I calculated it at 445 CFM, but lobux posted above that the theoretical max is 439.37 CFM.

 

210.9 cubic inches/1728 cubic inches/cubic foot = 0.12204861 cubic feet displacement.

0.12204861 * (7200 rpm/2) = 439.375 assuming 100% Volumetric efficiency. Yes, there is a little rounding off going on here, but not much.

This is also sometimes expressed at (displacement in cubic inches x rpm)/3456


Also, the amount of air we need to make 306 hp at 6400 rpm as Lexus claims...first we have to assume 0.45 BSFC (brake specific fuel consumption) and a 12.5:1 air/fuel ratio which is pretty good for most NA applications. We get:

2.723 * 306 * 0.45 = 374.9571 CFM which means we have a volumetric efficiency of 96.0% at 6400 rpm. Since this is our power peak, it is safe to assume the engine will not ask for more than 375 scfm of air unless you modify it.

It is possible to see the MAF readings with the appropriate software, so you can calculate VE for the entire rev range because the MAF will tell you grams/sec (lbs/hour) of air entering the intake. An easy way of determining an intake's worth is checking this number before and after installing the intake. However, the software to monitor this parameter isn't exactly cheap and the equipment to datalog it is also not exactly cheap. It's also not horribly expensive.

Click here for more explanation of the formulae.

 

I already have all that datalogging equipment and software hooked up. Maybe someone should send me some intakes so I can datalog the MAF with them.

 

LOL ...

You only used 8 decimal places! I calculated my 445.0000000000 CFM by using 3.5000000000 Liters. I don't see any point in calculating anything without at least 10 decimal places.

 

Displacement is 3.4560095295464 not 3.5 liters. That's the number I used out to 10 places, but I'm sure Excel used an even more detailed number because I specified only bore, stroke, and number of cylinders. I thought I sent you that spreadsheet?

This would certainly end all the discussion about which one flows best. It would be obvious if any of them actually flowed better than stock and which of them flowed best.

 

I did think about datalogging the MAF curve with both of my air filters, with and without the carbon screen, with and without the OEM cold air snorkel, and with both of my intake tubes, but I wasn't sure how relavent the data would be considering the number of hours it would take to do (ie. changes in temp, humidity, barometric pressure, etc.).

 

The MAF compensates for all of that stuff. It wouldn't work if it didn't.

 

That's good to know. I figured the ECU would have to compensate via all its other sensors (IAT, coolant temp, etc.).

 

No, the ECM knows airflow from IAT (intake air temp - usually integrated into the MAF) and the hotwire system. See below for complete explanation. (Bet you didn't know they heat your intake air with the MAF...)

 

Yea, you know, you do that thing to the other thing and plug in that MAF into the intake for the ECU to butt dyno the system.

Yea...who am I kidding?

Good discussion so far. If only we can get some hard data on it. Maybe someone (ooo..I don't know...let's say CrazyIS) sends the aFe intake to someone else (let me just throw out another name here...Gernby) and we can ALL (more names...let me see...how about lobuxracer, Gernby and *cough me cough*) analyze it together.

 

I doubt the hot wire MAF changes IAT by even .1 degree, but I still think IAT would be an important parameter in conjunction with MAF to determine the effectiveness of an intake design. If IAT wasn't important, why would there be an IAT sensor?

 

where are the dyno's!

 

While I do believe dyno results are helpful, I don't think there is any way that a dyno will give repeatable enough results to prove a 1-2% change.

 

You know I was kidding about the MAF heating the intake air...

It would be cool to buy all these intakes and test them using the MAF data as the determinant...There aren't that many to test right now and we could probably eBay them after we're done. Anybody got a spare $1.5k to buy these things?

 

Of course I know that you know that I know you were kidding. I just didn't want to look dumb in front of my friends.

I think the MAF data log testing would be very interesting, but the results would reduce the value of most of the intakes when we (I) tried to get rid of them on eBay. This may be one of those things where we need to get forum members to sponsor the test, and then Paypal the resulting procedes back to those sponsors (by percentage) after the items have been sold on eBay. That would be the only way I would be willing to participate. I wouldn't want to shell out $1500, test them all, then hope to sell them all again for $1200.