| Calculating turbo trim? - Click HERE for Original Thread |
| datslamd |
So to establish the trim of a turbo,
Take the trim of the compressor-X
((inducer^2)/(exducer^2))*100=x
and the trim of the turbine-Y
((inducer^2)/(exducer^2))*100=y
and a go lika so:
x/y= Overall turbo trim??? Is this correct and accurate as a way of establishing an important characteristic of a turbocharger?
Thanks |
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| tokes |
| Trim is virtually meaningless, unless you're using it as a simple situation to differentiate between different wheels of the same series, IE: TO4E 50-trim and TO4E 57-trim, but giving somebody the trim value of a compressor or turbine wheel all on it's own gives you absolutely no idea of how much power it can support. For example, a PT61/SC61 uses a 56-trim GT35R compressor wheel, and can support 630-650 WHP maxed out with no nitrous. A PT76 uses a 76mm compressor wheel that works out to be a 56-trim wheel as well, but will support about 1050 WHP maxed out with no nitrous. They are both 56-trim, but there is no relationship at all in size between them, other than the inducer and exducer of the compressor wheels shares a similar ratio. |
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| datslamd |
OK, but the OVERALL ratio is figured out by the formula above. I'm not actually trying to figure out the trim of a turbo, just better understand how they work. I realize that the general output of a turbo is dependant on several factors but if I can't even figure out the factors then I can't calculate. That's why I was so careful with my words. Not... careful... enough.
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| LeadSled |
http://www.forcedinductions.com/help.htm
I've waded through this site and many others trying to narrow down the turbo search and learn more... Its effed up at the bottom so you have to copy and paste onto word, but its good info.
Like tokes said, you generally don't refer to trim unless its the same turbo housing but different turbine/compressor wheels.
A/R and the turbo's map are the two main characteristics.
Here's a free program thats cool to play around with to see what you want. Its not exact and it doesn't have many maps but it helps.
http://www.turbofast.com.au/software/bin/turbocalc.zip |
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| datslamd |
I'll read the shit out of bof those sites and be back for more questions. Thanks.
Later |
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| chris f |
| think of turbo trim like a a prop on a boat. the more agressive the blade angle the more air/water it will move, the down side is it takes more power to drive it. |
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| Fish_e_o |
i thought trim was the distance in thousandths of an inch that the wheel's radius was away from the housing....:confused:
the smaller the trim the more efficient the turbo: the smaller trim will not alow as much air to not be effected by the wheel ... |
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| tokes |
quote:
Originally posted by Fish_e_o
i thought trim was the distance in thousandths of an inch that the wheel's radius was away from the housing....:confused:
the smaller the trim the more efficient the turbo: the smaller trim will not alow as much air to not be effected by the wheel ...
Nope. Minor squared over major squared multiplied by 100, has nothing to do with clearances between wheel and housing. |
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| datslamd |
quote:
Originally posted by Fish_e_o
i thought trim was the distance in thousandths of an inch that the wheel's radius was away from the housing....:confused:
the smaller the trim the more efficient the turbo: the smaller trim will not alow as much air to not be effected by the wheel ...
That's A/R. Area radius. |
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| LeadSled |
quote:
Originally posted by datslamd
That's A/R. Area radius.
No, A/R is the inducer nozzle area divided by the radius from the center of the shaft to the center of the inducer nozzle. |
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| LeadSled |
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| fatbastard |
Another point:
A higher "trim" turbo is typically more efficient in the lower pressure ratios, as the inducer and exducer are closer to the same size. A smaller trim is typically better at higher pressure ratios because there is less adiabatic heating due to the bigger differential between the exd/ind. Bigger trim turbos are subject to a more surge as well.
There are other factors, but it's a guideline. |
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