Do these 2 turbos have a different whp per boost pressure ?

[ka-t 300]

well if you have a .43 ar 57 trim turbo and a .63 ar 57 trim turbo both running at the same boost level would they be putting out the same whp level ?

[WDRacing]

No.

The .63AR will make more max power then the .48AR because it flows more total exhaust volume. The .48 places a slight restriction on total flow compared to the .63 but that depends on the amount of boost. If you're only running low boost, under 14 psi, then the amount of power will be negligible.

The .48AR turbo will also be on boost earlier not just off the line but every time the throttle is depressed your boost threshold with the .48AR turbo will be less then with the .63

It really depends on what your total power goal is. If it's 350 then I'd use the .48, if it's 400 then I'd use the .63.

Hope that helps.WD

[ka-t 300]

No.

The .63AR will make more max power then the .48AR because it flows more total exhaust volume. The .48 places a slight restriction on total flow compared to the .63 but that depends on the amount of boost. If you're only running low boost, under 14 psi, then the amount of power will be negligible.

The .48AR turbo will also be on boost earlier not just off the line but every time the throttle is depressed your boost threshold with the .48AR turbo will be less then with the .63

It really depends on what your total power goal is. If it's 350 then I'd use the .48, if it's 400 then I'd use the .63.

Hope that helps.WD

Lol makes sense I'm at 17 psi . also i'm trying to figuire out, how do you figuire out how much boost or whp can you run on just 93 octane. im thinking of trying to go for 20 psi ? I have the .48 ar 740 inj. 300zx maff on a jim wolf ecu. thanks wd.

[hannibal]

My 2 cents...At low rpms (3000), the wheels in the 0.48 are spinning faster so your making more boost and more power. At higher rpms when both turbos are making same boost, the 0.63 is making more power cause its wheels are spinning faster due to the less restrictive housing.

I dunno, I'm not really sure about that second part...

[WDRacing]

If the wheels on the .63 were spinning faster, the compressor wheel also attached would be spinning faster resulting in more boost pressure. The .63 AR moves more volume simply because there is more area for the exhaust gas to exit.

Take two 3 inch pipes, place a racquetball in one and a baseball in the other. If you have the same pressure flowing through each pipe then it's obvious that the one with the baseball will have more restriction right? But the one with the baseball is also going to "fill" up faster because there is more restriction. The faster it "fills" the more energy is directed at the turbine wheel causing it to spin.

Now with a turbo it's not the size of the wheel that's changing but the size of the housing, so the .63 will flow more because there is simply more room for the exhaust to move out.

***************************************

If you want to keep cranking the boost you're going to need a knock light to monitor for detonation. Or get a dual stage boost controller and run a single stage water injection system. That would allow for an easy 5-7 more psi with a medium sized nozzle. I'd be leery of running more then say 21-22 psi of boost with that .48AR. At that boost pressure it's going to be a pretty large restriction which will lead to higher egt's and possibly reversion.

WD

[C-Kwik]

Now with a turbo it's not the size of the wheel that's changing but the size of the housing, so the .63 will flow more because there is simply more room for the exhaust to move out.

Not necessarily. You can change the wheel trim and it will change the cross sectional area of the turbine exit. Changing to a different turbine family (i.e. T3 to T4) will also change this particular dimension as well.

Take two 3 inch pipes, place a racquetball in one and a baseball in the other. If you have the same pressure flowing through each pipe then it's obvious that the one with the baseball will have more restriction right? But the one with the baseball is also going to "fill" up faster because there is more restriction. The faster it "fills" the more energy is directed at the turbine wheel causing it to spin.

That's a rather difficult analogy to understand and may not apply correctly anyways. The first thing I think of with your analogy is relatively long pipes. In which case, the difference in time to fill up the pipe would be very small as the volume of the pipe with each ball is hardly that different. A better analogy might be to consider two different sized pipes.

Lastly, its not the filling up factor that drives the turbine. Its simply that a smaller orafice will speed up the air more than a larger orafice for a given amount of airflow. The additional airspeed provides more energy to spin the turbine. The problem with smaller orafices is it does restrict flow and it will require a much higher pressure differential to get enough air and velocity concurrently. This means more backpressure on the motor and thus less power overall. In extreme cases, it can not provide enough energy to drive the turbine to the desired boost levels.

[WDRacing]

Not necessarily. You can change the wheel trim and it will change the cross sectional area of the turbine exit. Changing to a different turbine family (i.e. T3 to T4) will also change this particular dimension as well.

Lots of things can change C, I was trying to explain the difference between the .48 and the .63 with everything remaining the same between the 2 aside from the exhaust housing.

The other description is just explaining the size difference. The "fill" and "velocity" terms refer to the same thing, just explained differently.

[hannibal]

Yeah, I gotcha Brian.

I get what happens at low rpm (the 0.48 spools faster) and high rpm (the 0.63 is less restrictive). But what happens in the middle?

My thoughts (please correct!)...Assuming same boost level, the wheels must be turning at the same speed and therefore power output should be the same. That must mean the 0.48 just has higher EGT because its more restrictive housing. I'm guessing this occurs thru 'mid' rpms until the 0.48 becomes too restrictive and just cant maintain the given boost level and power starts falling off.

Another analogy to help this make sense in my mind. Putting your thumb over the end of the garden hose makes the water shoot out faster. This is like the 0.48. Faster spool up because the gases are moving faster. But at higher pressure (flow?), your thumb over the end of the hose limits the amount of water that can escape. This reduces pressure after your thumb, or the pressure seen by the turbine wheel. So boost and power fall.

[WDRacing]

With these two turbo's the mid range difference will be small. The top end will be noticeable but not by leaps.

To pick the best turbo out of these two you really just need to sort out the end goal power wise. If it's between 350 and 400 then I'd use the .48AR just because it spools faster.

I had the .63 version attached to my TO4E compressor in 50 trim and I didn't think it was laggy at all.

Chano's example of 2 different sized pipes is a better one then mine btw. For the record, if I have a question about a theory or idea, I usually ask Chano's opinion about it

The thumb/garden hose thing closes an opening and increases the velocity of whatever is trying to vacate the hose.

When trying to compare the AR housings in mid range, try to think of a free flowing exhaust system like a straight through RS*R vs a system with a resonator and a slightly more restricted muffler such as the Flowmaster. One is going to allow the motor to breath better and be more efficient.

WD

[ka-t 300]

With these two turbo's the mid range difference will be small. The top end will be noticeable but not by leaps.

I had the .63 version attached to my TO4E compressor in 50 trim and I didn't think it was laggy at all.

Chano's example of 2 different sized pipes is a better one then mine btw. For the record, if I have a question about a theory or idea, I usually ask Chano's opinion about it

The thumb/garden hose thing closes an opening and increases the velocity of whatever is trying to vacate the hose.

When trying to compare the AR housings in mid range, try to think of a free flowing exhaust system like a straight through RS*R vs a system with a resonator and a slightly more restricted muffler such as the Flowmaster. One is going to allow the motor to breath better and be more efficient.

WD

are you talking whp or fly wheel horse power?

[ka-t 300]

With these two turbo's the mid range difference will be small. The top end will be noticeable but not by leaps.

To pick the best turbo out of these two you really just need to sort out the end goal power wise. If it's between 350 and 400 then I'd use the .48AR just because it spools faster.

WD

Are you talking fly wheel horse power or whp Wd ?

[WDRacing]

How many people do you know aside from the factory that talk in terms of crank power? I don't know anyone...

IMHO unless you're directly referring to tuning a motor on the dyno by itself, then power to the wheels is what is being discussed.

So...WHP is what I'm referring to

[ka-t 300]

How many people do you know aside from the factory that talk in terms of crank power? I don't know anyone...

IMHO unless you're directly referring to tuning a motor on the dyno by itself, then power to the wheels is what is being discussed.

So...WHP is what I'm referring to

I was just making sure. some times people get numbers confused when they are new at this , but i know your not new at this. lol

[C-Kwik]

Lots of things can change C, I was trying to explain the difference between the .48 and the .63 with everything remaining the same between the 2 aside from the exhaust housing.

The other description is just explaining the size difference. The "fill" and "velocity" terms refer to the same thing, just explained differently.

I know what you were talking about. But the mental picture I created meant others could do the same and the wrong assumptions can be made. I do like your reference to a garden hose. That's probably much more in-line with what you were trying to create a visual of.

[WDRacing]

I was just making sure. some times people get numbers confused when they are new at this , but i know your not new at this. lol

Me thinks that's a slight "old age" jab

[ka-t 300]

Me thinks that's a slight "old age" jab

we are on the same page thats all that really matters. nothing serious intended. cars are rated at the fly wheel wwhen they spec them out for the dealer ships. so some times people get that mixed up when they are saying some thing about how much horse power a car has. you have helped a lot with info for my project thanks.

[WDRacing]

It's all good homie

[dsm turned nismo]

the bigger turbo will make more power at same psi of boost because of the greater volume of air produced volume is where the power is produced

[WDRacing]

The turbo's have the same compressor. So the volume output is the same. The only difference is how much the exhaust housings will flow. The larger housing will have less back pressure so it will have a higher peak hp.

WD