VE >=< Size of turbo? Need something explained to me.

[Guest Mekkahfire]

So say that you make 400hp at 22psi on a T78.

 

Why couldnt you make 400hp at 22psi on a TD06?

 

If the intercooler piping and intake manifold are filled with enough air to create 22psi, wouldnt that be the same amount of air either way??? And if its a constant 22psi, then its physically the same amount of air MOVING through the engine too..

 

You would think the only difference would be the RPM and Duration in which you will make 400hp. I can certainly see a larger turbo making 400hp LONGER than a TD06, maybe the TD06 would run out of steam. I can also understand the difference between spool times and the reason behind them...

 

But the whole hp@psi is different on different size turbo's due to "VE" thing..

 

I dont understand, can someone that knows explain?

[Rotarded1647545491]

I dont understand, can someone that knows explain?

 

 

Where do I begin?

 

Um, NO!

 

Search, read, learn. Then ask intelligent questions.

 

Mrrrrrpph, Here is a start: http://www.smokemup.com/auto_math/turbo_size3.php

 

Lazy rasssin frackinnn mrrrrph.

[Mojoe]

LOL. I was just going to post,"I know who can, but they will tell you to do the research". Had you in mind Mike.

[Guest Mekkahfire]

That link explains positively nothing.. Its a turbo size calculator. lol.

[Rotarded1647545491]

LOL. I was just going to post,"I know who can, but they will tell you to do the research". Had you in mind Mike.

 

Yeah, I was gonna flame. How freakin hard is it to understand that it's not the "peak" hp that the turbo produces, It about where you want the power and how usable is it?

 

AM I SPEAKING GREEK HERE?

 

That link explains positively nothing.. Its a turbo size calculator. lol.

 

That caluclator show you exactly what you pick a turbo for. If you truely understand VE, you should be able to figure out the rest.

[Guest Mekkahfire]

...Did you even read the origonal post? I dont need an internet calculator to "figure out" what turbocharger is right for my car.. Compressor maps pretty much do that for me.

 

Read my question. Im not asking what turbocharger is right for my car.

 

I want to know why different turbochargers make more or less horsepower (peak) at the same PSI. The way i see it, air is being forced into the engine at a certain pressure, and i cant understand why the source would matter.

[Rotarded1647545491]

Learn how to read a compressor map. if you are on the wrong side of the surge line, in a lower efficiency range, or are over spinning the turbo you have the wrong sized turbo.

 

I made over 400 rwhp @16 on stock twins in my FD. I also made 410 rwhp @ 16 on twin gt28rs on the same motor. The usable power band on the GT28s was MUCH larger. The stockers were on the cusp of becoming hair dryers and would have lasted about 30 pulls before they became oil sprayers.

 

I bet I could have made 450 on the stockers.....ONCE. If I didn't grenade the turbos, the super heated hot air would have popped the motor.

 

Peak HP is for dyno queens. It's usable power that wins races.

[Guest Mekkahfire]

Peak HP is for dyno queens. It's usable power that wins races.

 

Yes, i understand this and completely agree. However this is not what im asking. lol

[hot_wire]

I've always thought of a turbocharger like a fan. Think of two fans with identical motors and gearing but different diameter blades. When you turn the fans on, which one will get up to speed (spool up) quickest? Right, the smaller one. The large one will take longer to reach its peak air movement, but once it does, it will move a lot of air.

 

Now you have to enter the engine into this. As your RPMs and useable power increase, so does the amount of air and fuel used (leadfoot=bad gas milage) Go back to the little fan - its pushing a minimal amount of air, but pushing it when the car is only at 4500rpm. The engine doesn't need all of that air, so 22psi of pressure builds up. By the time you get to 6k rpm though, that little turbo is out of steam since it can't push any more air, and boost is tapering off to 8psi.

 

A big turbo would still be spooling at 4500 RPM but would produce its 22psi later in the powerband... say around 6500 RPM. Since the engine is more powerful at that speed, the big turbo crams more air into it, and gets more power out of it!

 

A V8 with a gt17 would be silly. My saab with a gt4billion would be less useful than it is now.

 

Did any of that make sense? I need something constructive to do with my time

[Guest Mekkahfire]

Why do 2 different turbochargers make different amounts of peak horsepower at the same PSI.

[hot_wire]

The small one peaks earlier in the engine's rpms.

 

Are you feeling okay?

[351mach11647545510]

Why do 2 different turbochargers make different amounts of peak horsepower at the same PSI.

 

because of where they are making 22lbs. lets say said turbo make peak hp (lets say 400) around 4200 rpms. you put on a different turbo that will push out 22lbs but it's where in the rpm range that it is pushing 22lbs. the other turbo may spool sooner and it is more effecient at a lower rpm. so even the different turbo at 22lbs will make 400 hp at 4200 rpms but it may make 410 at 3500 because it has 22lbs there where as the original only had say 17lbs. am i making any sense?

[Guest Removed]

because of where they are making 22lbs. lets say said turbo make peak hp (lets say 400) around 4200 rpms. you put on a different turbo that will push out 22lbs but it's where in the rpm range that it is pushing 22lbs. the other turbo may spool sooner and it is more effecient at a lower rpm. so even the different turbo at 22lbs will make 400 hp at 4200 rpms but it may make 410 at 3500 because it has 22lbs there where as the original only had say 17lbs. am i making any sense?

http://i5.photobucket.com/albums/y196/gearhead559/funny%20shit/mechanickittah.jpg

[Guest drumer919]

You arnt factoring in the RPM's, if one is making 22psi at 3500 RPM's and the other is making the same 22PSI but at 5000RPM's (where the engine is using alot more air so the turbo has to be moving alot more air to keep the same psi) then the one that is making the 22PSI at the higher RPM is obvisly going to be making more power for the same reasons that an NA engine makes more HP at a higher RPM.

[SPLN SUX]

Why do 2 different turbochargers make different amounts of peak horsepower at the same PSI.

 

 

Anytime you deal with a fluid you have two things to factor in, flow pressure, and flow velocity. Your smaller turbo is simply pushing the 22psi into the motor more slowly. The higher flow velocity of the intake charge, the more power youre going to make. Think about electricity, with voltage and current. Your flow rate is Voltage, your pressure is current. You can have 50,000 volts at .1 amp, or 100amps. Its still 50,000 volts, but one is going to kill you when you get shocked lol. In your case, its the opposite. The "current" is the same, but the voltages are different... well thats a no brainer... the one pushing more CFM is going to make more power.

[copperhead]

pressure does not equal volume

[Mallard]

I'm guessing you're asking this because you've run through the calculations for power and see that the power calculated is based off the PSI in the manifold (Turbo 101 on http://www.turbobygarrett.com), which is true. So that would mean the 22 psi on your engine would make the same power no matter what turbo is providing it.

 

However, the equation does not take into account a few things. 1) You will be at different efficiency ranges on each turbo. One will be putting out hotter air than the other, which costs power...unless your intercooler is overkill and can bring both intake temps down to the same level. 2) Exhaust pressure. A larger turbine housing will lower the pressure in your exhaust manifold, effecting your internal EGR, how much fresh air is entering the cylinder, etc. Obviously, if you're letting more air into the cylinder you will make more power.

[Miller]

I don't see why you wouldn't understand. Taking a bigger turbo and a smaller turbo, though, both the same in similarity, are still like comparing apples and oranges. What A/R do they have, how big is the inducer and exducer, what is the exhaust housing size? blah blah blah, there are a lot of factors. If you feed the same amount of pressure into these turbos, with specifications being different, there are going to be different variables as a result.

[Mallard]

I don't see why you wouldn't understand. Taking a bigger turbo and a smaller turbo, though, both the same in similarity, are still like comparing apples and oranges. What A/R do they have, how big is the inducer and exducer, what is the exhaust housing size? blah blah blah, there are a lot of factors. If you feed the same amount of pressure into these turbos, with specifications being different, there are going to be different variables as a result.

http://www.turbobygarrett.com/turbobygarrett/tech_center/turbo_tech103.html][/url]

◊ Calculate required manifold pressure required to meet the horsepower, or flow target:

 

MAPreq= [Wa*R*(460+Tm)]/[VE*(N/2)*Vd]

 

Where:

 

· MAPreq = Manifold Absolute Pressure (psia) required to meet the horsepower target

· Wa = Airflowactual(lb/min)

· R = Gas Constant = 639.6

· Tm = Intake Manifold Temperature (degrees F)

· VE = Volumetric Efficiency

· N = Engine speed (RPM)

· Vd = engine displacement (Cubic Inches, convert from liters to CI by multiplying by 61.02, ex. 2.0 liters * 61.02 = 122 CI)

 

Notice that predicting power output for a given manifold pressure has nothing to do with the type of turbo you're using. The reasons for the power difference is due to my previous post. On a compressor map you will plot corrected air flow and pressure ratio for a given engine. Those values will not change, but their position on the map will vary. So basically the differences will be in your exhaust pressure and intake temperatures (unless I forgot somthing else). Yes, the A/R and exhaust housing size will effect this, but it wasn't the answer to his question.

[Guest Mekkahfire]

I'm guessing you're asking this because you've run through the calculations for power and see that the power calculated is based off the PSI in the manifold (Turbo 101 on www.turbobygarrett.com), which is true. So that would mean the 22 psi on your engine would make the same power no matter what turbo is providing it.

 

However, the equation does not take into account a few things. 1) You will be at different efficiency ranges on each turbo. One will be putting out hotter air than the other, which costs power...unless your intercooler is overkill and can bring both intake temps down to the same level. 2) Exhaust pressure. A larger turbine housing will lower the pressure in your exhaust manifold, effecting your internal EGR, how much fresh air is entering the cylinder, etc. Obviously, if you're letting more air into the cylinder you will make more power.

 

 

Perfection! I definately didnt factor in AIT's and smaller turbine restrictions..

[Trjackson]

Wow, Mekkah, you remind me of the Adam sandler/Jack Nicholson movie, Anger Managment. When Jack, who was a well known psychologist, asked Sandler who he is. Sandler said, I like to do this and that. Jack replied no, tell me who you are! Sandler replied, I am a fun loving person, yada yada. Jack simply stated, listen it is a simple question, don't describe your personality, tell me who you are! Haha, and Sandler blew up!

 

Regardless, CFM, VE, Turbo efficiency and RPM make power directly. lbs of boost makes power indirectly!

 

Ty

[Guest Mekkahfire]

I missed the part in this thread where i blew up

[Trjackson]

I never said you blew up, I said you reminded me of that scence!

 

Ty