Hello,

I have a modification question about the 12cm wastegated housing. Most people won't even talk about the 12cm, it seems to be some sort of sore spot. Even when I pointed out that my towing EGTs dropped when going from a 16cm to a 12cm, they will still suggest that I go to a 16cm, 18.5cm, 21cm...36cm, 59cm, 1000cm or bigger yet! I just say "Heck, why I don't I just take the turbo completely off!!" Zero back pressure and lots of smoke, that's what we want!! Sorry about the ranting...

Anyway, off to my question. I have a 12cm with an HX35 on my 92 Dodge that I use for heavy towing. Would there be any benefit to drilling through the wastegate hole and on into the front port to allow the dumping of all 6 cylinders instead of 3? This was the only concern that I had with using the wastegated housings. I'm thinking that it would give a more even backpressure relief at high RPMs and possible hp gain. I don't think the 12cm makes as much backpressure (with a working wastegate) as everyone says it does and if it did I would expect to see the boost keep climbing after the wastegate has opened. This may happen on a heavy fueled-high rpm engine, but it doesn't seem to be the case with my truck.

Thanks.
Mike

 

Yes you can drill the housing and yes, it will help, according to member Wannadiesel. Wannadiesel is in the 'more heavily fueled' category and needed to keep the boost from climbing on his wh1c. Search his user name and check out his pics and posts---I'm sure he'll chime in here before too long.

greg

 

Did somebody say my name?

https://www.dieseltruckresource.com/...threadid=57304 is the thread on that mod. I did it because with the wastegate wired open the truck would make 37 psi! The housing is still too small, but without the water/meth on boost is under control. Turning on the water/meth sends me up to 35 psi again.

Mike, I agree with you about the 12 cm housing. I love the 12 cm housing, and I think more people should use it. Until you go to POD's it moves plenty of air. It's great in traffic with stock injectors and some pump tweaks, it's the housing Dodge should have put on the trucks in the first place instead of waiting until '94.

The two drawbacks to a 12 cm housing on a 1st gen are: 1. You have to move/shorten the downpipe. A lot of people want bolt-on.
2. If you have a 5 speed you really need a compressor side with MWE like an HX-35 or a WH1C. This drives up the cost, although MWE can be a DIY project if you have access to a big enough lathe.

 

The mwe missed if you just get the 12cm housing, You get mwe if you go to a hx-35 right?
-Jim-

 

Thanks for the link Dave. It looks like a good project to play with. I also emailed Ted Jannetty and he says he's been doing this for years. He also recommended that I drill the hole to 1/2 the size of the wastegate hole, he's probably thinking about the exhaust pulses. I realize that I probably won't see a performance improvement, but I can rest knowing that the front half of the engine is getting a break like the back half. I'm still at a loss why everyone is frowning on the 12, even the guys at Piers. But the proof for me was in the pyro and if I get to the fueling where the 12 chokes and egt goes up, then it's time for a bigger turbo or twins. For my setup, going from a 16 to a 12 lowered my EGT by 100 degree at 2500 and lowered EGT by 150 below 2000, not to mention an ablity to leave rubber off idle. So, would I rather let off the throttle with the 16 and let the ticking time-bombed powerstroke pull away or would I rather keep my foot buried and pass him so I can watch him blow up behind me instead of out in front? Why am I even asking that question when I should be diving for the tool box?

Later
Mike

 

Right. All turbos that came from the factory with the 12 cm have MWE. You'd think Cummins knew what they were doing or something.

 

i thought an hx35 would bolt up with no mods ?

 

it will, if you have an intercooled set-up.

 

im missing something, what has a intercooler to do with the exhaust?

 

ahhh, i'm tired. misread. 12cm housing will bolt up just fine. the hx35 compressor housing needs attention if mounted to a non-IC motor. it has a v-band clamp outlet.

 

I have an HX-35 off of a 99...the exhaust hook-up is completely different from my H1C.

Short of whackin'off the neck of the exhaust outlet on my HX-35 so I can slide the pipe over it and clamp it on (argh,can you say "Hack job"),how do I hook this up without spendin' money(OK, I'll admit,I'm poor AND cheap )?

If I HAVE to buy an exhaust outlet for this turbo...what would be the best "bang for the buck" way to go?
If I want go with PODs (or some other bigger injector) in the future,should I just change the whole exhaust housing? Where would be the best (read cheapest) place to get what I need?

Thanks a bunch in advance,

Vinny

 

Vinny-
You should be able to loosen up the exhaust and shove it back enough to make it work. If you know somebody who can weld tubing, pull the downpipe off the truck and have them cut off the flange and weld it back on minus some pipe.

If you plan to go with POD's in the near future, swap housings. The 12 cm isn't big enough for POD's and a tweaked pump.

 

On the later 2nd gen hx35's the elbow is cast with the back plate. Using a plate form a 94-98 12v you get an exhaust ring type flange the same as the 1st gens. You need to find an earlier rear plate and unbolt your rear plate and swap, or possibly use a downpipe from a 2nd gen (modified).

 

Got an email from Ted Jannetty today explaining some backpressure specs of the 12cm housing. Up to 30 psi, the HX35-12w is 1 psi boost per 1.5 psi drive pressure. At 35 psi is climbs to 1 to 2, which is going out of the HX35 performance map. They way he explained it is how often do we drive at those pressures and are are we willing to sacrafice the low end performance for low drive pressure at 35 psi boost? Personally, I like an engine that likes to work, not one that has to be babied when hauling a load. So, I drilled the hole and took her for a drive. With the wastegate set for 24 psi, which should have the fuel pin buried at that point, it pulls hard right off the idle in 4th. Wastegate opens at around 2000 rpm, but it still pulls to the governor at 65 mph just as hard as it did with the 16cm. Max post pyro EGT with the 12cm is 600 degree during the pull, with the 16cm I would easily hit 850 during the same run. I think I'll stick with the 12!!

Mike

 

Mgrant: Good information! I think I'm sold now

Hey Wannadiesel, how hard is it to drive around the flutter if I were to just get the 12 housing?