Question for all of you running T25's....

[CanadianTSi]

cooler denser charge.


it's the same volume at the same pressure.

CFM incoming air > CFM consumed = boost psi.

same boost psi = same incoming air quantity/volume.

Sorry but this is just wrong. There have been MANY threads about this, do a search and learn something

 

[daren_p]

Ok I agree about larger turbo's allowing you to run more boost and still be in their effiency range & also that they produce cooler, denser air at higher boost levels compared to a smaller turbo, obviously giving you more power (denser air=more oxygen=more power). My problem is still this if you log both a t25 and 50 trim @ 15 psi you may get 25 lb/min out of the t25 while you get 35 lb/min out of the 50 trim. Now when I log both of these with dsmlink as far as I know these values are calculated from the MAF, therefore inlet temp would make a difference in airflow but the effect of the turbo heating the air after its compressed should have no effect on this measurement as its "further down the line"? Just saying 10 psi is the same on every turbo is still complete bs IMO as they are not the same, as far as performance goes.

 

[Attack Eagle]

Sorry but this is just wrong. There have been MANY threads about this, do a search and learn something

Hmm, thread on Tuners vs physics.

I think I'll stick with my physics studies.

And I am going back to a t25. It works better for thetype of non full throttle, sub 60mph driving I do.

 

[Attack Eagle]

Ok I agree about larger turbo's allowing you to run more boost and still be in their effiency range & also that they produce cooler, denser air at higher boost levels compared to a smaller turbo, obviously giving you more power (denser air=more oxygen=more power). My problem is still this if you log both a t25 and 50 trim @ 15 psi you may get 25 lb/min out of the t25 while you get 35 lb/min out of the 50 trim. Now when I log both of these with dsmlink as far as I know these values are calculated from the MAF, therefore inlet temp would make a difference in airflow but the effect of the turbo heating the air after its compressed should have no effect on this measurement as its "further down the line"? Just saying 10 psi is the same on every turbo is still complete bs IMO as they are not the same, as far as performance goes.

That is the thing, you aren't measuring volume after the turbo... You are measuring speed (mas reads SPEED not volume) before the turbo. 15 psi is already more than you can boost to redline on a t25. Your "test" is flawed, as are your results. You would have to measure both in cfm at the same boost, 10. or measure the cfm output for a given energy input interms of velocity x volume on the turbine wheel.
If you wanted to perform this test you'd have to take a instant hz reading at 10 psi at exactly 3500 rpm under identical conditions. now since the t25 is less efficient a turbo you would see a reduction in performance except under low boost/rpm conditions where it getting on boost and recovering faster would be better than a larger turbo.
Daily Driving is low/boost low rpm driving. I can't USE a t28. To use it to it's fullest I am shifting at 7500 with my foot to the floor, I don't like that. I am entering corners trying to get it in first so it will spool by mid corner. I bought the car because it was quick without demanding WOT for performance.

This is my family car, not a race car. I don't like the way the t28 performs and feels in normal driving compared to my t25. I would never have gotten rid of my old t25 except that it went out (every 45k) and a friend gave me a t28 for free and I thought I'd try it.

 

[russman]

It depends on how fast you stomp on the gas, what gear and speed in that gear, etc. If I get on mine in 2nd its insta-spool to 15psi like 2400 rpms and holds until about 5.5K. I'm looking into getting a hahn side mount, Evo II o2 housing, and 2.5-3" downpipe soon though. Then I'll have crazy spool times. Anyway, all in prep for my turbo upgrade hopefully next summer.

Anyone have a hahn 2G side mount? I'd like to hear some user feedback on them. If I'm planing on a big or small 16g is it plenty? They say it handles up to 400HP.

 

[Thomas91169]

ok guys

i just went back to my t25 from a ported evo16g and sbr cast manifold(20psi by 3400rpm)

the t25 was reaching the stock boost level(13ish psi, stock bcs is now controlling it) just lightly passing traffic in 3rd gear. maybe 40% throttle.

THIS IS NORMAL. its a small ####ing turbo.

and people saying psi=psi are right. PSI in a t25 is equal to PSI in a 60trim.

however.......

its all about the airflow. if you are flowing 24lbs/min at 15psi on a t25, you are prolly flowing 50lbs/min at 15psi on a 60trim. airflow makes the power, psi is how it gets in there. thats why its better to buy a large turbo and run large amounts of airflow at smaller amounts of psi. this is what honduh's do, they buy huge ass turbo's and only run 7-10psi but flow shitloads of air. rather smart IMO, better than trying to run 40lbs/min+ on a 16g@25-30psi maxing it out when you can do 50lbs/min on a 50/60trim at 20psi.

so dont worry dude, your car is fine, though testing for boost leaks prolly wouldnt hurt.

 

[suicidal2af]

cooler denser charge.


it's the same volume at the same pressure.

CFM incoming air > CFM consumed = boost psi.

same boost psi = same incoming air quantity/volume.

You might want to go hit the physics books again.

Pressure and volume are 2 completely seperate measurements. They may be the same between 2 turbos, but that doesn't mean they necessarily are.

You brought up the denser/colder air argument. This is exatly WHY volume and pressure are not the same between multiple turbos.

Imagine a box that is one cubic foot. It is filled with air. If you heat that air, it will expand, and pressure will increase -- but volume will not change. Now release pressure until it is back at the pressure it started at. Suddenly, volume(measurement of the number of air molecules present) is lower -- at the same pressure.

Now apply this to a turbo and an intake tract. A turbo that heats the air more is going to fill the tract to the same pressure, at a smaller volume of oxygen....and a more efficient turbo will heat the air less, netting a higher volume of oxygen at a given volume of air and pressure.

 

[Attack Eagle]

You might want to go hit the physics books again.

Pressure and volume are 2 completely seperate measurements. They may be the same between 2 turbos, but that doesn't mean they necessarily are.

You brought up the denser/colder air argument. This is exatly WHY volume and pressure are not the same between multiple turbos.

Imagine a box that is one cubic foot. It is filled with air. If you heat that air, it will expand, and pressure will increase -- but volume will not change. Now release pressure until it is back at the pressure it started at. Suddenly, volume(measurement of the number of air molecules present) is lower -- at the same pressure.

no you jsut said the volume was the same and you released pressure. When you released pressure you cooled the air remaining in the box. It still has one cu ft of air in it... at a slightly higher temperature than before with equal pressure and volume. Or do you have a layer of vacuum floating on top of the layer of air? This relationship between pressure ant temp is what makes (for example) your a/c condensor or your turbocharger work. You reduce volume, increasing the pressure then bleed off the heat caused by compression.
This increases density.

Now apply this to a turbo and an intake tract. A turbo that heats the air more is going to fill the tract to the same pressure, at a smaller volume of oxygen....and a more efficient turbo will heat the air less, netting a higher volume of oxygen at a given volume of air and pressure.

AH HA, but is a 50 trim really more efficient than a t25 at 250 cfm and 10 psi pressure...

That is, is its outlet temperature lower, and does it spool as quickly giving more Torque area than the t25?


rmember Boyles law is only 1/2 the equation, there is also charles law, or together you can call them the Ideal gas law. temperature pressure and volume are all interconnected.

NOw if we are providing the same PSI at the same CFM consumption of the engine, then our volume outout will be the same IF the temperatures are the same. you may be right that there is a huge difference in temp, but so far I have seen nothing that tells me that a small turbo at peak efficency is going to be outperformed by a bigger turbo operating well out of it's efficiency range, nor that one or the other will have greater volume flow at the same PSI and temp. This is why CFM ratings are at a specified PSI and temp.

I don't see the huge turbos being that efficient over all at low boost of say 10-11 psi, because the increased mass's increased spool time means that you have a lot of lost torque, and a loss of exhaust energy from the missing increased effieciency of larger combustion events leads to further increased spool times. ONce the exhaust energy reaches the level to spool the turbo and they come on board at 10 psi then you might see a few hp difference at the top of the power and vs the 25 as it runs out of flow and moves of its efficiency island, but does it make up for the losses the bigger turbo posted earlier? I hypothesize that it doesn't. ESPECIALLY in any motorsport activity that consists of something other than keeping the right pedal down as much and as long as possible.

NOW the VOlume will be the same. period. vs the same cfm consumption you have to feed in the exact same amount in CFM of air to increase the pressure . The temp has some bearing on the DENSITY of the charge, but the volume is the same irregardless. It has to be or the pressure would increase or decrease. How you get the cfm, hot air, or cool air doesn't change the cfm flowed to get a certain PSI. Now the weight between one cubic ft of hot air, and 1 cu ft of cool air is different, ie they have different densities, but the CFM for any given PSI with an equal consumption is the same. I don't care if you blow hot air or cold, the volume required is the same. GET it?

But in the end there are millions of people back home without electricity, food, water, and even shelter right now and though this is entertaining it's utterly meaningless.

 

[suicidal2af]

no you jsut said the volume was the same and you released pressure. When you released pressure you cooled the air remaining in the box. It still has one cu ft of air in it... at a slightly higher temperature than before with equal pressure and volume. Or do you have a layer of vacuum floating on top of the layer of air? This relationship between pressure ant temp is what makes (for example) your a/c condensor or your turbocharger work. You reduce volume, increasing the pressure then bleed off the heat caused by compression.
This increases density.



AH HA, but is a 50 trim really more efficient than a t25 at 250 cfm and 10 psi pressure...

That is, is its outlet temperature lower, and does it spool as quickly giving more Torque area than the t25?


rmember Boyles law is only 1/2 the equation, there is also charles law, or together you can call them the Ideal gas law. temperature pressure and volume are all interconnected.

NOw if we are providing the same PSI at the same CFM consumption of the engine, then our volume outout will be the same IF the temperatures are the same. you may be right that there is a huge difference in temp, but so far I have seen nothing that tells me that a small turbo at peak efficency is going to be outperformed by a bigger turbo operating well out of it's efficiency range, nor that one or the other will have greater volume flow at the same PSI and temp. This is why CFM ratings are at a specified PSI and temp.

I don't see the huge turbos being that efficient over all at low boost of say 10-11 psi, because the increased mass's increased spool time means that you have a lot of lost torque, and a loss of exhaust energy from the missing increased effieciency of larger combustion events leads to further increased spool times. ONce the exhaust energy reaches the level to spool the turbo and they come on board at 10 psi then you might see a few hp difference at the top of the power and vs the 25 as it runs out of flow and moves of its efficiency island, but does it make up for the losses the bigger turbo posted earlier? I hypothesize that it doesn't. ESPECIALLY in any motorsport activity that consists of something other than keeping the right pedal down as much and as long as possible.

NOW the VOlume will be the same. period. vs the same cfm consumption you have to feed in the exact same amount in CFM of air to increase the pressure . The temp has some bearing on the DENSITY of the charge, but the volume is the same irregardless. It has to be or the pressure would increase or decrease. How you get the cfm, hot air, or cool air doesn't change the cfm flowed to get a certain PSI. Now the weight between one cubic ft of hot air, and 1 cu ft of cool air is different, ie they have different densities, but the CFM for any given PSI with an equal consumption is the same. I don't care if you blow hot air or cold, the volume required is the same. GET it?

But in the end there are millions of people back home without electricity, food, water, and even shelter right now and though this is entertaining it's utterly meaningless.

All fine and dandy, but you're missing one important point:

Air doesn't make power. Oxygen does. We're talking volume of oxygen.

But moving along, you sacrifice low-end torque for high-end horsepower. Horsepower is a measurement of a car's ability to create power over time -- this is what matters after the holeshot. Sure, you lose the kick-in-the-pants feeling, but the car will be faster overall(in a straight-line anyway). Sure, you'll make less power on an HX40 running 10psi because of how miserably far out of its efficiency range is...but comparing something like a 14b to a 16g, you will always make more power at a given psi AOTBE. Hell, look at 1g's -- at a lower psi on a lower compression engine, they make nearly the same power as a T25-powered 2G. Crank their boost up to 13 or 14psi and I guarantee they're making a noticeable bit more power.