INLET SYSTEM COMPARISON

KENNE BELL “GIMME 5” vs. JLT BIG AIRNothing is more important to supercharger efciency than the inlet system that feeds it. At Kenne Bell, we spend a lot of time and money on the ow bench, dynos, supercharger dyno testing inlet systems and throttle bodies to guarantee our inlets are optimized.

Our Shelby Gimme 5 Rear Inlet System ows more air and, therefore, has the highest HP potential of any Shelby inlet system - except the new BIGUN. It connects to the largest highest cfm throttle body (2150 cfm) and matching manifold opening. It was designed to support up to 1600HP on a rear inlet 4.7L

It has come to our attention that a replacement inlet system by another vendor is being offered as a “bigger” and better upgrade for the Kenne Bell Shelby Gt500. Let’s look at just why “bigger” is not always better and why it does not automatically ow more air and produce more HP. We believe that any manufacturer has an obligation to keep their customers informed of issues that may have a negative effect on the performance or reliability of their products.

INLET SYSTEMS - WHEN BIGGER ISN’T BETTERLet me also say that if the JLT was truly both bigger AND better, we wouldn’t be having this conversation. That is not the case, so we cannot recommend this kit. Whoever conceived this product apparently wrongly believed that a single bigger component is everything. Hyping the largest part size e.g. a “massive 155mm MAF” can get you in trouble with inlet systems as you will see - and generate a response from us.

AIR FLOWFirst of all, any inlet tract (lter, canister, meter, pipe, throttle body) is limited by the size and cfm rating of the smallest component in the chain - not “boosted” by the largest advertised part. Example: It doesn’t help to mount a larger opening 155mm funnel to the end of a straw - and boast about it being “bigger” than the straw or a Kenne Bell 128mm meter. Regardless of how big the funnel is, ow is ultimately limited by the size and ow capacity of that smaller straw - AND what feeds the 155 or 128 meter. We learned early on that size isn’t the only thing with everything.

The JLT incorporates a similiar “funnel” concept - relatively large round 155mm (6”) lter and 155mm MAF meter. Unfortunately, it bends and necks down to 4.5” at the nal component, the KB 168mm x 79mm (6.5”x4.1”) throttle body. Like the straw, it is smaller and, therefore, more restrictive than the funnel and lter.

METAL vs. CARBON FIBER vs. PLASTICAlso, the carbon ber looks glossy and smooth on the outside, but it is rougher on the inside. It’s the way carbon ber is. The rougher inside diameter is more restrictive to ow because of the higher C-factor (wall surface). It’s why plastic, copper and aluminum tubing have a C-Factor (Williams & Hazen) of 140-150 and cast iron steel is 100. And why smoother wall piping is the overwhelming choice in any industry where max ow, low loss and higher efciency are paramount.

Unlike the JLT, the Kenne Bell “Gimme 5” standard kit inlet tube is a big smooth wall, straight (no curves), chrome plated 5” aluminum. And it is the shortest straightest distance between the 5” lter and our throttle body - a straight shot.

In their literature, JLT bashes the proven, higher cfm Kenne Bell “NO METAL TUBING HERE” inlet pipe. But since 2009, the Kenne Bell Mammoth has outowed and outperformed the competition on our Ford Shelby, 2V, 3V, Camaro and Hemi Kits. Mark Dubers street Shelby recently made 1425RWHP on a Dynojet using the very same original Kenne Bell Gimme 5 Rear Inlet System shipped on all Shelby Kits. How much HP do you think the 1850 cfm JLT carbon ber would lose vs. the Kenne Bell 2050 Gimme 5 on Mark’s car?

FILTERS JLT 6” vs. KB 5” (Inches x 25.4 = mm)Again “size only” is misleading. A larger lter opening (6” vs. 5”) is not a guarantee of higher air ow. On the contrary, the KB 5” ows at least 2450 cfm or 20% more than the JLT 6” (2050 cfm) because of several factors including shape, exit lter pleats, surface area, end cap etc. Oops. The biggest advantage all KB lters enjoy is

the superior discharge radius design. That is key to the 2450 cfm ow. Example: Add a radius to any pipe and the ow increases 5-53% DEPENDING ON RADIUS SHAPE. A 5” pipe is 1640 cfm. Add the 5” KB lter to it and it doesn’t lose ow. Flow actually increases a whopping 53% to 2512 cfm (see actual test). See how a well engineered 5” with a ared entrance stomps the same size pipe without one - and a larger 6” with relatively little or no are. And yes, our lter was over designed to ow more air than our 2050 entire system to allow for contamination (2512 vs. 2050). So how efcient is the JLT “bigger opening” 6” lter and radius compared to the KB 5” lter and radius? Again only 2050 vs. 2450. What’s all that hype about their lters that ow 20% LESS air?

PIPE SHAPEThe system photos say it all. The KB 5” is a straight full size no bend - no reduction design that eliminates turbulence by encouraging a laminar (straight) ow pattern. Again, physics and common sense tells us that the ideal path for air or uid between any 2 points is a straight same diameter full open smooth wall pipe. The JLT has curves complicated by a reduction of size and shape from 6” round tapering down to a smaller 6.5”x4.1” OVAL discharge to the throttle body. Not exactly the ultimate design shape.

THROTTLE BODYKenne Bell offers the largest highest cfm throttle bodies for the Shelby - up to 2350 vs. the competitions 1900 cfm. The above comparison tests were conducted on our ow bench with the same Kenne Bell 168mm 2150 cfm throttle body so as to not limit the JLT to the smaller stock size 148 x 65mm throttle body pattern used by all the other companies. 13% is a big number in our world as it chokes off a lot of HP.

DRY FILTERSFinally, JLT offers a dry lter. Think about it. There is a reason for oil soaked lter media . . . IT REMOVES MORE CONTAMINANTS. At least according to my tests and what FRAM ran for me in 1990. DO NOT use these “dry” lters on Kenne Bell superchargers. Like any supercharger or turbo, even ne particle debris and dust are not encouraged. Not rocket science. Just common sense. We have used S&B lters on our turbo and supercharger kits since 1989. No problem with their oiled lters. None better.

In summary, the Kenne Bell Gimme 5 Inlet System ows 2050 cfm vs. JLT 1850. That’s 11% better and big potential HP losses if using the JLT. We can prove the KB 5” lter design and shape, coupled to a matched 5” stratight smooth aluminum pipe is far superior to a hodge podge combination of a lower cfm 6” lter and 6” pipe opening that tapers into a curved tapered rough wall carbon ber pipe.

On lower HP Shelby applications with smaller stock or 1900 cfm FRPP throttle body and manifold bolt pattern, the JLT may be adequate as it certainly ows more than the stock Shelby system by a wide margin on our ow bench. However, on the higher HP Kenne Bell Kits, our larger more efcient 3.6, 4.0, 4.2 and 4.7 superchargers demand a maximum air ow inlet tract. Even our Gimme 5 was not adequate for some Kenne Bell customer applications. That’s why we offer the 2550 CFM BIGUN Throttle Body and Rear Inlet Cowl Manifold that is capable of supporting 2000HP - without NOS.

Some points worth mentioning:1. An inlet system cannot be “too big” or ow too much air. If it’s oversized, you have the exibility of increasing HP without restriction. A mere 1 psi inlet loss can be huge. 1 psi resulted in a 44HP loss when testing our BIGUN inlet system on Mark Meiering’s 1749HP Shelby motor. We have documented in excess of 100HP losses on restrictive inlet systems.2. The only truly accurate way to read inlet loss is with a sensor behind the throttle body on the dyno or a HP calibrated ow bench capable of duplicating engine air ow.3. Always use an oversize oiled lter to compensate for debris build up. Or clean more frequently. Again, we use a 2450 cfm lter (22% larger) with a 2050 cfm system.4. Stay away from large diameter (4” and larger) plastic hi-mol tubes etc. in the inlet tract. They tend to distort and leak at the rubber couplers.5. JLT claims their heat shield “seals” to the hood. Better review that claim. If the hood rests on or close to the lter, air ow is obviously impeded. We test the hood and inlet system as an assembly on the ow bench. You may be surprised at the ow with the hood closed. 6. We did ow test the complete JLT with the snorkel lter installed in the heat shield. It lost up to 100 cfm depending on where the lter is located. Someone should have done this before making claims. That is what

ow benches are for. Our advice is to refrain from bashing the Kenne Bell chrome aluminum tube and redesign the kit as it’s no match for the factory KB Gimme 5.

And a mere .5 psi can be 30HP. What does all this tell you about a stock rated 400HP air box and lter that is used on a 650HP supercharged application. Remember that switching to a $549 JLT, you were led to believe, will increase HP but carries another unfortunate consequence for our customers - the cost of a new tune ($450).

We hope this discussion has been helpful and informative. For more real world interesting and factual dyno and ow bench testing of inlet systems and throttle bodies, you may want to check out:http://www.mustangandfords.com/how-to/engine/mmfp-1109-throttle-body-guide-air-apparent/viewall.htmlhttp://www.superchevy.com/how-to/transmission/1306-boosting-your-horsepower-gettin-air/viewall.html

Kenne Bell “Gimme 5” lter and pipe outow 6” on same Kenne Bell 168x79mm 2150 cfm throttle body. Smaller 148x65 and 148x72 throttle bodies (max 1900 cfm) further restrict ow to supercharger. Note big radius where KB lter meets pipe vs. minimum radius on 6”. We learned very early that size isn’t the only thing for every thing.

1850 CFM

2050 CFM

5” PIPE1640 CFM

5” PIPE WITH FILTER2450 CFM

Open pipe vs. same pipe with Kenne Bell 5” radiused lter entry. Illustrates importance of good air ow engineering in inlet tract. Flow benches don’t lie.

GIMME 5 FILTER2450 CFM

6” JLT FILTER2050 CFM

Many factors determine actual air ow of a lter other than size rating. Higher restriction lters reduce air ow and engine HP. Who doesn’t know that?

Complete GIMME 5” System (’07-’14 Shelby) matching big 168mm or Dual 75mm throttle body. Same kit used on Shelby Super Snakes and Shelby 1000. Note “straight shot” smooth wall chromed aluminum pipe. No cheap plastic or carbon ber here. The lowest cfm component will determine max air ow/HP, not the “size” of any single part.