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11-13-2001, 02:42 PM | #1 |
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CFM Flow Calculations, Graphs, Long
I have taken the liberty of calculating and graphing the EJ20 CFM rates given a 100% volumetric efficiency. Any real world flow results WILL be less than this. I have done it in 2.5psi increments from 5psi to 25 psi, and I have provided a baseline for 0psi. I have also included 3D graphs showing CFM flow based on throttle position at a given psi (20-100% throttle position @ X-psi)Hopefully, this can be of use to those of you who are selecting turbos. I know it has been for me
ASSUMPTIONS: 100% Volumetric Efficiency 85% Intercooler Efficiency 20 Degrees Celsius Ambient Temp 100% Compressor Efficiency (affects things less than you think in these calculations, btw, "normal" would be between 70% and 80% in the sweet spot) take care, rob p.s. Sorry it took so long, I had to find a photo hosting service that would allow direct links without paying Go ClubPhoto!
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Last edited by Conduit; 11-13-2001 at 05:02 PM. |
11-13-2001, 03:11 PM | #2 |
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right click the photopoint message, go to properties, highlight and copy the address and paste it into the browser address.
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11-13-2001, 04:48 PM | #3 |
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OK! Finally, I fixed it
This should spur some discussion |
11-13-2001, 04:50 PM | #4 |
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besides the assumption of 100% volumetric efficiency, what other assumtions have you made?
Great work BTW! |
11-13-2001, 04:54 PM | #5 |
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Excuse me, I am using 85% Intercooler efficiency, stock displacement of 1997ccs, ambient temp of 20degrees celsius, and a compressor efficiency of 100%, which I thought to be "ideal". I'd be happy to adjust these based on parameters you can come up with (if you want it mapped to a certain turbo compressor map, for example, to account for the obviously varying efficiency).
take care, rob Last edited by Conduit; 11-13-2001 at 05:01 PM. |
11-13-2001, 05:31 PM | #7 |
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Conduit:
What software are you using for this? Ben |
11-13-2001, 06:09 PM | #8 | |
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11-13-2001, 06:10 PM | #9 |
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Thanks for the graphs!
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11-13-2001, 06:18 PM | #10 |
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conduit... any chance you could plug in the numbers from this compressor map?
http://members.home.net/nmyeti1/ I have the PE1820 turbo compressor map on that page... -Nathan |
11-13-2001, 06:45 PM | #11 |
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I did this in Excel. When I get some time tomorrow, I'll do a sample map over on the PE1820. Pretty cool, eh?
I just have to get a handle on how to sample efficiency from the map, and we can do a volume of them for different turbos. |
11-13-2001, 06:53 PM | #12 | |
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Not sure on the A/R... depends more on where the points fall on the map. L A G, L A G , L A G, LAG, Sonic boom... hyper speed. Dreaming of a 2.5L spooling a T66 to 30psi. -Nathan |
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11-13-2001, 06:57 PM | #13 |
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I think you have T66 on the brain
I'll do that one too, actually. Also going to do the T04E 50 trim and the TS04, just to encourage uppipe developers *cough, discount, cough* |
11-13-2001, 07:08 PM | #14 | |
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-Nathan |
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11-13-2001, 11:50 PM | #15 |
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OK, here's the deal:
1. I've got a complete calculator finished. It is very accurate, but it does assume a constant VE, which it should not. I am too tired to correct for that right now, plus it's going to be useless since I can only base it on dyno output, which will change the whole thing depending on your mods. 2. The calculator will basically plot the corrected (for garrett maps, although I designed it to compensate if you know the manufacturer's baseline factors) lb/min flow of the engine @ x boost and x rpm. This creates a plot that you can overlay onto the compressor map and see _exactly_ what's going on. You can increase the accuracy of your map much more by accounting for the varying compressor efficiency. This also requires you to plug in 169 values. Or, you can assume a static efficiency and get a rough idea. I am not picking values out tonight, since I am supposed to be studying for a midterm...or, should start 3. The calculator is setup right now for rpms from 2000-8000 and boost pressures from 5-35psi. I assume this will be enough for most of us 4. The best news is, it's very modular, so I can easily adjust the resolution, etc. to best fit the map we are working with. What I need: 1. Someone to volunteer to retrieve data points out of compressor maps (for maximum accuracy, since the efficiency directly regulates the Temp-out of the compressor, and that is factored into the intake charge temp, which regulates the mass of the air going into the engine *breathe*). Or we can use the static value, as I said. I don't recommend this if you are looking at something crazy. AND 2. Someone to take a compressor map, and make the white part of the black and white map transparent. I have no decent graphics software. Then, we can overlay the two images together. Whatcha guys think, sound cool? BTW, I called it I-Calc. take care rob |
11-14-2001, 12:31 AM | #16 |
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BTW, Nathan, I ran the calc on the T66 using the standard EJ20...it's not pretty You aren't even on the map with this engine until 20PSI. To be in the efficiency range, you have to be at 35PSI, dead on my brother. You will also be able to support, sit down please, 986 cfm at 35psi at 8000rpm. There's the high end you wanted. I think you may need the 2.6 stroker
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11-14-2001, 01:11 AM | #17 | |
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WOW! I had wondered about that... what about a T61? -Nathan |
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11-14-2001, 01:30 AM | #18 |
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Done, I'm getting fast with these now
T61, begins spooling to 1 bar by about 4500 rpm (it will be higher in the real world), and isn't fully spooled at 1 bar until..7500rpm. BTW, two other turbos are starting to look really interesting... |
11-14-2001, 01:32 AM | #19 | |
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PM me if you want -Nathan |
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11-14-2001, 01:38 AM | #20 |
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Here's another one for consideration, again, remember, these are really minimums more than anything else, the actual rpms will be a little higher since I am using a static efficiency map right now and a 100% VE, but until more time is put into it...:
TS04, nicely spooling @ 1 bar @ 4500 rpm, fully efficient @ 1 bar, spinning like mad until 8500rpm nicely spooling to 22.5 psi by about 5k, nicely efficient til around 8k. (this pressure ratio is not in the sweet spot of this turbo). |
11-14-2001, 01:39 AM | #21 | |
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-Nathan |
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11-14-2001, 01:43 AM | #22 |
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Yes, all the maps I am using are here:
http://www.bsmotor.com/turbo/tabell.html BTW, take a peek at 40 and 50. TS04 is too burly for me I'm not building the 2.5 yet Hey, I can't see the entire pe1820 map, is something up with your site? |
11-14-2001, 02:16 AM | #23 |
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So I've been fiddling with the turbo calculator here. I plugged in a displacement of 2212cc (EJ22), a low RPM of 2500, a high RPM of 8000, and .9 bar (13.5psi), leaving the other values at their defaults. Even at this low boost level, that is over 400hp (and 544 cfm flow).
Does this sound reasonable? Shouldn't the calculator need the CR for the motor or does the VE take this into account? is the default VE of 95% realistic? If not, what is a better value? If the calculator is correct, what turbo is appropriate for this (specifically, would one of the RHF55 turbos like the VF30 or PE1818/1820 be in their efficiency range pushing that flow at that CFM)? Ben |
11-14-2001, 02:43 AM | #24 |
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Yep, that looks very close to accurate. VE is going to change with RPM, depending on how your system flows. The efficiency of the turbo will also be varying, affecting your intake temps and hence actual lb/min of airflow.
I can help you more if you can find me a compressor map for the turbos you want This thing has the capacity to be as fine-grained (or not) as you want. Think of it this way, that calculator plots 2 pts, this one plots 169 at once The CR doesn't actually matter, since it's a sliding scale each way for timing and CR. The VE is all that matters in these calculations. And you can never be over 100%, corrected. |
11-14-2001, 02:47 AM | #25 |
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I'd like to see it with the PE1820, for a start. If nmyeti's link doesn't work for you, email me for a local copy I have. I suspect the VF30 might work better (and I really want to see a map for the VF34).
Ben |
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