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[H]ard|On
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Old 10-10-2010, 05:26 PM [H]ard|On is offline  
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holy shit 20 psi? That should be good for over 300HP. Been looking for a GZE long block my self to get into my turbo build. How well does the stock GZE ecu handle 5-8psi when switch to a turbo?

Whats your sn on club4ag?
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Old 10-10-2010, 05:53 PM micrors4racer is offline  
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[H]ard|On
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holy shit 20 psi? That should be good for over 300HP. Been looking for a GZE long block my self to get into my turbo build. How well does the stock GZE ecu handle 5-8psi when switch to a turbo?

Whats your sn on club4ag?

wouldn't this heavily depend on which compressor he used?
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Old 10-10-2010, 06:14 PM [H]ard|On is offline  
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wouldn't this heavily depend on which compressor he used?

Yep. PSI is meaningless. Its a measure of resistance. 20psi on a small turbo does not equal 20psi on a large one.
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Old 10-10-2010, 07:52 PM Lurker is offline  
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wouldn't this heavily depend on which compressor he used?

we argued this in another thread - psi is dependent on the engine more so than the turbo. certain turbos will be more favorable as far as efficiency/temperature ramping at various psi's and flows but an engine can only pump so much air at a given velocity at a given pressure.
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Old 10-10-2010, 11:54 PM Dongboy is offline  
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Yep. PSI is meaningless. Its a measure of resistance. 20psi on a small turbo does not equal 20psi on a large one.
That's not entirely true. If the turbo can maintain 20PSI over the engines RPM range (meaning it flows more CFM @ 20PSI than the engine can use) then they will deliver the same power. A small turbo may not be able flow enough CFM at high RPM and will lose pressure. But, if two turbos can maintain the same pressure over RPM they should yield the same power (though could have different spooling characteristics).
Old 10-11-2010, 04:09 AM Stereodude is offline  
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That's not entirely true. If the turbo can maintain 20PSI over the engines RPM range (meaning it flows more CFM @ 20PSI than the engine can use) then they will deliver the same power. A small turbo may not be able flow enough CFM at high RPM and will lose pressure. But, if two turbos can maintain the same pressure over RPM they should yield the same power (though could have different spooling characteristics).


Not really.

Think about it this way. Which will provide more water? A garden hose at 20psi or a fire hose at 20psi?
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Old 10-11-2010, 06:53 AM Lurker is offline  
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Not really.

Think about it this way. Which will provide more water? A garden hose at 20psi or a fire hose at 20psi?

are they both then crammed back through the same exit pipe for a few feet? if so they'll both provide exactly the same output
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Old 10-11-2010, 09:53 AM Dongboy is offline  
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are they both then crammed back through the same exit pipe for a few feet? if so they'll both provide exactly the same output

Then why is a guy running 15PSI on a GT2870 making 350hp while im running 15PSI on a GT2554 making only 250hp? Both hold 15 to red line.

You are forgetting about the density of the air charge.
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Old 10-11-2010, 01:31 PM Lurker is offline  
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Then why is a guy running 15PSI on a GT2870 making 350hp while im running 15PSI on a GT2554 making only 250hp? Both hold 15 to red line.

You are forgetting about the density of the air charge.

Bernouli & Poiseuille would like to talk to you about laminar flow and various other issues
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Old 10-11-2010, 02:21 PM Dongboy is offline  
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we argued this in another thread - psi is dependent on the engine more so than the turbo. certain turbos will be more favorable as far as efficiency/temperature ramping at various psi's and flows but an engine can only pump so much air at a given velocity at a given pressure.

/thread (for the second time)
Old 10-11-2010, 03:27 PM mrselfdestruct is offline  
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Not really.

Think about it this way. Which will provide more water? A garden hose at 20psi or a fire hose at 20psi?
That depends on the opening at the end of the hose. If the opening can flow more GPM (Gallons Per Minute) at the given pressure then garden hose at can source at 20PSI it will flow less water, but it also won't have 20PSI either because there will be a pressure drop.

So, my statement was correct. If you have a garden hose that can push 5 GPM at 20PSI and a firehose that can push 50 GPM at 20PSI and I connect both to an opening that will only allow through 3GPM at 20PSI they will both deliver 3GPM. If I connect them both to an opening that can flow 7GPM at 20PSI they will flow very different amounts of water, but the garden hose won't have 20PSI anymore because it will experience a pressure drop.

The amount of air (CFM) you can push through an engine is limited by displacement & RPM. If I've done the math right, a 2.0L engine running at 7000 RPM with 1bar of boost will need 445.23CFM. So, if one turbo can only deliver 500CFM at 14.7PSI and the other can deliver 750CFM at 14.7PSI you will get the same power (assuming both are spooled and generating 14.7PSI).
Old 10-11-2010, 04:13 PM Stereodude is offline  
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The amount of air (CFM) you can push through an engine is limited by displacement & RPM. If I've done the math right, a 2.0L engine running at 7000 RPM with 1bar of boost will need 445.23CFM. So, if one turbo can only deliver 500CFM at 14.7PSI and the other can deliver 750CFM at 14.7PSI you will get the same power (assuming both are spooled and generating 14.7PSI).

Then the example I cited wouldnt be possible and everyone would be running smaller turbos that spool faster on these engines. Instead people are running larger turbos and making more power.
Which leads me to my next point. I somewhat agree with you about the piping. Sure its better to have the same diameter as the compressor outlet, but the throttlebody will always be the same(unless changed) if you go from a smaller turbo to a larger on the same engine. But power levels still increase.
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Last edited by Lurker; 10-11-2010 at 04:58 PM..
Old 10-11-2010, 04:30 PM Lurker is offline  
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Old 10-11-2010, 07:59 PM 4byTacoma is offline  
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Quote:
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Then the example I cited wouldnt be possible and everyone would be running smaller turbos that spool faster on these engines. Instead people are running larger turbos and making more power.
Which leads me to my next point. I somewhat agree with you about the piping. Sure its better to have the same diameter as the compressor outlet, but the throttlebody will always be the same(unless changed) if you go from a smaller turbo to a larger on the same engine. But power levels still increase.

So what you're saying is that with completely identical blocks/displacement/headers/throttlebodies/cams/everything, a big turbo delivering 20 PSI at 7000 engine RPM will provide more power than a smaller turbo also maintaining 20 PSI at 7000 engine RPM? So what, the same engine can now suddenly flow more air at the same pressure, displacement and RPM just because the turbo is bigger?
Old 10-12-2010, 01:43 AM Fiah is offline  
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