Click on a thumbnail to see the full-size image
The Obd Ii Shop: Will Machine Shops Be Able To Pass Added Technology Costs On To Their Customers?
By Norm Brandes
These days, OEMs push the envelope in terms of precision engine building techniques. Will machine shops be able to pass added technology costs on to their customers?
After a recent tour of the DaimlerChrysler Kenosha, WI, engine plant, I came away with a lot more questions than answers about the future of engine rebuilding, especially for small and medium shops. The procedures I saw may even cause problems for the large production rebuilders.
I watched two different production lines in operation. One line produced the 4.0L six-cylinder used in the Jeep. The other line made the 2.7L V6 used in the new Chrysler 300M, the Concorde and the Dodge Intrepid.
The 4.0L won’t present any special problems for an engine rebuilder; it is an old war horse with a cast iron block and head, and aftermarket parts are readily available. Furthermore, machine work to rebuild a 4.0L will not require any new equipment or skills.
On the other hand, watching a 2.7L being made raised a lot of questions about the challenges that will confront engine rebuilders. Although my comments are based on watching the 2.7L, one of DaimlerChrysler's most sophisticated engines to come off the line, all of the major carmakers are using similar techniques to produce their newest engines.
The deck, or joint face as DaimlerChrysler calls it, passes through a multi-step surfacing procedure using multi-blade polycrystalline diamond cutters. When the surfacing is completed, the deck on the 2.7L head is finished to a smoothness of 0.5 to 1.25 micrometers Ra. The finish is so smooth, you could mount a 2.7L head on the wall of your bathroom and use it as a mirror when you shave. Similar multi-step machining processes are used on all the critical surfaces of the 2.7L.
The largest production engine rebuilders might be able to afford the precision cutters and special setup jigs that the OEMs use, but the cost would be out of reach for most machine shops.
I know some people say extremely precise and smooth finishes can be achieved using conventional cutting and milling machines. All you have to do is reduce the feed rate to as slow as an inch per minute and use the sharpest cutting edge possible. To me, that is like saying a surgeon can do just as good a job with an ax as he can with a scalpel, he just has to take a little more time. There is no substitute for precision equipment and trained technicians when you have to do precision work.
The quality control checks were also impressive. DaimlerChrysler uses a special air gauge to measure the seal of the valve seat after it is installed in the head. The fixture is inserted into the valve seat and a metered amount of air is forced through the fixture. The amount of air leakage, which measures the quality of the seal, is read on a digital readout. Air gauges are fairly common in aviation applications, but this level of quality control precision is now becoming common in the automotive industry.
At another station, a computer-controlled set of electronic probes measured all critical valve dimensions including concentricity, roundness, deck-to-valve-seat height, valve guide clearance and the relationship between the valve guide position and the seat face. The computer program prompts the quality control technician to insert the correct probe for each measurement.
Then the readings from the probe are stored in the computer and compared to the pre-set production standards. Another computer-controlled system is used to measure the quality of the surface finish to make sure it is within specification.
During the production run, one head is pulled from the line every 15 minutes for quality control checks. Heads are also pulled for testing immediately after any cutting head is replaced or a major change has been made to any production equipment.
I don’t know of any aftermarket supplier who can provide this type of sophisticated gauging equipment for a rebuilder. Equipment suppliers I've talked to aren’t sure how they are going to meet the challenge of providing the machining and measuring equipment for rebuilding the latest engine designs. And even if the equipment were available, the cost would be out of reach for most shops.
Even the way the heads were physically handled in the factory would put many rebuilders to shame. After the final finishing cuts are made, I didn’t see another piece of metal touch any finished surface.
Whenever the heads were placed with the deck side down, it was on a piece of plastic to prevent scratching. Even the racks used to store the heads have plastic-coated pegs to avoid damaging the heads. Because the finish is so smooth, a special protective packaging must be used if the heads are shipped out of the factory.
As I was told about the special packaging used to protect the heads, I thought about all the times I've seen a rebuilder toss a set of newly machined heads into the bed of a pickup to deliver the heads to a customer. And how many times were those heads taken out of the pickup bed and dropped on a dirty workbench?
Do we need this level?
As aftermarket rebuilders, do we really need to match the machining and measuring precision of the OEs? I'm afraid that we do. For starters, the onboard diagnostic system, including the sensors and the programming, was designed to operate on an engine built to OE standards. Secondly, the engines were certified to EPA emission standards with engines built to OE standards. And last, but not least, component life and warranty coverage is based on OE standards.
Some rebuilders have a mistaken notion that their work won’t have to meet original standards if the engine is out of the original emission warranty. That idea is wrong. The OBD-II system on a car doesn’t measure time and it doesn’t measure mileage. It doesn’t matter how old the vehicle is or how many miles it has been driven because the computer system will continue to monitor emissions as if the vehicle were new.
OBD-II will set a MIL (malfunction indicator light) whenever the system detects a problem within the engine or when emissions exceed 1.5 times the standard at the time the engine was certified.
The current emission standards set by the EPA are tight, and they will get even tighter. The recent proposed change in standards, which will probably become official by the end of the year, will cut current NOx emissions levels by 90% by 2004. A margin of 1.5 times the standard doesn’t give a rebuilder a large margin for error. The emission levels are so low, any increase in emissions can quickly exceed the 1.5 time level and set a fault light.
The risk of setting a fault light will be greatest during cold starts. For approximately the first 90 seconds after a cold start, the mixture is rich and the catalytic converter isn’t hot enough to effectively do its job. Any problems with the rebuild that interfere with emission control are most likely to show up following a cold start.
After the systems are warmed up, a properly functioning catalyst gives the rebuilder a greater margin for error because the catalyst can absorb excessive emissions, up to a point.
In addition to possibly setting a MIL, if a rebuilder doesn’t match OE quality, they can run into other problems. For instance, customers reasonably expect their rebuilt engine to perform like new. If the rebuild is going to perform like new, it has to be rebuilt like new.
Then there are premature failure and comebacks. For example, OE and most aftermarket head gaskets are designed to work on a joint face that has been machined to OE levels of smoothness. The replacement head gasket can literally be torn apart if the mating surfaces are rougher than OE specification. For some engines, some aftermarket gasket suppliers offer replacements that supposedly can be used on a rougher than OE quality surface. Whether these modified gaskets allow the rebuild to reach original performance levels is still a question in my mind. And, in any case, the modified gaskets are only available for certain applications.
Who pays the price?
Perhaps the biggest question facing rebuilders trying to meet OE quality levels is who pays? The Dodge Viper with the V10 engine sells for about $70,000; the Dodge Intrepid with the 2.7L is in the low to mid $20,000 range; and the Dodge/Plymouth Neon with its four-cylinder engine lists for about $12,000. The three cars differ widely in price, but the technology to build their engines is very similar. More importantly, the cost to do major work on those engines won’t vary as much as the cost of the cars.
Obviously, the owner of a Viper is more likely to spend the money for major work than the owner of a $20,000 Intrepid. And there is a real question if the Neon owner can or will spend $1,500 or more for major rebuilding work on a four-to-five year old car that is worth less than $6,000.
Unfortunately, there aren’t enough Viper owners to go around to support all the rebuilders. How do we tell John and Mary Average that they have to pay a high cost for major repairs because the engine, from a rebuilder's point of view, is the same as the engine used in a luxury or high performance car?
I wish I had all the answers, but right now, all I have are a lot of tough questions.