KA-T Pressure Limits...

[AceInhole]

http://www.engr.uconn.edu/~cor...fold/

[Sil240]

i didnt read the whole thread cause there's too much stuffbut there is no such thing that a motor will hold "x" amount of hp/torque.Combustion chamber pressure does matter not boost pressure matters on wear of your motor. b/c if you have a 5 liter v8 you probably can run 20 psi b/c its a larger displacement and 20psi spread over 8cyl. but the combustion chamber pressure is lower than if you ran 20 psi on a 2.4 4cyl the combustion chamber would be higherboost is anything above 14.7 psi which is atmospheric pressure and the reason you can run higher amounts of boost on a supra and GN stock is bc those are 1)bigger 2)stronger motorsalso 12psi is 12psi doesnt matter from a t25 or a t77 its still 12lbs of pressure above atomospheric pressure t25 and t77 are just the size of the turbo

(P.S. if your running stock internals theres no way your running 20psi daily on your motor. and if you can id like to know how and see it)

[Mikel]

Sil240 Wrote:also 12psi is 12psi doesnt matter from a t25 or a t77 its still 12lbs of pressure above atomospheric pressure t25 and t77 are just the size of the turbo

Yes 12 psi is 12 psi no matter what size the turbo is, but the velocity of air is different..!! The bigger turbo will move MORE air at the same pressure...

You mean volume, not velocity.

Different turbos move different volumes of air at the same pressure ratio. Look at a compressor map :p

[95_240sx]

OK, So lets say that a stock engine with 10lbs of boost, is going to have an equaled out CR of about 16.8:1 ish, so you do the math, its going to have about 22:1 ish effective CR at 20psi, I dont know about you, but if a stock engine has 9:1 and 1klbs of downforce on the piston, double that and then some, you cant tell me that more boost doesnt have more wear, unless it IS built to withstand high boost like I have done, like Chris May and Jay have done, (difference is, mines not done so...) You can build an engine to withstand it longer, however, you cannot change the laws of physics.

Rick

[C-Kwik]

There is a difference between a motor being able to handle a boost load and wear. Neither are linked. They are two separate issues. A more immenent failure is usually the result of detonation. Wear has to do with friction. Certainly a higher load would result in accelerated wear. And certainly a higher load can lead to a part failure. But not to the extent that some of you seem to believe. Keep in mind that first of all, motors have this great chemical we dig out of the ground in them. Oil. Provided the viscosity is matched to the application with any decency and the condition of the oil is good(regular oil changes) adding a turbo won't add a significant amout of wear. An oiling system isn't so weak in a non-turbo car that suddenly rod bearings would all of a sudden be touching the rod journal. And keep in mind that even if you were to double the amount of air in a motor, the peak load is not doubled. Peak pressure will increase, but most of the increase in a turbo motor is actually realized after the peak pressure while the piston is still being forced down. The overall pressure is spread over the stroke of the piston.

Secondly, turbo sizing does matter immensly. Even if you had the same boost level, and temperature, if the turbine is a different size, it will affect power. Bigger turbines allow more flow and can net some very nice results by reducing backpressure. And by reducing backpresusre, the exhaust valves run cooler and are less of a threat to cause detonation.

If we are talking of how much peak boost a motor can handle, I'd agree more with Mikel. Wear is a separate issue. But a turbo motor shouldn't see a linear amount of wear in accordance to boost pressure. Frankly, it's fairly negligable.

[C-Kwik]

12psi is 12psi doesnt matter from a t25 or a t77 its still 12lbs of pressure above atomospheric pressure

Way wrong. Different turbos have different efficiencies at different flow rates. Efficiency directly affects how much the air is heated during the compression process. 12 psi at a given temperature is always the same. But 12 psi froma T77 will likely be cooler than 12 psi from a T25. Thus more dense and less likely to see detonation.

[AceInhole]

Way wrong. Different turbos have different efficiencies at different flow rates. Efficiency directly affects how much the air is heated during the compression process. 12 psi at a given temperature is always the same. But 12 psi froma T77 will likely be cooler than 12 psi from a T25. Thus more dense and less likely to see detonation.

However, you can make up for a turbo's efficiency with a good intercooler. The intercooler's efficiency matters far more than the turbo's efficiency.

[C-Kwik]

Yes, but that is poor fix to the problem of poor turbo sizing. Given the same intercooler, the more efficient turbo would still have a lower temperature. Secondly, if the two systems are both maxing out the available space for an intercooler, the only way to get better efficiency is to use a more efficient design. This will likely come in the form of an intercooler with a greater pressure drop. This means to reach the same boost level at the manifold, the turbo will have to boost to a higher pre-intercooler pressure, which means it will likely have a higher temperature to start with. Secondly, the turbo will have to work harder to create that much boost. A harder working turbo creates more backpressure. Its not as simple as you might think. Its good to be able to break it down, but you have to be able to apply it to the big picture, otherwise you may end up with results that can be less than spectacular.

On the flipside, do it right and you'll be amazed at the results. Nils can probably vouch for how effecient the HKS T04R is on the Supra. A friend and out one on a Supra. Running only 14 psi(I think it is 12 psi on stock turbos), the damned thing pulled out some 450 HP at the wheels. That's approximately 500 crank HP. Do the math and you're looking at some 180 HP increase over stock. With only 2 psi more. Certainly, there are some other things that account for it like the much better manifold design from HKS and the RMM downpipe, but 180 HP with a 2 psi increase is incredible. Turbo sizing works wonders for power. And it's probably seeing only a slight increase in load and wear. Absolutely negligible.

[WDRacing]

However, you can make up for a turbo's efficiency with a good intercooler. The intercooler's efficiency matters far more than the turbo's efficiency.

Ahh....no. The intercooler efficiency is important, but not nearly as important as the turbine efficiency. By pushing a turbo past it's window not only does it become a heat pump, but you'll spin the shaft far faster then its designed for. Which will lead to failure, plus your turbine wheel might unass itself.

The key to boosting the motor has been said like 25 times now. Eliminate detonation...I'm not saying you can run 25 psi on stock componants just cause your not suffering from preignition, but you can boost alot higher then then most people assume. 12 psi is not nearly the limit of the KA24.

I've destroyed a ton of RB20's do to overboosting and detonation. But once I added the proper amount of alcohol to the mixture and tamed the detonation, I was able to run 28 psi on stock internals, where as before I was killing motors at only 20 psi.

As far as regular wear to the engine is concerned, that is a silly argument. Of course your going to suffer from increased wear when you apply a greater force and any given object. It has nothing to do with CR or Boost. It has to do with the amount of pressure exerted on the object.

Hey Nils, if ya wanna run Alky/Methonal shoot me an email ro whatever. I've used it for the last couple of years. I'm surprised you never ran it on your GN.

WD

[Mikel]

Ahh....no. The intercooler efficiency is important, but not nearly as important as the turbine efficiency. By pushing a turbo past it's window not only does it become a heat pump, but you'll spin the shaft far faster then its designed for. Which will lead to failure, plus your turbine wheel might unass itself.

The key to boosting the motor has been said like 25 times now. Eliminate detonation...I'm not saying you can run 25 psi on stock componants just cause your not suffering from preignition, but you can boost alot higher then then most people assume. 12 psi is not nearly the limit of the KA24.

I've destroyed a ton of RB20's do to overboosting and detonation. But once I added the proper amount of alcohol to the mixture and tamed the detonation, I was able to run 28 psi on stock internals, where as before I was killing motors at only 20 psi.

As far as regular wear to the engine is concerned, that is a silly argument. Of course your going to suffer from increased wear when you apply a greater force and any given object. It has nothing to do with CR or Boost. It has to do with the amount of pressure exerted on the object.

Hey Nils, if ya wanna run Alky/Methonal shoot me an email ro whatever. I've used it for the last couple of years. I'm surprised you never ran it on your GN.

WD

That basically sums up my thoughts in the thread

I have SMC alky on my GN, 21psi with a lot of timing advance on the stock turbo, no detonation.

[Sil240]

timing advance? do you usually retard timing for boost or with alcohol you can advance the timing?

[C-Kwik]

Depends. If you are getting detonation then that is a possible solution.

[kevdog240]

11-12 pounds using just a 7:1/8:1 FMU? wouldnt that be VERY lean?

[Mikel]

timing advance? do you usually retard timing for boost or with alcohol you can advance the timing?

More timing will make more power (to a point, of course). If you aren't getting detonation, and you're already at the efficiency limits of the turbo, you can advance the timing for more power.

[WDRacing]

I also use the SMC Kit...best one on the market in my opinion. I'm working on a rising rate fuel pump so the volume will increse with boost rather then just dump in fuel.

WD

[Mikel]

I also use the SMC Kit...best one on the market in my opinion. I'm working on a rising rate fuel pump so the volume will increse with boost rather then just dump in fuel.

WD

I just upgraded to the dual nozzle setup, I'll see how it works when I put on the bigger turbo, stocker has got to go if the boost is going up. I've had my SMC kit since late 2001, not only is it very well made and easy to tune, Steve is a cool guy to deal with, willing to do pretty much whatever you request, and will upgrade an older kit to the new stuff at minimal cost. I highly recommend doing business with SMC :p