Rickard 993 Turbo

Okey sounds a little low i think but you are proberly right

So do you think i need to buy biger turbos, i want as much as possible with going inside the engien, camshaft will be okey

Maybe i should buy a stock TT and modyfie it, i thought the k24 was something nice to have

K24madness

Jean,

Love the sarcasim keep it coming.

Seriously though. Would you have tollerated having Todd tell you do not worry it the best XX component without giving you details?

Those of you who hand over your money without knowing what your buying are a sales persons wet dream.

K24madness

Seems like a cheap shot in my direction. So lets address the facts.

My history of building engines goes way beyond reading one book. I will say that formulas in corkey bells book are dead nuts on for turbo selection.

Race gas is the cheapest insurance possible against detonation. Many rod and head gasket failures can be traced to detonation.

The EBC is a far better choice than the uncontrolled boost spikes like the stock setup.

My motor has not been opened up yet because I have not increased the maximum loads on the rods beyond the stock setup. If you disagree then you clearly don't understand.

My research and development has allowed me to continue to find hidden HP. I share the results so that those who can think for themselfs and can benifit from my work. Guess you are not one of those people.



Now thats a great comparision. Lets see how a F1 car does in bumper to bumper traffic. Clearly they are two completly different objectives. Never understood why people like you make those comparisions. These are street cars.

TB993tt

These are NOT facts. The fastest race GT2 EVO cars ran factory Motronic which controlled the boost - properly done it will always give a fatter torque curve than a fixed boost.

Time to stump up the $1000 for the AX22 if you want to be taken seriously with any of these claims.

Jean

One should always remember not to judge others through what he reads on the boards, there will always be people that are better and worse than you, and you might be chronically humbled for life after you find out what some people here have achieved in their lives, just keep this in mind when generalizing your comments.

The rest is not even worth debating.

Geoffrey

Actually, the GT2 Evo used Tag Electronics with a Tag Electronics boost control valve. The valve looks like a fuel injector and is very fast, I have used them on occasion a long time ago. As I've said many times, the simple stock 993tt valve works very well, controlling the boost pressure to within 3-5kPa of the desired setting. It isn't the the limitation, the limitation is the ECU programming.

TB, your claim regarding the fatter torque curve is really applicable to an external type wastegate where you have manifold pressure working with the spring to keep the wastegate closed. The internal wastegate works the opposite, where manifold pressure opens the wastegate. The internal wastegates begin to open long before the desired boost pressure is met. This is one reason why Kevin shims the wastegate and has been looking for stronger springs to put inside the actuators. So, in an application where you have an external wastegate and a properly plumbed electronic boost controller (either by the ECU or stand alone), it will keep the wastegate closed until it reaches its predetermined boost level. If you use just a spring (factory 930 for example) in an external wastegate with manifold pressure, or an internal wastegate (like the KKK k16 and k24 turbos), then you will have boost bleed off before the desired boost pressure is reached and torque will be lost.

Todd uses the Garrett turbochargers because they tend to have less back pressure than the K16 based turbochargers. You can test this with a simple map sensor connected to the exhaust system.

TB993tt

I don't think you read what I said above

Nope, Motronic controlled internal wastegates also have much fatter torque curves than any fixed boost - this has nothing to do with the type of wastegate, fixed boost limits you to the preset fixed level whereas proper Motronic control constantly changes giving you a better potential when conditions allow.

Geoffrey

Yes, a proper PID algorithm like MoTeC or Motronic will allow far better boost control than just spring pressure. However, you cannot overcome the fact that the wastegates in an internal design open BEFORE the desired boost presure simply due to exhaust pressure overcomming the spring. This does not happen in an external wastegate design.

Kevin

One can deal with the gate by installing different spring tensions with progressive spring rates. I have 2 different spring rates available for K16 and K24's to allow the gates to stay closed longer and to withstand the exhaust backpressure that occurs with the design of the internal wastegate. For myself, I spend time machining the turbine housings to flow more air through the gate. The diameters are enlarged. The end result is a reduction of a "overboost" situation. With these two modifications one can eliminate premature gate exhaust gas venting and overboost situation.

The benifit of the internal wastegate over and above a external wastegate is the ability of the gate to instantly control the turbine wheel speed. The flip side is that once the boost target is reached the gates are shut, thus allowing the turbine wheel to spool up quicker than a external wastegate design.

Geoffrey

"The flip side is that once the boost target is reached the gates are shut, thus allowing the turbine wheel to spool up quicker than a external wastegate design."

Once the targe boost is reached, the turbine is already spooling at the proper speed and there is no need for more spool up. Both wastegate designs are good at maintaining boost and I've measured between a 3-5kPa fluxuation on both the internal and external wastegates.

Even with your larger springs, the internal wastegates STILL open before the target boost pressure is reached. While it is closer to the desired boost pressure, it still is opening prematurely.

Kevin

Sure,, Ah,, so lets say the we are in 3rd gear.. We are over 3500RPM's the Motronic will crack the wastegates open (4200 RPM's) to see if they are responding, ie it is checking to see if the wastegate system is actually working correctly( this is one of the reasons why EBC controled cars suffer with the Motronics) most likely at this time the gates are wide open.. You then shift your car, the turbine wheel is still turning, the bypass valves open directing the compressor side air back to compressor wheel, which actually keeps the rotating assy spining without drag from the engine RPM drop from the shift. the faster reaction time with the wastegates shutting allows the turbine wheel to spin up FASTER because of the physical location of the gate being so close to the turbine wheel. The faster reaction time and the ability to have the turbine wheel spin up faster produces boost quicker..

Geoffrey

Help me understand how "cracking the wastegates" improves performance. All it does is reduce turbine speed, nothing more, nothing less, that is the function of the wastegate, internal or external. And why do you need to "check to see if the wastegate system is actually working?" A proper PID algorithm is a closed loop system that has feedback from the MAP sensor and will adjust accordingly. If for some reason the wastegates are stuck closed (I've yet to see one on even a moderately maintained engine) the overboost protection will shut the car down.

When the bypass valves open, they do not have an effect on the compressor wheel. Yes, the air is bypassed into the air intake behind the MAF, but no, it isn't enough air pressure to substantially affect the velocity of air that is moving through the compressor wheel. Remember it is the turbine wheel that accelerates the compressor wheel, not the other way around. What does happen is that the restriction of the air hitting the throttle plate and the back to the compressor is removed by the CBV so the compressor/turbine assembly is free to continue to spin down unrestricted during a shift. Since the engine looses all manifold pressure when the throttle is closed, the wastegates are also immediately closed by the mechanical spring mechanism. At the end of the shift, the turbine is only beginning to spool back up once the throttle plate is opened and by that time, the wastegate has been closed for a long time. I don't believe there is a measureable difference in reaction time between internal and external wastegates.

pstoppani

I love how you guys know all these details... keep it coming... very informative (whether you agree with each other or not! )

Kevin

Again Geoffrey I am making my references to the stock Motronic. Not a standalone system or a modified hybrid ECU. The stock ECU will open or crack the wastegates open at 4,200 RPM +/- , if the the ECU doesn't see any change in the airflow across the MAF, the timing is pulled. If you are running a EBC, the ECU tries to open the wastegates through the frequency valve but often nothing happens because of the higher setting adjusted by the user with a EBC.. As a result you might have more boost (due to higher boost), the ECU pulls the timing and you have less engine power..

I have seen with my own eyes OEM manufactures testing with speed sensors on the rotating assy. When one shifts boost levels are usually at peak levels. When the throttle body is snapped closed, these high pressures are routed into the inlet ducting to the compressor housing (however, there are some BOV's that vent this to atmosphere, not the case with the 993TT and 996TT) For breif moments you can have you high boost pressure levels at the compressor wheel inlet. This pressure brief as it is aids in keeping the rotating assy moving.

On the 993TT the spin down is kept to a minimum. As you lay into the throttle, the exhaust heat and pressure starts to bring up the speed of the turbine wheel.. Since the wastegate is directly in the exhausts pathway in the turbine housings, the turbine wheel can react faster, and reach the target boost setting, which changes depending on conditions from the ECU. The manifold pressure does not go to absolute zero.. it is reduced and recycled through the Bypass valve and rerouted into the compressor inlet.. It is reduced to ZERO when you have a Greddy or HKS Bypass Valve that goes SHHHHH.. It is mecahically blowing off the pressure.. With the 993TT and 996TT this pressure is NOT dumped but re-routed. Imagine blowing up a large balloon, it takes time to bleed down the volume of air.. In this application the bleeding down is used to keep the rotating assy speed up.. Again, if you think of a pinwheel, you can spin the compressor wheel by blowing on the inducer side (the same side as where the Bypass valve dumps the pressure).. And in Geoffreys statement, Not just by having the exhaust turn the turbine wheel.. There are two ways to skin a cat, our cars benifit from all these engineering designs.

Geoffrey

Yea, I don't disagree about how the Motronic system works. An internal wastegate sill has the disadvantage that it opens prematurely on its way to reaching the target boost level. An external wastegate does not suffer the same issue. The manifold pressure will never go to ablsolute 0 or 0kPa, about the lowest I've seen is in the range of 22kPa. Since the throttle plate is closed, there is very little air going into the engine. Any residual boost pressure that is routed through the compressor bypass valve back into the compressor wheel is not going to accelerate the compressor/turbine assembly. It is a circular path.