I am just always so blown away by Bernie’s methodical and yet lighting fast diagnostics, watching Bernie makes me feel inadequate. Thanks Bernie for yet another great educational video..
Love the passion, Bernie! Fantastic seminar! Question on VE: the theoretical mass air flow (g/sec) = [inlet air density (g/L) x Displacement (L) x RPM (1/min)/2/60 (sec/min)]. For a 3.4L engine at 800rpm idle I get 9.7g/sec. Why is this not closer to the rule of thumb 3.4g/sec? Inlet air density I assume is 1.28g/L x 1/3 since the intake manifold pressure at idle is roughly 1/3 of atmosphere...
I'm studying this in depth to help diagnose fuel trim/lean problems now. Dry Air density at sea level 77 deg F is 1.184 g/L. (A penny is 2.5g for reference) Density is proportional to absolute pressure (MAP). It also depends on absolute Temperature, and to a lesser extent humidity. (search for Air Density Calculator) Pressure at sea level is 101.325 kpa, so you can think of a kpa MAP reading as a percentage of pressure and therefore density. So at an idle MAP of 26 kpa, air density is 26% of 1.184 = 0.308 g/L You must also take into account Volumetric Efficency (VE) of an engine which also varies greatly with RPM and MAP from about 60% to 90% +/-. (search for VE table) The RPM-VE relationship has to do with resonant frequencies of the intake and exhaust pulses in the manifolds and tuning these (think of playing a trombone). Max VE is always at peak torque RPM where the engine breathes the best. I have been using this info to try to calculate MAF, from speed density and always come up 10-20% more than I am seeing from my MAF sensor...(I don't have a known good/bad MAF sensor). I suppose I could always just unplug the MAF and see what fuel trim tells me, but what fun would that be :-), and besides that won't tell me if i have a vacuum leak or bad MAF. I was surprised at the MAP data when increasing RPM in Park when I graphed MAP, MAF, RPM, and Calculated LOAD, but then after thinking about it, it made sense. 27-->21-->24 Fuel consumption is MAF/14.7 while properly working O2 sensors are switching, and 12.7 under fuel enrichment at max power. Fuel density is 0.75 g/cc (75% of water). There are 231 cubic inches in a gallon, and 2.54^3 cc in a cubic inch.
Nice Question Ivan! I guess is because we have to consider ground elevation and air temperature into the calculations for proper air density. I recently found this channel, Bernie is awesome! Can't believe is still for free!
Ivan, the reason it is not closer to the rule of thumb, is because of the throttle plate, it is closed at idle. An engine at idle has a VE of 20% ish...The down and dirty formula I like is this (RPM/60) X (DISPl./2). So with your 3.4L engine at 800 rpm you get 22.7 g/s, BUT the engine is only 20% efficient therefore 22.7 - (22.7 X 0.8) = 4.5 g/s. But that 20% is also a rule of thumb. Theoretical Airflow for our use in diagnostics is best used at high engine rpms where we expect VE's of 80+%. I know it's been a year, hope this helps.
Every video I’ve seen from you is methodical and fundamentally gold! Thanks for spreading your knowledge, people like you make the whole industry better!
Around the 51 min. mark he speaks of the MAF voltage being low on this KIA. The "rule of thumb" measurement of 2.7v to 2.8v that he uses I 100% agree with, Just to point out this is a good number for a 6 CYLINDER engine... A 4 CYLINDER engine "rule of thumb" in my experience is 2.2V to 2.4V on the MAF testing. Great video as always.
Great explanation. I just replaced a MAF on my Toyota, getting code for lean on both banks. I only figured it was the MAF after running a 3 drive cycle procedure based on a Service Bulletin and seeing that the final MAF reading (with ignition on but engine off) was over the spec limit. New MAF did the trick.
Bernie great explanation. Can’t wait to watch the rest of your videos even the ones you have to subscribe to. Thanks so much for sharing your knowledge. Artie
The video is great, but I don't understand (21:00) the calculation. Let's imagine we have four cylinders engine - each revolution of the engine has TWO intake strokes. So if the engine produces 13,3 RPS, there would be 13,3 times 2 equal 26,6 Intake Strokes Per Second. In video we have 8 cylinders engine and only 3,33 ISPS. May be I haven't understood - English isn't my home language.
If the injectors have a higher rail pressure will they inject more fuel per ms if the injector hole size stays the same? Or is it just the size of the hole/time open that dictates how much fuel is injected?
Wow - amazing example of how to needlessly complicate the explanation of principles, that aren’t nearly as complex as all of this has been made to sound.
What occurs to me is that if the ALPHA N works, why are MAF sensors and MAP necessary in the first place. The car makers keeps making things more and more complicated every year.
Actually I just found out Bernie got a lot of his materials from the Bosch Automotive Handbook and just transferred the values into his tool. Smart. Been on a youtube fuel trim rampage and one of the other channels revealed his secrets
Hello,after Iam watching your video now I have a question in my mindthat I would like to ask you..in a 2.4 petrol engine at idle how could I get the right mass air flow (grams/sec) of an engine... Thanks .iam here in Darwin
It’s usually 2.4 Liter engine should be 2.40 grams per second that a rule of thumb to overcome the parasadic loss of the motor any questions feel free to ask
All your injector talk is irrelevant until you put it into an "engine", not a motor! Motor this, motor that, ain't none of ya replaced a windshield wiper engine! have you? How about a power window engine? Did ya replace one yet? No? An engine deals with combustion, regardless of internal or external. A motor is electrical, always! Both can provide a motive force, but only one runs on fuel. I feel we are too far past the time for kindness, it's time you and your kind start to get it right! It's not a motor, it's an engine. It's not an engine, it's a motor..... Learn the difference and teach it correctly!
do you just regurgitate nonsense you read on facebook and the internet? go look up the actual definition for a motor on google (it'll take you 3 seconds, promise) and get back to us. start thinking for yourself instead of going with whatever fresh meme is circulating. hint: google's definition includes pictures of engines
@@MrBeefsnorkel: Clearly you need to be properly schooled since you were obviously taught by the general ignorant populous. They have it wrong and so do you! Keep on regurgitating a lie if you like, but I'll keep on telling the truth the way it actually is!
Bro, maybe you are not aware that Bernie Thompson is probably one of the most respected and knowledgeable people in the United States at what he does. I just checked out your videos on reheating pizza on the barbecue grill and snowblower review and they kinda sucked.
