Originally Posted by
gearhead1186
agreed here.
not sure what your saying here but it doesnt sound accurate.
now I really wish I saved the logs from the dyno. im not sure if your talking about a 3rd or 4th gear pull. if your assuming 3rd gear pulls on a load dyno, then yes multiple fans will provide you a very good estimate of what you would be making on the street. if your talking about 4th gear pulls, there is actually more of a difference than you think. end of 4th gear your doing about 130+. I havent been to any dyno or even seen pictures of a dyno cell where they can emulate that kind of airflow. I took 4th gear logs with my car and the IATs and timing was a lot better than the logs I took on my first 4th gear dyno pull.
dyno graphs are by no means the end all but assuming similar conditions they do give you very useful information by eliminating the biggest variable of all.. the driver.
sorry for the tangent... back to 60-130s
yes, sorry for taking it off the topic... last things though.
air flow is needed for 2 things - air volume needed to reach inside the engine into cylinder for detonation and air flow to cool the air going through IC's. we both agreed that for a single run, u do not really need to replicate 120mph air flow to cool off IC's, especially if u use W/M cause there is not enough time for temp to rise enough to hamper the output.
so the only thing that u need to replicate 120 mph air flow is for air that goes inside your engine. lets say that to reach your max power ECU requires 1 cubic inch of air to reach your cylinder at particular moment (call it amount Z). Air that comes through your intake through Air Box/Open air filter is amount X. that variable highly dependent on a speed of a car, since the faster u go, the more air flow goes into air intake. for NA car, final ammount Z can never be more then X. or u run reach and damage engine. so correct air flow is essential on a Dyno to replicate real world 4th gear run. in forced induction car, that is not the case, cause u have X (air from outside) + Y (compressed air from Turbos) = Z (final number in cylinder). now, lets say on the street @120mph X is 0.5 cubic inch. so for NA car, u can tune as much as u want as long as Z = X = 0.5 inch. on Turbo car, u have Y which will supply extra air volume needed (up to a point, depends on a size of Turbo). it does not need speed of airflow from actual 120mph, cause it is forced, meaning sucking in Air. with or without speed. power of suction depends on a RPM of an engine/spool of a Turbine. now, for a street @120 u get 0.5 from intake and 0.5 from Turbo = 1 inch = full power. on a Dyno, even if you X is smaller then 0.5 inch, your Turbo (Tial 770)
once spooled creates so much air that it will compensate any volume that u wont get from outside (X). so say u get 0.25 from outside, Turbo will put up another 0.75", for a total of 1" and u will get total power. On the street, extra capacity of Turbo is either recirculated or dumped into atmosphere, but there is always some extra there. safety margin. cause outside conditions varry on weather, ellevation, air flow, etc. so i doubt any tunner tunnes the car for 100% capacity of a Turbo... cause u never know what might happen in real workd, and Turbo will only do 80-90%, then u can screw up an engine. So physically, Turbo will compensate (up to a point) airflow difference from a fan on a Dyno and real airflow @120. that is why talk about not being able to replicate airflow @120mph is not really accurate for Turbo cars. cause they do not depend on it as much as NA cars... Volume of air provided by big Turbines (605/770/GT28/RS6) is so big, and internal volume of 2.7L is so small, that i do not see how that small difference in air volume between fan and 120mph going through tiny intake opening can create a big difference in actual output on a Dyno.
again, i am not saying it is 100% true, but in my mind it is simple physics.
ps: i have my flamesuit on... :-)
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I'm less than a few weeks away to see what a true 770 car can do in the 1/4...
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