Just got an email from Cummins Turbo Technologies. After a week of emails and questions, they still will not give me a compressor map for the 3rd gen turbo: HE351cw, but they had this to say,

"Good Afternoon,

Thank you for your enquiry,

I have spoken with our technical team and they have advised me that the HE351CW will supply a maximum of around 67 lb/min corrected to Garrett mass flow parameter.
This occurs at a speed of 130 krpm which we do not recommend to exceed (same applies to the HX35).

Kind Regards

Nikita Toulcher
Cummins Turbo Technologies Ltd"



Well, what do you all think? The S300 or HTBG, Super B only flow 61 lbs/min.

Sounds like I made a wise choice in switching to this turbo!

 

But...the turbine of those S300 variants will far outflow the stock 3rd gen one for getting the hot air and restriction out of the back side.

You can only put in so much cool air when you can't get the hot air out as quickly.

 

What PR does it flow 67 at?

 

They wouldn't give me a map, it's a guarded trade secret. But looking at an HX 40 map or Garrett map with similar wheel inducer/exducer looks like it happens around 3:1 pr ratio.

http://www.turbobygarrett.com/turbob...esel_tech.html

 

Please notice that the link I just posted is of a GT 3788R. When I measured the HE351cw, it had a 60mm compressor and 87-88mm exducer. So even though the GT3788R has a 64mm compressor, it flows nearly the same as the HE351cw.

 

Using BD's numbers:

Super B: 57mm 61lb/min 425HP

425/61 = 6.97 HP per lb/min

Super B Special: 64mm 80lb/min 550-625HP

550/80 = 6.88 HP per lb/min
625/80 = 7.81 HP per lb/min

So HE351 at 67 lb/min

67*6.97 = 467 HP
67*7.81 = 523 HP


Using Garrett's equation: HP = lb/min x 60 / (0.38x22)

67lb/min x 60 /(.38x22) = 481 HP

 

Big Blue you are in my mind a true grass_roots type of hotrodder Nice work!!!

 

Those numbers are valid, but be careful what meaning you draw from them.

As previously mentioned, the compressor is only half the story. While the compressor can flow the mass required to make bigger power, it cannot do so in the low rpm range and at the required obscenely high PRs needed to make power on our CTD.

A PR OF 3:1 will support 355hp at 2700rpm with perfectly sustainable EGT.

But at 2000 rpm, that same PR of 3:1 will only sustain 278hp.

I'd venture to say that you are going to be pushing this turbo well past the measly 28psi or so of boost that a PR of 3:1 represents. That's the problem. To gain the spoolup required for driveability and emissions concerns, the turbine is so tight that the compressor is overboosting and pushing drive pressure way too high.

If you were talking about this charger as a secondary for twins, it's no big deal because you'll be wastegating around the tight turbine most of the gases. But as a single you have no way to correct the turbine/compressor imbalance on a "smog" turbo like the HE351.

If you had the option of a 16cm housing equivalent, you might be able to come close to using some of that 67lb/min capability. As it is right now, your compressor might as well just flow 40lb/min, because that's all you can use.

That's why larger A/R housings are more efficient, and it's all part of the efficiency penalty we pay for faster response.

That's why I was looking at the two small chargers for secondaries-- I could improve response AND efficiency going that route.

JH

 

Hohn, I knew you would eventually see this thread. I am hoping that I can derive sufficient power from the little turbine to meet my airflow needs and then use my big gate to bypass excess drive pressure. Only time will tell, but it definitely lights harder than my HX did. I still haven't gone over 17 psi as I am waiting for my boost controller and a Saturday so i can afford being down for a couple of hours.

 

Can't wait until Saturday???--try this:

http://www.geocities.com/chmwatson/FAQs/mbc.html

 

BB, the problem is that it's not that easy. If it was, there would be no reason to ever choose a larger housing-- EVERYONE would just run a tight housing for spoolup, then wastegate off the excess TIP.

Wastegates are intended to be a secondary means of turbine gas flow regulation-- AFTER turbine housing choice.

A smaller housing simply can't drive the turbine as efficiently. In other words, take two otherwise identical HX35s on identical trucks in identical conditions-- but one turbo has the 12cm housing, and the other has the 16cm housing. When both turbos are making 20psi, the larger housing will be driving the turbine more efficiently, and EGT with the larger housing will be lower.

I think the factory housings are way too small, because they are optimized for maximum spoolup (emissions) on a ~245hp (in my case) truck. Banks thought so-- that's why their big kit includes a 14cm housing.

So what happens when you take an already undersized housing, the simultaneously increase HP and make the housing smaller? OUCH-- double whammy of steps backwards.

JMO

 

I see your point Hohn. I'm just going to have test and see how bad of a bottleneck the 9cm really is. I have now discovered that the turbine wheel is 1-2mm bigger than the HX's. But other than that, the exhaust side of this turbo does not look too promising.

 

I can't even emagine how hot that turbo would run even with the fuel I'm running on my truck! It sure would be nice if you could get away with just passing the excess gasess out the wategate.Time for a bigger turbo

 

Resurrecting this thread for inquiring minds. 499.2 HP on a second gen, and several 3rd gens have now pushed it to 520 HP. Simply amazing what this turbo is capable of.

 

the stock 3rd gen turbos will make some good power for sure! their biggest problem is the restrictive turbine housing and wheel. you'd probably pick up 20-30hp easy by going to something like a 62-71/.08, but would it be worth the money to you? maybe not