TURBHOE

iTrader: (4)

i see a lot of people are going to bigger turbine wheels here lately. not so much on the compressors (78vs80). and it seems to make since, more flow, more top end power.... however, how is the spool compared to the smaller wheels? to me it would seem that it would spool as fast or faster due to bigger vanes to catch the air and more mechanical advantage over the compressor wheel. but thats just my thoughts.

so tell me, if you have went to a bigger turbine wheel how does it spool? does it actually have more top end power?

lglowe

iTrader: (3)

I've gone from 65-68-75-81 mm turbine wheels. ( exducer sizes) all 76mm compressor wheels. 65-68 wheels are fun and street friendly with insta spool, the 75mm made a lot more power up top with minimal spool loss and the 81 has crazy never ending top end with some loss of low end/ part throttle boost but starts making power on my 5.3 around 3600. I like the big boys

smokeshow

iTrader: (16)

A big turbine wheel does not spool as fast or faster... You can pick up some power from going up in turbine size, but if the compressor cannot keep up with the amount of air demanded by the engine, it can end up making less power with a bigger turbine due to some of the more complex compressor characteristics. I've done it before. Just keep in mind that there are two sides to the story when you increase turbine wheel size.

o2camaross

iTrader: (2)

The main thing considering spool time is the inertia of the shaft, turbine and compressor. Since the compressor is aluminum it is no big deal, but the bigger Inconel turbine has much more mass, therefor much more inertia. Ideally with properly sized crossover tubing and properly sized housing, you can make a larger turbine spool nearly as fast as a smaller turbine, but I don't think you will be able to make it spool as fast. My old on3 76 with the 64.5mm turbine exducer spooled instantly and was fun, but was a handful trying to get traction at low speeds and petered out up top. I can tell it was really choking it. Now Im running a 80mm compressor with a 77.5mm turbine exducer and 4" exhaust and it's a monster! It does not spool as fast but, if I give it the gas it will light off pretty quick. The slower spool time really helps with traction and it absolutely screams up top. It never stops pulling. Plus idk if it is the new turbine design, size, 4" exhaust, or a combination of them all but with an open downpipe and this bigger turbine it sounds awesome just cruising around. You hear so much turbine! It's like a diesel truck but deeper lol

gmc6.0

Hey o2camaross you have a video clip, sounds very interesting

Atomic

iTrader: (42)

The larger wheel has a much higher moment of inertia so it will accelerate slower, and on the same size engine, will never spool as fast. However there are strategies to increase spool response (spool valves, boost controllers,etc.)

A larger wheel has a large effect on drive pressure as well...in theory the lower the drive pressure the more efficient the engine setup, so you get more power with the same amount of boost.

o2camaross

iTrader: (2)

I don't have a video clip of the open downpipe exhaust but I have a video of spool time in 3rd gear at 65mph. It's pretty fast even with the bigger turbine. I also have a video of the old turbo in 3rd around 50mph or so. I'll look at them and see how they compare and if they are interesting Ill post them

TURBHOE

iTrader: (4)

So people are going to bigger wheels for better top end performance and less drive pressure more so than anything. I'm trying to figure out how to spool at low rpm Tcc locked for towing while still getting high end performance. Still seems compounds would be the way for that. But twins would be easier to do....

Atomic

iTrader: (42)

I vote compound, I want to see someone do it.

TURBHOE

iTrader: (4)

Lol yeah that's what my buddy said too. Hahaha. One problem I found so far is the rear ac. I might be able to work around it. But I not sure if I will be a me to run a good size down pipe.

I will be running enough gate to keep drive pressure low though. I don't want it to choke out on account of small turbo in the way.