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HX-35 holset
- Thread starter Samyguy
- Start date
SmithvilleD
Active Member
SmithvilleD
Active Member
SmithvilleD
Active Member
This link shows a few pictures of some of the range of turbine housings (gated, non-gated, various sizes, etc.) combinations that are available. Holset has such a wide range of alternatives & you're not going to find a company that knows more about diesel turbocharging - anywhere on the planet.
http://www.gillettdiesel.com/DodgeCummins.aspx
6.2 turbo's comment regarding the wastegate passage size in right on the money. Stock 6.5's don't seem to be able to fuel enough for turbine drive energy to exceed the internal 'gates capability to bypass enough around the turbine, so under those conditions, the wastegate/actuator can keep control of shaftspeeds/boost pressure. Add enough fueling capability & there will be a point where drive energy exceeds the original 'gate passages. Also the way the bypass exh re-enters the exh stream on the typical 12cm^2 creates a good deal of turbulence.
It's not uncommon for folks to port such an internal wastegate hole & put in a bigger flapper - to gain bypass flow capability. Haven't seen that in person on an HX-35, but would be surprised if it hasn't been done.
By comparison, check out the HY-35 cut-away pics in the earlier link. The one where both the turbine exit & wastegate flapper are both inside the circular diameter of the exhaust. Been told this one flows notably better. Would make sense as the trucks that turbo went on were rated at 305 hp.
http://www.gillettdiesel.com/DodgeCummins.aspx
6.2 turbo's comment regarding the wastegate passage size in right on the money. Stock 6.5's don't seem to be able to fuel enough for turbine drive energy to exceed the internal 'gates capability to bypass enough around the turbine, so under those conditions, the wastegate/actuator can keep control of shaftspeeds/boost pressure. Add enough fueling capability & there will be a point where drive energy exceeds the original 'gate passages. Also the way the bypass exh re-enters the exh stream on the typical 12cm^2 creates a good deal of turbulence.
It's not uncommon for folks to port such an internal wastegate hole & put in a bigger flapper - to gain bypass flow capability. Haven't seen that in person on an HX-35, but would be surprised if it hasn't been done.
By comparison, check out the HY-35 cut-away pics in the earlier link. The one where both the turbine exit & wastegate flapper are both inside the circular diameter of the exhaust. Been told this one flows notably better. Would make sense as the trucks that turbo went on were rated at 305 hp.
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Slim Shady
DEATH BEFORE DISHONOR
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Since we are talking facts and figures did anyone ever figure out the drive pressure needed to make the holset work? I know Buddy figured out the A-Team numbers, just wondering how they compare and how are IAT temps when used on the 6.5? Hopefully valid questions
SmithvilleD
Active Member
100% valid questions.
I've driven a stock 6.5 w/ exhaust & an hx-35w w/ 12 cm housing. It's IAT's were lower than the stock turbo, but could certainly be driven too high w/ too much boost.
Push 17+ lbs of boost w/ any turbo & it can benefit from an IC. Purely physics. A mythical 100% efficient compressor, will have comp outlet temps above 10-12 lbs boost that could use some cooling. Don't have to have one, but it's not random chance most OEM engineered turbo systems running above 10-12 lbs boost come w/ charge air cooling of one sort or another.
It's a good ways in the future, but I'll be datalogging my VGT turbo project to generate the statistically significant data sample volumes necessary for scientifically valid conclusions. This requires data volumes from integrated/synchronized datalogging that we have not really seen on 6.5 turbo's. I've got a good deal of research exp in my background
On the VGT project, a guy working in our group of 6.5/VGT experimenters, inquired w/ Holset for info & they not only provided comp map/efficiency data, but sent the turbo test stand data which generates the maps & maps themselves, all integrated in an Excel spreadsheet. Pretty impressive how information is starting to flow from turbo co's once they realize there might be a significant aftermarket for turbo's.
I've driven a stock 6.5 w/ exhaust & an hx-35w w/ 12 cm housing. It's IAT's were lower than the stock turbo, but could certainly be driven too high w/ too much boost.
Push 17+ lbs of boost w/ any turbo & it can benefit from an IC. Purely physics. A mythical 100% efficient compressor, will have comp outlet temps above 10-12 lbs boost that could use some cooling. Don't have to have one, but it's not random chance most OEM engineered turbo systems running above 10-12 lbs boost come w/ charge air cooling of one sort or another.
It's a good ways in the future, but I'll be datalogging my VGT turbo project to generate the statistically significant data sample volumes necessary for scientifically valid conclusions. This requires data volumes from integrated/synchronized datalogging that we have not really seen on 6.5 turbo's. I've got a good deal of research exp in my background
On the VGT project, a guy working in our group of 6.5/VGT experimenters, inquired w/ Holset for info & they not only provided comp map/efficiency data, but sent the turbo test stand data which generates the maps & maps themselves, all integrated in an Excel spreadsheet. Pretty impressive how information is starting to flow from turbo co's once they realize there might be a significant aftermarket for turbo's.
Since I put on my hx 52 my engine revs higher , it now has more exhaust flow, the only way I see to make the hx 35 work with out to much drive pressure is a back pressure driven waste gate, providing it flows enough. The vgt turbo should be great. a turbo with a 10 blade turbine would be nice, the ATT turbo seems to have a great report it looks like a switzer.
SmithvilleD
Active Member
Yep, just different steps on the turbine wheel & turbine exit size. Stock turbo exit ~ 2.1", hx-35 2.6"
I'll be interested to see how low the VGT turbo can go (drive pressure-wise) & maintain adequate mass airflow for conditions. From turbine wheel size, I wouldn't expect it can go as low as the ATT reports; but certainly lower than stock 6.5 turbo's.
The turbo co's continue to improve blade aerodynamics & housings as computational fluid dynamics has made their design to marketable turbo process quicker & more effective. As materials improvements allow more efficient designs, they get to the actual testable prototype very quickly now. You see power levels coming from turbine sizes (more modern turbo's) that I can't imagine could flow enough from past experience. But the dyno doesn't lie.
As the 6.7 Cummins do make their 350 hp rating, the turbine can flow enough exhaust to allow that. But at what drive pressures? I don't think the 6.7's stock HE351ve turbo is the one to push for the way higher hp that engine foundation can tolerate. But it should be capable of more mass airflow beyond where I plan to go w/ my 6.5.
The 6.7 Cummins guys playing w/ opening up the turbine at hwy cruise further than stock programming are seeing significant mileage gains. Makes sense.
I'll be interested to see how low the VGT turbo can go (drive pressure-wise) & maintain adequate mass airflow for conditions. From turbine wheel size, I wouldn't expect it can go as low as the ATT reports; but certainly lower than stock 6.5 turbo's.
The turbo co's continue to improve blade aerodynamics & housings as computational fluid dynamics has made their design to marketable turbo process quicker & more effective. As materials improvements allow more efficient designs, they get to the actual testable prototype very quickly now. You see power levels coming from turbine sizes (more modern turbo's) that I can't imagine could flow enough from past experience. But the dyno doesn't lie.
As the 6.7 Cummins do make their 350 hp rating, the turbine can flow enough exhaust to allow that. But at what drive pressures? I don't think the 6.7's stock HE351ve turbo is the one to push for the way higher hp that engine foundation can tolerate. But it should be capable of more mass airflow beyond where I plan to go w/ my 6.5.
The 6.7 Cummins guys playing w/ opening up the turbine at hwy cruise further than stock programming are seeing significant mileage gains. Makes sense.
On my 12 valve cummins I checked drive pressure on the h1c it reached as high as 70 psi at high rpms and not even much boost , you would never have know it ,I noticed it was directly related to rpms, at peak boost of 58 psi drive pressure was also high,the cummins dont mind quit as much. I never checked it on my 6.2 or 6.5 with that same turbo, wish I would have. I waste gated my hx 35 on the cummins at 40 psi back pressure and it will still almost hit 50 with the waste gate open, which is why Im not sure the 6.5 wont over boost past your wast gate setting since they have lots of exhaust flow.
SmithvilleD
Active Member
The key is the actual amount of mass airflow/exhaust flow. Not necessarily the engine displacement.
This is one of the things most of the diesel turbo books don't do a great job of explaining. Too many simply provide a table w/ displacements, & assume (not all that accurately) a 100% volumetric efficiency. ve varies at different operating points & our 6.2/6.5 heads designed so long ago aren't gonna get 100% ve done.
Yes, at idle/zero boost, a 6.5 is moving more lbs/min air. As the boost pressures & turbine drive pressures vary & change the "pressure balance" across the engine, all bets are off, as to simply saying the bigger displacement engine is moving more lbs/min air.
If everything else were equal, it would take less boost to make a given hp/torque w/ a 6.5, than 5.9 of displacement.
The variables: DI - vs - IDI, stroke/piston speed, & all the rest, make the issue less easy to see/compare by just looking at displacement & hp/torque.
But the boost level/hp made/displacement relationship is there. It sounds like you're around a pulling environment. If so, you'll prolly have noted the relative boost pressures run/hp made differences btwn the Cummins & Duramax folks.
This is one of the things most of the diesel turbo books don't do a great job of explaining. Too many simply provide a table w/ displacements, & assume (not all that accurately) a 100% volumetric efficiency. ve varies at different operating points & our 6.2/6.5 heads designed so long ago aren't gonna get 100% ve done.
Yes, at idle/zero boost, a 6.5 is moving more lbs/min air. As the boost pressures & turbine drive pressures vary & change the "pressure balance" across the engine, all bets are off, as to simply saying the bigger displacement engine is moving more lbs/min air.
If everything else were equal, it would take less boost to make a given hp/torque w/ a 6.5, than 5.9 of displacement.
The variables: DI - vs - IDI, stroke/piston speed, & all the rest, make the issue less easy to see/compare by just looking at displacement & hp/torque.
But the boost level/hp made/displacement relationship is there. It sounds like you're around a pulling environment. If so, you'll prolly have noted the relative boost pressures run/hp made differences btwn the Cummins & Duramax folks.
SmithvilleD
Active Member
Another good point on the drive pressure subject is what's tolerable for short durations - vs - what's tolerable on a pickup diesel that might get headed up a mountain towing heavy (& have to run under peak drive pressure conditions for 3 minutes - vs - 30 seconds).
Some of the incredible 1/4 times heavily turbocharged drag cars run, are done at ridiculously high drive pressures. Surviving for 9 seconds is doable. Same setup won't live long under top speed highway/track conditions.
Some of the incredible 1/4 times heavily turbocharged drag cars run, are done at ridiculously high drive pressures. Surviving for 9 seconds is doable. Same setup won't live long under top speed highway/track conditions.
You are right . Im going to say look at the rpm difference, a cummins peak power might be as low as 1500 rpms the 6.5 around 2500 rpms that and more displacement is a little bit of an issue. Always wondered why my 6.2 wouldnt rev past 4000 rpms even with a locked governor ,now I know, the exhaust was clogged.Must be why some people put parallel twins on 6.2 and 6.5s.
SmithvilleD
Active Member
Yes, on the manual tranny trucks (especially), you can physically feel things "tighten" up as the comp & turbine approach their limits/choke points.
Vibration builds above 2500 rpm, almost seems as if you can feel the cylinder exh puffs struggling to escape the cylinder :smile5:
I'm in no way saying the HX-35 is ideal for a 6.5 if you goals go beyond say ~ 275 hp. Because at that point, you're heading beyond what it can do well. But practically speaking, what % of 6.5 enthusiasts actually intend to go past 275 hp? And it looks to traverse nicely across the meat of it's comp efficiency (bit below it's ideal PR (boost) efficiency) where a lot of 6.5's will be doing a big chunk of their work.
Certainly some go past 275 hp. Lots don't.
For the more conservative goals, the HX-35's low cost availability & T3/easy adaptability to fit to the 6.5, make it worthy of consideration.
Regardless of what turbo, I think there might well be turbine flow/efficiency gains if we could do a more reasonable bend from where the stock 6.5 turbo location puts the turbine outlet.
I've gotten pictures from a few forum go-ers w/ body lifts to see what impact that might have on turbine outlet routing options.
Vibration builds above 2500 rpm, almost seems as if you can feel the cylinder exh puffs struggling to escape the cylinder :smile5:
I'm in no way saying the HX-35 is ideal for a 6.5 if you goals go beyond say ~ 275 hp. Because at that point, you're heading beyond what it can do well. But practically speaking, what % of 6.5 enthusiasts actually intend to go past 275 hp? And it looks to traverse nicely across the meat of it's comp efficiency (bit below it's ideal PR (boost) efficiency) where a lot of 6.5's will be doing a big chunk of their work.
Certainly some go past 275 hp. Lots don't.
For the more conservative goals, the HX-35's low cost availability & T3/easy adaptability to fit to the 6.5, make it worthy of consideration.
Regardless of what turbo, I think there might well be turbine flow/efficiency gains if we could do a more reasonable bend from where the stock 6.5 turbo location puts the turbine outlet.
I've gotten pictures from a few forum go-ers w/ body lifts to see what impact that might have on turbine outlet routing options.
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Samyguy
New Member
PIC's???
Acesneights1
New Member
FWIW the Guys running 60+ PSI Boost on Cummins usually either or ing the block or run fire rings. I wonder if that could be done to a 6.x .
I was looking into o ringing my 6.2 heads , sounds like it would be easier to do the block,also stock head gasket fire ring is a wire so dont know how wire on top of wire would work ,my cummins has stainless wire oringed head. If the 6.5 gaskets were made like the cummins gasket there wouldn't be a problem , probably wouldn't even need orings.
Michaeljp86
EVIL GENIUS
You had 60psi on a 6.2? I thought 25 was max with 18:1 compression?
25 is probably max safe boost,60 was maxing the turbo ,all turbos will peak at a certain psi when over fueled, I estimate my compression at 16 -1. Boost is also directly related to fueling you need lots of fuel for boost that high.
NCadam
New Member
so whats the best way to control the boost on a hx35 keeping it at about 18-20 (intercooled and head studs)???