real-world power gains

The butt dyno is the most unreliable power measuring device on earth.  I challenge anyone to "feel" a 5 or 10 HP gain on a 350 rwHP engine.  Yet many of the bolt-on Lightning mods produce horsepower gains in that range, with lots of people raving about how much quicker the truck now "feels."

Similarly, I discount aftermarket vendor claims not backed up with reliable dyno or track data.  For example, MAC claims that its "cold air kit" (which does nothing but draw HOT air from the engine compartment) adds 20 HP and "1/4-mile improvements up to 2/10's & 2 mph."  Assuming a 5,000 truck, going from 100 to 102 trap speed requires 24 rwHP.  Contrast this claim with the real-world dyno data from Dan below, where the "cold air kit" from a well-respected vendor caused a loss in power.

The best hard data in the world is before-and-after 1/4 mile trap speed comparisons, adjusted with the appropriate correction factors.  ET's are far too unreliable.  Real-world power is about area under the curve, not peak values.  Dyno testing can give you peak values and may give you a graphical idea of the area under the curve, nothing beats a full-throttle blast down the track for measuring as-delivered power.

dyno testing notes:

Some of the more reliable data I have found is presented below.

I do not claim to be an expert on Lightning tuning.  I present the following data and conclusions based only upon my reading of the massive number of posts on the issue on the NLOC, F-150 World, and F-150 Online message boards, along with books and magazine test data.  If anyone has any additional reliable data to provide, or disagrees with any conclusions, please e-mail me.

correction factors:

SAE represents more realistic standard conditions, STD artificially boosts numbers. I do not trust a vendor who uses STD numbers.  Found this somewhere on the Web:

"SAE (Society of Automotive Engineers), USA. Power is corrected to reference conditions of 29.23 InHg (99 kPa) of dry air and 77 F (25°C). This SAE standard requires a correction for friction torque. Friction torque can be determined by measurements on special motoring dynamometers (which is only practical in research environments) or can be estimated. When estimates must be used, the SAE standard uses a default Mechanical Efficiency (ME) value of 85%. This is approximately correct at peak torque but not at other engine operating speeds. Some dynamometer systems use the SAE correction factor for atmospheric conditions but do not take mechanical efficiency into consideration at all (i.e. they assume a ME of 100%).

STD or STP. Another power correction standard determined by the SAE. This standard has been stable for a long time and is widely used in the performance industry. Power is corrected to reference conditions of 29.92 InHg (103.3 kPa) of dry air and 60 F (15.5°C). Because the reference conditions include higher pressure and cooler air than the SAE standard, these corrected power numbers will always be about 4 % higher than the SAE power numbers. Friction torque is handled in the same way as in the SAE standard."

Dan's data:

The following data was carefully mapped by Dan McGuire on the same dyno.  The appropriate SAE correction factors were applied to each run.

NeedFourSpeed's data:

Richard Holdener's data:

The most compelling documentation of Lightning power gains I have seen to date is in Richard Holdener's excellent "Lightning Owners Get Screwed" article in the June 2002 issue of Muscle Mustangs & Fast Fords (the same test, with slightly different photos and write-up appears in the "Boosted Beyond Bolt-Ons" article in the October issue of Truckin').  Holdener, who probably knows as much about supercharging Ford engines as anyone on the planet, provided adequate airflow across the intercoolers and accounted for all variables during testing.  Note that these results were with the stock fuel system, stock exhaust, and without a chip (except where noted).  On the other hand, these tests were done with 100 octane fuel.  With pump gas, a chip may be needed.

Holdener noted the presence of vacuum in the stock airbox once the power levels started climbing.  He therefore added a cone filter and an Accufab throttle body.  It would have been better had Holdener added the throttle body and cone filter separately so that the effects of each could be measured in isolation.

The intercooler data is also suspect.  At 20.6 PSIG, the air leaving the Kenne Bell was reported as 307°. The air exiting the intercooler was 107°. Assume a 75° day.  (307°-107°)/(307°-75°)= 84% effectiveness.  Assume a 95° day and the effectiveness jumps to 94%.  Even assuming a 55° day, the effectiveness is still 79%.

These kinds of numbers seem extremely unlikely for an air-to-water intercooler.  This should not, however, effect the overall validity of the before-and-after results.

Bfb's data:

The below graph  shows SAE corrected numbers for stock (with K&N) versus Johnny Lightning Diablo Chip and 5 lb. lower pulley:

You can read more about these tests here.

conclusions:

From this data, I have concluded the following:

The stock airbox is fine until the power levels get above stock.  See Dan's data above.  Even then, the addition of a true cold air intake hose to the stock airbox may be a better solution than a cone filter.  According to Sal of PSP: "The stock or modified/stock airbox is fine if you run stock or up to +3 PSIG extra, but it's definitely not for trucks running over +4 PSIG. On the dyno, trucks set up like that will drop off in power early, from the lack of adequate airflow. Happens every time."

For some great data on so-called "cold air kits," click here.

The moral of the story:  If it ain't broke, don't fix it.  For stock engines, the stock airbox is fine.  For modified engines, get Powersurge Performance's "FASTAir" system ($200 + $175 for cone filter) or Johnny Lightning's cold air system ($275 with filter).  All other cone filter setups are suboptimal (but all open filters yield some cool blower whine!).

From a post by booboo454 on F150online (4/9/05):

I had over 10 dyno runs paid for in 1 day by C&L to test their 80mm MAF back in 99.

1) stock 325 rwHP.

2) stock with ~12" K&N air filter 325 rwHP.*********

3) stock with stock with ~12" K&N air filter and C&L MAF 325 rwHP.

4) custom chip on stock 355 rwHP.

5) custom chip with ~12" K&N air filter 355 rwHP.

6) custom chip with ~12" K&N air filter and C&L MAF 355 rwHP.

7) pissed off C&L with retuned ~12" K&N air filter and C&L MAF 355 rwHP.

8) pissed off C&L with retuned ~12" K&N air filter and C&L MAF 355 rwHP.

9) pissed off C&L with retuned ~12" K&N air filter and C&L MAF 355 rwHP.

10) pissed off C&L with retuned ~12" K&N air filter and C&L MAF 355 rwHP.

I would guess that there was about 30 minutes in between runs with a large fan @ ~40 degrees inside/garage door opened.

On a 99, a CAI filter and/or MAF doesn't do shit, sorry but it's been that way for years.

The single-blade throttle bodies are useful only as the airflow goes up.  Compare Dan's data with Holdener's data.  This would suggest that it should be one of the last mods done.  Additionally, while there are countless butt dyno reports of "increased throttle response," no one has shown increased HP on a stock or near-stock engine.

Cranking up the boost is the easiest way to produce power gains. Holdener and Dan ended up in roughly the same place--about 415 HP, but Holdener only replaced the pulleys, filter, and throttle body.  Admittedly, this comparison violates the "never compare different dynos" rule, but both tests started out at the same 350 HP baseline.  Holdener's tests may have provided better airflow also, thus increasing the intercooler effectiveness/better air density.  However, Dan's tests also showed the biggest gains from pulley swaps.

But at what cost?  Consider the graph to the right.  As one can see, the outlet temps are increasing at an increasing rate once the supercharger is driven past its point of peak efficiency, which appears to be about 6,000 RPMs.  In stock form, the Lightning engine spins the M112 at about 13,000 RPMs at engine redline.  The M112 is therefore already being substantially overdriven with the stock pulleys.

With the maximum boost setup tested by Holdener above, the M112 was spinning at 17,672 RPMs--WAY off the chart!  Just think about what the efficiency curve looks like at that point.  And that was with a stock chip with a stock engine redline--and 100 octane fuel.  Raise the redline to 6,000 RPMs on pump gas and there is a real recipe for disaster.

As stated by one tuner: "Expected gains from the 4 pound pulley is 40 lbs.-ft. torque and 15 HP.  Expected gains from the 6 pound pulley is 50 lbs.-ft. torque and 18 HP."  Another tuner concurs: "18 lbs.-ft. and HP by 8 on the 2 Lb. pulley, 40 lbs.-ft. and HP by 15 on the 4 LB. pulley, and 50 lbs.-ft. and HP by 18 on the 6 LB pulley."

As a rough rule of thumb (extremely rough), a perfectly efficient 15 PSIG should double the HP of an engine (normal air pressure is about 15 PSI, so 30 total PSI=15 PSIG).  Do the math and a perfectly efficient PSI should be worth about 6.6% gain.

Assume a 220 rwHP normally aspirated 5.4.  Add a perfectly efficient 8 PSIG (theoretical 53% gain using the above rule of thumb).  The expected rwHP should be about 335, which is about what one should expect from a stock Lightning.  Add 4 more perfectly efficient PSIG (another theoretical 26%).  That should yield 422 rwHP, which would be an 87 rwHP gain.

But it doesn't-- it only produces 15 rwHP.  A perfectly efficient 6 PSIG pulley should yield 467 rwHP!  But it doesn't--it only produces 18 rwHP, or a measly 3 rwHP gain for those extra two PSIG.

Now consider HP per PSIG.  Not only are the gains small with a 4 lb. pulley (only 3.75 rwHP per PSIG), they are even smaller with the 6 lb. pulley (only 3 rwHP per PSIG)!  This is compelling evidence that the Eaton is out of steam when overspun on a 5.4. 

The chart to the right shows rwHP per PSIG at the margin (i.e., what one gains per PSIG for the 2 pounds between a 4 and 6 lb. pulley).

Note, however, that we are talking only in terms of peak power--not area under the curve, which is what wins races.  The midrange increases can be large.  Because jacking up the boost is not a sin if the supercharger is not being overspun, it is surprising that no one has tried increasing the boost, but lowering the engine shift points and rev limiter to keep the M112 in a reasonably safe and efficient range.  It's all about area under the curve.  Lowering the redline to 4,500 would reduce max supercharger RPMs by 16.7%.  Using the max pulleys used by Holdener, that would result in a maximum supercharger RPMs of 14,700, only about 11% greater than stock.  Who knows.

Now consider the Kenne Bell twin screw.  According to Kenne Bell:

To compute the approximate HP your 100% stock Lightning will produce with the Kenne Bell [twin screw] and elevated vs. stock 9.3 psi boost, merely multiply the boost increase x 13.36HP.  Example: 9.3 stock vs. 15 = 6.3 psi x 13.36 = +84HP.  Note: At the same boost with no other changes, the [twin screw] made +16HP.  See Muscle Mustangs and Fast Fords June 2002 "Lightning Owners Get Screwed."

            . . . .

. . . The stock MM&FF Magazine truck we tested made 415HP with the 9"x2-3/4" pulley and 15 psi vs. 348HP stock (9.3 psi). That's around 13HP per psi. The other MM&FF truck with all the bolt on goodies made 415HP. Where's all the HP from all those "other" bolt ons? How much more power does the meter, headers, exhaust, inlet etc. really make? Again, we made 522 with all the stock parts except for a longer filter - and we never altered the chip!

Clearly, the better path to greater power is with more efficient boost, not overdriving the already out of breath stock Eaton.  Food for thought.

A chip may not be required.  I hate the idea of someone with a tiny fraction of the experience of the Ford and SVT engineers providing fuel and spark to my engine.  Get it even slightly wrong and BAM!  One $7,000 rebuild coming up.  While I have no doubt that there are competent tuners out there who can produce a chip with stock (or even greater than stock) reliability, I simply don't trust any of them.  Note that the standard advice seems to be that anything over a 2 lb. pulley will require a chip.  But countless people have run 4 lb. pullies with no chip.  As a matter of fact, I have never heard of anyone a 4 lb. pulley and no chip having any problems.  And the new Whipple/Ford Racing system promises up to 75 HP with no chip.

From Rich B of the NLOC boards:

I run a total of 13 lbs of boost with a cold air intake system (no air from the engine bay at all).  Everything else on the engine is stock.  No matter what the temp is outside, the truck runs smooth and strong with no detonation or black smoke and my stoichmeter is always indicating the ratio of fuel to air toward the fat side.  My plugs (still stock) also show perfect, balanced cylinder burn.  On heavy acceleration my stoichmeter indicates the factory computer calibrations are providing additional fuel keeping the mixture a few percentage points higher into the fat range. Nothing running lean here . . . only a very strong running engine.

From Ran JR of the NLOC boards:

I have 4#, JL ram air, & flip chip. Side 1 is for towing (rich), side 2 for sport (more aggressive).  For the past week my truck was detonating on both sides.  I thought it was the gas so I put in a new tank and it got worse.  I turned the chip off and I could not make it detonate no matter how hard I tried. Makes me a little mad that I wanted a towing program and it is still more aggressive than with no chip.