cougar

Still can't figure out what it is. Anyone have pictures?

Alec

The MWE slot is cut into the part of the compressor housing that surrounds the induction side of the compressor wheel. It allows air to leak back from the compressor wheel into the intake portion of the compressor cover. On the dodge applications, it was covered with a "silencer ring", which helped reduce the added whistle that the recirculating air produced. Allowing this air to leak back into the intake from the compressor wheel keeps the compressor from surging under high pressure low mass flow situations, thus allowing you to run a larger compressor wheel at higher pressures with low engine speeds. If you put a 12cm housing on a stock H1C turbo it is very easy to get it to surge in the 1700 to 2100 engine rpm range. (We spent months talking about that problem in these forums back in 2003.) I would NOT use a 12cm housing on a turbo without MWE. (I am nervous to contradict Mark, but I am reasonably sure the WH1C from the '94 trucks has MWE.)

In my opinion, the big question is at what engine rpm are your EGT's excessive? If you need to lower temps at 1700 rpm, you want a smaller exhaust housing, and a compressor that will work well with that . . . if you are running at 2800 rpm, and exhaust temps are rising, then you probably need a larger exhaust housing and a larger compressor wheel . . .

I am a "gear fast run slow" guy, for better or worse. On my old truck, I ran a stock 2nd gen hx35W with the waste gate actuator disconnected and was very happy . . . generally speaking, coolant temps became a problem before egt's. This was in small hilly country with 6 & 8% grades, but no 70+ mph highways. My "new" truck came with a PDR turbo and 16cm exhaust housing. Once I got the pump tuned to my liking, I could easily get toasty egt's in the steep hills, and really never got boost numbers much over 16psi (running empty). The turbo would start to really spool well with heavy fueling around 2000 rpm, but that doesn't work well for me in windy hilly country (50 mph is about 1950 rpm in direct). I finally installed a 12cm housing, with the wastegate wired shut. The truck is a whole different animal. You basically only need direct and overdrive when running empty at any speed over 30mph. On the other hand, running over 70, you are wasting fuel pushing excessive manifold pressure at low/no load.

For reference, this is from an article by "Calibrated Power". Obviously there are many factors that go into these results, but I think it is useful as an overall idea of the trade-offs in turbo selection.

Alec

Found this picture of a Holsett MWE slot after doing a search. You can just see the slot in the housing down at the bottom of the vanes and then opening into the area between the inducer and the collar for the intake tube at the bottom:

edwinsmith

I wondered what that was on my WH1C. The WH1C really performs well on my non-ic truck. It spools a lot faster which makes city driving a lot better. It's the most worthwhile upgrade I ever did.

Edwin

cougar

Thanks Alec, makes a lot more sense now. I will have to check the compressor housings to see if either has the slot. The HX probably does, the GDS housing not sure.
It's hard to pinpoint a particular RPM range as both boost and EGT sky rocket when you add even a moderate amount of additional fuel from where you were cruising. It's worse if you ad a load like a steep hill.
I think the 1st thing I need to do is get that 4" exhaust on. Then start playing with the turbo.

oliver foster

Be aware that the turbos with a wastegated housing will push the exhaust mounting flange back about a 1/2 an inch.

Use band clamps so you can move and adjust it as necessary if you swap turbos is my suggestion.

edwinsmith

When I put on my WH1C the pipe was pushed back. It almost hits the rear end housing. Someday I will get a muffler or a 4" system to fix it. Where it goes down from the turbo it is close to the firewall but not touching. I keep an eye on it though. Whenever I shut it down the dog shake makes something clang which I figure is the pipe hitting somewhere. Just to lazy to fix it.

ofelas

edwinsmith

I did that. I think it's just the tailpipe hitting the diff cover. I'll fix it someday but with my back getting on the ground hurts to much.

cougar

On my old 91.5 with the HTT turbo, the down pipe was against the frame. I used a rivet gun with a large diameter flush set to "modify" the pipe to get a 1/4" clearance. I wish I had kept that turbo now.

cougar

Yes it does, so where do I go from here?

Kansascrewcab76

I am running a HX35 from an 01, but my question is it worth it to upgrade to the 2nd gen charge pipes as well?

oliver foster

I would say it would be worth doing IF you also changed the intercooler and intake horn to the bigger diameter as well.
Using the bigger charge pipes but then necking them down into the 1st gen intercooler and/or intake horn seems worthless to me.

I used an HX-35 turbo, along with a 2nd gen intercooler, charge pipes, boots, clamps and intake horn on my '91.0 Poncho and my black crew cab.

Kansascrewcab76

lol, I posted that then thought, "nope have to change it all to really take advantage"
I have been looking at a PS intercooler, but modding the rad support is not in my plan. I need to just get this thing running