What, if any, is the performance difference between having an HX35 over a HY?

 

The HY had a smaller exhaust housing (9cm I believe) that allowed it to spool up faster to help the automatic trans get moving. The HX has a 12cm housing. The larger housing is a little slower to spool up, but allows more air to flow for cooler temps.

 

Thanks, that's why I love this site...that makes perfect sense, with my manual I have control of my shift points, which could cause hotter temps from higher rpms.

 

The Hy is a very limited turbo.....can't do much in the way of performance mods before it starts getting extremely hot. The 9cm housing is just way to small and doesn't flow enough air. However it spools probably the fastest out of any turbo out there for these trucks. Also these turbos have a hard lined wastegate.


The Hx has a lot more potential for HP upgrades. It spools a little slower than the Hy but not by much. You can upgrade the exhaust housings on this turbo to flow more air. They can also be used in a small twins setup.

The Hx is by far a more versitile turbo than the Hy.


~Nick

 

Hy35 has a smaller compressor as well. just a FYI,high RPM doesnt always mean high EGT,in fact most trucks are set to defuel after the 2700rpm power peak(24V),and as they do EGT drops rapidly,even as RPMs rise higher in most cases.

 

I rarely get it up to 2700...this is my daily driver/ commuter so I try to conserve some fuel. But what your saying, they stay hotter at lower rpms?

 

Not always at low rpm,they stay hotter when you are giving it the most fuel,and usually when you are either lugging it,or you have added hi performance goodies,such as injectors,and a box,and are at hi rpm/wide open,and you are making more hp than the turbo was designed for.Its called going off its map so to speak if you overspeed it or make more boost than it was designed for.Every turbo has a range is was meant to work in,once you pass its (sweet spot) most efficient part of that range,and keep going off its map,it gets hot.BTW,the HX35 is good to about 30-32psi of boost and low 300's HP,after that it isnt happy,and goes off its map.

If your truck is stock,and the air filters clean,you should not be able to get in trouble EGT wise,exception being bone stock HO 2001-2002 6 speeds are known to get pretty hot stock,when pulling real heavy.

 

Well my next purchase in the next month or so will be my gauges. What should I be considering "Hot" on the pyro?

 

That depends on how you mount it! 'couple of years ago, there was a fierce debate as to pre- vs. post-turbo mounting. I opted for pre-turbo, and bought the corresponding IssPro guage, calibrated/marked for those temps. I don't recall the exact numbers, but I can see graphically when my needle is reaching the end of the green, into the yellow. I have never gotten to the red yet. The idea isn't so much what temp, but how long at that temp is what counts!

 

If you're going pre turbo, 1250 degrees is the max for sustained temps. You can go higher than that for short runs and be ok. Stock truck, you won't be getting into much EGT trouble unless you have something wrong.