Burns Stainless Double Slips are Hand-Made, to Your Requirements and for Your Application.
You are likely familiar with the Burns Stainless double slip merge collectors used in many top-notched racing turbo-exhausts. But did you know that the double slip concept is also an excellent choice for many naturally aspirated applications, particularly street cars and other fuel injected applications? The purpose of the double-slip collector is to minimize exhaust leakage, while allowing for a slip-on collector. A slip-on collector is often preferred over a weld-on collector for ease of disassembly and to help alleviate thermal stress which can lead to premature failures.
Benefits of using Double Slips joints:
- forms an excellent seal - minimizing exhaust leakage
- provides flexibility - alleviating thermal stress that can lead to premature failures
- easy to disassemble - allowing quick modifications
In a race car, some exhaust leakage may be tolerable, but in a street application, exhaust leaks are verboten for several reasons. First, in catalyst equipped cars, leaks of exhaust gas from ahead of the catalyst are untreated and add to air-pollution. Second, exhaust leaks can be dangerous to the vehicle occupants and the noise is a nuisance. Finally, leaks can also allow air into the exhaust system causing erroneous lambda sensor readings resulting in less than optimum performance. This last reason also affects many race cars that rely on lambda sensor readings for proper fuel metering and tuning.
Burns takes special care when sizing collector slips, and in a perfect world, they should not leak. However, the tolerance in tubing size and the possibility of misshaped tubes can cause a poor slip fit between primaries and the collector, leading to leakage. When we build headers, we take special care to assure that the primary tubes are properly sized and shaped to assure a perfect fit. We use a hydraulic tubing expander for this purpose. Since many fabricators do not have easy access to this type of equipment, a possible solution is to use a double slip collector.
During a recent discussion with race engineers from an upper-echelon race team, I was told that they were able to reduce the fuel consumption of their endurance race motor by over half a mile per gallon simply by tuning their motors with headers equipped with double-slip collectors. This may not sound like a lot, but at a 24 hour race like Daytona or particularly Le Mans, it can make a huge difference.
It should be noted that another good application for double-slip collectors is in tight spaces where a standard 2" long slip cannot be accommodated. We do not recommend using single-slips shorter than 1-1/2". For applications where shorter slips are needed, the double-slip is a great option.
Any of our merge collectors can be ordered as a double-slip collector. For a 4-1 collector, the additional cost is less than $100. Double slips cannot normally be retrofitted since a wider spacing between tubes is needed to accommodate the sleeves. Also, double-slip connections can be purchased individually for use in other sections of your exhaust.
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Shop Double Slips from Burns Stainless
When you order a Double Slip Assembly from Burns Stainless, we will provide you with an outer and inner slip. The "outer slip" is welded to your primary tube. The “inner slip” is welded to the downstream pipe and slides between your primary and the "outer slip". You now have three layers at your joint instead of two which minimizes leakage.