Area under the oem torque curve

[Dino Dino Bambino]

what part of the stock 3v is most compromised by higher rpm?

A few things:

1. The stock powdered metal I-beam connecting rods are fine in N/A applications and will live up to 7300rpm but when you subject them to the higher cylinder pressures of forced induction, they are liable to bend or break if the engine detonates. You're also limited to ~450rwtq.

2. The relatively small bore limits the valve size and high rpm breathing. Ford already virtually maxed out the valve size on the 3V heads right out of the box. As a result, there's some degree of intake valve shrouding. Porting the heads can overcome that issue.

3. The stock cams were designed to optimize torque output from idle to 4400rpm, with the VCT retarding the cam timing at higher rpm to extend the power band. However power drops off beyond 6200rpm and the primary reason is the very short intake valve opening duration (196* @ 0.050" lift). Just about any aftermarket cam will add higher rpm performance but expect to trade away some torque below 4400rpm.

4. The stock intake manifold (with CMCVs removed) flows pretty well (250-260cfm per runner) but with a runner length of 14", its performance drops off above 6200rpm. The Ford Performance intake manifold has a larger plenum and a runner length of only 9.5", thus improving higher rpm breathing. The trade off is a loss of torque in the 3300-5200rpm midrange.

Since the subject of the thread is area under the torque curve, the first question to ask yourself is in what rpm range do you want to maximize it? The second question is do you want to keep the engine N/A or add forced induction?

Since the stock 3V engine was designed to operate safely from idle to 6500rpm, the most cost effective way to maximize the area under the torque curve in that operating range is to add a positive displacement supercharger kit. You could also add long tube headers but consider them optional rather than necessary, and there's no need to crack the engine open if you limit yourself to ~450rwtq (roughly 8psi maximum boost in a 2.3L supercharger) and 6500rpm.

If you choose natural aspiration, anything over 350rwtq from a stock 4.6L displacement would be outstanding. Most N/A engines with bolt ons & NSR cams (the most popular mods) are in the 320-340rwtq range. Anything higher than ~340rwtq is going to require ported heads and a higher valve lift than you'd get from NSR cams i.e. you'd need to go with VSR or, ideally, SPR cams.

 

[Enfield]

Went back and looked at the dyno chart for a road course-prepped 08 that I wanted but didn't get. It had FRPP heads and intake, a CAI, Kooks long tubes, and hot rod cams. On a Dynojet at 81 F. and low humidity, it turned 367 hp @ 5900 and 324 tq @ 4800. Torque was already passing 300 at 3800 and up to 275 by 3000; it stayed strong to 6k, and then dropped back to 275 by 7k. HP stayed up right to shutoff: 6450 on one pull and 6950 on the other. [Dyno was at the shop that had done all the engine work.] That seems to be pretty much FBO for an NA 3v, if ported heads can be called a bolt-on.

The original owner of my car had installed CAI, Bama tune, LTH, catless X, and UDP. He claimed 320/320, but I don't think so. It just doesn't start to feel strong until almost 5000 rpm. Great mpg's, though.

Given the inherent attractiveness [elegance?] of variable intake lengths, I'll just have to keep the stock cams and wait around for the right used blower setup. The great thing about this site is that everybody loves to spend big $$$ to get big power and other upgrades; that can be very addictive. So far this year the car has gotten paint fixed, top fixed, seats fixed [scheduled and paid for], new shocks and bushings, and new wheels and tires. Must learn to keep wallet in pants!

 

[Pentalab]

That is the key to a fun ride in a nut shell. You can play with all the mid range torque and power and not have to rev the hell out of it. Passing at hi way speed without downshifting is easy.

On my 2010 auto, stopped at a red light, (and manually shifted into 3rd gear). That's foot on brake, and 600 rpm.... (oem 1.5 krpm stall converter). Lights turns green, mash the gas, shriek of rubber, and off we go. That was with 285-40-18 's on the rear. For street use, in drive, it's effortless, pulls like a mofo. Put's me into the back seat when in 2nd gear. On the 5r55s, 2nd gear is 14% lower than 2nd gear in the manual. In 3rd gear, the 5r55s is 16.5% lower than 3rd gear in the manual. It's nice not having to downshift, and rev to the moon.