I'm sorry for the ignorance, Yes I searched I've read so many X=Y/VE=x-VE/ R, That my head is about to explode!

In laymens terms

Turbo a puts out 15 PSI and 280 HP

Turbo gt puts out 15 PSI and 415 hp

Why the diffrence? is it strictly a heat issue, If turbo a had a super duper I/C could it = turbo gt.



Ive read compressor chart thread, please answer in simple terms.

Thanks
Johny

 

You have to have more info, like what turbo A is and what turbo GT is; as in size. Size of compressor wheel, compressor housing, ex turbine housing ect.

From your numbers you gave, just means that at 15 psi, the GT flows alot more air than turbo a, producing more power.

www.turbocalculator.com, this site might help.

Good luck

Hai

 

the easiest explaination i could come up with is for you to try this.

get a straw and blow it as hard as you can to build a pressure of X. Now, try to do the same on a water hose and see if you could get X pressure. If you could, let me know how much harder to get X pressure.

 

It is the amount of air, not pressure that matters. Ie is there the same amount of air in a giant Dump truck tire at 15lbs as there is in a motorcycle tire at 15 lbs? Bigger turbo's move more volume of air. Also simply by not having to compress it as much, less density is lost to heat.

 

AIRFLOW, not PRESSURE


-Ted

 

Was this post neccessary? Zero R already asnwered the kids question and provided a decent example for him.

Then oyu post some silly phrase. Do you have anything else to keep you busy pal?

 

At least mine said something....unlike yours which was just a derogatory spat at my answer.
Just go away - you're not contributing anything useful to this thread.


-Ted

 

changing the straw would be like using a different motor. Your mouth would be the turbo... lol.

i'm not trying to start anything but i see what he's asking. He wants to know why turbo a makes more then turbo b if the motors are the same and the boost is the same. So 15psi thru the same motor with same intercooler and same piping, same ports, etc, etc. how does volume change if everything is the same.

well what changes is a couple of things.
turbo a is less efficient so 15psi @ a higher temp is less dense and so it's not the same as 15psi with turbo b @ a lower temp.

also changing a turbo greatly effects the efficiency of the motor. Remember your motor breathes thru the turbine so that would greatly affect power!

 

Many assume that engine is the restriction - if this were the case, then it would be true.

In reality, the TURBO is the restriction, not the engine.


-Ted

 

The bottom neck is usually the turbo. You have to look at the entire assembly in a system level. intake, i/c, engine, turbo manifold, turbo, and then exhaust. Each item will change the overall VE of the output.

Here're some examples

lets say the i/c has a pressure drop of 5psi. That means that the turbo has to produce 20psi to create 15psi output. Backpressure could easily be at least 20psi and possibly 30-35psi at equalibrum. Differential pressure between the output/input of the turbo significantly degrade due to back pressure and usually lowers the efficiency of the turbo. This has nothing to do with the backpressure needed to spool the turbo. It takes backpressure to spool the turbo and back pressure to keep the pressure up at higher rpm. It is the fact that it requires more back pressure than needed (which is restriction) that creates lower output.

if you have a high flow cat, the change in pressure between exhaust manifold and downpipe/exhaust system reduces dramatically. The lack of back pressure will slow down the spool of the turbo until back pressure builds up where it is significantly greater than the exhaust restriction. The turbo will started to build boost from there. Once it hits equalibrum, the limitation will be the exhaust flow (which is still greater back pressure than free flow exhaust). That's why you get lower output.

If you don't believe any of the examples above are true, stick a *BIG* vacuum system at the exhaust to suck out more cfm than the engine *estimated* output and see if you have a faster spooling system and higher output. This is also true by pressurizing the intake side of the system.


There're alot of talks about X turbo kit is better than Y turbo kit and/or X engine is better than Y engine but nobody really understands the reason behind it. I could be totally off but that's how I understood it.

 

i agree with your examples but in this case were talking about the same motor with the same boost with two different turbos.

 

It's really hard to say what he was trying to say based on what he asked. I could only assume that he was talking about just the turbo alone in the same car. However, the hp level he mentioned are definately not coming from the same car, same engine, same i/c, same turbo manifold, and exhaust. Turbo alone will not make *that much* difference like alot of people think. If turbo X flows 65lbs/min, and turbo Y flows 68lbs/min. I'm willing to bet that the output is the same on the same car with the same setup (assuming they're both running the same turbine trim and exhaust housing). However, if he's talking about a turbo X that flows 30lbs/min, and Turbo Y that flows 60lbs/min, I can see where he's coming from. He should also see that once it exceeds the flow rate of the turbo, the boost pressure will decrease.

 

yeah the numbers he's talking about wouldn't maKe sense if your talking about similiar sized turbo's.

Yes i also agree he didn't word his question clearly. But if we weren't discussing the same motor there would be to many variables involved. So this is why i assumed same motor with different turbos.

and on the turbo's not making a big difference it depends what you think a big difference is. just recently i changed two turbos on two customers cars.

one was a toyota 1.6 4ag. Motor exactly the same just different turbos.
first setup was a t3 50trim turbonetics at 23 psi the car made 302hp. Wouldn't make anymore if we raised boost since it maxed out the turbo. then i built a new header, it was using a log before, and a garrett gt3071. at 23psi we made 387hp. so a different turbo and header was good for 85hp at the same boost level.

another example is a 2 rotor just gained over 55hp with a just a turbo swap at same boost level.

 

Alien, I think your post was unecessary, and I like how you call me a KID, Im sure I'm older than you. Im 43 but still act like a kid,.d

Shawn I think you explained best its VOLUME

Steve, I hope you'll see my setup in Deleware on Nov. 19. Ive got a temp sender on both sides of my I/C, also water injection ,Im hoping to cool down the charge before the intercooler and water inj. after the I/C,


If my Idea works I'll post so all yall can Flame Away


Johny 43 years young

 

are you talking about the same engine with different turbos.
how would you increase volume if everything is still the same.

 

Are you still bringing that girl from your avator with you?

 

My fault, maybe I wasn't exactly clear either and volume was a semi bad word to choose. By volume I meant amount of air moved. Not space for air to fill.

 

What your hypothetical turbo mat be suffering from is the fact that it is out of its peak efficiency range, IE if you have a turbo that is capeable of flowing 72 LB of air at 80% efficiency and at the boost level that you are running it is only flowing 65 LB min then you are out of the thermal efficiency range. It will excessively heat the air just like if you overspining the turbo. This seems to be a common occurrence that I have yet to figure out. You will see a car that has a turbo that is capeable of flowing enough air to support over 700 hp yet they are only producing 450 hp. It would make more sense to use a turbo that when you were at peak hp you would be in the peak flow range of the turbo. The most logical way to choose a turbo would be to first look at the flow of the compressor and choose one that you would be right smack in the middle of the efficiency range for your projected hp. Then look at the turbine witch controls the speed of the compressor it will allways be a compermise between low flow/fast spool and and high flow/slow spool. Usually the larger the turbine the more hp you will make but you will have more delay in boost. Sorry I got off the subject a little but I wanted to get that off my chest for some time now.

 

I think you got your logic backwards. Any excessive flow will get bypassed to the wastegate limiting the amount of boost/rpm of the turbo. Ideally, you want to be able to run 100% turbo (i.e. w/o running the wastegate) so that you get the total exhaust energy transfering into the turbo and then back to the engine. however, this is not possible because boost will go up based on the limitation of the engine flow and rpm. This is why I think some form of feed forward design can bypass the wastegate all together and be 100% energy efficient.

 

Which part do I have backwards?

 

The part where you said the turbo is out of the thermal efficiency range below. A turbo capable of that kind of flow will have no problem flowing at 65lbs/min. I think what you meant to say is this. (if a turbo is capable of flowing 72lbs/min@80% but you're flowing 90lbs/min, the turbo could be out of its efficiency range because the turbo is flowing harder to maintain the flow which in terms heat up the air.)

 

The way I understand it is if you are outside of the peak efficiency either higher or lower the air will be heated too much. If the turbo is at peak efficiency at 72 lb min and you are flowing less or more the efficiency goes down. Granted it is probably better to under spool than it is to over spool the simple fact is that you are not running the right turbo for the application. Right?

 

no if that's the case, air temp will be signficantly high at idle and/or cruising.

 

At idle you are not makeing any boost. And at cruise you are not makeing very much if any boost. The efficientcy ratio is a thermodynamic ratio of how much the air is heated for a given increase in pressure. The higher the ratio the less the air is heated and vise versa so at peak efficiency the air would be heated the least as compared to the pressure ratio. But of course I did read this all on a package of string cheese. LOL

 

I may be wrong on my thinking if so someone please set me straight. Not trying to argue here I am as far from an expert as you can get. This is just what I have come up with in all of my research on turbos. Ths is some really good info tough. Mabe Zero R can help Pluto set me straight.