I am sure the Mivec has something to do with it. I only have 250 Miles on my EVO so I did not push it yet but got her to 5K under full throttle on short runs. The engine sounds different than the 8 and I clearly can here a vtech like sound above 4K.

 

Did you even read the link I gave you?

 

Its the muffler ...

 

Yes, but we know it's the MIVEC that helps with the spoolup. A bigger turbo without lightened internals won't magically spool faster than a smaller version of the same turbo.

 

Lighten internals and a larger diffuser design can spool faster ....

 

You got me there. I don't know what a diffuser is in relation to turbos.

 

I know what an engine sounds like and a muffler. The sound comes from the engine bay not from the back.

 

Im sure the difference in power is going to be similar to the difference in the 9.8 vs the 10.5 hotside issue....you won't really know until you start to tune, up the boost a little and get a good hold through redline. You guys lost me on the spool up issue.

 

I'm not denying that ... I've sat in the EVO 9 and Honda's with VTEC ... there is definately a slight change in engine noise when cam profiles or times change (you should really hear those honda's when VTEC kicks in)... but most of the noise/sound a car make is because of the muffler.

 

The diffusers are the fins of the fan/propellers ...

 

Not in this context, the diffuser is the rear area of the compressor housing...the smooth section that radiuses in from the compressor inlet between the exducer and the actual scroll.

 

The compressor wheel and turbine wheels sizes and dimensions stay the same. It now uses magnesium in part of the rotating assembly (i.e. lighter material). The stock turbine shaft/compressor wheel combination should therefore start to rotate slightly sooner (very slightly), due to less rotational inertia given the same exhaust energy. The larger compressor housing has a larger volume and this volume must fill with air before leaving the nozzle. It would be hard to say which one of those is more prevalent. Because one factor would cause the turbo to accelerate faster and the other would cause more of a delay in getting air to the engine. I would guess that the spool up times would be similar between an 05 turbo and an 06 turbo. The 03 and 04 turbos with the smaller turbine cross section should spool slightly faster, but have less ultimate exhaust flow.

My $.02

Brian

 

I saw the BM video where they showed a cross-sectional view of both turbines and the EVO9 one had a larger diameter turbine and spooled quicker too ...

 

It is not worth to get a new turbo without big difference

 

it's not a bigger turbo, the wheel has not increased in diameter, it has however increased in "depth" as in the blades stick out further into the inlet.

if you know how a diffuser works then you'll know why this "larger" housing makes boost faster. a diffuser expands air, which means it slows the air. air that is getting slowed at a fast rate with fast air behind it builds pressure quickly, the faster you do this the faster the boost will build up.

no... the diffuser is the french horn section of the snail, the part that snails around. you can't see this unless you have a cut away but it grows as it goes around, otherwise you'd get NO BOOST PRODuCTION, you'd get NONE, if you did not have a diffuser the pressure induced by flinging the air out of the snail would be offset by the fact that the speed of the air would increase drastically and we all know that FAST AIR means LOW PRESSURE!

you must view the video again, you'll see that the 9 turbo is offset a bit from the 8 turbo's height, this is because the diffuser is larger and the cut away for the 9 is TALLER. the wheel is not bigger as a bigger wheel is measured by how far the blades sit from the radius of the INLET, HOWEVER the blades to extend into the HOUSING more, which would actually increase the moment of intertia MORE.

what does all this mean? despite a higher inertial moment hte 9 DOES SPOOL FASTER and mitsubishi reported this. 12% faster spool... it's not TONS but an improvement over an ALREADY fast spooling turbo is incredible!

this turbo spools faster than the 10.5 equipt 8s. we're talkin' BOOST UP TIME NOOOOOOOOOOOOOOT torque numbers. if you measure hte TIME it takes, then you'll find that it does indeed boost faster. which should translate into a lower rpm (altho doesn't have to) and better transient response.