Kenne Bell Coyote Throttle Body Test - Big Deal
Kenne Bell’s huge new Coyote throttle body opens the path to 600-plus horsepower
From the September, 2011 issue of 5.0 Mustang & Super Fords
By Tom Wilson
Photography by By The Author
We're all hot rodders here, so let's ignore that a new 5.0-liter Mustang with a Kenne Bell blower already has the capacity to fry the tires at will. There is always a "need" for more.
In this case, the literal choke on the Kenne Bell party has been the stock throttle body. This is no surprise as the Kenne Bell blower kits for the new 5.0 engine all feature the company's aptly named Mammoth air inlet. Large enough to swallow a housecat, the Mammoth intake effectively eliminates intake restriction. Thus, the stock throttle body--a mere 80mm in diameter--can't fully sate even the standard Kenne Bell 2.8 blower's appetite, much less efficiently feed a 2.8H pullied for track action.
For clarity we’re showing...
For clarity we’re showing just four of the six combinations of throttle bodies and pulleys tested. The light blue/dark blue lines represent the largest pulley run with the stock and Kenne Bell throttle body. The red/green lines are the smallest pulley (highest boost) paired with the stock and Kenne Bell throttle body. As expected, the missing middle test would plot equally between the tests shown. Clearly Kenne Bell’s blower system allows dialing in the desired power, and these tests peak at just 13.4 pounds of boost. There’s a whole gaggle of steeper curves to be had once the supporting oil pumps and supporting hardware is available.
So, Kenne Bell has done the logical thing, developing a monstrous 168mm throttle body as an optional upgrade to its blower kits. This correctly sizes the new throttle body to the Mammoth intake found standard on all Kenne Bell 5.0 kits and so it's no surprise the new throttle body proved more efficient in its first magazine test. At $799, it's one of those big parts that a casual guy could do without for awhile, then add down the road as he steps up his program. Of course, according to our test, he'll have to be content with a mere 591 rwhp compared to the 637 rwhp he could have with the KB throttle body, but then, life just isn't fair.
Kenne Bell's supercharger kits for the '11-'12 Mustangs center on the 2.8 and 2.8H twin-screw blowers. Regular readers will recall the 2.8 blower is optimized for 8-15 pounds of boost, while the 2.8H does best from 15 pounds on up. Until now only the stock throttle body was available, and as the photos show, it is entirely overwhelmed by the huge Kenne Bell Mammoth air inlet.
As the dyno tests illustrate, the stock throttle body is a bit of a choke in the entry-level 8- to 9-psi range, albeit not a catastrophe at such easy-going boost levels. But, as expected, at higher boost and power the greater the stock throttle body lags. So, the more power you make the better the Kenne Bell throttle body pays off. It's tough to draw a line and say that above such-and-such boost you must have the big KB throttle body. To a great extent this depends on how you're using the blower. Street fans could wait a little--the track-oriented customer is more likely to want all he can get right away.
The situation is pleasantly complicated by the easy Kenne Bell blower pulley changes. Using inexpensive pulleys and tools, it's a 4-minute snap to swap KB pulleys. In practical terms, that means easy 8 to 12 pounds of boost on the street, then swapping the pulleys and moving up to race gas and something like 18 pounds of boost for some rowdy track action. Reversing the process puts the car back in still-powerful street trim for the drive home.
This also means that up to the 600-rwhp threshold, you can make the same power with the stock throttle body and a smaller blower pulley as with the big throttle body and a larger pulley. Considering the throttle body is $799 while the pulley and changing tool are $94, this might be a good way to go. On the other hand, the big throttle body is definitely more efficient, and if you're interested in over 600 rwhp, you'll definitely want or need it to meet your goals.
In the end, it's up to you. Just starting out with a standard 2.8 Kenne Bell kit for your pride and joy street 5.0? You'll be happy with a big pulley and the stock throttle body for a good long while. Buying a 2.8H kit for track action? Better factor in the cost of the big throttle body. In between you'll have to make the call depending on your hunger for power and fiscal leverage.
Ricardo Topete of GTR (left)...
Ricardo Topete of GTR (left) and Ken Christley of Kenne Bell (right) pulled all the levers, did the dyno driving, and made the tuning changes during this cooperative Kenne Bell/GTR test. Ken is putting final torque on a blower pulley change here; the whole procedure takes maybe five minutes.
Frank Lanzas’ ’11 GT wears...
Frank Lanzas’ ’11 GT wears its liquid-cooled Kenne Bell 2.8 blower and 168mm throttle body like a natural. The cavernous Mammoth air inlet casting at the rear of the supercharger, along with the culvert-like chrome air inlet tube, are part of the stock Kenne Bell blower kit for Coyote engines. Pricing for a black-finished KB Coyote blower such as this starts at $6,599 for the non-liquid cooled version; the LC blower shown here retails direct from KB for $6,899, plus $799 for the big throttle body. With the large 4.125-inch pulley seen here, this combination put 550 hp to the tires in a walk.
Kenne Bell has flexible adapters...
Kenne Bell has flexible adapters to fit the stock or KB throttle bodies to the KB inlet tube. The molded adapters—this one is obviously for the stock throttle body—are easier to install than many of the silicone pieces found in typical cold air inlets, cone filters, and the like. Note how the stock throttle body is installed with the electronics re-clocked upward for clearance. We didn’t have this sort of flexibility with cable-operated throttle bodies.
It may be that Kenne Bell's new throttle body is the largest production Ford throttle body ever. At 168mm along its major axis, it's a monster all right. Conceptually it's a pair of 80mm throttle bodies(!) with the center cut out, according to Kenne Bell's main man Jim Bell, so think of it as twice as large as Ford's 80mm Coyote mouthpiece. Jim says the unit flows 2,150 cfm by itself, and 2,350 cfm if you put a flared entrance on it. That's 1,500hp territory, so if you can't make power, it isn't the throttle body's fault.
The main trick with huge throttle bodies is making them driveable, especially near idle. This is simple physics due to the tremendous perimeter area of the big throttle blade. Barely crack it open and you have too much air, making the throttle touchy to the driver and impossibly responsive for the engine management computer to use for idle control.
Well, impossibly responsive until you dampen the engine with retarded ignition timing, says Jim. Once that was figured out, the barn door of a throttle body was ready to idle placidly at stock rpm. We did not drive Frank's car, but Frank and Kenne Bell techs say it's smooth as stock.
Jim Bell reports the throttle body is in stock and shipping now. The $799 includes the throttle body, adapter plate to bolt it to the Mammoth intake, and a Hypertech handheld programmer with the necessary tune.
To demonstrate the new throttle body Kenne Bell set up a simple test at nearby GTR Performance. Frank Lanzas black GT was once again strapped to the rollers--Frank's car prototyped the Kenne Bell manual-transmission 5.0 kit--and the stock and Kenne Bell throttle bodies were run. Additionally, we tried three different blower pulleys to show how the power gain increases with growing power.
There were no problems or unexpected delays. Swapping the throttle bodies and pulleys was straightforward, and the only other work was downloading the necessary tunes for the stock or KB throttle bodies as necessary. (There's no way the big KB throttle body will operate with the same tune as the stocker.) Downloading is done in the usual Kenne Bell fashion, with a Hypertech handheld.
Details of the results are in the nearby sidebars, but suffice it to say the new throttle body supports power into the 600hp range with laughable ease. More boost and power are coming with a smaller crank pulley/harmonic damper combination and a reinforced oil pump, but that's a story for another time.
Horse Sense: Normally Kenne Bell would have hosted this test on its in-house Dynojet, but it was tied up with another long-term project. Luckily GTR is just around the corner from Kenne Bell and has its own Dynojet, hence the neighborly visit.
With Ford supplying near-race engines to the showroom floor and aftermarket specialists such as Kenne Bell delivering well-engineered blower packages, it's getting ridiculously easy to dial in nearly any power level desired. Furthermore, there's no need to split hairs in this throttle body test. Each step shows a clear step up the power ladder, the curves not changing shape but simply getting steeper in response to increased cylinder pressure.
Occasionally listing just the peak numbers gives a surprising clear big-picture look at a test. This is one such time, as the peak rear wheel horsepower numbers show:
|Pulley||Stock TB||Kenne Bell TB||Gain|
It's especially clear from the synopsis that the large throttle body pays off increasingly large dividends as the power level goes up.
For the record, the test car was nearly stock save for the Kenne Bell equipment. Specifically, stock headers and catalytic converters were used; a Pypes after-cat kit gives it a muscular tone but likely didn't materially affect the results. A Kenne Bell Boost-a-Pump aids delivery of pump gas, doped to about 100 octane with canned octane boosters; and the ignition remains stock.
Accommodating the wildly different...
Accommodating the wildly different stock and 168mm throttle bodies on the intake tube requires adapter plates...
...Flush hardware and O-ring...
...Flush hardware and O-ring gaskets are features of both. Doesn’t the stock throttle body adapter’s small hole look like a restrictor plate in this context?
Small as it looks, the stock...
Small as it looks, the stock 80mm throttle body is all that’s truly needed up to 600 hp, although the larger KB unit delivers the bigger numbers more efficiently.
|Stock TB, 4.125 Pulley||KB TB, 4.125 Pulley||Stock vs. KB|
|Stock TB, 3.875 Pulley||KB TB, 3.875 Pulley||Stock vs. KB|
Ricardo did all the driving...
Ricardo did all the driving on his chassis dyno, while Ken manned the laptop. Kenne Bell supplies specific tunes for the blower kit, with either the stock or 168mm throttle body. For our testing, the tunes were downloaded directly by Ken, who also monitored the data logging to avoid any trouble. There wasn’t any.
If you have four hands, you...
If you have four hands, you too can change pulleys in record time! All Kenne Bell superchargers are designed for rapid pulley changes using a special $25 tool to hold the pulley while torquing the single retention bolt. Pulleys, which are available in 0.125-inch increments for $69, typically change in three to five minutes.
Sometimes the combination...
Sometimes the combination of blower pulley and belt length conspire to require moving the upper idler pulley during blower pulley changes. Such was the case during our test, but it’s no big deal. The idler pulley, seen here in the foreground with a blue, 6mm Allen retention bolt, is unbolted from its mounting plate, moved to the next of three available tapped holes, and reattached. The spring-loaded belt tensioner does the rest.
If anything, the 168mm Kenne...
If anything, the 168mm Kenne Bell throttle body looks even larger when viewed from its backside. KB considered a twin-bore design at first, but was able to make the higher-flowing, less expensive single-blade design work in the end.
There’s nothing trick about...
There’s nothing trick about the fluting on the upper and lower edges of the 168mm throttle body opening. They are simply machining marks left when whittling out the oval portion of the opening. They don’t hurt airflow (as if a little less would matter), and to smooth them would require switching to a smaller cutter and more time in the CNC machine. In other words, more cost.
|Stock TB, 3.625 Pulley||KB TB, 3.625 Pulley||Stock vs. KB|
Kenne Bell supplies its throttle...
Kenne Bell supplies its throttle body with the critical throttle shaft, gear, and magnet relationship already set, but without the electric motor, idler gear, or cover. Those items are pirated from your stock throttle body, as seen at right. The redundant Hall Effect sensor technology in the throttle body electronics is supplied by Pierburg and is notably more accurate then previous systems. It's one reason why there is no separate idle air circuit--a real triumph with such a huge throttle body.
Along with their other innovations, Coyote engines use new electronics in their throttle bodies. Previously Ford throttle bodies employed a carbon resistive wiper to generate the throttle position signal. This is a contact system where a metal wiper sweeps across a carbon plate, and like all mechanical systems, it is prone to wear and occasional failure.
Coyote throttle bodies replace the contact system with a solid-state magnetic sensor to track throttle blade position. A magnet is fixed to the end of the throttle shaft while a proximity sensor embedded on a small circuit board mounted close by the throttle armùbut not touchingùsenses the magnet's flux field to generate the necessary position signal used by the engine management computer. Except for the rotating throttle shaft, there are no moving parts, and with no contact, the system should easily last the engine's lifetime.
One consideration is the shaft and its magnet must be both the correct distance from and in the correct orientation to the proximity sensor. This is done during throttle-body manufacturing, so you don't have to worry about it. So, while the throttle body works differently, swapping the stock Coyote throttle body electronics into Kenne Bell's 168mm unit follows almost the same procedure as before.
In general, the stock throttle body cover is removed, along with an idler gear and small electric motor. The motor and gear slip in the KB throttle body, and the stock Ford cover is screwed on. The only details are setting the backlash in the gears, which is easily done using a tiny gauge as shown in the photos, and installing the required Kenne Bell tuning using a Hypertech handheld programmer.
Under the lid you'll find...
Under the lid you'll find it's a nicely detailed plastic piece with a inset red rubber gasket and a small circuit board. Just about in the center of the circuit board is a black square; it's the Hall Effect proximity sensor for the magnet on the end of the throttle shaft. Luckily the sensor and throttle shaft relationship are automatically set by the cover and throttle body housing architecture, so there is nothing to worry about during assembly.
Use your Torx 15 bit to remove...
Use your Torx 15 bit to remove the two screws holding the motor into the throttle body housing. As the motor comes free, you'll notice that it's lightly spring-loaded in the housing, so it floats loosely in its hole when the two retaining screws are loosened.
All that's left is to fit...
All that's left is to fit the motor, idler gear and cover to the Kenne Bell throttle body. You'll need to set the clearance, or lash, between the motor's gear and the idler gear. Kenne Bell provides a 0.015-inch wire gauge for this--fit it between the gears as you tighten the motor's two retaining screws. Because the idler gear covers the one motor retention screw, you'll need to just snug the motor's screws, temporarily fit the idler gear and check the lash, then remove the idler gear and tighten the motor's screws. It'll take maybe three minutes and a couple of tries to get the lash correct, but it's not difficult.