01 seconds it will have to stop, reverse directions and attain a speed of 250mph in the opposite direction. Massive G loads that increase exponentially with RPM.
The reason why it’s the exhaust to intake cycle and not the compression to power stroke is because the force of compression, ignition and power is actually pushing down on the top of the piston and helping to take the load induced by the change of direction off of the connecting rod. In fact the more power you make the less load on the rod during that change of direction (when was the last time that you heard that more power created less load?!).
So – the question is what pistons/ rods are the most durable – it depends on more on the RPM range you want to run that the power output. Penguin stated that he was going to operate fairly close to stock RPM range and for that range the stock forged rods are just fine – they will not fail. Even the stock pistons are quite capable and decent performers at those engine speeds. The only problem with both the stock rods and pistons is that they are very heavy compared to the various aftermarket parts available. If you want to up the RPM capabilities then the aftermarket parts become very attractive way to lessen the higher loads.
Weight examples –
Rods – Stock 837 grams
Carrillo – 720 grams
Pauter – 671 grams
Wossner / Arrow – 650 grams
Arrow Titanium – well under 500 grams(!)
Pistons – Wossner pistons are more than 100 grams lighter than stock.
03-31-2011, 10:25 AM
#9
The connecting rods are an interesting issue – and typically people don’t really address the need correctly. The original post is very telling and I will say the that Penguin established some very points in his post.
The ‘truth’ about 944 turbo connecting rods comes down to physics and math. If you don’t look at the physics then you are just blindly spending money. Most folks wrongly believe that the most stressful point of the cycle (for a connecting rod) is the power stroke. Nope. It’s the reverse in direction between the exhaust and intake stroke. At that point the piston has to change direction and the tensile loading of the rod is huge. To put it perspective – at 6k RPM the piston reaches a peak speed of approx. 250mph and in the space of .01 seconds it will have to stop, reverse directions and attain a speed of 250mph in the opposite direction. Massive G loads that increase exponentially with RPM.
The reason why it’s the exhaust to intake cycle and not the compression to power stroke is because the force of compression, ignition and power is actually pushing down on the top of the piston and helping to take the load induced by the change of direction off of the connecting rod. In fact the more power you make the less load on the rod during that change of direction (when was the last time that you heard that more power created less load?!).
So – the question is what pistons/ rods are the most durable – it depends on more on the RPM range you want to run that the power output. Penguin stated that he was going to operate fairly close to stock RPM range and for that range the stock forged rods are just fine – they will not fail. Even the stock pistons are quite capable and decent performers at those engine speeds. The only problem with both the stock rods and pistons is that they are very heavy compared to the various aftermarket parts available. If you want to up the RPM capabilities then the aftermarket parts become very attractive way to lessen the higher loads.
Weight examples –
Rods – Stock 837 grams
Carrillo – 720 grams
Pauter – 671 grams
Wossner / Arrow – 650 grams
Arrow Titanium – well under 500 grams(!)
Pistons – Wossner pistons are more than 100 grams lighter than stock.
The ‘truth’ about 944 turbo connecting rods comes down to physics and math. If you don’t look at the physics then you are just blindly spending money. Most folks wrongly believe that the most stressful point of the cycle (for a connecting rod) is the power stroke. Nope. It’s the reverse in direction between the exhaust and intake stroke. At that point the piston has to change direction and the tensile loading of the rod is huge. To put it perspective – at 6k RPM the piston reaches a peak speed of approx. 250mph and in the space of .01 seconds it will have to stop, reverse directions and attain a speed of 250mph in the opposite direction. Massive G loads that increase exponentially with RPM.
The reason why it’s the exhaust to intake cycle and not the compression to power stroke is because the force of compression, ignition and power is actually pushing down on the top of the piston and helping to take the load induced by the change of direction off of the connecting rod. In fact the more power you make the less load on the rod during that change of direction (when was the last time that you heard that more power created less load?!).
So – the question is what pistons/ rods are the most durable – it depends on more on the RPM range you want to run that the power output. Penguin stated that he was going to operate fairly close to stock RPM range and for that range the stock forged rods are just fine – they will not fail. Even the stock pistons are quite capable and decent performers at those engine speeds. The only problem with both the stock rods and pistons is that they are very heavy compared to the various aftermarket parts available. If you want to up the RPM capabilities then the aftermarket parts become very attractive way to lessen the higher loads.
Weight examples –
Rods – Stock 837 grams
Carrillo – 720 grams
Pauter – 671 grams
Wossner / Arrow – 650 grams
Arrow Titanium – well under 500 grams(!)
Pistons – Wossner pistons are more than 100 grams lighter than stock.
03-31-2011, 11:09 AM
#10
Nordschleife Master
The connecting rods are an interesting issue – and typically people don’t really address the need correctly. The original post is very telling and I will say the that Penguin established some very points in his post.
The ‘truth’ about 944 turbo connecting rods comes down to physics and math. If you don’t look at the physics then you are just blindly spending money. Most folks wrongly believe that the most stressful point of the cycle (for a connecting rod) is the power stroke. Nope. It’s the reverse in direction between the exhaust and intake stroke. At that point the piston has to change direction and the tensile loading of the rod is huge. To put it perspective – at 6k RPM the piston reaches a peak speed of approx. 250mph and in the space of .01 seconds it will have to stop, reverse directions and attain a speed of 250mph in the opposite direction. Massive G loads that increase exponentially with RPM.
The reason why it’s the exhaust to intake cycle and not the compression to power stroke is because the force of compression, ignition and power is actually pushing down on the top of the piston and helping to take the load induced by the change of direction off of the connecting rod. In fact the more power you make the less load on the rod during that change of direction (when was the last time that you heard that more power created less load?!).
So – the question is what pistons/ rods are the most durable – it depends on more on the RPM range you want to run that the power output. Penguin stated that he was going to operate fairly close to stock RPM range and for that range the stock forged rods are just fine – they will not fail. Even the stock pistons are quite capable and decent performers at those engine speeds. The only problem with both the stock rods and pistons is that they are very heavy compared to the various aftermarket parts available. If you want to up the RPM capabilities then the aftermarket parts become very attractive way to lessen the higher loads.
Weight examples –
Rods – Stock 837 grams
Carrillo – 720 grams
Pauter – 671 grams
Wossner / Arrow – 650 grams
Arrow Titanium – well under 500 grams(!)
Pistons – Wossner pistons are more than 100 grams lighter than stock.
The ‘truth’ about 944 turbo connecting rods comes down to physics and math. If you don’t look at the physics then you are just blindly spending money. Most folks wrongly believe that the most stressful point of the cycle (for a connecting rod) is the power stroke. Nope. It’s the reverse in direction between the exhaust and intake stroke. At that point the piston has to change direction and the tensile loading of the rod is huge. To put it perspective – at 6k RPM the piston reaches a peak speed of approx. 250mph and in the space of .01 seconds it will have to stop, reverse directions and attain a speed of 250mph in the opposite direction. Massive G loads that increase exponentially with RPM.
The reason why it’s the exhaust to intake cycle and not the compression to power stroke is because the force of compression, ignition and power is actually pushing down on the top of the piston and helping to take the load induced by the change of direction off of the connecting rod. In fact the more power you make the less load on the rod during that change of direction (when was the last time that you heard that more power created less load?!).
So – the question is what pistons/ rods are the most durable – it depends on more on the RPM range you want to run that the power output. Penguin stated that he was going to operate fairly close to stock RPM range and for that range the stock forged rods are just fine – they will not fail. Even the stock pistons are quite capable and decent performers at those engine speeds. The only problem with both the stock rods and pistons is that they are very heavy compared to the various aftermarket parts available. If you want to up the RPM capabilities then the aftermarket parts become very attractive way to lessen the higher loads.
Weight examples –
Rods – Stock 837 grams
Carrillo – 720 grams
Pauter – 671 grams
Wossner / Arrow – 650 grams
Arrow Titanium – well under 500 grams(!)
Pistons – Wossner pistons are more than 100 grams lighter than stock.
I know you were refering to the amount of power/rpm when you said "they will not fail" Chris, but I thought I'd just add this point of view
03-31-2011, 12:58 PM
#11
Three Wheelin'
When talking about connecting rod loading, keep in mind that the materials used in making connecting rods have a much higher tensile strength vs compressive strength.
03-31-2011, 03:41 PM
#13
Drifting
Oliver www.oliverconnectingrods.com are very good. They will custom make whatever you want/need. I'll get the weight of mine, but here is a quote from their website.
Oliver's engineers use 3D modeling, thermal imaging and fininite element analysis to build one of the strongest rods on the market. Utilizing a parabolic I Beam design, Oliver Rods help create one of the strongest bottom ends available! Every Oliver I-Beam rod is tested to withstand 12,000 psi of push and pull force similar to what most engines see above 10,000 rpms depending upon the application!
These "Extreme Turbo" rods are approximately 6-8% beefier than the standard Olivers. Either set of rod is capable of 800+ horsepower. For extreme boost. Average Matched Rod Weight: 647 Grams All Oliver Rods use 3/8" ARP Rod Bolt Hardware!
Oliver's engineers use 3D modeling, thermal imaging and fininite element analysis to build one of the strongest rods on the market. Utilizing a parabolic I Beam design, Oliver Rods help create one of the strongest bottom ends available! Every Oliver I-Beam rod is tested to withstand 12,000 psi of push and pull force similar to what most engines see above 10,000 rpms depending upon the application!
These "Extreme Turbo" rods are approximately 6-8% beefier than the standard Olivers. Either set of rod is capable of 800+ horsepower. For extreme boost. Average Matched Rod Weight: 647 Grams All Oliver Rods use 3/8" ARP Rod Bolt Hardware!
03-31-2011, 07:27 PM
#14
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The lighter internals do make the engine quicker responding!
03-31-2011, 07:34 PM
#15
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Just a little something to add, even though the stock rods are more than capable for most applications it's never a bad idea to change them for peace of mind. The poster also wrote "durability" and it's not that uncommon that stock rods fail. Perhaps not due to design or manufacturing flaws, but more to the fact that they are 25 years old with many, many miles.
I know you were refering to the amount of power/rpm when you said "they will not fail" Chris, but I thought I'd just add this point of view
I know you were refering to the amount of power/rpm when you said "they will not fail" Chris, but I thought I'd just add this point of view
In all the engine failures I have seen I have not seen a failure caused by a stock forged connecting rod. I have seen rod bearing failure weld the rod to the crank and then break the rod – that’s not the rods fault! I have seen several rods that have been bent by engine management failures – even these did not fail catastrophically – they either damaged the cylinder wall due to misalignment or just ran crappy enough that the owner took the engine apart. Rod bearing failure or engine management issues will cause any rod to fail – stock or after market. I still believe that the aftermarket rods are not stronger than stock – just a whole lot lighter!