Well, it only took me several more years to get done than I had intended, but I finally had English Racing swap out my BBK Full for a journal bearing HTA Green. I dynoed the BBK Full when I got there, and then I dynoed the HTA Green just before I left. With no changes to any aspect of the tune, the HTA Green powerband started about 200 rpm later, made about 1 psi more boost across most of the powerband, had the same power to about 5000 rpm, and then made 25 more whp out the top. Used the same WGA for both turbos and WGA preload was identical on the two turbos. Still on MAF, and the cams are HKS 272/278 which Aaron characterizes as between and S1 and S2. I did a quick measurement of the exterior dimensions of the compressor and turbine wheels as the swap was taking place, and the green is about 1.5 mm large for both wheels. Overall, the two turbos are nearly identical in power and feel about the same on the road.

The car only made about 485 whp which falls a fair bit short of other HTA Green setups I've seen that are making ~525 whp, so I'm looking for things I can do to make up the difference. For sure I'll do an SD swap, and I'm thinking about switching to S2s.

Thanks to everyone at English Racing for their help today!

BBK Full: 410wtq/460whp
HTA Green: 410 wtq/485 whp



EDIT: I finally got around to plotting up the datalogs for the dyno runs and found a bit of a surprise. Without thinking about it too much, I was expecting the HTA Green to have a lower turbine pressure because of its larger compressor and turbine wheels, but to my surprise, it ran higher turbine pressure across the powerband. I was assuming that the larger wheels allow more flow and would result in lower turbine pressure. I think this is a pretty fair arguement for the equivalent power levels of the two turbos up to 5000 rpm, so I am definitely preplexed by the higher turbine pressure for the HTA Green at 5000 rpm and below. Above 5000 rpm, the HTA Green is making more power, so I suppose I shouldn't be too surprised by higher turbine pressures there. Still, I was hoping for lower turbine pressure... Makes me wonder what the BBK Full would have done if I had cranked up the WGA preload a little more.

BBK Full datalog


HTA Green datalog

 

Interesting, thanks for sharing your results sir!

 

Better late than never.

Thanks for you contributions to the community!

 

what an awesome back to back. never seen that for those two turbos. green is clear winner if you ask me.

 

Power seems low for such high boost but that setup is spooling like crazy!

 

Well it looks like what we thought it would do.

 

Wow, this was the opposite of what I was expecting.

Now I'm thinking I should have purchased a BB HTA Green.

 

Nice comparo. HTA green is down 50hp and ~40 lb.ft at 3500 rpm though, would have to feel lazier under 4K now.

 

Thanks for doing the comparison I'm thinking bout both these turbos but will probably go green since it has more power potential. Enjoy your new setup!

 

Awesome back to back graphs. Thanks for posting this, just helped me decide which turbo I wanna get. BBK Full FTW!!!

 

What I was thinking too. I remember Aaron saying something like 25whp out top a few years ago. Nice data and comparo mrfred thanks for sharing!

 

sounds bad stated that way.
the green makes the same torque. it just starts 200rpm later. 300tq at 3500 for bbk, and 3700 for green. so for 200rpm of suffering, it gains nearly 2000 rpm of 20+ horsepower.

 

Sounds bad for the BBK stated that way heh. Depends what you're sensitive to. I couldn't even handle how slow the BBK Full was to recover between shifts and spool, so I moved to the Lite which I love. I'd personally really feel that 200 rpm, but each to their own.

 

The BBK suffers from surge at the front end of the powerband, and in order to prevent it, I had to reduce the WGDC below 4000 rpm. Once I get rid of that WGDC reduction below 4000 rpm, I might get back another 100 rpm of powerband if not the entire thing.

 

You may be misinterpreting what the dyno curve means. The 200 rpm later, slightly more gentle onset of the powerband at the low rpm range is not necessarily an indicator of the turbo transient time. I need to do some street driving to figure that out.