12 cm exhaust - testimonials please

["Mad Max"]

So the Nacho's turbo is making some noise and has more shaft side play than I'd like. So naturally, a fresh turbo is on the short list - it's going to be a PDR HX-35. But of course that means a smaller-than-stock exhaust housing, and I need some real-world reports on 12 cm collars on a NON-towing rig.



My RC is not a hauler - it is a trail truck that hauls itself and eventually a couple ATV's to the camp ground. No major trailer weight, etc. It's got a full 4" exhaust including, of course, one of our own 4" DPs. Sticks are currently stock, and driveline includes a 6BT/518 w/ DTT clam, 203/205 doubler, 3. 55's and 36x15. 5 tires. It cruises on the highway like a dream and when doubled-down it crawls like a tank.



I'm looking to get quickest spool without choking the exhaust. The highway gears, tall tires, and DTT clam load the engine good and hard. I know a 14 will be great, but I'm real curious how a 12 will perform. I'm tempted to try it just for the hell of it.



Our '93 Ram is the tug boat and has a 14cm collar and it works perfect. A 12 cm collar would be to constrictive for that rig particularly under big loads. But the RC..... I'm trying to find a good, valid reason not to go with a 12 cm collar.



At a most I'll use a 14, but I'm real tempted to go with a 12. So, anyone have a good reason why I shouldn't... or should??



Thanks



- Sam

 

["Mad Max"]

The one thing that I need to keep in mind is the Ramcharger is a lifted 4x4 and has very wide tires while my '93 is 2wd and a lot lower, so the RC's wind resistance has a much bigger affect than the Ram, and while the RC will do 80 mph it takes some decent throttle - 65 mph is fairly easy. So I'm thinking the RCs weight (7000 lbs) along with the wind resistance may be too much for a 12 cm housing... . shoot I just don't know. I'd really like to 'borrow' a 12cm collar from someone and try it out. Anybody have a 12cm housing laying around that I can try out?

- S

 

[cerberusiam]

Considering your setup and use, I doubt you will have any problems with a 12 or even a newer 10 as long as you match the compressor correctly.



Spoolup gets better as you drop the exducer housing sizes and modify the wheels, but, you need to get the inducer big enough to flow good air at lower pressures. Curious what the specs are on the PDR turbo, inducer, exducer, etc?



A 12 should work quite well, an extended tip 10 off a 3rd gen would work even better and allow a bigger inducer. They light almost instantly and have a broad map.



Don't be too worried about restriction in your application as you generally won't see enough load and rpm to cause issues. We frequently tow 20k for days with no egt or restriction problems.



All depends on what you want to spend and how much new technology you want to incorporate.

 

["Mad Max"]

Thanks Alan. I'm leaning towards the 12, and they are the same $$$ as the 14. As I understand with PDRs 35, the cold side has a bigger impeller than the stock 35, and I'm thinking that might just make up for the increased fuel rate through the hot side. I think it's worth a try, but other than your input I don't have much real-world data to go on.



This rig (the Ramcharger) isn't going to get a lot of 'fuel' - nothing like our '93, so the 'heat' should be better managed/lower overall than in the '93, and since it isn't going to be towing heavy I'd prefer to go for the increased spool time for street/low speed off-road use by using the 12. My curiosity alone makes me want to at least try it... .

 

[cerberusiam]

The 12 should work fine and I definitely wouldn't go bigger than that.



If you want a cheaper alternative to try out and see how you like it, check ebay and craigs list for an HE341 off an 03-04 CR truck. These will have a 56 mm inducer and a 60 mm exducer on a single throat housing that is flow comparable to a 12 housing on the older turbos.



You can pick these up a lot of times for a couple hundred and decide how you like it then invest a comparable one. Sell the HE to the rice burner guys as they are always wanting them.



Another option to think about.

 

["Mad Max"]

what do you think the effects/results would be if I kept the stock H1C and did the 12cm housing? The turbo has enough side play to warrant a rebuild, and that's a lot less spendy than a new one. I don't need a new one, just one that is good to go, but the lag is terrible. My fuel isn't cranked through the roof so I'm thinking the 12 might work well with a stock turbo.



I don't have gauges in this truck yet but I can't imagine with 'stock' fueling a 12cm would send the H1C past 20 psi would it?

 

[cerberusiam]

what do you think the effects/results would be if I kept the stock H1C and did the 12cm housing? The turbo has enough side play to warrant a rebuild, and that's a lot less spendy than a new one. I don't need a new one, just one that is good to go, but the lag is terrible. My fuel isn't cranked through the roof so I'm thinking the 12 might work well with a stock turbo.



I don't have gauges in this truck yet but I can't imagine with 'stock' fueling a 12cm would send the H1C past 20 psi would it?

Max, Max, "stock" fueling and its gonna stay there????? :-laf:-laf I KNOW you know where the full power screw is.



Stock fueling should not be a problem if you are careful. I would worry more about the play and upgrading the compressor would be probably close to the same cost as fixing the original. I understand the cost thing but I HATE the idea of cleaning out an induction system worse.



If your careful with the loud pedal it should work fine, but, I think it will max the compressor pretty easily on an H1C. However, you will have a WG (right?) you can set so it would be fine.

 

["Mad Max"]

- oh yeah, definitely know where it is, just not sure I want to tap into it yet. Wasn't planning to wastegate it... but I think you're right - maybe I should.



So I've been searching all morning for a solid answer to this question, so here it is:



Is a smaller exhaust housing... overall... better or worse for a high-elevation Cummins?



Actually... it's a moot question. I know a 14 works fantastic on my '93 so obviously smaller is better, and I'm just trying to convince myself to get a 12 on the RC. I think it's time for good ole' trial and error.....

 

[peobryant]

With nearly stock fueling, I think you will really like the 12cm housing. Everyone says a 12cm housing an automatic don't go together, so I guess you'll have to be our test mule.

 

["Mad Max"]

Everyone says a 12cm housing an automatic don't go together, so I guess you'll have to be our test mule.

It'd be my pleasure - I've been called a lot of things but never a lemming... .



As it turns out my 2nd gen buddy Trevor up the road did an ATS Aurora turbo combo on his rig and has the 12cm/HX-35 sitting on a shelf - I offered to give it a new home if only a rental, but I think it'll likely stay there and I'll hook him up some other way down the road. He and I live vicariously off each other like that...

- S

 

["Mad Max"]

here's the hardware. What I need is the standard '1st gen' back plate for the housing to replace the 2nd gen back half. Thoughts??



#ad

 

[JStoll]

I have the 12cm2 on my H1E? 1993 turbo
really good bottom end instant power
I just need a much larger compressor section, more fuel, a larger exhaust system & intercooler & yeeeehhhhaaaaahhhh

OO crap I went there again

I did make 200WHP with the stock 89 turbo with just pump tweaks & an open 3. 5 exhaust
probably a little more then that now with an intercooler, bigger injectors & turbo

blah blah ... . I love my truck
JAK

 

["Mad Max"]

Cool - I was able to find one locally this morning at a turbo shop - they had a couple lying around and I got it for cheap. Also sourced the steel gasket at my local Kenworth dealership Cummins #3535001. I still don't know what the original application is for this plate - maybe early 2nd gen 12V?



Here's what the parts look like -



#ad




So now it's time to clean everything up, bolt it all together, and see how the beastie runs afterwards - woot! woot!



- M2

 

[Midnite]

I may have missed it, but have you advanced the injection pump timing at all on the Ramcharger? If you bump it up a little it'll drop your EGTs some and help compensate for the more restrictive exhaust housing.

Mike