Here is a UK company that does the Green with BBs, 4 inch shroud, ceramic coating etc.

http://www.turbodynamics.co.uk/downl...reenTurbos.pdf

 

Yeah, I know....this one will cost only $5500,- + Now maybe you understand me asking for FP to offer this kind of options for a lower price.

 

I dont think the HTA will have a 4 inch shroud. Or will it have it? How about bb? I still think they are different turbos

 

I was kind of bored this morning so I thought I would think about this and I think if you increase the surface area of the turbine blades proportional to the rotating mass of the new components then the radial acceleration of the rotating mass will remain constant.

For interia as you said F = ma = PA. So if you hold a constant pressure P (exhaust pressure from the engine) and increase A (surface area of the turbine blades) such that it is linearly proportional to the mass of your new rotating parts, m, then your radial acceleration would be a constant, a, and you would have the same "lag". Basially you have a = PA/m. Also, you can flow more air and hold the same pressure if you increase your flow rate, and the area (say from 9.8 to 10.5 for example) which is the whole point of upgrading the turbo in the first place. Somebody correct me if I missed something here.

 

I'm humbled! LOL

Josh

 

While what you are saying is essentially correct, there are two issues that affect at what rpm a turbo reaches a given boost level - one is the design of the turbo, and the other is lag. The first is the trade-off between at what rpm a turbo reaches the desired boost vs. when it runs out of capacity to maintain that boost at high rpm. The other is if a turbo cannot respond to changing input from the engine due to inertia.

Here is some info from Wikipedia (very good info on turbo's there btw):

I'm guessing here, but I think the HTA version is a standard green with a clipped wheel?

 

I think it's interesting to look at what FP is selling to the subie folks as the HTA Green:

http://store.forcedperformance.net/m...Code=WRX-Turbo

On this page you'll see thumbnails for a GREEN and a GREEN HTA. Also notice the prices. Anyway, the subie GREEN HTA delivers "over 56lb/min without an increase in turbo lag". That's much bigger than what Robert was talking about in this thread initially. Hmm, over 56 lbs/min, sound familiar? Take a look at the pictures. What you can see of the compressor wheel looks just like the 3076HTA which flows about the same. A compressor like this could be "almost too big to call a Green".

Gary

 

The Subie HTA Green pushes 56lbs per min, the FP 3076 HTA for the EVo pushes 57, these would be a better comparison for capacity. The subies displacement is 2.5 litres so the comparison is not exactly the same.

 

I agree. All I was basically doing was showing the equation for inertia and the linear relationship it has to mass and surface area because in someones post they said it would be "impossible" to reduce lag without lowering the mass of the rotating parts. That is not true necessarily because lag would be caused by how long it takes to get the rotating mass in motion enough to create the desired boost level and as you pointed out mass alone is not the sole factor or this. So reducing rotating mass alone might not be the answer but certainly we can prove that by actually increasing the mass we can still get the same radial acceleration if the surface area is linearly proportional to the mass. Alright, that's enough nerd talk out of me...

PS: Wikipedia has definitions posted by whoever so you can never really trust it as a reliable source. Take it all with a grain of salt and if it makes sense then go with it. Here what they have posted seems to be true but in general all definitions on that site are posted by guys like you and me so I would never trust it as an accepted source of information like a published encyclopedia or something like that.

But with that all said I agree with you. Good stuff here. Food for thought if nothing else.

 

I am unsubscribing from this thread. I am tired of getting my hopes just to be let down.

 

awsome man i need one wish i had my greencard so i can get a job nd have money to buy one

 

You are guessing wrong.

All FP HTAs have a billet CNC cut compressor wheel of their own proprietary geometry and design. They are not "clipped" existing wheel designs.

 

I stand corrected; so what is the relationship between a "green" and an "HTA green" then (since the name seems to imply they are related somehow)?

 

Since the HTA Green has not been released, it would be difficult for anyone but FP to answer your question. If it's an HTA, though, it will have a different and unique to FP "HTA" compressor wheel.

You can see the mods for the current Green on the FP webpage.

 

That's what I was suggesting. I was saying that the Subie HTA GREEN compressor wheel and the FP GT3076HTA compressor wheels are mighty similar, looks and flow spec, and suggesting that the "larger variant" that they are testing now might be using almost the same compressor wheel.

By the way the FP GT3076HTA is not specifically "for the EVO". It is a normal rotation turbo with Garrett GT30 turbine and a T3 turbine inlet, so it is for anybody who wants to do the whole T3 thing.
The Subie compressors are also normal rotation. So it's not like FP already had an off the shelf wheel ready to go into the evo 9 turbo to make this "larger variant". But it would have been pretty simple if these wheels are cut from billets on a CNC milling machine from a dataset, like the "regular" evo green wheel is. Press the button that says "transform - mirror" and presto, you are well on your way to a dataset for the reverse rotation version of the wheel (for the evo).

The billet wheels are one reason why these turbos are kinda expensive. They are not just stamped out like friggin cookies. After looking at prices on turbos from HKS, Greddy, and some of the other specialty turbo shops, I gotta say FP is doing a great job combining high technology and performance with reasonable prices...

Gary