I am using a .81 P trim PT67, and I would like to measure the pressure differential(pressure ratio), on this, and some other turbos. I hope to get an accurate picture of what ARs, and trims are just too small to to get really fast spool and good top end. The intention is to aid me in my quest for the quickest spooling turbo that will make 450rwhp. So if you have done this yourself, where did you measure, and what where your results. Also, if you have not done it, but feel you know the best two places to be measuring, let me know.
I realise on the face of it the answers are obvious, but rather than assume I know what to do, I am asking the question. I will certainly be sharing my data. I am also using EGTs as a guide, but the more data the better. Last, if you used a particular set-up to measure that worked well for measuring, what was it. Thanks in advance, Carl

 

Hello, Helllooooo is there anybody out there?????

 

Carl,

i assume by "differential" you are attempting to relate exhaust manifold (EMP) pressure to intake pressure....

i have been logging EMP for 1200 miles on my setup and have learned a few things.

i run two TO4E 46 trims ( 82 lbs/min) w T3 backsides. this is my third summer ( wisconsin) of R&D and really the first period where i wasn't dealing w engine issues etc...

it is also the first summer where i added two logged pre turbo egts and an exhaust manifold pressure ( EMP) logger. i log both EGTs and EMPs.

based on EMP i switched up 2 housing sizes to .82 and a wheel size to stage 3. unfortunately i am working w T3 hots and you are T4. additionally i am using two of course.

currently i log 13 psi of EMP in the vacuum side of the map. at one bar my EMP rises about 7 psi to 20. spool is still excellent, one bar almost immediately whenever i put my right foot down. my turbos are designed to work optimally at one bar/ pump gas etc.

as to sizing...

i solve for the inducer area and the exducer area and divide by two.

my setup currently runs two 4.99 sq in compressor wheels and two 4.522 turbines for a ratio of 1.1 to 1. i previously was at 4.387 cold 4.339 hot. or 1.01 to 1. that was w .48 hotside housings. i dropped almost 20 psi of EMP w the switch to .82 and a 4% larger hotside wheel. no spool problems, less EMT and EGT and lots of topend.

comparatively,

turbine wheel sizing

my setup (w 2 wheels)----9.045 sq inches
O trim-------------------------5.422
P trim-------------------------5.894
Q trim-------------------------6.646

looking at Precision's site... the PT67 has a 3.31X2.62 cold wheel which works out to 6.998 sq inches. that should flow 57 lbs and make 430 rw rotary hp.

there are 4 hot side wheels... the 2.92X2.542 is 5.88 sq inches so the cold side is 19% larger. there is a 3.11X2.695 that is 6.65 making the cold side 5% larger. also a 3.2X2.96, 6.88 sq inches making the cold side 2% larger. the 3.11X2.695 wheel looks good to me.

as to housing size... set up a EMP logger and look for my approx numbers. as you find the optimum your egts will also optimize.

good luck,

howard coleman

 

Awesome info as always. A question, or two, and a link. According to your calculations, and others, this turbo should flow ~57lbs/min, yet HKS literature states 70lbs/min, and precision lists HP potential at 780hp. The dyno results for this turbo, tend to support the 70lb number(I think). for instance, on a Supra(apples to oranges, but an indacator of turbo capacity none the less), @ ~18 psi the turbo dynos 520-540rwhp, @25 psi ~600-635rwhp, and @30psi 680-760( I think the range here is due to wide variations in set-up and tuning). Anyway, are those numbers consistent with the 57lb/min calculation, or the 70lb/min statement? The size you would choose is the Q trim, which on a Supra, in back to back testing, yielded ~5% more top end, but a ~300 rpm slower spool to ~18psi. I also noticed that when the target boost is 25-30 psi that the spool up is dramatically faster. I think this is due to the boost controller attempting to prevent boost overshoot at the lower boost levels. The aforementioned phenomena is evident on many of the dynos I have seen. The higher the target boost, the faster the spool on EBC controlled cars. If you look at Andi Baritichis dynos at ~18, 21, 24, 28, and 32 psi you will see what I mean, the difference is unreal. Your thoughts? Thanks, Carl

http://www.moreboost.org/turbo_detail.htm#PTE67

 

Here is a dyno of the same turbo I am running at 29psi on a MKIV Supra. 70mph=~4000rpm, 90mph=~5000rpm. http://www.moreboost.org/graphics/turbos/CTC67_VG3.jpg

 

carl,

sorry not to have responded earlier but i was out of the loop for a couple of days.

my error re the PT67 flow. i just est'd off the wheel size. i am surprised at it's lb/min given the dimensions but it certainly backs up the 70 number w hp at the wheels.

assuming it is a 70 lb wheel...

a piston engine if optimised will make about 10 times the #.

a rotary will make 10 times the number divided by approx 1.3. (that's why i mentioned "rotary" rwhp.)

using your numbers on the supra site and equating them to rotary hp

18 psi---520-540---400-415 rotary
25 psi---600-635---461-488 rotary
30 psi---680-760---523-584 rotary

another method--

70 lb/min/10 times 144.71 cfm/1.92= rotary rwhp or 527

it would seem that if you are looking for quickest spool and 450 rwhp maybe you might do better w a slightly smaller (60 lbs) wheel. also i would pay great attention to the boost necessary to get the 60 pounds. road racing, as you well know, puts great heat stress on an already challenged system and if you can find something that does it at one bar you will be doing yourself a favor. perhaps the pt67 is the setup and you won't have to be running it at full blast to get your 450. btw, that's the reason i designed my twin setup. my turbos will make 82 pounds at one bar running 105,000 rpm w good efficiency and spool. great for road racing. i am still tuning so don't have numbers as yet. i am really shocked at how much fuel it eats in the upper ranges.



keep us updated,

howard coleman

 

Howard, Thanks, I'll keep everyone posted on the progress. I appreciate you taking the time to share the formulas. Carl