Holset hx35/40 vs hx40 w/ 12cm housing. Spool question.

[boostadd1ct]

This isn't going on my dsm going on my other project car with inline 6 2.5L.
Im asking here since I know tons of people run holset here. Not so much on the other forum.

Anyways hopefully you guys can help me out with this.

I want something for street use that can make 600rwhp on pu mp with meth.. Or if possible just pump gas. I also want a faster Spool as posible.

I've decided that hx40 is my main option.
My question is this. How much slower will an hx40 with a hx35 12cm housing that's been machined-spool compare to a hybrid with hx35 turbine and housing also 12cm

I'd like to go hybrid but should the turbo blow I'd like to just be able to pick up another cartridge and swap it in. An hx40 will be able to do that with machine 12cm hx35 housing.

A hybrid would require rebuild should it blow.

Both will be utilizing true twin scroll.

Is there any other smaller housing I can get machined to fit the hx40?t3 or t4. Twin scroll prefered. Unless it will out spool a twin scroll set up and meets my goal.

And yes I search. But i don't think the tech covered this.

Thanks

 

[JusMX141]

My question is this. How much slower will an hx40 with a hx35 12cm housing that's been machined-spool compare to a hybrid with hx35 turbine and housing also 12cm

...and my answer is it's literally impossible to know, ESPECIALLY since you're not using it on a 4G63 which is primarily the user base of our forum.

Is there any other smaller housing I can get machined to fit the hx40?t3 or t4. Twin scroll prefered. Unless it will out spool a twin scroll set up and meets my goal.

I've seen guys get 12cm2 HX35 housings machined for a HX40, but I know the inducer tip height on a HX40 is more-narrow than a HX35....10mm on the HX40 versus 11mm on the HX35. Doesn't seem like a lot, but it can make a difference in spool when the center housing sits in at the same depth. I'm not sure what they're doing to combat this- possibly machine the groove deeper by 1mm them machining 1mm off the face of the housing as well.

I'm sure it can be made to work but I don't know what the cost of doing so would be.

 

[boostadd1ct]

...and my answer is it's literally impossible to know, ESPECIALLY since you're not using it on a 4G63 which is primarily the user base of our forum.


I've seen guys get 12cm2 HX35 housings machined for a HX40, but I know the inducer tip height on a HX40 is more-narrow than a HX35....10mm on the HX40 versus 11mm on the HX35. Doesn't seem like a lot, but it can make a difference in spool when the center housing sits in at the same depth. I'm not sure what they're doing to combat this- possibly machine the groove deeper by 1mm them machining 1mm off the face of the housing as well.

I'm sure it can be made to work but I don't know what the cost of doing so would be.

thanks for the reply. Ya after you explained it like that I may have a hard time finding a machine shop that can do that. for relatively cheap that is.

hmm i guess hybrid it is then.

thanks

 

[Boostdriven]

I've ran HX35/40 hybrid on my brothers DSM with 12cm HX35 housing on a none divided manifold and I want to say it would hit 30 psi at about 4500 rpms in 3rd gear. HX35 12cm housing is about the same size as bullseyepower (BEP) .70 a/r T3 single scroll and this housing is proven to make serious HP in the DSM world. You can get BEP housing for either HX35 or HX40 and it would spool about the same as a 12cm housing on either or the turbos, hybrid or HX40.

12cm housing is about the smallest divided housing u can get for the holset turbo, at least as far as I know. If you already have a divided manifold you can run a none divided housing with that manifold without any sacrifices. On your engine I would say you would see 30 psi of boost around 3600-3900 rpms with a hybrid turbo and 30 psi around 3900-4300 with a straight HX40. If I remember correctly there is a company that makes T3 .63 a/r housing for the HX35, its not internally gated and I believe it has a 3" v-band out. You could run that housing on HX35/40 hybrid and would get even faster spool, probably 30 psi around 3400-3700 rpms but I think that housing might be a bit small to make 600 on pump gas.

Also keep in mind that in order to make HX40 wheel fix HX35 chra you will have to machine the chra behind the compressor wheel to accommodate for the larger exducer.

 

[Awd-laser]

If running the twin scroll 12cm housing on a single scroll manifold, how much of a difference would knife edging the center make?

 

[JusMX141]

If running the twin scroll 12cm housing on a single scroll manifold, how much of a difference would knife edging the center make?

Knife-edging is bad...I recommend rounding the divider.

Knife-edging creates turbulence by allowing the exhaust flow to shear, changing the striking angle...which can cause inconsistent velocity through the formation of an eddy (think fluid dynamics, not Van Halen ). Rounding the divider gives the fluid a smooth path to travel no matter the angle of entry.

Think of it this way- the honeycomb found in a Karman Vortex Mass Airflow System adds a bunch of knife-edges for air entering the sensor to flow over. Knife-edging encourages an eddy or "whirlpool" effect just after the flow division...this whirlpool is what the airflow sensor actually reads to determine airflow. Remove the honeycomb and you increase flow but reduce the sensor's ability to do it's job.

 

[Boostdriven]

Knife-edging is bad...I recommend rounding the divider.

Knife-edging creates turbulence by allowing the exhaust flow to shear, changing the striking angle...which can cause inconsistent velocity through the formation of an eddy (think fluid dynamics, not Van Halen ). Rounding the divider gives the fluid a smooth path to travel no matter the angle of entry.

Think of it this way- the honeycomb found in a Karman Vortex Mass Airflow System adds a bunch of knife-edges for air entering the sensor to flow over. Knife-edging encourages an eddy or "whirlpool" effect just after the flow division...this whirlpool is what the airflow sensor actually reads to determine airflow. Remove the honeycomb and you increase flow but reduce the sensor's ability to do it's job.

Agreed also knife-edging cast is bad idea because cast after many heat cycles it has a tendency to crack. The knife edge would be a weak point and the last thing you want is a piece of metal going through your turbine wheel.