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Rb25Det Unique Problem

abr33

By abr33,
in Engines & Forced Induction

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Legionnaire Collaborator

Legionnaire

Posted
Posted

The amount of air that goes through the bottle represents work done, more air means more work. Pressure inside the bottle represents efficiency - the lower the pressure, the more efficiently the work is being done. Different sizes of holes represent turbo sizes and how they affect efficiency. Bigger turbos generate more power than small turbos because of two main factors:

1)they pump more air mass more efficiently by themselves (higher airflow with lower compressor discharge temperatures)

2)they increase engine volumetric efficiency (big turbine housings are less restrictive than small ones)

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GTScotT
GTScotT

Hey mate, I get the impression you are being serious... So I will give you as best a response as I can. The above guys are actually correct. Your problem is your ECU. The ECU is not able to cope with

abr33
abr33

OK OK,,,, i reposted cause i thought i put it in the wrong section... And i realise most of whats said, but i used to run 13psi with stock turbo with no issues, and i do intend on getting the ecu don

abr33
abr33

G'day guys, my r33 gtst auto has a problem. When at wot it goes like the clappas until 5k, then holds back. If in 3rd or 4th it will sorta cut out as well, 1st aint so bad, running 11psi but when abou

Beer Baron Grand Master

Beer Baron

Posted
Posted

Thanks for your replies guys, I'll get my head around it one day. Still what I am confused about is that my boost gauge lead is taking the boost pressure right at the intake just before it goes into the engine. So both turbos are having to move 10psi of air through the same size (volume) intake pipe all the way to the boost gage sensor as it enters the engine.

If I get a bigger turbo do I get a bigger pipe? In that case it will be running more flow of air at 10 psi because of a bigger intake pipe.

I UNDERSTAND that a Bigger turbo is capable of moving more air.

With the illustrations of the bottle I am guessing that your mouth is the turbo and the bottle is the intake pipe? Whether bigger or smaller lungs, if they hold the bottle at 10psi and leak out of a little hole... how is it different.

I know I am missing something somewhere.

no you still don't understand. PSI is a measure of PRESSURE. it has nothing to do with any quantity of air. turbo's are measured in lbs/min that is pounds per minute of airflow. wolverine's example was perfect. in that example your mouth is the compressor of the turbo (supplying the air), the body of the bottle is the engine and the bottom where you poke a hole/bigger hole/cut if off is the exhaust side of the turbo.

understand that the turbine housing stuck on the side of an engine is a restriction to exhaust flow. it's literally robbing your engine of some energy (power) and using it to drive the turbine which drives the compressor, the compressor compresses air and stuffs it into your engine. the bigger the compressor the more air it can compress at a given moment and the bigger the turbine the less restriction there is to flow in the exhaust.

the other problem is you are thinking about this in terms of a static measurement. you must include some measurement of time to compare these things. hence turbo's flow potential being measured in lbs/min of air flow. as in how many pounds can this compressor provide in one minute (at a given pressure).

the pipe on your engine has nothing (little) to do with it. change nothing else but your turbo. a standard turbo is still only going to flow X amount of air per min at 10psi and a much bigger turbo is going to provide much more air per minute at 10psi,

and I thought wolverine's was the best explanation so for. :blush:

oscar32 Mentor

oscar32

Posted
Posted

I am pretty sure that there would be MANY people who don't understand that a larger turbo at the same boost flows more air.

I liked the coke bottle example :)

bubba Grand Master

bubba

Posted
Posted

Wow there are some grossly inaccurate comments in here..

PRESSURE is related to flow, it is actually FORCE x AREA.

The more pressure for a given area, the higher the flow (which is why when you wind the boost up you get more power.. turbo is flowing more air).

Keep the flow the same but decrease the area, and the pressure goes up. Increase the area (LESS RESTRICTION), and you will flow more for same pressure.

Turbos (like engines) are an AIR PUMP, in laymans terms, the bigger the PUMP the more air it will PUMP.

A small pump moves LESS air for a given pressure than a larger pump.

I'm not sure how I can simplify it any further.. suggest howstuffworks.com or some similar site.

senilykSkylines Collaborator

senilykSkylines

Posted
Posted

I am pretty sure that there would be MANY people who don't understand that a larger turbo at the same boost flows more air.

I liked the coke bottle example :)

not everyone starts off knowing everything : b

89CAL Grand Master

89CAL

Posted
Posted

Wow there are some grossly inaccurate comments in here..

PRESSURE is related to flow, it is actually FORCE x AREA.

The more pressure for a given area, the higher the flow (which is why when you wind the boost up you get more power.. turbo is flowing more air).

Keep the flow the same but decrease the area, and the pressure goes up. Increase the area (LESS RESTRICTION), and you will flow more for same pressure.

Turbos (like engines) are an AIR PUMP, in laymans terms, the bigger the PUMP the more air it will PUMP.

A small pump moves LESS air for a given pressure than a larger pump.

I'm not sure how I can simplify it any further.. suggest howstuffworks.com or some similar site.

No flow is related to pressure difference. No pressure difference = no flow. Think about a bottle of gas, sitting there with 100psi of gas in it let's say. No flow but 100psi

Now plug it in or open the tap and gas flows out. This is because atmospheric pressure is 14.7psi and the gas bottle has 100psi in it. Large pressure difference so large flow. You can't just say more pressure = more flow. The true statement really would be more pressure difference = more flow (across the same cross sectioned area)

abr33 Proficient

abr33

Posted
  • Author
Posted

Cheers to all with a positive input, iv ordered injectors and will be running a map ecu when i get it tuned which will be asap. Im not building the auto any stronger yet, the bloke at the shop said they are good for 300kw without dramas, and i didnt go out and buy the to4 it came with a head i got all second hand. He said with my setup ill be able to get 400+ kwatw but with standard driveline its obviously a stupid idea. And i do intend down the track to put 3k stall in it, therefore having a turbo that big will not really disadvantage me. Any ballpark figure of torque at how many revs you think? Iv learnt alot from most of you and thanks for all the input.Im sorry if i upset a few of you through my stupid questions or arrogance or any other reason. I do intend to be an active member on here as this is a great site and awesome info available, especially as most of you have been through the same troubles im working through with my build, so anyone with a grudge please forgive me about the bad start. Thanks very much guys

abr33 Proficient

abr33

Posted
  • Author
Posted

If u want to get along with everyone dont say things like - its just physics mate, implying everyone else is wrong

I know, i thought it was right, but after learning about the 'flow' side of it all versus pressure, i would'nt hesitate to retract that comment. So for what its worth im sorry

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Sarumatix Veteran

Sarumatix

Posted
Posted

This thread has been very rewarding for all parties. Could do with a little less rage but we're getting there :D. Here is some interesting reading for you Amon,

http://www.automotivearticles.com/Turbo_Selection.shtml

GTScotT Grand Master

GTScotT

Posted
Posted

Wow there are some grossly inaccurate comments in here..

PRESSURE is related to flow, it is actually FORCE x AREA.

Having another read over the thread, the most that was said was pressure does not = flow. Which was made reference too quite well.

The science involved in determining flow does include pressure however the relationship is not direct. This is the most that has been conveyed, which is a realistic explanation for those struggling with the concept to begin with. I would say it takes a while to master the concept in total.

Remember blokes are normally interested in cars/books/beer or women and generally only two at a time. EVERYONE likes beer and women so your likely to find most on a CAR forum arent likely to like books that much

**NB - Statement not relevant to Discopotato03 - it is guaranteed he likes atleast 3 of the above, women not too sure :rolleyes:

onboostR33 Apprentice

onboostR33

Posted
Posted

dude PSI and air flow are two different things flow is the volume of air, psi is the pressure or force how fast the air travels,, think of it this way get a foot pump a bike tyre and a car tyre pump the bike tyre to 20psi count how many pumps it takes then, the car tyre to 20psi , the car tyre has alot more volume than a bike tire right? there fore it will take more pumps to get it to 20psi at the end you still have 20psi pressure in both tyres but the volume of air will be much more , same as a turbo mate you understand?

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