I installed my hx 35 with my existing 16cm exhaust housing and didn't gain any boost pressure, but I didn't turn the pump at all since. What I am wondering is if I put the 12cm housing that I got with the turbo will I get more boost and how much higher will my exhaust temps be when pulling trailers. Basically what is the optimal exhaust housing size?

 

The HX-35 and H1C are pretty much the same on the top end, it's at low RPM and heavy load where the HX-35 has an advantage. This is why you didn't gain boost. Putting the 12 cm housing on will put you up around 30 psi and drop your EGT while towing. The reduction in turbo lag is really nice, too. If your boost isn't passing 35 psi you don't need to worry about the wastegate on the 12 cm, just leave the actuator bolted on so the wastegate stays shut.

The optimal turbine housing size really depends on what modifications you've made and what you use the truck to do. On a truck with stock injectors that's a general purpose truck, the 12 cm wastegated is hard to beat, especially on a manual trans truck. Quick spool-up and plenty of boost, with a wastegate to keep you from overspeeding the turbo. The 16 cm is better for a truck with big injectors, or one that spends most of its time on the highway doing 70 mph (or more ). I run the 12 cm because I drive in heavy traffic most of the time and never tow, so fast response is the most important thing - I can live with the side effect of high EGT when accelerating past 80 mph.

 

And I'm the opposite of wannadiesel...I spend most of my driving at 70 (or more) so I like the free breathing of the 16 and not having to look at the pyro.
So alot depends on your type of driving.
Try them both and let us know which one you like

Jay

 

I'm gonna take a bit of an opposing position as well.
The efficiency map on the H1 as well as the HX is roughly 26-28psi...maybe a tad more on a good HX35.
Beyond that you are quickly dropping out of the turbo's operating range. At 35psi you well out of it...
Even a hybrid 35 will have a map limit of about 35-36psi.
In addition the 12cm is an extremely responsive housing. Because of the very small inlet to the 12cm housing the higher boost levels create high/very high drive pressures.
Basically this means that the pressure at the exhaust housing inlet is equal to or higher than the boost pressure at the intake manifold. That is not a desireable thing. You end up with hot exhaust gases backing up trying to enter the housing and in the interim, those gases begin to heat up/scorch the housing/turbo system.
I recommend you use the wastegate properly on housings like the 12cm and even the 14cm housing. They do what they are designed to do...limit boost to keep you from entering that "high drive pressure" region.

No flame here ... just my thoughts for what little they are worth.

pastor bob...

 

hey pastor, how can i check the drive pressure? and what kind of #'s will i be looking for?

 

You can pull your pyro probe temporarily and rig up a gauge, use copper tubing for obvious reasons. From what I've read drive pressure is usually equal to or higher than boost pressure. Apparently 50 psi is not uncommon on the new trucks.

I'm gonna try turning the TurboMaster down to 28 psi, I'll let you guys know where the EGT's go. I've got a lot of respect for the pastor's teachings.

 

My 93 peaks out at 25 psi, should I hook up the wastegate. I can feel the backpressure on the 12 at about 2100 rpm and up it flattens out where with the 16 it would run up to 2600 fast. I like the 12 better because I get more boost a lower rpm. I don't rev that often, I try to drive at a about 16-1800 rpm, but I miss that extra 400 rpm when accelerating up hill getting ready to shift with a load.

 

With my HX35 and a 14 wastegated hot side I have set my wastegate to be fully open at 32 psi which equates to 30 psi at the intake manifold. This combination is very strong on the bottom end and excellant for towing. It also delivered 378 RWHP at Dyno Mania 2004. The very slight turbo lag I felt with the original turbo is gone.

In that trip from Portland OR to Surrey BC and back I saw 23.4 mph.

Bob

PS Stay tuned for comming events

 

I'll agree with Bob B.....
You don't really need to go thru the time consuming process of checking drive pressures..unless you want something to do
You should use a metal tubing like a steel line...maybe an armored brake line would work... then coil up about 4-5 coils maybe 3-4" in diameter. Run the line along the firewall and just before it reaches the firewall, put in a slightly larger piece of tubing and use a filter medium...no laughing here now....use a round "hygein" product...yup, you know what I'm referring to.
Then hook up to your boost gauge.
This test must be very short in duration for obvious reasons.

The alternative is to use the known map values as your guide.
A stock h1 series turbo is at it's map limit when it reaches about 26-27psi. The Hx series is a bit higher...maybe 28-30psi in new condition.
The real problem comes when you use a very small exhaust housing. While you may be "inside the map" on the particular turbo you are overdriving the compressor with excess fueling and no wastegate to protect your from overspeed.
Yes, you can drive these turbo's to high 30's and even low 40's but there is absolutely NO doubt you are well over the map limits and WAY over the ability to produce "usable" boost pressure at reasonable temps.
Just don't over drive them and you're good to go.

pastor bob...

 

I have been able to drive it for a while now with the hx 35 and it makes a huge difference on the bottom end, it starts making boost a lot sooner. I tow a lot so I think i'm going to stick with the 16 cm housing. Also looking at the 12 cm housing it looks like it is longer than the 16 and I would have to modify the exhaust to put it on, am I right or is it just my imagination.

I'm going to turn the pump up more now and see how much I can get now.

 

Yes, the downpipe needs to move back about 1.5 inches fro the 12 cm housing.

 

I just got back from a 1300 mile round trip to Kansas City & back...

HX35/12cm2 with wastegate welded shut.

Post turbo Pyro Probe...at 75-80mph empty I was at 550*

With a 22' Car Hauler, with a Ford Model A and a bed full of parts on the way home at 70mph I was at about 550*

With the Model A in the bed and a '54 Ford Sedan on the trailer...550* at 65mph

I maintained low EGT's by keeping the boost at the right level over the hills & grades. I like the 12cm2 housing, but wouldn't mind trying a 16.