The F119 power modification thread

And now for the subject of the intake manifold.

In my opinion this is where THE BIGGEST restriction is in the induction of the stock engine. As we know Ferrari runs the engine like two 4bangers. Splitting the f119 in half, the way Ferrari has it breathing, 3405cc ÷ 2 = 1702.5cc or 1.7L of displacement for each bank of the engine. Few years back, to satisfy my own curiosity, I cc'd the stock plenum and each side of the plenum came in at 1825cc, or 1.8 liters of air. What do you know about that? A 3.4L engine breathing through a 1.8L plenum. So it appears that the stock plenum volume would be plenty adequate for supplying the air the engine needs.

Or is it?

A rule of thumb I am familiar with is, you want the plenum volume to be 1.2x to 1.5x times engine displacement. Keeping with Ferrari's half/half intake system, and breathing based on 1702.5cc (half the engine)/ 1.7L of displacement x 1.2 = 2043cc / 2.0L of plenum volume the engine would need. While the smaller chamber volume of the D/G engines may be okay for lower rpm, it wasn't enough to satisfy the needs of the H engine at 7750rpm. I think it's a pretty safe bet to assume at higher rpms each plenum is completely evacuated of air, and the engine is left sucking through the 54mm TBs. After having running these numbers it becomes a little more clear with the H block engines got a taller plenum. I will not be surprised if the H plenums cc at 2.0L. But that was the lower rule of thumb. Multiplying the estimated plenum sizing by 1.5 engine displacement x 1702.5cc = 2553.75cc / 2.55L of plenum volume. Uh Oh , me thinks me sees a problem and that problem is NO AIR!!!

But wait is gets worse.

I read this SAE paper on plenum sizing on small restricted engines The Effects of Intake Plenum Volume on the Performance of a Small Normally Aspirated Restricted Engine I think our engines qualify as small and restricted. They tested plenum volume from 2-10x engine displacement. Up to 8x displacement they saw small gains, and over 10x displacement they saw much better gains. A plenum 10x the displacement of the f119 would have to hold 34,050cc OF AIR!!!! There is no way we could fit that under the engine lid. Well NO WONDER individual throttle bodies make more power, they have the entire atmosphere to breathe from.

But hold on, let's think about this a minute. Run as two separate 4 cylinder engines the plenum would only see an induction pulse once each intake stroke. Dividing the entire engine displacement 3405 ÷ by the number of cylinders 8 = gives each cylinders a displacement of 425.625cc, I'll round that up to 426cc or .426L per cylinder. Now multiplying 426cc X 10 = a plenum volume PER cylinder of 4260cc, or 4.2L of air.

Yeah that stock dinky ass little 1.8L plenum just ain't gonna cut the mustard.

I believe this is why AndyH's, and Steve Maxwell's f119s are making north well of 400hp, and why the Dyson race car makes 500+hp. Their engines aren't being suffocated anymore. Their modifications (ITBs/HUGE plenum & TBs etc) allow the engine to ingest the amount of air it is capable of taking in, and thus make the power the f119 is capable of producing.

 

Ah yes, good ol' Helmholts resonance.

Let's have a look at resonance tuning, yet another reason why the f119 doesn't make the power it's capable of.

Resonance tuning an engine has been around since the 1960s. Mitch I'm sure you understand and know the formula for it.

For those of you that want a more scientific explanation of Helmholtz resonance I'll leave it to "those educated in acoustical tuning". Here is a paper from the University of Minnesota http://www.me.umn.edu/~hork0004/2006-01-3654.pdf and another paper from Duke Universtiy on the subject. http://dukespace.lib.duke.edu/dspace/bitstream/handle/10161/8818/Shami_duke_0066N_12365.pdf?sequence=1

But for those that don't, and for the rest of us Stooges,

Basically what happens is, as air is entering the engine through the intake it starts to resonante (vibrate). Based on the length and diameter of the runner, or the volume and shape of the plenum, or the length of the intake pipe, it will resonate at different frequencies. The resonating creates pressure which contains energy. The next time you are at a car show, go to the audio area where the stereo shops have the cars that pump out the bass. If you are allowed to sit in the car do it. When they crank up the volume you can actually feel the acoustical pressure of bass pushing against your body. That same accoustical pressure is created in the intake at certain rpm's and can be used to force more air into the cylinder.

When the air is traveling down the runner into the cylinder it has energy built up from the momentum of the air. When the intake valve closes all that engery bounces off the back of the valve and travels back up the runner. Once it gets to the end of the runner it turns around and travels back down towards the intake valves again. Once it gets back to the intake valves that would be considered the 1st bounce, or the 1st harmonic resonance. Back and forth, back and forth it bounces inside the runner. As it bounces it loses energy. Think of it like when you drop a rubber ball. The 1st bounce of the rubber ball is the highest, the 2nd less high, the 3rd bounce less, the 4 bounce even lower, so on and so forth until the ball stops bouncing. Same deal with the bouncing pressure wave (resonance) inside the runner. The object of resonance tuning is to capture the energy of the bouncing wave and time it so that the intake valves open just as the wave is arriving at the valves, and thus force more air into the cylinder. This can be done by adjusting the length of the runner and the cam timing.

There is a basic formula for estimating the length the runner needs to be in order to capture the engery from the the harmonic resonance. In an ideal world you would want to capture the 1st order harmonic resonance. If I remember correct to tune for the 1st order harmonic you need to dived 174,000 by the desired rpm to get the approximate length. The rev limit on early 348s is 7500rpm. At the engine speed the intake runner would have to be 23.2"/589.28mm long. That's almost two feet long, and there is no way you are gonna fit a runner that long under the 348 engine cover, nor under practically any other engine bay for that matter. Here are the basic formulas for calculating runner length for the various harmonics.

1st order harmonic : 174,000 / divided by engine rpm = estimated runner length
2nd order : 132,000 / rpm = length
3rd order : 97,000 / rpm = L
4th order : 74,000 / rpm = L
5th order : 57,000 / rpm = L

The 1st order is the strongest, but the runner length can't reasonably fit under the hood. Next strongest is 2nd, then 3rd, 4th is very minimal hardly anything really, and 5th isn't even worth calculating for. So ideally you tune for 2nd and 3rd order harmonic. That will get you in the general vicinity but you will need to do testing, and plenty of it, on a dyno to fine tune the best length for the desired rpm and harmonic.

So where does the runner length of the stock 348 intake fall? When measuring the length of the intake you measure the entire length. That is the intake runner + the intake port in the head. You measure from the back of the intake valve to the outer most opening of the intake runner. The total runner length of the stock intake measures approximately 11" long (279mm). To capture the 2nd harmonic you would have to spin the 348 engine all the way up to 12,000rpm. To capture 3rd order you would have to spin the engine to 8,800rpm. Because of the length of the factory intake, and because the factory rev limit is 7750rpm (for the later models) the f119 is confined to the 4th order harmonic. Basically a little puff of air in a very narrow 500ish/rpm band @ around 7000rpm (+/-). The wrong length runners and not enough rpm to take advantage of any significant affect via acoustical tuning, aka Helmholtz resonance. So no acoustical supercharging with the stock intake for the 348.

Once again the f119 is suffocated in it's breathing, and another reason why it's my opinion that the stock intake manifold is THE biggest negative factor in the restricted power output of the 348. It never had a chance from the get go to make any serious kind of power because it can not breathe.

 

Not dumb at all.

Part of the issue is the design of the engine bay, in particular the deck lid. Because Ferrari chose to configure the deck lid/engine cover with the same design as the 328, 308, and 246 it restricts the length of the runners. Now had Ferrari glassed in the 348 engine bay ala the F40, 360, 430, 458, 488 THEN you would be able to make the runners the length needed to capture the 2nd harmonic.

Having said that I believe it may still be possible to get the correct length runners. If the runners could somehow be crossed to the other side of the engine, rather than just straight up, it may be possible to the get needed length for affective resonance tuning utilizing the 2nd order harmonic resonance. But that entails redesigning the WHOLE intake = BIG DOLLARS $$$!

The other thing that will help is more rpm. The higher the engine is spun the shorter the runners can be. I'll use the 3rd order harmonic for this example. If we target for hitting 3rd order at 7500rpm the runner length would have to be 12.93" long. That is almost 2" longer than stock. We're as if we are able to remove the rev limiter, and rev the engine to 8000rpm, the length needed to hit 3rd order harmonics drops down to an estimated 12.125"' just a hair over 1" longer than stock. Let's raise the target revs to 8500rpm. At 8500rpm the runner length only needs to be a mere 1/2" longer @ 11.41". That is short engough to still fit under the stock engine lid. Now it's not 2nd order harmonics, but 3rd order is better that 4th order. The usable rev range for 3rd order acoustical supercharging is approximately 1,000rpm versus about 500ish/rpm for 4th order. But.....you still get the affect of 4th order at around 6500ish/rpm, PLUS 3rd order at 8500rpm.

It's my feeling this is why the 355 makes more power with the higher revs versus the 348. It is able to take advantage of the 3rd harmonic, where as the 348 cannot, in addition to the f129's better breathing capacity. I am curious to know what the total runner length is of the f129 engine. Hmmmmmm?

So my guess is, if the f119 rev limit is raised to 8250 and a 1"-2" (depending on the engine lid room) spacer is placed between the bottom of the runner and the head, we just maaaaaaay be able to capture that 3rd harmonic and gain a bit more power.

How do you eat an elephant? One bite at a time.

The only way to know is to build it and test it.

Cubic dollars, cubic dollars.

 

You would have to build an entirely new intake manifold in my opinion. While the Ross machine stuff is handy I think the ideal manifold would have to be designed with the use of a cad computer, or similar. That way the design could be tested virtually with computational fluid dynamics (cfd) and refined before it is made. After it gets made then it would be tested in the real world, and adjustments made again if necessary. Probably the fastest way to make the test manifold would be with a 3D printer.

 

Excellent article I am VERY familiar with.

Here are a bunch more of his articles you can read for free Prof Blair & Associates Home Page - Published Articles

Also Professor Gordon P. Blair's book, "Design and Simulation of Four-Stroke Engine" is most excellent.

Any of you involved in racing karts will want to read his books on two stroke engines.

 

No argument here, which is why you must test, test, test, and test some more until you get it right.

I was fortunate enough to meet a guy who actually built an intake that took great advantage of harmonic tuning. He told me he had hours upon hours of dyno testing to refine the length of the runners. The calculations got him in the ballpark, but like you said, the engine never lies, and it was all the testing that got the results he was after. He even did a modification on a test intake he made where he moved the location of the throttle body. Everything else remained the same and it lost 7-8hp, just from a throttle body relocation.

 

Because it really isn't plug-n-play. When you go to ITBs you lose the mass airflow sensors (maf) and need to run manifold absolute pressure sensors (map), the intake compensation valves goes away, the idle air control valves are removed from the intake, the secondary air injection from the exhaust goes away, the vacuum lines for the fuel pressure regulators must get rerouted, the oil vapor recirculation tubing is removed, for the 348s that have gas tank fuel vapor recovery purge lines those have to be delt with. It's not an unbolt-bolt on then drive away situation. Not that it can't be done because it can and has been done. But after you bolt everything up it MUST get tuned. That there is the biggest hurdle, the tuning.

But even if you get all of that accomplished, how many are willing to pay what it takes? Seriously, how many? Take Fabspeed 348 headers for example. They are TOTAL plug-n-play headers, and the ONLY off the shelf headers for the 348. Fabspeed spent many hours of design, dyno testing, not failing to mention lots of money, developing headers the help the 348 produce more power. All plug-n-play. But how many 348 owners have a set of Fabspeed headers, or anyother customs headers on their cars right now??? I have a set of custom headers, and know of three others that have the Fabspeed headers. The headers have been dyno proven to make more power than stock. You would have expected to see every 348 on the planet running around with after market custome headers. Yet sadly we don't.

So why should any one develope a plug-n-play ITB setup, or better intake manifold setup, when the current off the shelf stuff the majority of 348 owners aren't even buying???

I think that is why there hasn't been one developed.

Having said that, there still are those of us that WILL hotrod our 348s and make more power, regardless of anything off the shelf being available.