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7-Blade HX35 vs 8-Blade HX40

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NewTurboTuner

15+ Year Contributor
535
21
Jul 21, 2006
Rslv, Arkansas
So if the 7-Blade HX35 flows 60lb/min, and the 8-Blade HX40 flows 60/min..... what are the pro’s and cons of the two turbos?

Why would anyone use a 8-B HX40 if they could get a quicker spoiling HX35 that’d make the same power?
 
The part you're missing is the HX35 will only flow that much *in a suitable turbine housing*. Often this means the HX40 will either spool near the same or possibly even quicker if it's being used in a small a/r turbine housing where the HX35 in the same size housing would be severely limited; of course that small housing is also going to hurt the HX40's ability to make big horsepower as well.

The common 8-blade HX35 compressor is 56/83mm and the common 8-blade HX40 compressor is 58/83mm...the 7-blade HX35 wheel is smaller at 54/78mm but is a revised design that is more-aerodynamic in addition to being lighter and allowing higher shaft speeds to be achieved.

So if you're using a DSM-flanged housing with a 60 lb/min goal go for the HX40 for sure as I don't think any HX35 in the .55 housing has made beyond the mid-50's. If you're using a T3 housing and would prefer something quick-spooling, forget both and use the HY35 which is a 54/78mm HX35 compressor on a 65/58mm HX30 turbine and was found on 99-02 Dodge trucks with an automatic transmission. The HY35 will have a straight outlet on the compressor cover just like the HX35....not to be confused with the HE341 from 03-04 Dodge trucks that has a 90* bend on the compressor outlet.
 
I should have specified which turbine housing, in my mind I don’t think about the smaller DSM housing for them. I think more along the lines of the Open-T3 Bep housing or the stock 12cm^2 HX35, & 16cm^2 HX40, because I want them to be able to run up to their full potential.

I’m in the process of deciding what Holset I want to go with. Over the years I’ve tried many very different turbos 14b, 16g, 20g, gtx2867r, FP3065, FP88HTZ. I like the idea of a budget friendly, robust, reliable turbo in the 500-600+whp range (e85).

I have trouble deciding if I could live with a 7-blade hx35 (reading as they flow around 60lb/min, same as 8-blade hx40). Or skip up to the super 7 & 6 Blade hx40.

I just wonder if I should skip over the idea of a 8-blade hx40, if it’s possible the 7-blade hx35 will give me the same flow but better spool too?
 
Other Holset turbos interest me aswell but I don’t see as much info on them and am worried I may get something I don’t want. What is the HY35’s max lb/min flow?

What about other hx37 type variants?

This all being discussed in the context of Open-T3 &/or T3^2 exhaust housings.
 
Bastarddsm I’ve spent hours upon hours reading through Tuners over the the last 11+Years I’ve been here. Searching and reading dosent always get you want you want to know. I’ve read enough past holset posts to know you had horrible taste for divided manifold setups how bought that LOL.

On the “Holset FAQ” thread in the discription of HY35 it still says it’s potential is untested. Maybe someone has tried it by now but I didn’t see where. How bought you contribute to the post instead of waste of your time with the age old “search”. Anyways the HY probably isn’t for me cause I’m more focused on more pwr, vs faster spool. I was just curious enough to ask it’s max flow that’s all
 
This is probably irrelevant but I ran both the 7 blade hx35 and the 7 blade hx40 in the .55 bep housings.

As far as spool goes, logged 400rpms difference.

Lbs/min:
50-53lbs/min - hx35
54-56lbs/min - hx40

And honestly I thought the hx35 was a lot more fun of a turbo for a street car doesn't seem like much but the 400rpms..
Was noticeable especially since I didn't change my Rev limit I kept it at the 8,000rpms for both.
 
slowwhite yes that does help. Even though it’s not 7bHX35 vs 8bHX40 gives good account of the spool differences. Although with the smaller .55 housing the spool maybe closer together, than larger T3 options.

If both the 7-Blade HX35, & 8-Blade HX40 flow at a similar 60lb/min (except HX40 has noticeably more lag), then it may not be any reason to run a HX40, unless it’s a 7 or 6 Blade HX40 that can flow closer to 70lb/min.

This is what I’m seeing and wondering about. Helps to more finely narrow the choices down between spool or top end power.
 
To the original post, I think the larger turbine wheel would be the the main difference, not just the compressor wheel specs. It would seem that even if the HX40 were to make the same power, you wouldn't have to lean on it as hard.

From where the thread is going, I'm not sure if the HY35 could be considered "untested" or "unproven" at this point. It's been in the 600whp range more than once and trapped around the 140's. It sounds like exactly what you are looking for, really.
If spool is a concern, and divided is out of the question, the manifold it's mated to should be looked at. Specifically small runner, which is efficiently matched to the power range of those turbos (HY35 or HX35 in the T3 open housing, and open T3 HX40).

Cheers!
 
The 8 blade Holset HX40 comes in sooner and has a smoother transistion to high boost. The 7 blade HX40 is 5-600 rpms later than the 8 blade but hits much HARDER. I can report later on the difference compaired to a Super 6 when the ole girl is back up and running later this year with new mods. :sneaky:
 
I wish I had a log on this computer to show how my 8 blade hx40 spooled on a .70 ar t3 housing. I want to say car was at full boost on wastegate (26psi as logged in link) by 4400rpm. my car went 10.89 but I was having fuel pump issues as well so I think it should've went faster.
 
That sounds about right for my 8 blade also. The difference was the strength of the motor when boost came in with the 7.
 
Just looked at my turbo its a 8 blade hx40 in
55 bep. But want to see what she will do on the .70 ar, with the twin scrolls set up. Plan on getting her running soon.
 
That’s good feedback on the 8 vs 7 Blade HX40. Seems I’ve read that less blades have better high Boost efficiency, and more blades have better low boost efficiency; makes sense.
 
All good feedback guys thanks. I ask because I’d like higher HP for a street/strip Drag-Grudge race car. But also my heart loves a hard hitting turbo, which is more fun on the street. I know I wouldn’t be unhappy with a HX35, but the car is targeting drag race so I need the top end too.

I already have a manifold bought for my setup.
You must be logged in to view this image or video.

It’s one of the old Punishment Racing T3^2 manifolds, 1.5” runners (schedual 40 I’ve heard). Im considering either 12cm^2 HX35, or 16cm^2 HX40.

The KICKER is..... mine is a Auto car. So Ive gotta buy a converter and turbo that match. Makes my desicion more complicated. But maybe that also means i don’t have to worry about spool as much if I go higher stall. Idk it’s my 1st Auto DSM so all new to me (part of the fun though).
 
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I' running a hx40 8 blade in a .55 housing, waiting to see how she does, it' a street car, but do have the t3 on my list if upgrades going , for low end torque not a high horsepower car.
 
All good feedback guys thanks. I ask because I’d like higher HP for a street/strip Drag-Grudge race car. But also my heart loves a hard hitting turbo, which is more fun on the street. I know I wouldn’t be unhappy with a HX35, but the car is targeting drag race so I need the top end too.

I already have a manifold bought for my setup.
You must be logged in to view this image or video.

It’s one of the old Punishment Racing T3^2 manifolds, 1.5” runners (schedual 40 I’ve heard). Im considering either 12cm^2 HX35, or 16cm^2 HX40.

The KICKER is..... mine is a Auto car. So Ive gotta buy a converter and turbo that match. Makes my desicion more complicated. But maybe that also means i don’t have to worry about spool as much if I go higher stall. Idk it’s my 1st Auto DSM so all new to me (part of the fun though).
You might want to contact @MorrisonFab and @beansblacktsi as they both have auto twinscroll hx35s and hx40s respectively.
 
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