billet compressor wheels--6/6 vs 7/7 vs 11 blade??

[gorganl2000]

been doing some research....and seeing some different designs now

can anyone share their experiences/knowledge regarding the different blade counts and the impact on spool and power curve?

 

[Rev]

I have been looking at this too ... a difficult question to answer.
The 6/6 is supposed to have more space and run cooler so breathing better than 7/7 at some speeds but these all vary in secondary blade height which effects things.
Tips have been added now for more outer spool and flow these vary in height also some billet is stronger and will handle stress better.
Blade height has been increased for more flow and is supposed to reduce surge and yet 11 blades take a different approach.

Some blades are meant to be in antisurge housings some arent. Some can have a small increased ratio of compressor to exhaust wheel for reliability some have upgraded shafts and thrust bearings to increase this ratio.

IMO because Lighter billet wheels have more surface for the same weight they are getting more flow which is causing more surge so newer turbos are controlling some surge with openings in the compressor housings and recently it seems the 11 blades are shaped to go faster as they have more swept back blades but still with a lot of weight close to the shaft rather than at the perimeter. This will reduce moment on the bearings at really hi speed but the ones that don't have a lot of blade on the outer wheel for spooling fast look more like racing turbos.

Some alternative Billets are increasing the height of blades to increase flow area without adding to surge and will keep weight close to the shaft as well.

I saw some 2004-2007 Volvo R k24 billet compressors with longish blades described this way -
k24 6/6 - This wheel is best suited to mid-range RPM power development 2800-5800 ( +22hp )
k24 7x7 - This blade design carries power through the mid range RPM for more street/strip car ( + 123hp )
k24 11 blade gtx - Is best suited to upper RPM power development 3800-7500 a more 'touring car' power band. ( +37hp )
They make more air but were shifting the stock turbo torque of 1950-5250 up the rev range.

It could be said having the compressor wheel max flow more than the exhaust wheel max. speed can yield is just be adding unnecessary blade weight that has to be spooled.

 

[gorganl2000]

thanks a lot rev...some great info there

that 7x7 figure i guess is an error?....maybe 23hp?

is this whp or bhp?

looks like the 7x7 is the sweet spot for street cars....a compromise between the 6x6 and 11 blade

do you have link to the volvo stuff?

 

[Rev]

Glad you appreciate it, still more analysis needed and some running examples would be good.

I don't think the 7x7 is and error they gave an actual figure for the compressor of up to 420hp I just subtracted that from stock power they havent given boost level and these new billet wheels are rated for ridiculous boost levels.

I compared the figures to the stock wiki power this would be fhp I think but remember these engines are 2.5L airflow.

I have read other sites saying 7x7 was giving good results but I wonder if this applies to smaller turbo diameters?
The other thing to notice is the shaft size diameter is sometimes being reduced this is to give a wider blade area.

This link has the 7x7 at the bottom there are 2 different 11 blades to look for.
http://www.ardideas.com/K24-Billet-compressor-wheel-66_p_119.html

 

[gorganl2000]

yeah,,,with the reduction in shaft size and the extended exducer tips and aero design changes....seems they are able to possibly increase air flow

that's assuming that things were not optimal before with the stock cast wheel

but seeing that even the old time hybrid/hiflow ct9s yielded some results....maybe the new billet wheel "design/size improvements" are onto something

 

[Rev]

Still working on what to do but agree those hyrbids performed well.

My objective will be to get more flow right across the range with a lightest possible exhaust and compressor combination. That then allows greater flexibility for tweaking ports, manifold etc to optimise velocities.

With 1.3litre car things have to be well designed as you have no air flow to spare and boost is needed.


ps. I read people found some 11 blade billets were significantly heavier than the
advertised weights.