I am looking into replacing my GM-4 with the more common HX/HY35 turbocharger... Who has done this change and what can I expect?

I am aware of the fabrication issues regarding the exhaust elbow/Down pipe, What else might I be missing?

I don't care about all of the other mumbo jumbo in compressor maps and fitting it to a V8, I realize the HX/HY is designed for 5-6.5 Liter displacement engines(I.E. Inline 6 diesels)..


So, Please show me pics of completed systems and share the thoughts of the process... Thank you All for the input !!!!!:rockit:

There is some pics of my WH1C(the older brother to the HY35) in my garage.

This quote is from my post on another thread here at dieselplace called Turbo Swappin'

I used an Hx-35W for my 6.5L diesel project. A, 94 Camaro, application is much different than the truck platform, but FWIW here is some info and a pic.

About the Holset Hx-35W.

1) It has the same exact oil drain flange as the GM-4. The oil pressure inlet has a weird thread, so I used a Cummins OEM pressure supply line, cut it and spliced it to my own 1/4 oil feed line (from block)

2) Yes, the turbo can be "clocked" in different positions. Making it easier to adapt.

3) I don't have any type of drive pressure gauge (soon), but I'd place a bet on this thing being ALOT more efficient than the GM-X series.

4) The air inlet for the HX-35w is exactly 4 inches. So I bought a 4inch K&N filter, fits great.

5) The pressure outlet from the compressor has a flange, that needs to be mated to the OEM Cummins aluminum pipe with clamp, or have something welded on/cut off to adapt. The inlet on our 6.5L intake is 2.5", very similar.

6) Exhaust Turbine inlet is the exact same as any GM-X series

7) Exhaust turbine outlet. If you want to mate this with your OEM style exhaust you will need to do some fabrication. However, I bought a mild steel Hx-35W flange from FlEbay, bolted to the exhaust housing and welded a 3 inch exhaust pipe to it. It also holds the factory wastegate shut, so I can use the 40mm External one I have. if interested I'll try to locate the guy.

Hope this helps.

Midniteplowboyy, WOW...

Thank you for the information

That is an AWESOME setup you have!!!! When you get a Boos gauge please let me know what you get for PSI on the compressor side?? Just out of curiosity why did you use the H1C turbo? I realize its the predecessor to the HX/HY35, however the HX35 is capable of more performance..

Did you have a problem with the exhaust manifold adapting without modification?

Again thank you for the help, Your insight is VERY helpful and greatly appreciated.

This quote is from my post on another thread here at dieselplace called Turbo Swappin'

I used an Hx-35W for my 6.5L diesel project. A, 94 Camaro, application is much different than the truck platform, but FWIW here is some info and a pic.

About the Holset Hx-35W.

1) It has the same exact oil drain flange as the GM-4. The oil pressure inlet has a weird thread, so I used a Cummins OEM pressure supply line, cut it and spliced it to my own 1/4 oil feed line (from block)

2) Yes, the turbo can be "clocked" in different positions. Making it easier to adapt.

3) I don't have any type of drive pressure gauge (soon), but I'd place a bet on this thing being ALOT more efficient than the GM-X series.

4) The air inlet for the HX-35w is exactly 4 inches. So I bought a 4inch K&N filter, fits great.

5) The pressure outlet from the compressor has a flange, that needs to be mated to the OEM Cummins aluminum pipe with clamp, or have something welded on/cut off to adapt. The inlet on our 6.5L intake is 2.5", very similar.

6) Exhaust Turbine inlet is the exact same as any GM-X series

7) Exhaust turbine outlet. If you want to mate this with your OEM style exhaust you will need to do some fabrication. However, I bought a mild steel Hx-35W flange from FlEbay, bolted to the exhaust housing and welded a 3 inch exhaust pipe to it. It also holds the factory wastegate shut, so I can use the 40mm External one I have. if interested I'll try to locate the guy.

Hope this helps.

Did you do an external dump on your wastegate? Or plumb back into the exhaust at a place where you can do a smoother merge? Gotta be room for improvement over the common flapper valve's that merge so close to the exducer?

Are you using some type of standalone electronic boost control w/ the external gate?

Thanks much for sharing. These forum's really help evolve 6.5 ideas/hardware.

Did you do an external dump on your wastegate? Or plumb back into the exhaust at a place where you can do a smoother merge? Gotta be room for improvement over the common flapper valve's that merge so close to the exducer?

Are you using some type of standalone electronic boost control w/ the external gate?

Thanks much for sharing. These forum's really help evolve 6.5 ideas/hardware.

The wastegate on my setup is an external Synapse 40 mm. It is just like most gasser turbo setups. Yes, it dumps back into the exhaust and merges well. The flange on the exhaust housing holds the internal one closed, it is not used.

Take a second look at the pic in my previous post.

External wastegates are a great improvement over internal ones. it allows for more boost control, boost climb, creep, and ramp rate. I have a Manual (twist-knob style) controlling my boost pressure. Full adjustable from inside the cockpit. Synapse gate itself is also adjustable for boost, and valve pre-load.

The problem with internal ones, they are generally small in size and can be easily overwhelmed when alot of performance parts are added, to any turbo diesel.

For a mild truck application (turned up IP/boost, inejctors) an internal wastegate is more than enough flow.

For racing applications like mine go external.

Midniteplowboyy, WOW...

Thank you for the information

That is an AWESOME setup you have!!!! When you get a Boos gauge please let me know what you get for PSI on the compressor side?? Just out of curiosity why did you use the H1C turbo? I realize its the predecessor to the HX/HY35, however the HX35 is capable of more performance..

Did you have a problem with the exhaust manifold adapting without modification?

Again thank you for the help, Your insight is VERY helpful and greatly appreciated.

I've got it set to where it stays below 15psi for the most part, it'll creep up to 20psi if I stay in it hard/long enough though. I've seen it hit 25psi before I could get out of the throttle a few times when I first installed it trying to get the wastegate adjusted down.

I used the WH1C because I had it lying around, its off a 94 auto. I dont think I need a bigger turbo right now, I need more fuel, its matched up pretty well for the most part to my truck with 3.21 gears/low rpm cruise.

It'll bolt right on like the other holset's. The oil feed line is metric O-ring, its something like 12 x 1.5mm but cant remember for sure, I bought an adapter that went to the GM 1/4" pipe thread/ 3/8" flare adapter. Or you could go straight to the 3/8" 45º flare(think thats what size the GM oil line is).

The oil drain needs t be bent just a little. The hard part is the downpipe and aircleaner(4" compressor inlet also, I used a 4" 90º hose to a 3" pvc 90º pipe with a bung in the side for the CDR).

The wastegate on my setup is an external Synapse 40 mm. It is just like most gasser turbo setups. Yes, it dumps back into the exhaust and merges well. The flange on the exhaust housing holds the internal one closed, it is not used.

Take a second look at the pic in my previous post.

External wastegates are a great improvement over internal ones. it allows for more boost control, boost climb, creep, and ramp rate. I have a Manual (twist-knob style) controlling my boost pressure. Full adjustable from inside the cockpit. Synapse gate itself is also adjustable for boost, and valve pre-load.

The problem with internal ones, they are generally small in size and can be easily overwhelmed when alot of performance parts are added, to any turbo diesel.

For a mild truck application (turned up IP/boost, inejctors) an internal wastegate is more than enough flow.

For racing applications like mine go external.

I hadn't looked at the pic yet. Yeah, I've used a few Tial & HKS external 'gates on different past gas turbo engine projects. Either because the original setup no longer offered enough bypass capacity, or for faster, more precise control.

It's nice not needing blow-off or bypass valve on these diesels with no throttle plates.

Which turbine housing size did you use? I gather the 12 & 14cm2 are the most common & probably sized about right for a 250 - 275 hp 6.5 effort.

Which turbine housing size did you use? I gather the 12 & 14cm2 are the most common & probably sized about right for a 250 - 275 hp 6.5 effort.

Not sure. How would i go about determining that?

I've got it set to where it stays below 15psi for the most part, it'll creep up to 20psi if I stay in it hard/long enough though. I've seen it hit 25psi before I could get out of the throttle a few times when I first installed it trying to get the wastegate adjusted down.

I used the WH1C because I had it lying around, its off a 94 auto. I dont think I need a bigger turbo right now, I need more fuel, its matched up pretty well for the most part to my truck with 3.21 gears/low rpm cruise.

It'll bolt right on like the other holset's. The oil feed line is metric O-ring, its something like 12 x 1.5mm but cant remember for sure, I bought an adapter that went to the GM 1/4" pipe thread/ 3/8" flare adapter. Or you could go straight to the 3/8" 45º flare(think thats what size the GM oil line is).

The oil drain needs t be bent just a little. The hard part is the downpipe and aircleaner(4" compressor inlet also, I used a 4" 90º hose to a 3" pvc 90º pipe with a bung in the side for the CDR).


Midniteplowboyy, Thank you for the information.. I will be looking forward to building my turbo Swap.... When you ran the boost up to 25psi, how was the engine responding to the extra boost? How long was the 25psi sustained for? Also with the boost pressure at its highest(25psi): what was your EGT's during your boost pressure?

I hope I'm not boring you with these Questions?? I am really interested in learning as much as I can before this undertaking..

I am sure the Oil feed lines and return lines won't be a problem, also building an intake shouldn't be a problem either especially with your info. Again thank you for the help.. I am hoping that with a larger and more efficient turbo the EGT's will be lower..??????

Currently I am running Heath Diesel's HO Injectors, HP4 Program, so I am hoping that there is enough fuel to go with all of the EXTRA Air.. Correct me if I am wrong but you are running an Intercooler.

Not sure. How would i go about determining that?

From what I can gather, there have been HX-35 turbine housings in:
21cm2 - casting # 3519297
18cm2 - #'s 3519410 & 3522778
16cm2 - #3521927
14cm2 - #3580651
12
HY had a 9cm2 (not a divided housing like the others).

Haven't found any casting # documentation yet on the 12 or 9.

I've been told Dodge historically started the pickup Cummins 5.9 with big, loose, efficient at higher rpms, turbines as they figured most diesel pickup buyers would be familiar with that style diesel engine response. As the market grew & branched out beyond users that towed almost exclusively, buyers started asking for a more responsive, quicker accelerating diesel so Dodge/Cummins moved to the later, tighter turbine sections - until going to the variable vein types.

Midniteplowboyy, Thank you for the information.. I will be looking forward to building my turbo Swap.... When you ran the boost up to 25psi, how was the engine responding to the extra boost? How long was the 25psi sustained for? Also with the boost pressure at its highest(25psi): what was your EGT's during your boost pressure?

I hope I'm not boring you with these Questions?? I am really interested in learning as much as I can before this undertaking..

I am sure the Oil feed lines and return lines won't be a problem, also building an intake shouldn't be a problem either especially with your info. Again thank you for the help.. I am hoping that with a larger and more efficient turbo the EGT's will be lower..??????

Currently I am running Heath Diesel's HO Injectors, HP4 Program, so I am hoping that there is enough fuel to go with all of the EXTRA Air.. Correct me if I am wrong but you are running an Intercooler.


Its only run that much boost for split seconds, only long enough for me to get out of the throttle after seeing the guage spike, dont know how the EGT's were, I'm too scared to run that much boost sustained.

Like mentioned though its about all the air it needs for the fuel I got, untill I put a 4 plunger DB2 pump on it. Most of the time from a dead stop I can lay into and I'll be running 85 when the EGT's get to 1000-1100ºF if that helps, I rarely have seen it hit 1200ºF. Thats in a heavy truck, turning six 22" wheels/tires/adapters(about 800 pounds), with 3.21 gears in texas.

Yes its intercooled, 24"x12"x4" core, 3" inlet/outlet, but a 24x9x4 would fit better(top of mine dont do much its tucked up behind the bumper). Most of my mods are listed in my sig or garage.

9235-12-04 and 9500-12MM ,from discounthydraulichose dot com ,is what I used to make the oil feed line a bolt on operation.


HTH,