Garrett GTX40/88R turbocharger billit compressor wheel
The following year Garrett released GTX versions of the 28RS, 30R, 35R, and 42R skipping over the 40R, and giving it NO LOVE. Now why should you care? Well if you look at the horsepower ratings of those turbo’s you start down at 450 hp with the GTX28RS. Then move to the 600 HP rating of the 30R. From there you go to the 650-700 hp rating of the GTX35R, and finally end with the 940 HP rating of the GTX42R. So you go from a 700 hp capable turbo to a 900+ capable turbo. Now some would say: “great if you want the big HP just go for it and jump to the big 42R”, but the response difference (some call that lag) between the two turbo’s is not even comparable.
In a discussion enginebasics was having with another enthusiast, the turbo currently to go with between the 35R and the 42R that is somewhat updated technology is the GT40/94R. A turbo that is old school, but still able to pack a punch. This turbo is right in the middle being that it is good for 800 wheel hp. The problem there again is that the difference between the GT35R and a 40/94r is a big difference. Many find that on a 2.4L or smaller engine the difference to be around 600-900 RPM.
NOW FOR GARRETS NEW RELEASE!!! Garrett has just announced that it will be releasing a GTX version of the GT40/88R, obviously named the GTX40r or as it is properly known the GTX40/88r. This is exciting news to fill the gap between the GTX35R and the GTX42/94R. A user should expect just 300-400 rpm more “lag” till full boost is reached when compared to its smaller 35R brother, but like everything in the world of turbochargers, this less responsive turbo comes with a bonus, and that is more power. The compressor map for the new GTX40/88R is showing a capability of 84 lbs a minute. That is good for roughly 840 wheel horsepower.
One thing to note that is interesting about this billet version of the GT40R is that fact that Garrett usually runs slightly different sized inducer and exducer sizes along with going to the 11 blade design. While the new turbo does have an 11 blade compressor wheel, the inducer wheel diameter and exducer wheel diameter maintain the same sizes:(click for larger image)