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Cummins Exhaust Manifold: Steed Speed Installation

Cross Thread, the UNOH Diesel Club pulling truck shows off a little on the UNOH campus with Instructor and Diesel Club faculty advisor Aaron Roth behind the wheel. The truck pulls locally and regionally whenever the team can finance a trip. The truck is competitive in the 2.6 class and has placed as high as 3rd at a Union City, Ohio, pull in 2014
1. Cross Thread, the UNOH Diesel Club pulling truck shows off a little on the UNOH campus with Instructor and Diesel Club faculty advisor Aaron Roth behind the wheel. The truck pulls locally and regionally whenever the team can finance a trip. The truck is competitive in the 2.6 class and has placed as high as 3rd at a Union City, Ohio, pull in 2014

Even on a stock engine, cracks in a cast exhaust manifold are not unusual. Cast manifolds tend to get brittle and even shrink and expand a bit during thermal cycles. Put a stock manifold onto a high-power, high-heat competition engine, where the manifold can regularly get to a light-up-your-life glowing red state, the thermal cycles are more intense and can lead to an earlier failure.

MAXIMIZING FLOW

Another issue to consider is flow characteristics. A stock, or even an ordinary aftermarket cast manifold may not have optimal flow or velocity characteristics. That is partly the rough finish of a cast manifold—but mostly the size and shape and length of the runners. The efficiency (and therefore power) idea for a turbo diesel is to direct exhaust flow while keeping the exhaust velocity as high as possible and delivering the most “push” to the turbine with the least amount of restriction along the way (ie: quick turbo spool up).

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A cast manifold can be designed to maximize flow and velocity with the size and shape of the runners, of course, but to achieve that requires a lot of prototyping and mold making to get it done. The cost of doing that can lead to a product that isn’t always “optimized.” Even when size, length and shape are optimized, the roughcast surface finish remains an issue.

STEED SPEED SOLUTION

If you go looking for a high performance exhaust manifold for your diesel, you will find many options available. Many of them are very good, but we found one that is virtually unique on the market, which addresses the usual problems very differently than the average manufacturer.

Steed Speed in British Columbia, Canada, has taken a road less traveled. In fact, as far as we can tell, it’s a totally unique idea. It’s unique enough that Steed Speed owns the patents for manufacturing manifolds in this particular way. Leen and Julie Steed have been in the manifold business for 15 years. Having started with manifolds for turbocharged gas engines, they began building diesel manifolds about six years ago.

2. The Steed Speed manifold is almost suitable for a display as sculptural automotive art. The Diesel Club ordered a manifold with a wastegate flange, though it was not initially employed and a cover is used to block it off. Wall thickness is generally about ¼ inch on the 1018 mild carbon steel. Steed Speed currently makes manifolds for Cummins and Duramax.
2. The Steed Speed manifold is almost suitable for a display as sculptural automotive art. The Diesel Club ordered a manifold with a wastegate flange, though it was not initially employed and a cover is used to block it off. Wall thickness is generally about ¼ inch on the 1018 mild carbon steel. Steed Speed currently makes manifolds for Cummins and Duramax.

The Steed Speed exhaust manifold starts with pieces of 1018 billet steel (in the case of a Cummins manifold, it’s 1 x 4 x 26 inches) that are then CNC-machined as identical top and bottom pieces for the “log.” A weld channel is built in at the edges for strength. Steed Speed then TIG welds the two halves together and coats the assembly with black Techline (a ceramic-based coating). The result is a very strong, thermally and dimensionally predictable manifold that is virtually immune to cracks and carries a lifetime warranty.

The CNC process allows for very precise internal dimensions, so the contours can be designed to deliver maximum energy to the turbo. As experimentation and field tests indicate beneficial changes, they’re very easy to implement, so product improvement is ongoing and continuous. The benefits are many. Leen Steed reports the first noticeable benefit is a drop of 200 degrees of EGT, or more, due to the improved exhaust flow and drop in drive pressure (assuming a correctly sized turbo, of course) and often an extremely efficient drive-to-boost pressure ratio at nearly 1:1. As to power, some recent testing on a 3rd Generation 5.9L Cummins – with no other changes but the manifold – showed a modest 20-25 hp peak power increase. What’s more impressive were the dramatic changes in the power curve, with a 140 hp upward bump in the curve at 2,000 rpm. This is due to the improvements in exhaust gas velocity forcing the turbo to respond sooner and more quickly.

After a couple of manifold failures due to the heat produced by the 950+ hp 24V Cummins in the University of Northwestern Ohio’s Diesel Club pulling truck, the tech team decided to go with a Steed Speed manifold to eliminate the possibility of a reoccurrence. They chose the straight flange unit with a wastegate port. Because the turbo flange on the new manifold was parallel with the head ports and not angled down, some adaptation was necessary, though it was relatively minor.

The Steed Speed manifold is not cheap, but if you have been cracking manifolds in attempts at making horses, it’s probably worth the coin. DW

3. We were not able to test this ourselves, but it’s been noted by others that the Steed Speed manifold is one of the few that can deliver a performance increase simply due to its design and construction. Certainly the ports and runners are smooth as glass and huge compared to a stock manifold. They are also carefully designed to maximize the flow, velocity and even scavenging effects.
3. We were not able to test this ourselves, but it’s been noted by others that the Steed Speed manifold is one of the few that can deliver a performance increase simply due to its design and construction. Certainly the ports and runners are smooth as glass and huge compared to a stock manifold. They are also carefully designed to maximize the flow, velocity and even scavenging effects.
4. The welding work is top notch and weld channels are incorporated into the parts for maximum penetration without the welding breaking into the runner. The charcoal grey ceramic finish will last a lifetime if you don’t chip it with careless handling. It’s not particularly vulnerable, but if you want to maintain the sharp look, you should avoid chipping it. Other colors are available, but Leen says this one is the most durable.
4. The welding work is top notch and weld channels are incorporated into the parts for maximum penetration without the welding breaking into the runner. The charcoal grey ceramic finish will last a lifetime if you don’t chip it with careless handling. It’s not particularly vulnerable, but if you want to maintain the sharp look, you should avoid chipping it. Other colors are available, but Leen says this one is the most durable.
5. Step one of the installation is to remove all the old manifolding and gaskets. The Steed Speed manifolds use standard gaskets and hardware, but they are not included with the manifold.
5. Step one of the installation is to remove all the old manifolding and gaskets. The Steed Speed manifolds use standard gaskets and hardware, but they are not included with the manifold.
6. Bolting on a performance manifold might require new hardware due to differences in configuration between the new and the old manifold. This is on a case-by-case basis and adaptation is usually not needed on the direct replacement manifolds.
6. Bolting on a performance manifold might require new hardware due to differences in configuration between the new and the old manifold. This is on a case-by-case basis and adaptation is usually not needed on the direct replacement manifolds.
7. In the case of the pulling truck installation, the turbo had to be reclocked and both the inlet and exhaust connections were adapted to fit.
7. In the case of the pulling truck installation, the turbo had to be reclocked and both the inlet and exhaust connections were adapted to fit.
8. Ready to pull. Reports from the drivers indicate the turbo is much easier to light and the truck seems to have gained back a little mid-range power.
8. Ready to pull. Reports from the drivers indicate the turbo is much easier to light and the truck seems to have gained back a little mid-range power.
SOURCES:

Steed Speed

250.766.7136

SteedSpeed.com

University of Northwestern Ohio

419.998.3120

UNOH.edu

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