I have the Buschur stage III and it is fabulous.
If I get the stage IV I will only gain 10-19 hp.
I am assuming I can run more boost.
My turbo does not seem to be anywhere near it's limit because it can run much more boost than the car can handle.
I know (think) this because I get an overboost condition very easily.
Here is the question...
Why do I need a "bigger" turbo to gain more than 10-19 hp and why won't a bigger turbo just create an over boost condition even more easily?
Am I experiencing brain fade or what?

 

a bigger turbo will gain you more horsepower at the same pressure because it flows more air volume in the cylinder, more flow= more power
And no, you shouldn't run more boost with the turbo (unless you use race gas)

 

This is what I am struggling with, How is there more volume if the pressure is the same and the internals of the engine are the same?
Am I missing something very obvious?

 

23 views and no more help?
I guess I am not the only person that can't answer this.

It takes x amount (volume) of air to fill a cylinder to a certain psi no matter how big the compressor is. RIGHT?

 

Where a lot of power is gained from going to a large turbo, with respect to the turbine housing, this is due in part to the reducd back pressure between the turbo & cylinder. Yeah, the stock turbo can only flow about enough cfm to support ~375 / 400 bhp.

So for people who have mods that would allow the engine to inhale more air, they benefit more by the larger turbo 1st off, they are also realizing a backpressure reduction due to the larger exhaust housing. Which enhance their power gains.

Backpressure is a power killing *****!

Thats why people who run these large turbo's see some serious high rpm power, because of the reduced backpressure with the huge *** turbine housing. That is also why they cant make 20 psi of boost below 5K!!! Oh wow, look at the power i'm making, dont forget about the power they are not making below 5k! Meantime, duesce-bag debbie just yanked you in a ford escape V6 from the stop light hurrying to buy her super sized tampons at walmart with little timmy drooling back in his car seat.

Not a pretty picture.

As far as over boosting, thats why you have a boost controller / wastegate.

Turbo size is also dependant on what it is that your trying to achieve.

 

Did you consider heat? A larger turbo won't heat the air as much as a smaller one at the same flow rate, right?

 

Don't worry about it, it seems that MANY people on this board are more concerned about psi than they are about volume. It's a common misperception that more boost = more power. Well, here is an very simple example.

Say you have a straw that is 1" in diameter. And with that straw you can blow air through at 10 psi. And say you can blow 100 lbs an hour.

Now take a second straw, that is 2" in diameter and blow at 10 psi. You're going to end up blowing 200 lbs an hour because of the extra VOLUME of air flowed.

Now this example isn't perfect and obviously the numbers aren't exact. But, it's the same idea. More volume = more power. NOT psi.

But then there is PSI. Now this is interesting because many turbos are able to boost to high PSI levels. But turbos also have an efficiency range. Meaning even tho the turbo can spool to 30 psi, the turbo isn't necessarily going to be moving that much more air than it does at say 20. That's why you must check out the turbo efficiency maps to find where you're car is going to make it's most power.

One real world example would be my old 1.8t with a k03 (inlet the size of a quarter) vs my friend 1.8t with a gt30r on it. I spiked at 23psi and he spiked at 9. He beat me in every race by so many car lengths I decided to give up. Again, it's not psi, it's volume of air flowed.

I hope this clears it up for you. I tried to keep it nice and simple. If you have any question, just ask and I'll try to help you the best I can!

 

This information is helpful.
I am getting closer to understanding.
Is the overboost condition caused by not enough fuel or air?
I still have the question of volume.
I understand that volume not just psi equals power but,
if the "chamber" is the same then the volume should remain the same
if the psi has not changed. Right?
This is where I lose comprehension.
Maybe I am looking at it wrong.
Thanks for the help so far.
More help would be appreciated.

 

In other words...

The boost gage measures psi at the engine.
In order to meet thet psi, it requires the same volume.
If you put ten pounds of **** in a five pound bag, the bag will experience much more pressure right?

 

DOn't even think about psi. PSI is just a pressure.

THink of it this way. A cylinder with a small turbo can hold 12 oz of air but a big turbo can force the cylinder to hold a liter of air in the same cylinder.

 

bolsen
Thanks again for the help.
I know it is frustrating to explain it to someone.
psi and volume are directly related right?
I know you said to ignore psi but let me ask it this way...

Imagine your engine is ready to fire.
There is an exact amount of volume and pressure in the cylinder.
If you change volume then the pressure HAS to change.
You cannot increase one without increasing the other unless...
The only way to get more volume without more pressure is to lower the air temp.
AutoXer mentioned lower heat with a turbo upgrade.
Is that the key factor?

 

Well, yes and no. Volume is volume, so a cylinder with 0.5L displacement is only ever going to hold 0.5L of air. But I know what you mean, the big turbo can suck more than a liter's worth of air from outside and jam it into the cylinder. I'm going to guess the guy who's asking the question is an engineering student and is being pretty technical about the meaning of "volume," hence the confusion.

What we're really after is getting more mass of air into the cylinder. Remember (or look forward to) freshman chemistry's PV=nRT, or n = PV/RT, and n is the key. Higher boost pressure (P) is good, larger displacement (V) is good (but we can't change that), but if you only get that higher boost pressure along with a higher temperature (T) you're losing ground. And that's what happens when you push a small turbo too far outside of the sweet spot on its compressor map. BTW, does anyone have compressor maps for the 16G and common alternatives? Just curious.

Dave

 

Hmm, a lot of people seem to be asking the same question.

No offense bolsen, but this is not really correct.


Not necessarily very "obvious", but it doesn't help that some of the explanations you may have been given are not physically sound. See a previous post on this topic: https://www.evolutionm.net/forums/sh...e=2#post984647

 

TragicallyHip, you need to differentiate between boost (a pressure) and "cylinder pressure." They are not the same measurement.

 

I understand they are different but, they are directly related.

djh
I am not an engineering student.

What makes sense to me so far is that a bigger turbo can produce larger
volumes of air at a lower temp.

Thanks for all the help so far.