Turbo housing change, 21cm to 12cm

[J DeMaio]

Hey guys:



A buddy of mine has an old 12cm turbine housing and I was considering trading them out. How much better performance will I have? How hard is this to do? Does anything need to be modified? (exhaust) Would you guys recommend hooking up the wastegate or not? How much better would boost #'s and EGT's be after this?



Thanks,



John

 

[BushWakr - RIP]

I've never run a 12cm housing but I can guarrantee that you'll see rocket spool up compared to the larger 21cm.

You will need to modify the exhaust. I think you'll need to have about 1 1/2" cut off (just behind the turbo/exhaust coupler) and once done it makes going back to the 16,18,or 21cm (who'd want to) hard since you'll need an 'adapter' or new downpipe to re-connect.

You should see more boost for the fueling your using, how much I'm not sure. I gained about 2-3 psi going from the 18. 5cm to the 16cm housing on my truck.

The wastegate is a good idea and personally, if its got one, use it.

You can prevent 'high drive pressures' from working against you at upper end fueling.



Here's a link from a thread that I just had with PW. While it is specific to me, it does explain a bit about boost/pressures/housing sizes/wastegates etc.



http://216.235.147.117/forums/showthread.php?s=&threadid=53119



Hope that is of some help.



Regards, Bob.

 

[Joseph Donnelly]

The 21 is way too sluggish for even trucks with added fueling. The 16 is the smallest taht is readily available without a wastegate. It would be a good compromise. The 12 will spool fast but is somewhat restrictive on flow. It is OK for a stock engine, and will be much more responsive. you will have to remove 1. 25" from the dowmpipe as the wastegated housings are that much longer.



If I had only the two choices on a stock engine, 12 or 21, I'd definitely go for the 12. However, the 16 is good and much less hassle as it is a drop in, same length as the 21.

 

[Power Wagon]

I've got the wastegated 12, about 217 HP at the wheels (260-280 engine hp), and EGT runs about 850 after a minute long WOT run.



The 12 made such a dramatic change in how it ran, I had to re-learn how to drive the truck on wet roads. Turbo lag? What's that? With the stock auto and converter, banging the pedal down gets you about 1-2 seconds of waiting for boost and then it's BANZAI!!! It spools immediately, with the auto, at any speed. I would guess from idle, it takes about 2 seconds before the tires start to spin on pavement. That's not power braking, just hitting the pedal.



For comparison, in 1/10 of a mile, my truck gets to about 55.



30-35 across a long intersection.



If you're at an intersection and just nail it, the black from the tires starts about 4-8 feet from the line you were waiting at. Takes only that far to get the boost up and all the ponies pulling - about 10 feet or so.



Now compare that to your truck with the 21

 

[JLEONARD]

John,

I went from an 18 to a 16 and am happy with the change. Just a little turbo lag left, very tolerable. There's power available just about all the time I need it, which is mostly at highway speeds.

I just installed a new H1C this week since the old one was beyond rebuilding. I have the old(original) 18 cm housing available if you would like to try that out over your 21 to experiment. Just pay the shipping from CT and it's yours... PM me if you are interested.

-- email address removed --

 

[Steve Campbell]

If you do not mind a stupid question....

What size exh housing came stock on a 90 CTD?

 

[J DeMaio]

Okay guys:



How much better will my truck tow with that smaller housing? What exactly has to be done to my downpipe? I know it has to help it out a ton due to the way it is now. Where does the wastegate hook up at? Any more info would be greatly appreciated



Thanks,



John

 

[AlK]

Steve,

I believe the 1990 came with the 18. 5cm2 housing.

---

Al

 

[BushWakr - RIP]

Alk, you know, this is one thing I could NEVER keep straight in my head. I thought the 18. 5 came into use around mid 92.



Anyway, the housing will have the size cast right into it, atleast my stock 18. 5 cm did Steve.

Just have a look around the body of the housing and see if you can find/feel it. It may be lower down on the housing and hard to see.



As far as towing goes, depending on housing size, RPM, fueling, and load the smaller housings have the potential to get you right up there in terms of EGT's.

Of course you can always drop down a gear, and bring your RPM's up, this will lower EGT's. OR you could ease up on fueling as a solution.

From what I've learned here, the smaller housings spool up faster initially, but also have the potential to "run out of air" at the upper end. You end up with high drive pressure which can actually work against you and cause a loss of power, and higher EGT's.

You need to tune the sytem to your application. Seek professional advice. ..... actually, I think we ALL need professional advice in here... .



Bob.

 

[AlK]

Bob,

In a previous discussion dealing with turbo housings Piers provided the following.



89-91. 5 had 18. 5 housings WH1 turbo

91. 5-92 had 21 housings WH1 turbo

93 went back to the 18. 5 WH1 turbo

94-2000 have 12 housings HX35 turbo

2001 ETC have 9 & 10 housings HY35 turbo

2001 ETH have 12 housings HX35 turbo

Hi performance Cummins run the HX40 16 or 18 housings or the H2E with a 17 housing

---

Al

 

[BushWakr - RIP]

Hey great Alk, I cut N' pasted that into my turbo diesel directory for future memory failures. (Happens alot, in fact I write my phone number and address on my hand when I leave home in the morning..... only problem is, I keep forgetting NOT to wash my hands... . bummer...



Thanks again bud !!





Bob.

 

[JLEONARD]

(From what I've learned here, the smaller housings spool up faster initially, but also have the potential to "run out of air" at the upper end. You end up with high drive pressure which can actually work against you and cause a loss of power, and higher EGT's. )



Bob,

Yes I have found the above to be true, except for the higher EGTs.

With the stock 18. 5 housing, my truck would still be accelerating pretty hard at 90 mph. With the 16 housing, acceleration flattens out around 90... . kind of a moot point though, as we normally don't have to go that fast to dust the "other" brands.

I think my EGTs are lower thru the whole range with the smaller housing.

Be advised I don't tow anything.

 

[BushWakr - RIP]

JLEONARD,



Am I understanding you corretly when you say yours 'flattens out' around 90 to mean that the max boost starts dropping away, or just doesn't climb anymore?



Bob.

 

[JLEONARD]

Boost doesn't climb any more, it stays around 25 and the acceleration seems 'flat'.

The truck will still go faster, but the strong pull is gone. Feels like the restricted exhaust effect because of the smaller housing.

Bear in mind I still have a stock exhaust system.

 

[Bob Beauchaine]

I've run a 14cm2 wastegated turbo from Banks for about 8 years and am quite happy with it. The turbo lag was virtually unnoticeable until I had the 230hp pump put on. Now I can just bearly feel it for about 1 second if I hammer it - which I rarely do. I can't tell you when it flatens out as I run at 80 or below. I can accelerate going up a 6% grade hauling my trailer with little or no trouble. I swear my truck grins everytime I pass the "other" brands while going up 6% grades My EGT guage is pre turbo and has never gone above 1150.

Happy trails

Bob