Does Boost Blow the motor?
Feb 12, 2010, 06:16 AM
#1
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Does Boost Blow the motor?
For my question, Im talking motors in general not just 4g63/4g64 and the motor is no forged internals, but is rated for 350hp&tq
My question is what causes the motor to fail, then amount of boost or tq/hp that the motor is making. As we all know a bigger turbo will get more hp at smaller boost levels than a smaller turbo. So lets say the big turbo makes 350Hp&Tq at 15psi and the smaller turbo makes 350Hp&Tq at 30psi. Given that they were both on the same setup to make that hp&tq, would the motor with the smaller turbo motor blow because its seeing 25psi or would it have to have more Hp&Tq?
It seems to me it would have to be making more than 350Hp&Tq to blow the motor regardless of boost as the Hp&Tq are relate to the actual Amount of air(cfm) being forced into the motor not psi.
My question is what causes the motor to fail, then amount of boost or tq/hp that the motor is making. As we all know a bigger turbo will get more hp at smaller boost levels than a smaller turbo. So lets say the big turbo makes 350Hp&Tq at 15psi and the smaller turbo makes 350Hp&Tq at 30psi. Given that they were both on the same setup to make that hp&tq, would the motor with the smaller turbo motor blow because its seeing 25psi or would it have to have more Hp&Tq?
It seems to me it would have to be making more than 350Hp&Tq to blow the motor regardless of boost as the Hp&Tq are relate to the actual Amount of air(cfm) being forced into the motor not psi.
Last edited by 3gEclipseTurbo; Feb 12, 2010 at 06:22 AM.
Feb 12, 2010, 06:25 AM
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I can say when I had stock internals + stock turbo I was doing abou 1.7 bar about 6k miles and evrth was ok, aftrwards I installed M2cams + fullrace street + fpgreen ported and was doing 1.6bar and I made 3-4k miles evrth was OK
I beieve if AFR & EGT are OK evrth will be ok) sure if you dont make more yhen 1.7-1.9bar
my friend during dynomade 2.35 in stock motor for a couple of times evrtn is OK
I beieve if AFR & EGT are OK evrth will be ok) sure if you dont make more yhen 1.7-1.9bar
my friend during dynomade 2.35 in stock motor for a couple of times evrtn is OK
Feb 12, 2010, 07:31 AM
#5
First off, if you have two identical cars, but one is running a stock turbo, and the other is running a 35r. And both run the same boost, there will be VERY LITTLE difference between the two cars speed wise. The 35r car will make a tiny bit more power boost for boost because of improvements in VE due to less exhaust back pressure, and also a slightly cooler inlet charge due to improved compressor efficiency. But these gains are minor.
The biggest gain you will see from going to a larger turbo is that you can run higher boost levels more efficiently. The stock turbo simple cannot run 30 psi very efficiently, and it bleeds down if you do hit that boost. A 35r can run 30 psi efficiently and hold it. Not to mention you will really see gains for boost levels over 30 psi.
The biggest stress on an engine, if you forget about a bad tune and detonation, is the inertial forces from RPM. The mechanical forces from combustion are not as strong as the inertial forces created when a piston has to stop, accelerate, stop, etc.
Larger turbos generally will give you more top end, and therefore, your likely to want more rpm from a larger turbo, especially if you are on a 2l and large turbo, where you might not be making full boost until 6k rpm.
Anyway, all food for thought. Nothing to be afraid of in terms of boost. But the tune needs to be safe, and don't push a turbo beyond it's efficiency. That means make sure as you add boost while tuning, you are making sure the car is going faster. If you add boost and don't go faster, then you're running too much boost.
The biggest gain you will see from going to a larger turbo is that you can run higher boost levels more efficiently. The stock turbo simple cannot run 30 psi very efficiently, and it bleeds down if you do hit that boost. A 35r can run 30 psi efficiently and hold it. Not to mention you will really see gains for boost levels over 30 psi.
The biggest stress on an engine, if you forget about a bad tune and detonation, is the inertial forces from RPM. The mechanical forces from combustion are not as strong as the inertial forces created when a piston has to stop, accelerate, stop, etc.
Larger turbos generally will give you more top end, and therefore, your likely to want more rpm from a larger turbo, especially if you are on a 2l and large turbo, where you might not be making full boost until 6k rpm.
Anyway, all food for thought. Nothing to be afraid of in terms of boost. But the tune needs to be safe, and don't push a turbo beyond it's efficiency. That means make sure as you add boost while tuning, you are making sure the car is going faster. If you add boost and don't go faster, then you're running too much boost.
Feb 12, 2010, 08:18 AM
#6
First off, if you have two identical cars, but one is running a stock turbo, and the other is running a 35r. And both run the same boost, there will be VERY LITTLE difference between the two cars speed wise. The 35r car will make a tiny bit more power boost for boost because of improvements in VE due to less exhaust back pressure, and also a slightly cooler inlet charge due to improved compressor efficiency. But these gains are minor..
Feb 12, 2010, 08:28 AM
#7
As I said, the bigger turbo will improve VE, but it's nominal.
Also, the stock turbo can't run 30 psi efficiently, so it's a bad example. 20 psi for a stock turbo and bigger turbo is a better analogy because both turbos are efficient at that boost pressure.
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Feb 12, 2010, 08:33 AM
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Im not just talking evos, that means not the stock evo turbo either. This is weither or not its the amount of boost blows the motor or the hp&tq does.
Say the motor is good to 350hp&tq does it matter how much psi it takes to get there? Given a good tune. Can boost alone blow a motor? or will it be the hp&tq that the boost is producing blow the motor?
Say the motor is good to 350hp&tq does it matter how much psi it takes to get there? Given a good tune. Can boost alone blow a motor? or will it be the hp&tq that the boost is producing blow the motor?
Last edited by 3gEclipseTurbo; Feb 12, 2010 at 08:51 AM.
Feb 12, 2010, 08:47 AM
#9
The straw analogy isn't helpful. Boost is a measure of resistance pushing air into the motor. Two cars with the same VE, the same boost, and same charge air temps will = the same airflow.
As I said, the bigger turbo will improve VE, but it's nominal.
Also, the stock turbo can't run 30 psi efficiently, so it's a bad example. 20 psi for a stock turbo and bigger turbo is a better analogy because both turbos are efficient at that boost pressure.
As I said, the bigger turbo will improve VE, but it's nominal.
Also, the stock turbo can't run 30 psi efficiently, so it's a bad example. 20 psi for a stock turbo and bigger turbo is a better analogy because both turbos are efficient at that boost pressure.
show me one stock turbo car that makes 535whp/421wtq @ 20psi
Feb 12, 2010, 08:54 AM
#11
Also, I find it very hard to believe an Evo makes 600 hp at the flywheel at 20 psi. What does it make at 40 psi?
Feb 12, 2010, 09:02 AM
#12
Look buddy... throw a stock turbo on that car and tell me what it would run. The stock turbo would make more peak torque, and probably only be down 20 or 30 atw at peak HP.
Also, I find it very hard to believe an Evo makes 600 hp at the flywheel at 20 psi. What does it make at 40 psi?
Also, I find it very hard to believe an Evo makes 600 hp at the flywheel at 20 psi. What does it make at 40 psi?
Feb 12, 2010, 09:06 AM
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forget stock turbos or names of turbos theyre pointless for my question.
Say the motor is good to 350hp&tq does it matter how much psi it takes to get there? Given a good tune. Can boost alone blow a motor? or will it be the hp&tq that the boost is producing blow the motor?
Say the motor is good to 350hp&tq does it matter how much psi it takes to get there? Given a good tune. Can boost alone blow a motor? or will it be the hp&tq that the boost is producing blow the motor?
Feb 12, 2010, 10:07 AM
#14
Look buddy... throw a stock turbo on that car and tell me what it would run. The stock turbo would make more peak torque, and probably only be down 20 or 30 atw at peak HP.
Also, I find it very hard to believe an Evo makes 600 hp at the flywheel at 20 psi. What does it make at 40 psi?
Also, I find it very hard to believe an Evo makes 600 hp at the flywheel at 20 psi. What does it make at 40 psi?
My car tuned by me-
92 octane / S2 / TBE / O2 housing / SD / etc.
Stock turbo /2.0L/ 23psi- 355whp
3586 /2.0L/ 23psi- 496whp
3586 /2.2L/23psi- 570whp (compression and displacement were the increase here)
As you can see though, keeping everything as close to the same as possible on the same car, conditions, and parts (only the turbo) I picked up 140whp peak.
WHAT BREAKS IT
Cylinder pressure and/or RPM. Cylinder pressure can be compression, boost, timing and how all three of these interact. There is a reason I tout the 400 ft lb rule on a stock bottom end. I have made that number at 34psi and 27psi. If I had a big enough motor I could make it at 23psi (and have).
Feb 12, 2010, 10:48 AM
#15
No picking on you, but while you do have the general tech down pat there is truth in bigger turbos make more at less than a stock turbo. It goes beyond VE. This is CFM at its finest and thats why the straw analogy DOES make sense.
My car tuned by me-
92 octane / S2 / TBE / O2 housing / SD / etc.
Stock turbo /2.0L/ 23psi- 355whp
3586 /2.0L/ 23psi- 496whp
3586 /2.2L/23psi- 570whp (compression and displacement were the increase here)
As you can see though, keeping everything as close to the same as possible on the same car, conditions, and parts (only the turbo) I picked up 140whp peak.
WHAT BREAKS IT
Cylinder pressure and/or RPM. Cylinder pressure can be compression, boost, timing and how all three of these interact. There is a reason I tout the 400 ft lb rule on a stock bottom end. I have made that number at 34psi and 27psi. If I had a big enough motor I could make it at 23psi (and have).
My car tuned by me-
92 octane / S2 / TBE / O2 housing / SD / etc.
Stock turbo /2.0L/ 23psi- 355whp
3586 /2.0L/ 23psi- 496whp
3586 /2.2L/23psi- 570whp (compression and displacement were the increase here)
As you can see though, keeping everything as close to the same as possible on the same car, conditions, and parts (only the turbo) I picked up 140whp peak.
WHAT BREAKS IT
Cylinder pressure and/or RPM. Cylinder pressure can be compression, boost, timing and how all three of these interact. There is a reason I tout the 400 ft lb rule on a stock bottom end. I have made that number at 34psi and 27psi. If I had a big enough motor I could make it at 23psi (and have).