How to read the HX35 & HX40 compressor map(s)

[dsm-onster]

Morphius, you are welcome to add any or all of this information to the Holset FAQ you are compiling.

The hx35 and hx40 has piqued the interest of many DSM enthusiasts, one of biggest questions for any little known turbo charger is what does the compressor map look like? There are several maps out there floating around for each. But there are misconceptions about flow because the numbers are misread or misunderstood.

Lets start with the hx3* series turbos. There are 2 compressors. The 56mm inducer 8blade and the 56mm inducer 7blade. The hy35 shares the same compressor as the hx35, and straight from the Cummins, Morphius received this compressor data in spreadsheet form labled HY35W-E7765AX which he plotted graphically. Much thanx to Nick (Morphius) for this and all the data he's collected and the continued input he's had on the subject of Holset turbos.

You must be logged in to view this image or video.

As you can see the flow axis (X- axis) is disguised as mass X SQRT( T/p). It needs to be converted. We see the same mass flow perameter on the hx30e-7765AX compressor map AND see a conversion on top to lb/min.

You must be logged in to view this image or video.

So to convert to 58lb/min from the mass perameter 76.5: 76.5 X 58/76.5 = 58 or 76.5 X .758 = 58lb/min. Also we see the same suffix 7765AX for this hx30e map. Also this map looks nearly the same shape as the map plotted by Morphius but with less rpm lines. Thus both maps are the HY35 map and the hy35 compressor flows 58lb/min at 60% efficiency. The 7blade hx35 compressor is identical to the hy35 compressor. Therefore the 7blade hx35 flows 58lb/min at 60% efficiency.

Now what of the 8blade hx35? On the hybridz forum one submitted the part number for the 8blade hx35 asking for the compressor map (before Holset began refusing to yield copies of their maps). And below is what he got. Notice the 7755AX suffix:

You must be logged in to view this image or video.

Clearly shows 53-54lb/min on the axis in the top of the map.

This was the largest hx35 compressor flow up through 1997. Here is a PDF published by Holset concerning their hx35 turbos and the map of their highest flowing compressor in the series. Largest HX35 compressor before 1998. Multiply the mass flow by 60 and then by 2.2046 to get lb/min. Close to the 60% flow of the 7755AX 8blade hx35 compressor map.

Another 8blade hx35 compressor map: Unofficial, but detailed.





Now lets get to the hx40. Here's two maps published by holset. First shows both the standard hx40 (58mm inducer 8blade) and the "super40" or "hx40 pro" compressor:

You must be logged in to view this image or video.

Remember that holset likes to use it's own mass perameter. The super40 doesn't flow 90lb/min. That would make it a little overhyped . Remember to multiply that number 90 by .758. Which comes to 68lb/min. The standard hx40 flows a mass perameter of 82 kg/sec*SQRT(T/p) or 62lb/min.

Here's just the super40 from a holset published PDF: largest hx40 compressor. Again convert to lb/min by multiplying by 60 then multiplying by 2.2046.

Here's the 8blade hx40 compressor map missing the 127K rpm curve for some reason (all the other similar hx40 maps have that rpm and same major diameter: click, click, click):

You must be logged in to view this image or video.

Here is it rendered in CFM with that last rpm curve included: standard high flow hx40 in cfm.




And finally here's a Cummins published PDF of all the highest flowing compressors of each frame size. Again multiply kg/sec by 60 then by 2.2046 to render lb/min flow:

You must be logged in to view this image or video.

These maps confirm the above numbers and maps.

So. . .

8blade hx35 = 52-54lb/min.
7blade hx35 = 58-60lb/min
8blade hx40 = 60-62lb/min
Super40 or hx40 pro = 68-71lb/min.

 

[viperlp01]

Ya that clears up my confusion on the x axis.. One other thing I have a hard time bringing in is where do you look at the map for the lb/min you should get.. Do you look into the center of the island or do you look at the very out side ring. Also what decides where in the ring you are??

 

[dsm-onster]

If you want to look at maximum safe flow look at the farthest 60% efficiency point to the right.

The flow of the setup (what's accurately logged) and the PR you are in determines where you are on the map.

 

[Morphius]

This is good. Cool. I'll be including this thread as a link in the FAQ.