strange turbo mod?

[david]

You will not find a turbine impeller with so few blades.

On compressor impellers with same dimensions and same impeller design characteristics the fewer blades would have the following impact:

1. Less airflow on the lower turbocharger revs

2. Faster spool ( less weight)

3. Better top end flow because one less blade need to "cut" the air

that's just what i thought.
so having less blades is not so bad after all.
i can live with less airflow on lower turbocharger revs

[driftin jo]

Just to back up my statement ;

Turbine Wheel Cutback
Turbine Wheel Cutback is a machining process which enables the turbocharger to increase power output by reducing back pressure. This process does remove some blade material from the turbine wheel which normally results in a slight reduction in turbocharger response. If you're unsure of how back pressure influences a turbocharger imagine running a marathon with a finger up your nose!

From; http://www.turbodynamics.co.uk/servi...bine-upgrades/

What you have said is correct , unfortunately he was talking about the comp wheel being cut back no the turbine.

[Billman]

that's just what i thought.
so having less blades is not so bad after all.

It depends on what do you need. In holsets the 7 blade super 40 wheels gives 2 lbs less flow at the top but has a much wider map than the 6 blade (both 60/85mm). That's why holset doesn't make any hx40 with 6 blades anymore. Wider map is better than 2 lbs more at the limit.

@
DriftingJo

Don't where you are referring to but at the 1. Post he says exhaust compressor. I believe he talks abou the turbine impeller

[david]

Took my spare K24 to a long-standing turbo refurb company today for a refresh.
The place is small and run by a couple of old boys which I suspect know a fair bit about turbos. They have all the kit included balancing machine etc.
Whilst I was there, they offered to cut back the exhaust compressor wheel slightly as it would improve pick up
I don't doubt their knowledge BUT if that was the case - why didn't KKK do it in the first place!?
Any thoughts?
Thanks

Oh, and just for info - they charged £130 for rebuild and balance with all new seals/bearings etc - including a 360 deg bearing. seems like a good price?

[david]

[QUOTE=Billman;541416]It depends on what do you need. In holsets the 7 blade super 40 wheels gives 2 lbs less flow at the top but has a much wider map than the 6 blade (both 60/85mm). That's why holset doesn't make any hx40 with 6 blades anymore. Wider map is better that 2 lbs more at the limit.

so do you agree that this could be a good upgrade on k24,if your after a faster spool at topend.

[S-Express]

he he - seesm like I've opened a can of worms here.
I'll pick up my turbo tomorrow and ask him if he did cut back the impeller or not.
I didn't ask him to - he just offered!
Hope to get it fitted late next week - will let you all know how it goes

[driftin jo]

It depends on what do you need. In holsets the 7 blade super 40 wheels gives 2 lbs less flow at the top but has a much wider map than the 6 blade (both 60/85mm). That's why holset doesn't make any hx40 with 6 blades anymore. Wider map is better than 2 lbs more at the limit.

@
DriftingJo

Don't where you are referring to but at the 1. Post he says exhaust compressor. I believe he talks abou the turbine impeller

arr I see yes , I just saw the words 'compressor wheel' , I now see that he obviously meant the turbine wheel .

[Error404]

Took my spare K24 to a long-standing turbo refurb company today for a refresh.
The place is small and run by a couple of old boys which I suspect know a fair bit about turbos. They have all the kit included balancing machine etc.
Whilst I was there, they offered to cut back the exhaust compressor wheel slightly as it would improve pick up
I don't doubt their knowledge BUT if that was the case - why didn't KKK do it in the first place!?
Any thoughts?
Thanks

Oh, and just for info - they charged £130 for rebuild and balance with all new seals/bearings etc - including a 360 deg bearing. seems like a good price?

Where abouts is that place dude? Going to get my K24 done at some point

[JP]

Not George in Twickenham area is it? Cutting back the impeller blades will do 2 things. It will make the turbo spool faster, but as it has smaller surface area and a bigger gap to the housing it will also shift less air per rpm. The question is whether one benefit outweighs the other downfall.

Personally I don't think it's worth it as the K24 struggles to flow much more than 285-295hp as it is so although you may make a bit of extra midrange torque you will loose some of the top end power. (although some have seen just over the 300mark I'm still dubious as to how accurate the figures are looking at the compressor maps).

Which is the exact opposite of cutting back the exhaust blades which will give less mid for improved top end. Personally I wouldn't bother knowing my driving style however it may suit yours, ultimately it is one of those suck it and see scenarios where until you tried it you wont know.

[popdemonic]

I have only seen the turbo shop done the K24 by bore the compressor housing and have the K26 compressor wheel
on it.Inot sure about the result though,