Mike Murcia

Well, despite my several emails to the seller, as well as giving him my phone number, he sold the turbo to someone else stating that he lost my contact info. At least I know a bit more about the K27 now.

Duke

Excellent discussion!

So the hotside in reality works something like this:
A bigger hotside requires more exhaust flow before it starts to produce backpressure. This backpressure makes the turbo compressor to start build boost.
Given the same compressor, at X boost the 8# hotside produces less backpressure than the 6#, making the effective VE higher. Resulting in more air ingested by the engine at every revolution.

All to the cost of a higher rpm threshold of when the hotside starts to produce enough backpressure to allow the compressor to start building boost.

Am I right??

streckfu's

As I understand it, it's not exactly more required exhaust flow but given the same exhaust pressure it will take the #8 turbine longer to reach a given RPM. Since the compressor is driven by the turbine, any given boost pressure will arrive later in the engine's RPM range.



I'm pretty sure that the compressor is only capable of flowing a certain amount of air regardless of the turbine size. The larger turbine may produce less backpressure resulting in higher effiency but wouldn't the difference in air volume through the compressor be negligable?

Did this make sense to anyone but me?

eclou

Duke,

exhaust flow turns the hotside turbine, which is connected to the compressor wheel. The compressor wheel pushes more air into the engine which then comes out as exhaust. The smaller turbine will spin up faster than a larger one, but eventually the compressor linked to the smaller turbine will push so much air that the resulting resulting exhaust will build up pressure (back pressure) in front of the turbine. Since the smaller turbine has a smaller hotside exit (#6 outlet is smaller than the #8), the exhaust gas has more of a restriction to flow through and thus at a certain point the back pressure will impede flow through the engine between the compressor and the turbine. So at a certain point, the backpressure will hinder further performace gains (higher rpm) on a turbo with a smaller turbine vs larger.

Eugene

Duke

This sounds right, but since pressure doesn't equal flow I suppose 20psi less backpressure at 6000 rpm makes quite a differance in the CFM the turbo is pumping at X boost.

jimbo1111

There is a point where the decreased surface area on a #6 turbine blade will reach it threshold and no matter what you throw at it. It won't spin any faster. The added exhaust will flow right throw the turbine blades without effecting the rpm's. Around 5200 rpm. The added sq. surface area on the #8 turbine will utilize the exhaust volume better at higher rpm and allow more rpm than a #6. At the cost of slower spoolup. This is the point at witch the #8 turbine will give you the added hp till redline.

Dan87951

I see powerhaus sells the K27 7200 variety, anybody know the current price on those?

Tomas L

I think you're pretty close to the truth.
The power at the turbin shaft is a function of pressure drop over the turbine (backpressure) and flow through the turbine. The turbine has, as the compressor does, different efficiency at different pressure drop vs flow. When the effiency of the turbine drops, to keep the boostpressure constant the wastegate has to close, and increase the flow through the turbine and at the same time backpressure also rises.
This is a common misconception. It is not the turbo thats decides the flow in to the engine. The engine can be seen as a displacement pump that each revolution pumps 2.5/2*VE litres. The turbo can't change this fact unless it's extremely missized. What the turbo efficiency does is to decide which density the intake air has.
In short, the engine decides how much air that is taken in each revolution, and if we can increase VE by reducing backpressure then the volume air flow into the engine will increase.

Tomas

turbo951fan

$1,450 was the last price I saw for the 7200 clipped

mwc951

I pain $1395 for my PowerHaus K27/6-7200 w/ good core exchange. Non clipped, when I ordered David said he was no longer offering the clipped compressor wheel. The turbo was a true bolt-on, PRE-INDEXED, with all gaskets, o rings, water inlet fitting & exhaust sealing rings & seals. PowerHaus is a pleasure to deal with!

Kevin M

I have a K27 7200 in my car currently. It is being replaced in about two weeks with a different turbo. Any interest in this turbo? It seems to be in fine shape and has the water and oil cooling.
Thanks,
Kevin

porshhhh951

I have been gone for awhile. I just read the entire thread. My eyes hurt now....thanks alot guy's.

pk951

http://www.stealth316.com/2-turboguide.htm

This can help to understand more about turbos, and compressor maps,and probaly some misconceptions about them.

Dan87951

Why aren't they selling the clipped version anymore? Did David explain why?

mwc951

I didn't ask & he didn't offer. The posts I've read from guys who have them have all reported marginal results. From that I assume PH no longer offers them due to lack of consumer interest.