89dieselkong

Ok, I have the 18cm with the Stage IV on there now. Cruise temps are between 600 and 700 at 65-70mph. Boost is around 4psi. I can hit 37ish in about a second on the boost gauge when I stomp the pedal in 5th, and EGT's will climb into the red if I stay on it. However, when running through the gears, I never manage to hit more than 25psi before I run out of RPM and have to shift. I don't think I am getting full potential.

I ran the 12cm W/G when I first bought it, and cruise temps were the same, and boost was running around 10psi at cruise. When I stabed the throttle in 5th it would shoot past 40psi (wastegate not hooked up) in less than a second and EGT's again would go into the red if I stay in it too long. The difference is that I can run the 12cm over 30psi boost running thought the gears, utilizing it more.

My original though was that I might be pushing too much fuel for the 12cm because it felt a little restrictve at the top end, sorta like there was a bottle neck somewhere, but I have seen a lot of folks on here that are easily pushing more fuel than I am and running the 12cm. Which do you think I should go with? Does hooking up the wastegate really make that big a difference? I appreciate the advice everyone.

Oh yeah, driving style, mixed highway/city, towing less than 5000lb. once in awhile. Mostly a hod rod truck with some work thrown in.

G1625S

Put the 12 back on and enable the wastegate. You're only getting half of the benefit of the 12 (fast spool) having the 'gate disabled. The other benefit is being able to control boost and manage exhaust flow so the small housing doesn't become a restriction. Cowboy_Customs just put one on his truck after swearing up and down that he'd never run one now he's grinning ear to ear. Did you drill the divider in the 12? You definitely will be able to push the limits of the 12 with your setup, but 99% of the time, it's gonna be superior to the 18. Once you've got the 'gate hooked up, get an inline boost controller and set it down to about 28-30 psi. Things will cool off nicely and your HG will thank you

frostie

You do know they make a 14 and 16 housings as well. 16 is the best all around I have found.

89dieselkong

Thanks Greg, I just finished putting the 12cm back on. I ended up drilling the divider this time I was going to go a little more extreme and take the divider down like you did, but I am going to see how this runs before I tackle that project. I am going to enable the wastegate, it looks like there is a port already tapped on the housing for the stage IV, so I think I am going to run it from there to the actuator. Once that gets together, I am going to post some new numbers.

G1625S

Good deal Any boost source will do. Work with what you've got. I'm not entirely satisfied with the drilled divider, so I'm glad you didn't try that. It definitely hurts spoolup....but will hold me to 28psi even with all the coals to it in 5th. A decent compromise, I guess.

ChevellePull

So check this out fellas..

I called powershop up here in the great pacNwest and the dude told me that he would sell me a take off 12 cm housing for $100 plus I would have to buy the adapter for another $100, but that it would be cheaper than going with the 16 cm for $275!! I was nice to the guy, I know he needs to make money, but really how much did he pay for the "take off part" he's selling for $100 bucks? Anyway, he was really selling me on the 12cm housing (besides the price), but I see all you guys are such big fans for the 16 cm... Whaich way should I go?

jake

Ilikebikes

Go 12cm, you'll love the spool up. You're pretty low on the fuel side of things so you'll be fine with it.

You don't need any adaptors to run a stock, 2nd gen 12cm housing. The housing is a decent price for the 12 (I also paid $100) but you may be able to find it cheaper other places. I remember that when I was looking for a 12 about a year ago, they were getting harder and harder to find.

Edit: As for the 16cm being $275 from the local shop, check out www.htturbo.com. I think the 16 is around $175, but I haven't checked in months.

ChevellePull

Yeah HTT does have those 16cm for $175... The guy at the shop told me I would be saving by getting the 12cm and the adapter for $200... basically, i think he was trying to sell me on the stuff he had onhand vise going with the 16 he would have to order... I dunno...

so the $100 is good for the 12 cm housing though, huh? and I do not need that adapter?

Thanks again (as always) for your help...

Jake

Ilikebikes

If the 12 is in good shape with a working wastegate, I would spend $100 on it but not a penny more.

You don't need any adaptors. Sounds like that guy was trying to make another benjamin off you. All you have to do is to move your downpipe back about an inch or so to make up for the extra length of the wastegated housing.

ChevellePull

Awesome... I will have to go up there when I get back in to the country... I will make it a "dad and son day" away from mommy... She'll never know....

89dieselkong

Yeah I finally got off of work and took her out for a spin with the 12cm. I love it as much as i did before. I ordered a boost controller and am waiting on that to hook up the wastegate. In 5th and hammer down I can easily hit 40psi+ really quick but under normal driving the spool up is right where I need it to be Cruising speed 65-70mph and temps 600-700 with the stage IV.

The 12cm bolts right up to the stock location, no adapters are neccesary (sp?) All I did with the down pipe was move it about an inch-inch and a half back and tightened it back up (had to cut about that much off the other end as well)