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Turbo Tech: Calculating Turbocharger Compressor and Turbine Performance Advantage with the New Honeywell Garrett GTX Gen2

by Khiem Dinh

 

Honeywell Garrett launched the GTX series about a decade ago featuring a stronger billet compressor wheel which allowed updated compressor aerodynamics to increase power using the same sized turbo. This past year, Honeywell Garrett released the GTX Gen2 turbocharger lineup featuring an again improved compressor wheel design along with other updated turbocharger features. Follow along and we will teach you how to estimate the power a turbo can make along with turbine matching and show the difference between the GTX and GTX Gen 2 turbos.

 

In this image, we overlaid the new GTX Gen2 GTX3582R 82mm compressor map with the older Gen1 map. The Gen2 update did something very difficult engineering wise; it increased both the maximum flow and also the map width. The new surge line on the left of the map is further to the left, giving the Gen2 compressor more usable flow range.

 

Step 1: calculate compressor mass flow and pressure ratio. We did this once before in our article on compressor mass flow. In the absence of real engine data, you’ll have to make assumptions for values such as BSFC, A/F ratio, and pressure drops of the air filter and intercooler.

 

Here are my engine performance targets for my hypothetical turbo setup on Project S2000. We estimated the values from existing dyno data and using a few adjustments to go from NA to forced induction. You can see how we did it by checking out the article on calculating compressor flow. We are targeting a bit more than double the torque and power of stock with a flat torque curve from 3000rpm to 8000rpm.

 

After calculating the mass flows we will need to hit my torque and power targets, we calculated the required compressor pressure ratios so that we could plot the points on compressor maps.
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Comments
Dan DeRosia
Dan DeRosialink
Monday, April 24, 2017 4:51 AM
I keep seeing the Gen2 compressor maps come up and this article provides a good place to ask... for the "end" points you graphed, you're on the Gen2 map and not the Gen1 map and obviously it will be more efficient there, but it seems like the Gen1 map will have better efficiencies at most of the points between those points - wouldn't that overwhelm the better efficiencies at the 3000rpm and 8000rpm points?
spdracerut
spdracerutlink
Monday, April 24, 2017 5:54 PM
The Gen2 is down a couple points peak efficiency in the middle of the map. But, your average end-user only cares about max power. So in my GTX3071 example, the Gen2 makes another 50hp over Gen1 in the same turbo size. With Gen1, the end-user would have to step up to the 3076 and incur a few hundred rpm loss in spool and added inertia to make the same power as the Gen2 3071.
Dan DeRosia
Dan DeRosialink
Tuesday, April 25, 2017 10:02 AM
That makes sense... I'm just trying to get a better understanding of the tradeoffs. Somewhat thinking out loud, it seems like accepting lower efficiency in the middle of the powerband might hurt midrange power at a given boost level due to increased backpressure... which might mean tradeoffs with larger AR and an overall peakier response.

All that aside, the GTX3584RS map looks like it could be interesting for a big ported 2-rotor, though I somewhat doubt the turbine would keep up.
Dan DeRosia
Dan DeRosialink
Tuesday, April 25, 2017 12:18 PM
Oh, btw, thanks for laying out the math - I'd meant to get around to doing that but you know about round 'tuits.
spdracerut
spdracerutlink
Wednesday, April 26, 2017 7:16 PM
Yeah, some mid-range efficiency given up and therefore power. But no one is really maximizing a turbo in the mid-range, so a simple increase in boost pressure will make up the efficiency difference to get to the same power.

Now where it WOULD make a difference is in an OEM application where they have very specific operating points. Like a semi-truck which will operating in a very specific portion of the map. In this case, a few points of compressor efficiency could mean a 1% fuel economy improvement. A class 8 semi-truck burns over 12500 gallons of fuel on average a year. So 1% of that is 125 gallons and at $3 a gallon, that's $475 a year saved. That's 75000 miles a year assuming 6mpg. A truck lasts 10 years, so that's potentially almost $5k savings in fuel costs by a simple few points better compressor efficiency.
Dan DeRosia
Dan DeRosialink
Wednesday, April 26, 2017 8:21 PM
I suppose things like that also explain how a bunch of turbo makers... ahem... without Garrett, BW, MHI or IHI's resources manage to make things that are competitive at some types of racing - I imagine if you can eke out a bit more flow out of (for example) a given inducer size that you're limited to by doing something weird, it doesn't matter as much if the efficiencies aren't as great in the middle compared to the fact that it's still on the map towards the edges.
spdracerut
spdracerutlink
Wednesday, April 26, 2017 11:14 PM
Everyone also designs to different fatigue life criteria...
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