Adam W Posted April 25, 2003 Share Posted April 25, 2003 How many litres/minute of air is a 3l engine sucking in at 6000rpm? I was thinking it was 3l displacement x 6000rpm = 18,000l/m. Then divide by two because it's a 4 stroke engine. But 9000 litres a minute is an INSANE amount of air! We just got a new vac pump at work and I was hoping to use it for some flow restriction testing, but it's the size of a small bungalow and it still "only" does about 1000l/min of flow. I was thinking that would be plenty but according to my calcs it's nowhere near! Quote Link to comment Share on other sites More sharing options...
Adam W Posted April 25, 2003 Author Share Posted April 25, 2003 Plus if you're at high boost (say 1.5 bar for the purposes of the test) then you're using even MORE air . . . I'll be amazed if those numbers are right but I can't see where I've gone wrong . . . Quote Link to comment Share on other sites More sharing options...
Syed Shah Posted April 26, 2003 Share Posted April 26, 2003 Air capaciy (in Cubic inches per min) = (rpm x displacement (ci)) / 2 For the Supra (183ci) at 6000rpm, this gives us 549000ci per min (317.7CFM) or 8996l/min So eirther we are both wrong, or your calcs are indeed correct. After this, you need to work out V.E [ (actual cfm / theoretical cfm) x 100]. And, to work out what it actually flows, we need to know what CFM of air the turbos flow at a set pressure 1.2bar would be ideal)???????? Quote Link to comment Share on other sites More sharing options...
Steve Cargill Posted April 26, 2003 Share Posted April 26, 2003 This was done about a month ago. I did a search and came up with this thread. http://www.mkivsupra.net/vbb/showthread.php?s=&threadid=7326&perpage=3&pagenumber=7 I estimated 300L per second at 6K RPM and 1 bar boost using fag packet maths. Quote Link to comment Share on other sites More sharing options...
JamesG Posted April 26, 2003 Share Posted April 26, 2003 I think it would be a little less (about 7 per cent less?), as you've got to fit some fuel in there as well. James. Quote Link to comment Share on other sites More sharing options...
richardharmon Posted April 26, 2003 Share Posted April 26, 2003 If 7% of the 9000 l/min were fuel, that would be about 630 l/min of fuel! I thought that the correct air to fuel ratio was 14 to 1 by mass, not volume. Petrol is about 750 times denser than air (rough estimate) so under these conditions we are looking at about 0.8 l/min of fuel (0.009% by volume) based on the ratio by mass. Quote Link to comment Share on other sites More sharing options...
Steve W Posted April 26, 2003 Share Posted April 26, 2003 300 LITRES per SECOND ! ! ! that does sound a lot ! ? If you talk about it another way, 300L = ~66 'Gallons' of Air... That's ~1 1/2 x 45 Gallon DRUMS of air a SECOND ? ? ? ? THRU' the likkle air intakes ? ? ? JUST sit a count 1 second... " 0....1 " ...... and try to imagine 1 1/2 DRUMS of air SHOOTING up the air intake.... let alone trying to get thru' the air filter:conf: You're SURE we're not missin' something out ? ? ? Quote Link to comment Share on other sites More sharing options...
Syed Shah Posted April 27, 2003 Share Posted April 27, 2003 Originally posted by Steve Cargill I estimated 300L per second at 6K RPM and 1 bar boost using fag packet maths. Not as simple as that though. Because a T-88 will move more CFM of air at 1bar than stock turbos etc. Quote Link to comment Share on other sites More sharing options...
Steve Cargill Posted April 27, 2003 Share Posted April 27, 2003 Originally posted by Syed Shah Not as simple as that though. Because a T-88 will move more CFM of air at 1bar than stock turbos etc. The turbo will, but boost guages are normally fitted off the throttle body which is a fixed size. The air may well be cooler though and so denser for the same pressure. Quote Link to comment Share on other sites More sharing options...
Syed Shah Posted April 27, 2003 Share Posted April 27, 2003 But to move more air (higher CFM rating), at the same pressure, the bigger turbos would simply move it faster, wouldn't they??? That would allow for more air at the same boost pressure. But feel free to correct me here. Quote Link to comment Share on other sites More sharing options...
Steve Cargill Posted April 27, 2003 Share Posted April 27, 2003 Originally posted by Syed Shah But to move more air (higher CFM rating), at the same pressure, the bigger turbos would simply move it faster, wouldn't they??? That would allow for more air at the same boost pressure. But feel free to correct me here. Yes, they would at the turbo, but the restriction on the air going into the engine - where the boost is measured - will be roughly the same (possible small difference due to less back pressure during valve overlap?). At 6k RPM and 1 Bar there should be the same volume of air - mass could be different though. If it was moving faster you may get a bit of extra air pushed into the cylinder due to momentum of the air column. There was a big thread some time ago about different turbos and power levels at the same boost. Quote Link to comment Share on other sites More sharing options...
Guest Usmann A Posted April 27, 2003 Share Posted April 27, 2003 Great stuff! Quote Link to comment Share on other sites More sharing options...
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