I didn't say a 16 will flow more. With the mods he has it will be able to get more air in to help cool it down. A 18 at his level (or even a little more) won't spin fast enough to be at at it's peak efficiency. Now if he had about 75 more hp, towing egt's may be cooler with a 18.5 vs 16.
My "magic housing" was hands down, a 14 non wastegated with my old PDR HX-35. Could make 37-38 psi at this elevation.
One thing to keep in mind is not every truck, even with seemingly same mods, will spool the same. Some guys have told me thier 18.5 would spool instantly. If it does than I would not change it. Mine didn't........and still was laggy with the 16 housing.
Kurt

 

My 18.5 was just starting to make boost at the defuel point of the stock gov spring. It was a total pig at this altitude. When I put on the 16 it was like night and day.
It is a little slow to build boost depending on the RPM of the engine at the time of throttle mash, but once it does it crams you into the seat pretty hard.

 

There's an 18 on your truck right now.

 

Not trying to argue with anyone, just clarifying my opinion Pulling anything, the turbo will spool well no matter what. There will be a good load on the engine. He'll get about the same amount of air into the engine with either housings but the 18cm will flow more, hence keeping it cooler. The peak efficiency is around 30psi give or take a few and the 18 will definately spool to that, especially with a load. Now if the 16 will run cool enough for his settings than go with that if you think its worth $100 for 2 less squared centimeters. For pulling I think an 18 kills a 16 in almost every aspect. Price, flow, etc..)
Again, trying not to offend anyone. I respect everyone's opinions and I definately don't know everything.

 

No arguing here either. Like I said, even with same mods trucks will spool differently. Mine ran cooler pulling a load or not with the 16 vs 18.5 and spooled better.
Kurt

 

Also keep in mind that when you mash the fun pedal on an auto you're almost instantly over 2000 RPM (with the stock torque converter), which helps spoolup quite a bit. Honestly I don't think the 16cm is worth it for an auto truck. I'd say get the 18.5, and port match it to the manifold. If the spool is still too slow, try a wastegated 12cm, that way you won't have to spend much on exhaust housings.

I wouldn't spend over $50 for either an 18.5 or a 12; they're often people's "spare" or "left-over" housings, so they should be pretty willing to get rid of them.

 

does any1 know what size i have on my beater, and what i should get, just highway driving and pulling and fun in town! thanks

 

You have a 18.5cm. Get a 16, you'll love it. Good bang for the buck.

What part of El Paso do you live in?

 

the westside, howcome, you ever come throught here?

 

Sometimes I have jobs in Las Cruces. Are you over by the old steel mill?

 

Just went out on the freeway and timed how long it takes my engine to come up to full boost from at near zero boost cruising at 55 and 70. In both cases (at about 5,000ft elevation) it took a full five seconds to hit max boost. That is a lot of lag, but I really think several seconds could be attributed to the altitude.
My 18.5cm would have taken much longer to spool.
I'm hoping that the water/meth system will cut the turbo lag down a bit and clean up the coal train smoke some.

 

And my current 21 would probably take even longer to get to full boost. My guages will be arriving tomorrow(egt and boost) and hopefully I can get them installed this weekend. Then I will get some baseline numbers from where I'm at and have something to compare the 18 to.

 

As many know and have found out, most diesels dont come on full power right away, (affectionately called lag) and its probably a good thing. Diesels make huge gains over gassers in the torque area. With as much torque and power as a diesel makes, if it were a gasser with a roller cam and barked like a dog, it would rip up stuff quicker than you could fix it.
Nitrous and methanol, and propane injection are exceptions to what im talkin about and you know what your getting into when you do that and make provisions to control it as much as you can and stuff still gets shredded. Be thankful theres a little forgiveness (lag) there.

 

Yeah, that's a good point. With these heay front-biased trucks, traction is an issue, even on dry pavement. With the posi 4.10 I have to be careful not to beak the rear loose pulling out on a turn in 2nd and 3rd, even with my modest power increase since modding began.

 

dan man im not too sure but didnt the 91.5 already have the 18.5 on them