HI!... If that formula is true, then that's probably why we are having a hard time getting any more power out of my truck with the stock heads and cams. I'm at about the limit right now in N/A for with the stock heads and cams. But that will be fixed soon............ eh MIKE?

 

maybe maybe not. i saw it in a magazine but magazines have been wrong before. only thing i can base it on is that the 2v heads flow about like the late 80's early 90's 5.0 mustang gt and you just dont see to many of those making more than 300 hp with stock heads and cams.
funny how ford has a 2 v head that flows 163 cfm and the 4v flows over 250. somewhere inbetween would make great power which is probably where the 3v is.

 

Hi BrotherDave & Neal,

Oh boy, these are the posts I dread, because despite my experience, I'm *not* a math major..............

There are all kinds of formulas, and like most hot-rodders I've used a number of them over the years, especially in race motors - but I don't recall if I've ever seen that one before specifically - I don't remember it off the top of my head.

The reality is I'm not generally competent enough in math to prove out or dispel various formulas - aside from spreadsheet work.

There are a few seemingly obvious points...............

We have to remember that CFM ratings are only accurate for the exact amount of pressure drop used to generate that specific flow rating - now 163 is not too terribly far off for a stock intake port on stock heads on a mod motor, but we still have to realize that this CFM rating is *only* at a specific pressure drop - everywhere else the numbers will be different, thus a set equation like that seems problematic. Engine rpms are a variable - if we spin the motor faster (I.E., in effect changing pressure drop), we can generally stuff more air into it - until we reach the actual physical flow/rpm limitations. Also, volumetric efficiency is not addressed, only by inference via CFM - so what are we going to assume as a maximum, 100% ve (load) on an N/A motor? Well, that might be fine with most stock N/A motors, but even with stock heads & cams we have customers with F-150's who are making that much power and more in N/A trim - we also have customers using stock heads & cams, normally aspirated, in these F-150's, who are showing in excess of 100% ve (load)............

So no, I don't necessarily buy that as a correct and true "absolute" limitation proving that we can only make a maximum of 335 HP NA on the 5.4 motor.

And once again, I do have to remind before this gets into a prolonged discussion of math, as I said before I am *not* a math major & thus can't really "hold my own" in such a discussion, despite my experience.

We also have to realize a little-known fact about the valvetrain design in the Ford modular motors, which is that at higher lifts and at higher rpms, on both SOHC & DOHC motors, the "rocker" (follower, etc.) does not have a consistent fulcrum point throughout the lift & rpm range - thus it does not yield consistent lift numbers, which skews such formulas drastically. There was a recent article in MM&FF that showed a company gaining in excess of 40 HP on a near-stock 4.6 DOHC motor (well, it had a blower that was disabled) just by redesigning the follower to effect a more consistent valve lift - no other changes were made to gain that power, just the change in the follower design, which allowed a much more consistent amount of lift with the same cams thru the rpm range. I think the article was called something like "Modular Rock & Roll," if memory serves, and was within the last 6 months.

So while I am by no means qualified to argue this mathematically, by virtue of our experiences and what I've seen others do, I don't buy that we are strictly limited to 335 hp in N/A trim for the 5.4 motor.

And for Neal - no, this is not why you are making "only" the power you are - which is darned respectable even with the tune being off with the 90mm MAF, as we've been discussing lately. Your power & A/F's on the 80mm MAF are not bad, but the 90mm tuning needs work, as it's running lean with the 90mm on there - as we suspected. And now, for the first time in 3 years, we finally have some data (albeit limited) to be able to do some proper work on the tuning of your truck - we had zero data before (in terms of A/F's, MAF, load, etc.). It's not easy tuning a custom application where the MAF has been changed by the seat of the pants with absolutely no data. Even with as many of these F-150's as we have provided custom tuning for over the years, while we got it close enough to not throw a check engine light with no data, there's just no way to know precisely what slapping a different MAF is actually going to do to load, timing, A/F's, etc., or what we need to do to make it dead-nuts on - that's why we need that data, so we can see the actual net effect - only *then* can we really correct for whatever is found.

The bottom line is, we'll definitely see some more power from the tune for that 90mm MAF on your truck, and you're already hitting in excess of 100% ve (load) with stock displacement values.