It seems that the 12v engines came with larger exhaust housings on the turbo and a bomb is to go to the 16 housing. Yet on the 24v most say that going from the 12 to the 16 would not be a good improvement. Does the 12v respond better to the larger housing than the 24v?

 

I don't know about the 24v's, but when I switched from 12 cm2 housing to the 16 cm2 housing I was supprized how much of a difference it made. First thing you notice is how little boost it run compared to before the switch. Before I would be at around 10 psi running down the highway at 65 mph. Now same speed same highway I see 2-3 psi, and it will fall off quick, which leaves 0 psi alot of the time. But at the same time it will build boost very fast when it is needed, then fall back off. The egt's are lower, average probally 100 degrees lower on normal driving. I have not pulled with this settup yet, but I expect to see lower EGT's on long pulls, and more power.

 

Some big engine (big truck) cummins gurus have told me that increasing the housing will give less of a seat of the pants feeling but increase economy pulling and increase horsepower in the upper ranges and is a good improvement. As well as lower EGT's

 

[quote author=Haulin in Dixie link=board=7;threadid=20598;start=0#msg193272 date=1065416869]
It seems that the 12v engines came with larger exhaust housings on the turbo and a bomb is to go to the 16 housing. [/quote]

Just to be straight. All manual trucks from '94 to '02 came with the HX-35 and a 12cm2 wastegated roughly at 20PSI.

I think in '00 The Auto trucks came equipped with an HY-35 equipped with a 9cm2 housing wastegated at the same, ~20PSI boost.


A bigger housing will help top end, and towing, but will make your truck not as "quick" around town.

Spool-up time will be slower, and also, higher in the RPM, but top-end performance (2,000RPM+) will be much better. EGT will also be lower WOT, but wil be slightly higher cruising.

Merrick Cummings Jr

 

Great info Merrick and just what I need. Another question is how would a HX40/16 affect the ISB for towing heavy?

 

It will affect the driver in this way ;D
and the truck this way 8)

You might experiance more smoke on the bottom end, and if you do alot of city driving your MPG may drop, but when towing you might see more MPG, unless your foot tries to stay rested on the radiator,, like mine

It will do good things for you,, IF you are pushing your '35 hard allready,, but as "just an upgrade" without any extra fuel, it wil probably make your truck doggier all around.

Merrick Cummings Jr

 

Merrick thanks for the info. Looks like an expensive thing to try, might work out might not. I have the 275 injectors and the EZ have no plans to build it past that. The vast majority of the miles on my truck is 70 to 75 mph at 1900 to 2100 rpms. When it sees a hill it gets what its got, downshifts are at 1800 and then carry the 2500 2600 on up the hill. I generally feather it out at the crest. Little city driving. Empty at 15,000 pounds I cruise at 70 to 75 never have to shift.

Now and then while loaded I come up on a PS or a Max and well all bets are off ;D ;D

 

Ya, I'd like to hear something on this, as I'm thinking of upgrading my HX40/35 hybrid from a 12 cm2 housing to a 14 cm2 housing. I've got an unpinned Edge Comp & 275 injectors, and am wondering whether I've got enough fuel for the 14 cm2 housing. (Don't want to pin the pump, like to keep the VP44 happy for a while.) Sounds like a similar issue to HIDixie's.

 

I'll take the easy way out of this one and say go look at the holset web site. I looked the other day and it deals with questions like these. The tech tips and link buttons at the top of the page is also a great source of information. Good luck on your research.

 

You do not want to run an HX40 with an EZ and 275's you will be very unhappy with the results. If you are having egt problems now the 16cm housing is one option. I have a modified wastegated 14cm housing that may be a better option, and you could utilize it if you decided to go with the Hybrid later. I can put a HX40 compressor on the 24valve turbo, but I have to machine the cartridge and change to the older style exhaust housings if you want it wastegated (recommended) the 14 mentioned above is a good housing with the hybrid. Contact me for more info.