highest boost SR20?

[Syntax360]

I was just wondering what's the most psi someone has seen a SR20 run? I'm just curious, I don't really care if it's highly modified, i just want to know how crazy some people are :-) Thanks!

[I H8 UR DSM]

I know someone who runs 67psi.

[SRdave240]

Well, I think that will take the cake. *thread hijack in progress* Now, what is the most boost anyone has ever run on stock internals - and I'm not talking about 1 time down the track and then the whole thing blew up.

[I H8 UR DSM]

Well, I think that will take the cake. *thread hijack in progress* Now, what is the most boost anyone has ever run on stock internals - and I'm not talking about 1 time down the track and then the whole thing blew up.

21 psi on a t25 is different than 21psi on a t3/t4 and different than 21psi on a T51r, so not really a fair comparison...i have run 20psi on stock internals if that means anything..i dunno

[S13240]

21 psi on a t25 is different than 21psi on a t3/t4 and different than 21psi on a T51r, so not really a fair comparison...i have run 20psi on stock internals if that means anything..i dunno

I agree here!

[SRdave240]

why is that? Is it a matter of at what rpm the 21 psi is built at?

[Thecollector]

To me 15psi is a safe bet under normal driving conditions and 21psi for racing. I wouldnt run that high all the time unless you replaced the gaskets. Wouldnt you blow something if you ran high psi without the proper mods?

[pampadori]

20psi on a t25 isn't going to have very chopped air, it will be hot air, it just isn't the same amount of air as on a bigger turbo. 65psi? on a sr20det? my dad drives a truck that runs 70+psi of boost. but he doesn't have a throttle body, and he runs 1500psi+ of fuel pressure.shaun

[I H8 UR DSM]

65psi? on a sr20det?

shaun

yep

[Samabra]

Quote »20psi on a t25 isn't going to have very chopped air, it will be hot air, it just isn't the same amount of air as on a bigger turbo. [/quote]

I think what Jesse was saying was about the airflow of the turbos, cause across the board, a bigger turbo, in addition to being efficient at higher boost, is plain and simply going to flow more at the same amounts of boost.

For example if say I have a stock T25 on one SR20DET, and a T3/T04B on another SR20DET, both have the same mods except for the turbos, if they are both dyno'd at say 7 PSI, the T3/T04B is going to dyno more RWHP, basically because it can flow more air than the T25.

Chris

[S13240]

I think what Jesse was saying was about the airflow of the turbos, cause across the board, a bigger turbo, in addition to being efficient at higher boost, is plain and simply going to flow more at the same amounts of boost.

For example if say I have a stock T25 on one SR20DET, and a T3/T04B on another SR20DET, both have the same mods except for the turbos, if they are both dyno'd at say 7 PSI, the T3/T04B is going to dyno more RWHP, basically because it can flow more air than the T25.

Chris

WORD!

[creophus]

Sweet! I'm learning. Keep it coming guys.

[pampadori]

I ran 20psi on a bone stock motor for 6 months. took the motor apart and everything looked great. compression was also fine. a motor that has always had good oil and bearing wear is minimal, can take a beating for a very long time. shaun

[SRdave240]

OK, this whole same psi with different turbo thing kinda has me perplexed, theoretically. Measuring temp and psi just before the intake manifold, if these two numbers are the same at the same rpms on two different turbos, I can't see one would make more whp than the other.

Somebody please explain.

[I H8 UR DSM]

so your saying a sr20det w/ a t25 running 20psi is going to be putting out the same amount of hp as a t3/t4 at 20psi?

wouldnt that mean no one would upgrade turbo's for more power?

[pampadori]

first of all, that won't happen with a t25 and a t3/to4 hybrid. the small turbine wheel causes a lot more exhaust backpressure. this causes combustion temps to rise also. this presents detonation. which will cause a lack of power...and possible engine damage. the compressor on the t25 isn't really as limiting as the turbine side in my opinion. this is one reason that just popped into my head as to why.there are many more i'm sure.shaun

[SRdave240]

so your saying a sr20det w/ a t25 running 20psi is going to be putting out the same amount of hp as a t3/t4 at 20psi?

wouldnt that mean no one would upgrade turbo's for more power?

No, not realy, I'm just asking for a more technical explanation. I'm trying to learn here. I am a pretty smart guy, I'm just new to turbos.

[I H8 UR DSM]

I'm not very technical, but see if this works a little...

20psi in a t25housing is the same amount of pressure as 20psi in a t4 housing (obviously)....BUT the t4 housing is larger, therefor it would take a lot more air to cause 20psi of pressure....so the t4, larger turbo, has more air flowing through it as 20psi, which would indirectly give you more HP....it takes less air to cause 20psi in a smaller turbine housing, ya know? so although they are both at 20psi, the larger turbine has more air in it.....

think of it as a quart vs a gallon of water....you can have a qt of water, sealed at 10psi, and a gallon of water sealed at 10psi...the gallon obviously has more 'water' in it, so when you open both caps, the larger container is going to flow more...ya know?

basic, but i think it expresses the idea

[I H8 UR DSM]

Mr. Wizards world!

[miteymax86]

The key to SRdave's statement was, "same rpm" if you have 2 turbos that run the same amount of boost at the same temp at the same rpm you should have the same amount of HP, as HP is depent on the burn of your A/F ratio, which with equivalent amounts of boost and temperature should be equal, provided the engine's timing is the same. The HP will be the same at that given RPM.

[Cyberkreig]

Good explanation jesse.. I dont understand ALOT about turbo specs yet... but why arent turbos explained as "CFM @ RPM " instead? That seems to be the information we all really want anyway?

[pampadori]

Well the compressor wheels are measured in lbs/hr which is kinda a good thing. i usually look at how large the wheels inducer is. what i have never understood, is why you get surge with a little turbine wheel and a large compressor wheel. can somebody explain that one?shaun

[Gregariousgreg]

I H8 UR DSM's explanation is good. But incase you want it explained a different way, here goes:

If you have a bigger turbo it will hold a larger volume of air. The measurement PSI means pounds per square inch which is a measurement of density. So for example, if the area of one turbo is 1 square inch (for the sake of simple numbers) there will be 15 pounds of air forced into the engine. But if the turbo has pushing in air over an area of 2 square inches it will be pushing in 30 pounds of air even though it is running at 15psi also.

[SRdave240]

Both of those staements make perfect sense to me. I guess my lapse in understanding was in where the pressure is measured. You are saying it is measured in the turbo housing - correct? If it was measured at the intake manifold, all psi's would be equivalent - assuming all other factor are equal - correct?

thanks for the education guys - i will learn alot more when i actually install my SR.

[undertaker]

I H8 UR DSM, got any more dtails on the sr that ran 67 psi. like why, what it used and how long it lasted or is expected to last?

i regularly run 18psi on my gtir, have had it up to 20 but usually run about 16 for reliability.

[240Z TwinTurbo]

Both of those staements make perfect sense to me. I guess my lapse in understanding was in where the pressure is measured. You are saying it is measured in the turbo housing - correct? If it was measured at the intake manifold, all psi's would be equivalent - assuming all other factor are equal - correct?thanks for the education guys - i will learn alot more when i actually install my SR.

You haven't been taught very much by any of these explanations. Do not equate PSI to flow as PSI seen is a function of many things. What creates the pressure you see? For a given compressor speed, any resistance to flow will create an increase in pressure. A good example is to place a pressure gauge on your air compressor line and start it blowing. If you place your finger over the nozzle the pressure in the line will increase, but you have actually decreased the flow coming out of the nozzle. Now to answer your question of how 2 different turbo's with the same running pressure and intake temps can make different power on the same motor. When you look at the compressor maps they are rated in lbs/hr which relates to the density of the charge. What does a compressor wheel do? It compresses the air making it more dense. Sorry, I like to ramble. So, for a bigger turbo it will pack more air molecules into a fixed volume as compared to a smaller turbo. Even though you have the same pressure you have more efficiently compressed the air molecules, making the charge more dense. The more air molecules you can pack into the motor the more power you will make. Just to give a real world example, if you are running a whimpy T25 @ 15psi you may make 300hp, but swap to 60-1 @ 15psi and you may make 350hp. No more boost, but more air molecules are put into the motor. Turbine efficiency and other factors do affect you ability to make more power, but I am just trying to convey how this stuff works in a simple way. I hope this helps.

[Gregariousgreg]

Actually you can learn from what myself and I H8 UR DSM posted. Don't just blow off our explanations. It comes across as a bit rude. Not to mention incorrect.

You do bring up a good point that I didn't though in your example of putting your finger over a nozzle. That example also helps to explain the importance of backpressure in an engine. Without back pressure, a turbo can't condense air.

You are a little off on one thing though. "for a bigger turbo it will pack more air molecules into a fixed volume as compared to a smaller turbo. Even though you have the same pressure you have more efficiently compressed the air molecules, making the charge more dense."

A bigger turbo running at 15psi is packing the same amount of POUNDS PER SQUARE INCH as a smaller turbo, hence the measurement 15psi. A big turbo is putting the same amount of molecules per a given volume as a smaller turbo, but the volume of the turbo is bigger and therefore forces more molecules into the engine.

The effeciency of a bigger turbo does not manifest in it's ability to make the air more dense, it is that it can make and maintain that density for a larger volume of air.

I explained that with simple numbers in my origonal post. 15psi over an area of 1 square inch means there is 15 pounds of air pressure flowing into the engine. 15psi over 2 square inches (a bigger turbo) means 30 pounds of pressure being pushed and is flowing into the engine.

[240Z TwinTurbo]

If you have a bigger turbo it will hold a larger volume of air. The measurement PSI means pounds per square inch which is a measurement of density. So for example, if the area of one turbo is 1 square inch (for the sake of simple numbers) there will be 15 pounds of air forced into the engine. But if the turbo has pushing in air over an area of 2 square inches it will be pushing in 30 pounds of air even though it is running at 15psi also.

I am not being a jerk, but you are wrong and your explanation is wrong. PSI does not equate to density or in any way "VOLUME" as you have said above. Density is mass/volume and PSI has no volume. Pounds/in^2 is force/area, not volume. You are somehow trying to equate 15psi of boost and say that is 15lbs of air is forced into the engine. NO NO NO! That is 15psi of pressure, not the weight of the air molecules pushed into the motor. Please don't call me out on this again or I will slam you with the technical explanations.

[pampadori]

SLAM HIM! no really, it would help the rest of us out...i'm sure he won't be mad if you show some prove, right jesse?

from what i remember, 15 at the nipple connected to your intake manifold going to your boost gauge is going to have the same pressure as the gapping hole that is the throttle body. the difference in power will come from the efficiency of the compressor (and also the backpressure in the exhaust but...).so efficiency is the difference. what is it and how is it measured?efficiency is the "sweet spot" of the turbo. all turbos are efficient, just that some are efficient at 45lbs/hr and others at 10lbs/hr. efficiency (going from memory and my memory is sometimes jaded) is measured by the amount of heat caused by compressing the air, above that minimum figure that is in the Ideal Gas Law...that some old dude figured out the equation for. PV=nRT

volume is density. density is effected by temperature. less dense air makes less power. the more heat in the matter, the lower its internal energy....the first law of thermodynamics says...the change in internal energy of a system is equal to the heat added to the system minus the work done by the system....heat is a form of energy and therefore the more energy in heat form, the less for combustion-gofast form.

now, the smaller turbo has to spin lets say 120,000rpm to make this 15psi. or 7,200,000 rotations per hour. and lets say the radius of the comp wheel is 6 inches. thats 43,200,000 in/hr, or 63,360 mph at the tip of the wheel. the wheel cutting thru the air causes friction which causes heat, but also causes the molecules in the air to bounce of eachother at much higher rates and collide and crap...and now i'm lost...i can't explain why this is so bad for power, other then it causes heat, and uses a large amount of the internal energy as kenetic energy(63,360mph has a lot of kenetic engergy)*bong* ....what the hell just happened?? did i just type this gargon? it makes no sense to me again... shaun

[pampadori]

....maybe.....i forgot to type maybe at the end that post as to not be hounded by the smart guys that actually know physics and stuff.shaun