This article is a follow up on our previous article that went into detail explaining the possible causes of and solutions to the S54 rod bearing failure problem. If you read that article you’ll remember that we suggested a proper solution to the S54 rod bearing problem would be to modify the engine design entirely. Since we campaign these engines in endurance racing we didn’t find any of the solutions available on the market today to be sufficient to produce the reliability we required for endurance racing.
To address this we wanted to address the major cause of the problem, insufficient rod bearing width. As we discussed before BMW had a good reason to make the S54 bearings as small as possible, this reduces frictional losses which will increase horsepower and efficiency. Unfortunately, when it came to the rod bearing, its clear they took it a little too far. Our goal was to create a cost effective solution to help those people who had already spun their rod bearings or needed to rebuild their S54 in the near future. Since we’ve been doing stock rebuilds for a while now we know the cost to rebuild an S54 using OEM parts, especially when there has been engine damage. Even the cost of just replacing rod bearings on a BMW is usually over 500 dollars in parts and labor. Once that is done you are still left with what we feel is an inferior rod and piston combination that will probably need to be re-addressed in the future. The biggest cost of the S54 is when a rod bearing has been spun and a crankshaft has been damaged significantly.
This is where we can help, we created a crankshaft modification kit that addresses the issue of the undersized rod bearing on the S54. What we did is actually quite simple and is very similar to what we’ve done on some of the stroker engines we engineered in the past. We chose a commonly available rod bearing that was a good proportion wider than the S54 stock bearing but also slightly smaller in diameter. The intention of this was to allow us to take damaged crank journals and have them re-ground to accept our wider bearing. Once the crankshaft is modified we then heat treat, nitride, and re-balance it. This service costs 950$, just a bit more than a standard crankshaft repair service for all 6 rod bearing journals.
This modification has many benefits, both in engine reliability and in economics. Most obviously the wider rod bearing will increase the surface area upon which the rod bearing and the crankshaft journal have. This increased oil volume will provide increased protection against crankshaft journal to rod bearing contact and prolong the overall life of the rod bearing. For more details on this please refer to our previous article. The remaining benefits have a lot to do with the economics of rebuilding an S54 engine. The cost of OEM BMW parts have always been high, but we chose rod bearings, and rods that are available from almost all aftermarket rod manufacturers and are, in most cases, off the shelf items. This means that bearings are economically priced and so are rods, it also gives our customers a choice of which rod manufacturer they prefer. They can use our economical option or specify a rod from any aftermarket rod manufacturer of their choice. We’ve also chosen a longer rod than the OEM S54 rod giving which many feel provides a performance advantage. A more easy to quantify advantage will be in weight savings. The S54 rod with bolts weighs in at 640 grams while our rod weighs in at just 546 grams. That is a weight savings of 96 grams (14.8%) per rod and 564 grams in the rotating assembly. Piston weight will be similarly reduced.
Once the rod has been chosen we measure compression height and are able to order custom pistons to whatever bore and compression ratio we require for that particular rebuild. We encourage you to check the pricing on OEM S54 piston rings and once again you’ll see why the economics of our rebuild makes sense. In most cases you will be getting a completely rebuilt S54 that has eliminated the most critical factory design flaw, for just slightly more than it would cost to rebuild your S54 to OEM specifications.
Click the link for more detailed pricing on our S54 Rod Bearing Widening Kit.