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Boss Intake Boost - Flying High Again
Examining the effect of a high-revving boss manifold on a vortech-blown coyote.
Anyone who's been to a car show lately knows the Boss 302 intake manifold has rapidly become a hot commodity for Coyote-powered Mustang GT owners. The short-runner, rpm-happy RoadRunner intake holds obvious promise for high-rpm hi-jinks, and even if extra performance isn't needed, its tunnel-ram sex appeal is simply too attractive for many to pass up.
After our first, "Man, that looks cool," sighting of a Boss intake on an otherwise stock GT, our additional thought was how well-suited the Boss intake was for centrifugal supercharging. Positive displacement screw blowers have been the rage for years now, but they don't even use an intake manifold so the Boss intake is nothing to them. But blow-through centrifugal supercharging is married to the intake manifold, and the idea of an efficient centrifugal force-feeding the racy Boss intake instantly had our speed lust redlined.
It didn't take long to ask Vortech if they could put together a Mustang GT/Boss intake combination with its standard V2 blower kit for '11-'12 Mustangs. Though already too busy with engineering work, the staff readily agreed. The parts were gathered from Ford Racing and Vortech's parts bins, and Vortech's own red '11 Mustang GT test mule was soon gussied up with the new intake.
One concern was the 5.0-liter Coyote engine's variable cam timing. Ford had cautioned that simply bolting a Boss intake to a Mustang GT 5.0-liter wasn't going to gain much more than 8 naturally aspirated horsepower until the intake cam timing was retarded. Vortech took the advice to heart, fiddling with the cam timing on the Coyote-Boss hermaphrodite, but in the end concluded the existing cam timing strategies in its stock '11 Mustang GT kit were optimal. This makes sense when recalling Vortech had already optimized the cam timing for its standard kit with custom cam timing; at wide open throttle, there wasn't much to be gained after that no matter what intake was used.
Besides dyno testing, Vortech ran its combination at Famoso dragstrip test and tune nights in Bakersfield, California, plus we attended our sister publication Motor Trend's test day at the Fontana quarter-mile to obtain GPS-derived test data and log some quick seat-of-the-Levi's time.
Given the car's road race chassis dress, we didn't expect stellar dragstrip e.t.'s, but we were a little surprised that even with Mickey Thompson DOT slicks traction completely won a rousing game of hide-and-seek. Launch rpm was minimal or the whole thing went up in smoke, and the rodeo continued in the first three gears simply from an excess of power. So a sharp e.t. never did emerge, but consistent 126 to 128-mph trap speeds tell the real story. The Vortech GT/Boss combination's best test e.t. was 11.6 seconds, but it has the stones to hustle out a 10-second pass given traction. That speaks volumes about the potential of this otherwise stock car with daily driver manners.
Dyno data is presented nearby, but suffice to say that with moderate boost, a tick over 500 lb-ft of torque in the mid-5,000-rpm range and just shy of 640 hp at a zinging 7,300 rpm, this one packs the goods.
From behind the wheel, we found the Boss combo far more fun and exciting than anticipated. The last few Vortech cars we've driven were mainly Three-Valves wearing Vortech's out-of-the-box tuning, and frankly, they were a little under-whelming. Call us jaded, but while the power delivery was impressively smooth there just wasn't enough of it.
Not so with the Vortech GT-Boss combo. Puttering around on the street, driveability is stock, and from low rpm you can lean deeply on the throttle for quick speed adjustments without fear of nuclear power punting the whole works sideways. While it may sound a bit goofy when discussing a performance car, the Vortech-Boss combination does just fine going to the store, through the drive-thru ATM, or grunting along with stop-and-go traffic.
Hit the gas and it's another story. The power ramps up smoothly from idle to redline, and you can't identify where the stock Coyote's low-end power is first augmented by the supercharger, but as rpm builds, the thrust simply swells. Things feel good by 3,000 rpm, but that's still stock Coyote power talking. At 4,500 rpm, the band is definitely starting to play, and by 5,500 rpm, things start happening in a major way. The top-end charge is burly, and there is a definite sense the combination would just love to run through redline and many rpm beyond.
There was can't-avoid-it wheelspin in first and the top of Second and Third gears, and the high-rpm pull is so strong that there's a compelling urge to visit the right, lower corner of the tachometer often. It's fun.
Of course, there is no torque hit as with a screw blower, but the perceived power rush at high rpm has a sporty feel all it's own. Considering our test car was running stock rear axle gearing, the overall grunt was excellent, and we don't recommend steeper gearing. Given a touch of rpm it's already a snappy combo. Our only other recommendation is our now blanket remark that eliminating 500 pounds of vehicle weight would be the best thing since the introduction of aluminum pistons. One of these monsters in a Fox...
Our first take-away from the blown Coyote-Boss hybrid is the stock intake manifold is an impressive bit of engineering. It obviously makes more oomph at normal street speeds, and works unexpectedly well with extra-curricular rpm and boost. Practically speaking, it's free (can't beat that pricing) because it came with the car, it's emissions legal, and probably ekes out a touch more fuel economy if you want to split hairs.
Still, the long-runner stock intake does taper off at high rpm. When you're packing a twin-cam, four-valve V-8 that loves to rev, the Boss 302 intake delivers in the high-rpm range. The decision is just how much rpm are you going to realistically run. For a run-around street car, the stock manifold is the hands-down choice, so that's an easy call. Move on to a dedicated track car and even then this test--along with reports from racers such as Justin Burcham at JPC Racing who have been experimenting with naturally aspirated and centrifugally supercharged Coyotes--shows the Boss 302 intake manifold is a close call.
Ideally the rpm must be kept high, which not only means revving to past stock redline, but closer-than-stock ratio gearing to keep the engine buzzing. Terry "Beefcake" Reeves, for example, has gone from the stock intake to the Boss and back to the stocker in his Vortech-boosted '11 automatic 5.0, with the stocker proving faster. A close-ratio-manual-trans driver might beg to differ.
Back in the real world of street cruising and burger-stand heroics there is the Boss intake's visual sex appeal. It just makes you feel good when you open the hood. Considering the Boss intake retains more mid-range than we thought--it isn't as a dog until 6,500 rpm or anything like that--then running the Boss intake and the Vortech blower is certainly good when the hood goes up.
Another strong impression was just how good the Vortech supercharger felt with this combination. We've been fed a steady diet of screw blowers lately, and yes, they pack bomb-like torque hits at almost any rpm coupled with a fine top-end charge. But they also have something of a flat personality that contrasts with the sparkling high-rpm Vortech centrifugal. The Coyote engine-RoadRunner intake combination with just entry levels of Vortech boost drives like a stocker when that's all you want or need, but tears it up with a nuclear high-rpm charge when you have the bit in your teeth.
And finally, road racers that we are, we couldn't help but think what a driveable, lightweight, and scary fast combination this would be for an open-track toy. Tach it up!
Pumped UpFord has done us all a large favor by giving the modern 5.0-liter Mustang with a generously sized fuel system capable of handling much higher than stock power levels. Naturally it runs out of capacity at some point, which Vortech engineer Mike Regan puts at around 575 rwhp. In other words, venture past Vortech's standard Mustang GT blower kit and you're going to want its new Max Volt fuel-pump booster.
The Max Volt amps up the stock electric fuel pump so it can maintain the system's nominal 58 psi of fuel pressure. The Max Volt is offered for use with almost all the electric fuel pumps, so older Vortech-assisted Fords can use it too. In basic terms, it can give half again the pump's regular output because it can supply up to 22 volts to the pump.
The Max Volt is Vortech's own design, and is offered in two versions, both in aluminum housings with the same boosting capability, but one features full adjustability via a USB port for sophisticated racing applications. All Max Volts use a microprocessor and the latest circuit technology for precise voltage output control no matter the vehicle's battery voltage.
The standard Type 1 Max Volt retails for $229.95 and is suitable for all street applications. The Type 2 Max Volt is a race piece offering considerably more input/output tuning; it retails for $349.95.
On The DynoVortech's in-house MD Mustang Dyno sees extensive development work, but returns hugely low numbers compared to the more common Dynojet dyno. So we asked Vortech to take its Boss-intake mule around the corner to a local Corvette shop's Dynojet for the representative numbers shown here.
As you study the results we think you'll agree the Boss 302 intake looks like serious fun, but to make it pay against the stopwatch will take a serious effort involving building the car around a high-rpm engine--think lightweight and a close-ratio trans. The stock manifold is the only way to fly below 5,500 rpm, making superior torque for daily driving, but it also hung in there nicely on horsepower given a little extra boost. If daily driving with an occasional squirt to high rpm is your thing, the stock intake is the way to go. The Boss intake, however, makes a great upgrade. It surprised us by losing minimal torque and showing real gains in the rpm stratosphere. If any sort of track driving or eye-watering rpm is how you roll, the Boss intake and custom tuning is your thriller.
So we asked Vortech to take its Boss-intake mule around the corner to a local Corvette shop's Dynojet for the representative numbers shown here
Standard ImprovementVortech's standard 5.0-liter Coyote engine application has been available for about a year, and as is normal with Vortech, the company has been quietly reviewing and updating this Mustang GT kit. Of course, the proven Vortech blower hardware hasn't required any changes, but a minor bracket change was implemented after the first few kits were shipped. The real news is tuning specialist Lance Keck put in the laptop hours with the '11 Mustang GT application, refining its habits for maximum streetability. Most of the calibration updates have centered around low-speed driveability to gain "bone-stock" idling and a complete lack of surging.
Lance says he hasn't increased the power ratings for the standard kit, but there may be some confusion because of the notoriously low power ratings that come off Vortech's Mustang-brand chassis dyno. On Vortech's dyno, Lance has found most '11 Mustang GTs post 440 to 450 rwhp after bolting on the standard Vortech blower kit. The occasional high achiever might put up nearly 460 rwhp. These figures would be more like 550 rwhp on a Dynojet using our typical SAE correction factor.
As Lance points out, the Vortech tuning is aimed at reliable street power, and the Vortech tune is already against the limit of 91-octane pump premium gas (which is right at 550 rwhp no matter what blower, nitrous, or turbo you're talking about). Thanks to the Coyote's adaptive knock control, Vortech is able to set the ignition timing tables so the knock sensors keep the engine safe with 91-octane fuel as found on the West Coast and automatically accommodate East Coast 93-octane gasoline with three to four more degrees of ignition timing with no input from the owner. That's worth 30-40 rwhp, so East Coast readers can expect more like 580 rwhp from their Vortech-assisted 5.0-liters.
Since our first story on Vortech's 5.0 Mustang GT kit, the company has also released its Competition Air Inlet Upgrade option. This is a definite improvement, gaining another 25 rwhp on any dyno. Likely ready as you read this is an eight-rib drive belt system Vortech is engineering for the racy, high-boost boys. It's too early to guess at its pricing, but clearly the system is aimed at extreme applications where high boost and rapid on-off-on throttle applications make belt life difficult.