nocab72 Posted March 1, 2004 Report Share Posted March 1, 2004 Can anyone find me the CFM Flow Rates for a stock RB26? I've exhausted my searching skills... Trying to do some turbo modeling. Thanks! K Quote Link to comment Share on other sites More sharing options...
Devils Advocate Posted March 1, 2004 Report Share Posted March 1, 2004 Gee Kyle, lemme go check the manual for mi.... Oh, shit, I DONT HAVE ONE. I feel all inferior now Quote Link to comment Share on other sites More sharing options...
Trouble Maker Posted March 1, 2004 Report Share Posted March 1, 2004 Can't you just assume a certian VE. Use thoes and your known displacement and max RPM and you can caluclate air flow rate for a given boost pressure. This boost pressure (compression ratio on the compressor maps) and flow rate will put you at a certian point on the compressor flow maps. Or better yet you could find the compressor flow maps for your turbos and find a stock dyno chart. Use this and known or assume driveterian loss (will give you engine power). Assume a BSFC. Assuming a certian boost pressure (stock ECU can probably change it slightly) you could work backwards and calculate VE. These methods can be extended across the rpm range to make sure your not just sizing the turbo for max RPM but so that you don't run too ineficient down or hit compressor surge no-no land down low. Or if your calculating VE to calculate it across the RPM range as it might (will) change due to intake tract, exhaust tract, head and cam flow dynamics (as flow rate increases air speed will also increase, but differently obviously for different orfice sizes, then you reach super sonic and everything reverses, you go turblant and your power starts to drop off). I guess I'm kind of confused. Knowing your displacement, at a given RPM and manifold pressure, assuming a VE, there should be a given CFM (air flow rate). (If I'm remembering right, been a while since I brushed up on my engine/turbo theory, can someone back me up here). There are equations to do all of this. p.s. don't take any of this to heart till I go read up on my Croky Bell. Quote Link to comment Share on other sites More sharing options...
Guest stevil Posted March 1, 2004 Report Share Posted March 1, 2004 2.6L 157 ci 7500 rpms 10 psi Perfect NA CFM would be 340 CFM ((CI x RPMS)/3456). Using a VE like 90%, it would be less, like a realistic 307 CFM. Now add boost, and factor in various temps... is it 75 degrees out or 40? Using an intercooler? Numbers can vary so much based on temps... If you had an awesome water to air intercooler that cooled the boost way back down to 75 degrees ambient, you would use 516 CFM at 10 psi. (307 CFM x 1.68 density ratio). Looks like about the most CFM possible, or 35.6 lbs/min Other hand, if you had no intercooler at all, at 75 degrees, 10 pounds of boost and assuming 70% turbo efficiency, you would use 420 CFM (307 CFM x 1.37 DR), 28.9 lbs/min. If you had a front mount that was 50% efficient on a 75 degree day, same turbo efficiency, you would use 463 CFM (307 CFM x 1.5 DR), 31.9 lbs/min. For compressor maps, 10 psi would be 1.68 pressure ratio. CFM x .069 = lbs/min. Looks like you want something that flows good around 30-35 lbs/min. Quote Link to comment Share on other sites More sharing options...
Turbo Ben Posted March 2, 2004 Report Share Posted March 2, 2004 How about this Kyle, don't worry about it. Just slap a huge single on there, add a shit load of fuel, and call it a day. Quote Link to comment Share on other sites More sharing options...
nocab72 Posted March 3, 2004 Author Report Share Posted March 3, 2004 here is what I got, modeled after a SR20 example a friend found for me: http://flathat.woodstream.net/R33/rb26compressormaptech.html K Quote Link to comment Share on other sites More sharing options...
Brandon Posted March 5, 2004 Report Share Posted March 5, 2004 very cool, that may be a usefull example in the future Quote Link to comment Share on other sites More sharing options...
BiG BeN Posted March 5, 2004 Report Share Posted March 5, 2004 it'll be useful when i find that .6liter stroker kit. Quote Link to comment Share on other sites More sharing options...
Trouble Maker Posted March 6, 2004 Report Share Posted March 6, 2004 Originally posted by BiG BeN: it'll be useful when i find that .6liter stroker kit. It is based on equations that can be applied to any engine. Quote Link to comment Share on other sites More sharing options...
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