94AWDcoupe

iTrader: (125)

so snail turbo has a titanium compressor wheel for GTX3582R. I always thought ti. would be lighter. but I ask them and to my surprise the wheel weigh 185 grams. (stock 35r 123 grams) I ask why make wheel from ti. and the following was their response. it has me wondering if this is true:

TommiM

iTrader: (19)

It could be possible. Sort of the same thought that a heavier flywheel will store more enertia= helps keep the car going when already at speed.

wingless

iTrader: (15)

I believe the the 16g rs wheel is Titanium aluminide (sp?) and the marketing behind it was for sure, less inertia = better transient response.

The above is baffling to me as well Perhaps TiAl is different animal than Ti?

nollij

iTrader: (21)

That is the turbine. This is in reference to the compressor which is typically aluminum.

It seems they are trading spool-up and response for more inertia which I have thought to be the opposite of what you want out of a Time Attack vehicle.

wingless

iTrader: (15)

Ah yes he said compressor. My bad.

dolson222

iTrader: (9)

Though based on their response it seems to be filling the holes in the turbo power/torque delivery in the mid RPM range by adding the inertia where repsonse issues should already have been overcome or at least are far more easily overcome by keeping momentum in the wheel when it would be fighting through maybe a higher load section of its pump/efficiency curve based on housing and wheel design/shape/size.

SWOLN

iTrader: (6)

Didn't know we were at the point of optimizing the weight of the wheels now on turbos. Is this why the EFR Turbos fall off up top because they are too light?

ctfpevoVIII

iTrader: (4)

Does the ti wheel hold up to heat very well? Not saying I know but just asking?

mrfred

iTrader: (50)

The comp wheel would be made out of a titanium metallic alloy, e.g., Ti6Al4V. Its higher density than aluminum alloys, but its also stronger. Its probably possible to make a comp wheel from Ti that's just as light as an Al one.

ctfpevoVIII

iTrader: (4)

Thanks for the response.

03whitegsr

iTrader: (8)

AFAIK, titanium was used at one point to deal with hub burst issues. Super high pressure ratios and huge diesel engines that could spool massive turbos instantly where causing low cycle fatigue issues.

Garrett went to "boreless" compressor wheels and I think Holset or IHI or one of the other companies went to billet titanium.

It's about strength as far as I know.

I could see what they are saying but I think the wording is a little funny. Some of the drag car guys have picked up on this high inertia thing. Basically, once you get the heavy wheel up to speed, extra inertia will help keep the shaft speed high between shifts. More shaft speed after a shift means more boost through the midrange revs.

This is on cars running stuff like CO2 boost controllers and bypass type anti-lag/launch control and are absolutely maxing out the turbo. Some have started going over to journal bearing turbos because they use larger shafts and thus more inertia.

I don't think you want titanium in anything where response after letting off the throttle matters though.

The JDM RS turbo uses a magnesium compressor wheel and titanium turbine wheel to lower inertia for improved transient response.

211Ratsbud

iTrader: (1)

I wonder how much of a trade off the high inertia vs low inertia is really worth? I mean I don't see a turbo with a high inertia option or low inertia option , so like you implied it's gonna come to splitting hairs. I'd really like to get a TSS set up to my vi-pec and see what things really effect it.