Turbo Advice Needed: S13

[Dustin240]

TO4b or T3> 8psi is 8psi........... A TO4b can give the engine more total volume but that's because it can go higher in boost pressure. I think the real factor is how much total volume (space) u have in your intake piping.The more volume the smaller the pressure drop will be at the time of the intake stroke.


Modified by Dustin240 at 7:57 PM 10/29/2006

[Chezedik]

NO, 8psi is not 8psi. In terms of increase in dynamic compression, then yes, but in terms of VE increase, NO. Since the air comes pressurized from the turbo, it can pressurize 100cfm to 8psi, or a larger turbo can pressurize 200cfm to 8psi. Flow is a more important factor than boost capability as far as turbo choice is concerned. So a larger turbo will use a larger FMU because it is moving more air, which in turn requires more fuel.

[C-Kwik]

TO4b or T3> 8psi is 8psi...........

Wrong. For a given PSI a lower efficiency turbo will be heating the air more, resulting in a lower density charge. The volume is the same, but the actual mass air density is different. An intercooler can help with this, but that means to reach the same pressure and density at the intake manifold, you would need to put out more pressure from the turbo. Lastly, higher efficiency in a turbo compressor comes from better aerodynamics at the given airflow and pressure ratio. That translates into less energy required to drive the turbine. This means that the turbine can be driven with less exhaust gas energy and allow the wastegate to bypass more air. What this results in is less backpressure. When you start to add up all the end results of the more efficient turbo, you can see how more HP is easily made...even for the same boost level.

[Dustin240]

How about total energy put down to the road threw the entire rpm range?A smaller turbo will start making power sooner. And a big turbo will have a little more power up top but not enought to overcome the wider power band of the smaller turbo.

less energy required to drive the larger turbine, better aerodynamics >that energy is almost free so how cares.

And chezadik, A small turbo can make 100cfm to 8psi, or a larger turbo can pressurize 200cfm to 8psi. Thats what makes a large turbo better on larger engines but engine can only hold so much air. So if a turbo can make 8 psi in the cfm range of the engine your good.

[C-Kwik]

How about total energy put down to the road threw the entire rpm range?A smaller turbo will start making power sooner. And a big turbo will have a little more power up top but not enought to overcome the wider power band of the smaller turbo.

less energy required to drive the larger turbine, better aerodynamics >that energy is almost free so how cares.

And chezadik, A small turbo can make 100cfm to 8psi, or a larger turbo can pressurize 200cfm to 8psi. Thats what makes a large turbo better on larger engines but engine can only hold so much air. So if a turbo can make 8 psi in the cfm range of the engine your good.

I wasn't talking about bigger or smaller. I said more efficient at a given pressure ratio and flow rate. I made no reference to size at all...quite deliberately. The tendency is a larger turbo's peak efficiency island occurs at higher flow rates and pressure ratios and smaller turbos tend towards the opposite. But this is not always the case.

And if you want to argue top end vs having a broad power band, take not the RPM at which each shift at redline lands you in each gear. The only time you'll see less than about 4000-4500 RPM is in 1st gear. You'll spend about 2 seconds in 1st gear in a 1/4 mile while the rest of the time is spent in all other gears at higher RPM's.

No energy is ever free. While turbos use a lot of the excess energy being expelled out of the exhaust, turbos still create backpressure on the motor. Smaller turbines are generally more restrictive and require higher backpressure. Especially when the compressor is in an inefficient range. Larger turbines are less restrictive and even less so when it's in the compressors higher efficiency ranges. It's not uncommon to see small turbos run more backpressure than boost. It's not uncommon to see large turbos have less backpressure than boost.

I'll try to restate the point chezedik was trying to make a different way. You can fill a 0.6L cylinder with 8 psi of air at 100 degrees farenheit or fill it with 8 psi of air at 200 degrees(don't use the numbers as realistic, just making a point here). The cylinder filled at 100 degrees will have much more air than at 200 degrees. 8 psi of 100 degree air and 8 psi of 200 degree air is not the same.

[WDRacing]

Its fun watching people argue about turbo's with Chano...He's he type of guy that very rarely mis-states somthing. In fact, he makes sure that what he does say is almost impossible to disprove...unless of course you are as smart as I am.

If I wanted a real low boost car...say 4 psi or so, I'd use a small turbo. But who the hell REALLY wants that? Why 4 when 14 is so much better. At 14psi, the output temps of a properly sized turbo and a small T3 are quite substantial. Enough that more timing retard will be needed on the T3 where the other could run quite a bit more advance.

WD

[Chezedik]

Kwik, you are so good at explaining things, that you can make my point better than I can. Thank you.

[Dustin240]

This is fun, U guys keep talking about temps> thats what a innercooler is for right.

On the street that broad power band is nice. But not so much for racing.So what I got from this is a turbo with a higher efficiency range has less back pressure, thus a little more power. But the pressure is the same and the density. A turbo with a higher efficiency range is just like taking off your muffler

[WDRacing]

Actually no, thats all wrong...

[C-Kwik]

Kwik, you are so good at explaining things, that you can make my point better than I can. Thank you.

No prob. You explained it fine. Dustin just looked at it a different way so I simply restated it in a way that clears it up for him.

[C-Kwik]

This is fun, U guys keep talking about temps> thats what a innercooler is for right.

On the street that broad power band is nice. But not so much for racing.So what I got from this is a turbo with a higher efficiency range has less back pressure, thus a little more power. But the pressure is the same and the density. A turbo with a higher efficiency range is just like taking off your muffler

The problem is, you are looking at the end result of the turbo and ignoring all the things that go on in a turbo. While intercooling can help bring temps down it requires more boost from the turbo to reach the same pressure and temperature at the intake manifold. 8 psi at the turbo outlet at different temperatures is going to have a different density or mass of air. If you were to cool both to the same temperature, the air that was hotter to begin with will have to cool more and if it is to fill the same volume, the pressure would have to decrease more. So in order to have the same pressure at the intake manifold as to more efficient set-up, the turbo would have to pump more air and pressure. This in turn creates additional heat over the already less efficient set-up requiring the intercooler to pull more heat out of the charge air. The higher boost requires more exhaust energy with the less efficient turbo already requiring more energy than the higher efficiency turbo. The hotter charge air will also require more work from the intercooler. This can become an issue at the track if the intercooler can't shed the heat effectively. The higher efficiency turbo is going to keep intercooler temps lower which will reduce the chances of heatsoak.

So, you can make 8 psi at the intake manifold with the same temperature and density using different turbos, but at a cost of less power and more burden on the intercooler.

[Dustin240]

Quote,If you were to cool both to the same temperature, the air that was hotter to begin with will have to cool more and if it is to fill the same volume, the pressure would have to decrease more. So in order to have the same pressure at the intake manifold.

Thats why my waste gate source is after the innercooler. But your right. And the end result is what matters the most, if you have the air coming right out of the turbo into the engine, a more efficient turbo is way better.

Did u know hotter air flows faster and better? Just being a pain

[Chezedik]

It doesn't matter if it is intercooled or not, a more efficient turbo will make more power (notice I did not say better, since what is better for you may not be for me). If it is intercooled, and the intercooler is 72% efficient, then it will be 72% efficient to either turbo's charge. If one is cooler to begin with, then it will be even cooler when it is on the other side. Efficiency of the turbo is the only factor that can change this.

[C-Kwik]

Thats why my waste gate source is after the innercooler. But your right. And the end result is what matters the most, if you have the air coming right out of the turbo into the engine, a more efficient turbo is way better.

Did u know hotter air flows faster and better? Just being a pain

That's not what I've been saying. A more efficient turbo is ALWAYS better.

Hotter air is thinner for a given volume and pressure. If the same volume of air and pressure flows, cooler air will be denser and be moving a higher mass of air. And in terms of making more power, moving a higher mass of air is more important.

[Dustin240]

How much power diff would u say there is from a T3 to a T4 OR T3/04?At lets say 13psi.

[Florida240sx]

Need more info. Too many variables. you need all the same trims and everything in the turbos to make the readings correct. On those turbos though your going to average out most likely within a few HP 280-300. one will be better at 4k while one is better at 4500 while one is best at 5k.

[crzycav86]

How much power diff would u say there is from a T3 to a T4 OR T3/04?At lets say 13psi.

In very general terms, probably 250-300hp vs 350-375hp.

Everything these guys are saying is correct. You need to do some more research before you embarass yourself.

[Dustin240]

U guys just gave me my research and thanks. Had to under stand how u came up with the info. Now there's less BS coming out of my mouth.

[WDRacing]

Good I was tired of wearing these boots everytime I came in here

[Thoughtful_One]

Okay, all of this information is very good. Many times on forums, there is too much being thrown around based on a friend's uncle's mother's boyfriend experience. I see how effiency plays a role in turbo-charging. I will include an updated list of what I will do/plan to buy:

Parts I Plan to Use:

- T3 (most likely out of a 300ZX unless I can find an appropriate flange)- Unfortunately I may have to go with an eBay manifold unless I find a good used one- eBay downpipe- 2.5-3" exhaust piping with used hi-flow cat.- stock injectors- eBay FMIC - BOV (brand is pending)- Walbro 255lph fuel pump- FMU (8:1)

- I plan to change my clutch, flywheel, fix idle issues, replace water-pump, and find out why the car is throwing a crank-angle sensor code.

How does this look now?

[Chezedik]

Fix your issues before you turbo, then you should be fine with what you have. You will probably only make about 200hp, but it will be more affordable than an SR swap with good torque. So good for you.BTW, the Z31 T3 uses a special 7 bolt out flange, you can get it from blaastperformance.com, don't ask me how I know.

[hannibal]

I was gonna mention Blaast. Chezedik searched for a source for a while IIRC...

I think I mentioned the 1st gen Eclipse/Talon as a cheap, commonly used BOV. Theyre on Ebay for about $30-50

[Chezedik]

I sure did. Also, I now have the 1G DSM, and it fits well. Also, later if I want to go with the RS, you can just waller out the holes and it fits.