#12 exhaust housing

[bvanetten]

At what RPM level does the #12 housing start to effect air flow and EGT's? What is the best RPM range to run a #12 housing in? Also, what are the best RPM ranges to run a 14 or 16 housing?

 

[hdm48]

It's not the RPM that is the issue, it's the total volume of gas (exhaust) running through it. If it is ported it will flow more but stalling due to excesive back pressure will still take place.

If you are not pulling heavy loads and running an automatic it shouldn't be a problem. Higher EGTs may limit you a little on how long you can stay on the throttle up hills.

It all comes down to how hard you want to run your truck.







Dave

 

[BushWakr - RIP]

Dave is quite right... . the smaller inlet passage on the 12's and 14's create a "back up" of pressure or, drive pressure.

It can happen when, as Dave notes, the volume of exhaust gases reaches a point were it can't enter the housing quick enough and that results in extremely high drive pressure.



This "backing up" creates enormous increases in EGT's because of the extreme rise in cylinder temps which in turn results in heat saturation of all the components. The compressor side of the turbo cannot keep up with the rising EGT's and it feeds on itself.

As heat saturation becomes greater and greater the rise in 'ambient air temps' also results in EGT rise.

For every 1*F rise in ambient (intake temp) the EGT will rise roughly 3*F... . see the monster coming...



So, 2500 RPM under full load/fuel on an aggressive setup can be brutal on a 12cm or 14cm but on a 16cm or 18cm it's not an issue. (assuming they are all non-gated housings)



pb.

 

[bvanetten]

Ok. My Toy Hauler, loaded will be ab out 8000lbs. I'll be towing Memorial day from Phoenix (1200ft elev) to a place called Big lake (9000ft elev). Along the way their are several 6 to 8% grades that are several miles long. Look at my Sig. , am I asking for trouble? Should I put a 16 on the Burb? Or maybe put the original 18 back on...

 

[bvanetten]

Here's the sig again. I just updated it

1972 Chevy Suburban with 1990 D350 4x4 CTD Chassis, 47RH transmission w/ 89%DTT guts, 12cm housing, PDR tweaked pump w/3200 rpm GSK, 2nd gen intercooler, POD injectors, PDR Modified H1C, 3 1/2" exhaust w/ Walker high flow muffler, Rear disk

 

[JDMills]

Dave, PB,

Why is it that a Automatic appears to be more forgiving (if I understand correctly) to EGT then a manual transmission? If one is pulling a hill with the identical load, one truck being a auto, the other being a stick, will there be a difference in EGT between the two? (with a 12 cm housing)

Just curious

Jason

 

[BushWakr - RIP]

I think that it rests for the most part in the "forgiving" nature of a fluid coupling as opposed to a solid state coupling like a clutch.

So long as the clutch doesn't slip you have more load applied to the engine with a manual trans.

When you reduce the load you reduce the EGT's.

Strangely though you can get along much better with a wastegated housing since it basically prevents you from "getting into trouble" by doing it's job purgin excess pressure, preventing the high drive pressure's. It basically (assuming it's set right) keeps the turbo from going beyond it's efficiency map.

That is one of benefits of a hybrid turbo. You extend the map noticably and improve the compressor efficiency giving you coolor boost all thru the extended map range... .

A 'gated housing is perfect for towing and higher altitudes because you get quick response with control over your upper end boost levels/temps.



BTW... how do you like your setup Bruce ???





pb... .

 

[bvanetten]

All grins so far. From stopped to about 30 lbs boost is about 1 1/2 to 2 seconds. Better idle quality. Less smoke, more power. So far, lower EGT's. I havn't pulled yet, that will be next week. I do have one concern... When I hit about 20lbs boost I get a weird noise under the hood. The boost gauge starts to flutter and hop about 3 psi and every time it drops I get a high pitched whistle. Almost like a leak in the charged air side. I've pressurized the system from the turbo outlet to the tailpipe with 40 lbs of air and have no leaks so I'm a bit confused. I'm going to call Piers Monday. Any ideas?

 

[BushWakr - RIP]

It sounds like a bit of compressor cavitation. When I sent in the turbo I asked them to machine it prevent/reduce that.

Chat with Piers and he'll do what needs to be done... . assuming that it's something needed.



pb...

 

[Stomp]

I am sure glad I found this site, but some of the things I have done in the past would sure be frowned upon by this group. I had a H1C with a 12 housing on it. It had a waste gate, but it was blocked off. Got 45 pound of hot boost out of it. It would hit 1800* on the pyro mighty quick. I made 338rwhp and 790ftlbs of torque. Wow I am sure glad it didn't come a part on me.



Stomp

 

[dpuckett]

From my experience, a 12 is fine for running empty with 3. 54s and an auto w/OD. ANy lower geraing than that, and you are overrunning the housing/ turbo set up. I went back to an 18 on my 91, as the 12 was just too restrictive with my 4. 10s and fuelling. EGTs didnt change, but cruise boost dropped considerably. If you have the time and $$$, I'd put a 16 on there and be done wih it.



Stomp, I dont EVER want to hear you whine about your MPGs again. Sheezz... ... . :-laf



Daniel

 

[bgilbert]

Here's the sig again. I just updated it

If its a 4x4 chassis then you need to update your sig again. D models=2wd. W models= 4wd. ~ W350.



JMO but POD'S, 12cm housing, +- 15k gcvw, big hills or even flat ground towing = HIGH EGT'S. 12cm housing not recommended for towing.

 

[bvanetten]

Oops. Fixed the sig... W350.



Just did a test run with the trailer, I will be putting a 16 housing on soon.

On a mostly flat road, maybe 1% grade. 65mph at 1770 rpm locked in OD...



transmission temp = 175

egt's = 1000

boost = 16



Truck weight = 7000

Trailer weight = 7000



I won't be pulling hills in OD obviously but I think it was a good test anyhow.



PB. This turbo sounds different, aside from the cavitation. Before turbo wine was a high pitched whistle, sweet sound really. Now it's more of a winey screech. Much more annoying. And then at about 25lbs it starts to cavitate...