12-26-2002, 09:40 PM
Hey guys, i had a question about T3/T4 turbos. Normally when people list the specs on their larger turbos the include stuff like
52 lb/min wheel
and other whatnot...
AR is the Aspect Ratio correct? the larger the number the larger lag/more power
I don't know what the different 'trim's are...
I'm not sure what is meant by lb/min wheel... Is that lb's of air per minute? Which wheel? compressor or turbine? Also, do you have 2 sets of these numbers for the 2 different housing/wheel combonations?
01-01-2003, 11:23 PM
A/R is the area to radius ratio. If you look at a turbine housing closely, you'll notice that the area inside gets smaller as it goes inwards towards the turbine wheel. You're correct about the general idea on what A/R does when it comes to lag and power but it's usually not as simple as that. There are other variables that contribute to lag and power.
Trims describe the wheels of the turbo. The blades of the wheels have two radiuses. They're called the inducer and the exducer. Trim is basically a description of the difference in size between these two. There's a formula using the two radiuses to know the trim but I can't remember it right now. Generally, the larger the trim, the closer the inducer and exducer's size is.
lb/min is exactly as you said, lb's of air per minute, that flows through the wheel. Techinically, you can have this measurement for both the compressor and the turbine wheel but this flow rate is more useful for the compressor side.
So, with the figures you listed this is what normally it means.
The .82 ar describes the turbine housing
60-trim describes the compressor wheel (turbine wheels are usually described differently, stage I, II, etc...or P-trim, O-trim..depending on the turbo)
and 52 lb/min wheel is what the compressor wheel is rated to flow.
01-02-2003, 12:53 PM
01-29-2003, 10:51 PM
I've always wondered this too, thanks ;)