Stage-Tuning The 6.4L Power Stroke

Stage 3: Firestone R4Tech rear suspension syste, H&S Performance Black Maxx Tuner

Published in the October 2010 Issue October 2010 Build, Feature, PowerStroke Ryan Harris

Power StrokeR4TECH

We've always been believers in air bag overload systems. But we never really gave much though to there being a much better rear suspension setup than a factory 3/4- or one-ton rear suspension matched with a good set of air bags.

Fortunately, Sanlois Rassini-a suspension and disc brake component manufacturer-did give thought to a better system than that. They developed the R4Tech, a leaf spring/air bag hybrid rear replacement suspension system, and teamed up with Firestone Industrial Products to pair their leaf spring design with Firestone's air bag technology.

How does it work? Air bags (one on each side of the axle) are coupled through air lines. With no load on the suspension, the system rides softer than a factory leaf pack found on 3/4- and one-ton pickup trucks. As the load on the suspension is increased-through trailer tongue weight or payload in the bed-the air bags' pressure is automatically increased. An air compressor and reserve tank are mounted to the truck, along with height control and dump valves. The complete system senses suspension ride height and automatically increases or releases air pressure as load changes.

The factory leaf spring packs (leaf system and overload springs) are removed and replaced with the R4Tech leaf system. The R4Tech is designed to control the axle like a 4-link suspension with the lower control link, while a J-spring controls axle wrap and brake hop, like a trailing link system. You get better performance than a 4-link system, because you have the benefit of the single leaf-over-axle rather than relying completely on air ride.

Installation requires no drilling or welding, although it is a pretty hefty job. You need to remove the factory leaf springs, blocks, stops and hardware and replace it with hangers, mounts and brackets. It takes time, but the ride is worth it.

Another cool feature we like is the kneel feature. It lowers the rear end of the truck for easier loading and trailer coupling. Once you're hooked up or loaded down, the automatic ride height adjustment takes over.

The R4Tech is up to 140 pounds lighter than the factory rear suspension. On a truck like our heaviest-in-class 2008 Ford F350 project truck, the weight reduction is welcome.

We installed the R4Tech system on our truck earlier this summer. Since then, we've towed everything from a 20-foot car hauler with ATVs to a 30-foot bumper-pull travel trailer. The R4Tech system handles rides extremely smooth with no load. In fact, it's a vastly better ride than the factory F350 rear end could offer. But what really surprised us was how smooth and stable the R4Tech handled under loads. All of the jars and thud feedback you would get form the factory leaf pack were gone. The R4tech system rode incredibly well. No swaying, no hopping, no front-end drift. And the system is completely hassle-free. All you do is hook onto your trailer and go. The R4Tech system should be standard equipment on each of the Big Three's premium models-it's that good.


We went looking for the ultimate in plug-n-play horsepower for our 6.4L stage build, and we think we found it in HS Performance's Black Maxx tuner.

If it looks familiar, don't worry. H&S Performance uses private-label tuner units that are similar to the PMT. But looks are all the two have in common. The Black Maxx is designed to run alongside a DPF-delete exhaust system (off-road racing applications only, of course.) for maximum performance. Like most tuner/monitor systems, the Black Maxx comes standard with engine parameter monitoring features, like boost, EGT, coolant temp, oil temp, corrected speed, engine rpm, etc (up to 20 parameters). It can read and clear trouble codes.

The hardware is a two-color system with five buttons on the left side and two on the right.

One of the perks of the Black Maxx hardware over some of the competition is the ability to select tunes on the fly. No need to stop and reflash the ECM to step up or down a level. The Black Maxx also allows for transmission tuning on the Ford Torque Shift with 6.4L Power Stroke applications.

H&S is also working on a menu which allows for full control of nitrous and/or water/methanol injection.

While the Black Maxx comes preloaded with three "Mild" tunes, you can download custom tunes from the H&S Performance website. You can flash your Black Maxx module with "Easy" tunes, which are 40, 80 and 130 horsepower tunes ("Mild" includes 80, 150 and 225 horsepower tunes). Or you can opt for the "Hot Damn" tunes, which are 80, 175 and 250 horsepower tunes. A built transmission is required for `Hot Damn" tunes. All three tune packs also include a 0 horsepower level for transmission tuning.

Here's what we like about the H&S Performance Black Maxx tuner for the Ford 6.4L Power Stroke:

Cold Coolant defueling. As long as the truck's engine coolant temperature is below 140-degrees F, the Black Maxx automatically keeps the tuning at level 0 (no added power). It's a fail-safe system for dummies. And we've seen enough dummies running hot tunes to more than justify this feature.

On-the-fly tuning selection. Picture this: you're running a towing tune and some glow-light ricer pulls up alongside, thinking he's filming for the eighth installment of Fast and the Furious. Would you rather hit a button and put the street racer in his place, or pull over, reflash the ECM, and spend the next hour waiting for the next ricer to come along? Easy choice.

Throttle response. We've tested four major race tuners for the Ford 6.4L. The Black Maxx has the best throttle response of any of them. Its tuning throws loads of fuel at the bottom end, lighting the twin turbos quickly. The throttle response is superb.

Power. Breaking 12.5-inch-wide 35s loose under the heaviest crew-cab on the market is no easy feat. The Black Maxx's "Mild" 225-hp tune can do it.

Mileage. We're doing a long-term test to see where the real numbers stack up, but we've been running the Black Maxx long enough to know that it offers some considerable improvements.


Firestone/Sanlois Rassini R4Tech

H&S Performance

Flo-Pro Exhaust
4-inch Stainless Downpipe-back system

BD Diesel Performance
6.4L Boost Scoop

Prosport Performance

Fox Racing Shox

PML Covers


Mamba Offroad Alloys
Type M1 22x9.5

Nitto Tires
Dirt Grappler M/T 325/50R22

Powerlabs Diesel

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