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In Reply to: ERT Under Pulley Problem (long) posted by PKE on July 20, 1999 at 11:36:17:
We hear you and would like to set the record straight regarding our underdrive pulleys. We have had about a 10% complaint record on our underdrive pulleys, which is at least 9 1/2% more than we expected and 10% more than we wanted so we have taken a very close look at this product to sort out what may be the problem. What I am about to report to you is what we have already told the three dealers we sent the pulleys to.
First, let me address the a/c belt throwing problem. Note, please, that I said a/c belt, not crank belt nor fan "belt" (?) as one fellow implied. We all take problems seriously, whether we think they are real or not, and in this case, obtained measurements on the crank pulley, u/d pulley, and a/c pulley en masse. It appears that there is a fairly large variation in tolerances with the stock a/c pulleys. It also appears that BMW matches their stock crank pulleys with the a/c pulleys when building automobiles to ensure minimal variation. The tolerances with the underdrive pulleys are .0025 inch compared to .0020 inch for the stock crank pulley and .0065 inch for the stock a/c pulley. Our u/d pulley is CNC produced, thus the close similarity in tolerance to the BMW stock crank pulley. When we ship out an underdrive pulley, we do not know what the variation of the customer's a/c pulley is, so about 10% of the time there is some problem with alignment. This problem is easily alleviated by shimming the a/c pulley so its face is coplanar with the compressor pulley face. We have done this and in every case where we have had a complaint, it has successfully solved the problem.
Second, I would like to address the issue to which Jim Conforti referred, that is crank shaft damage. We were made aware of a potential problem, by Will Turner, where a combination of our pulley and the lightweight flywheel may be causing excessive stress on the crankshaft. If true, this could be a very serious problem - so we investigated by hiring an outside source to look at the problem. The results are as follows:
The stock crankshaft, stock crank pulley and stock flywheel were evaluated to determine their harmonics and other characteristics. Then the stock crank pulley was replaced by the u/d pulley and tested, the stock flywheel was replaced by the l/w flywheel and tested, and, finally, the two aftermarket items were tested together. As suspected the u/d pulley was causing some slight imbalance; but, surprisingly, so was the l/w flywheel at twice the variation as the u/d pulley. And, together they were causing significant imbalance. Apparently, the crank pulley with its harmonic blaancer was minimizing the imbalance of the l/w flywheel. When the two were mounted together, they were reinforcing the harmonic imbalance at a point in the crankshaft which caused concern.
Apparently, the u/d pulley by itself, and, even the l/w flywheel by itself do not present a threat to the operation of the engine under even race conditions. But, the two in combination cause a potential situation where crank damage "might" occur. It became apparent during the testing that CNC'd parts can have a balancing problem and that because and item is manufactured on a CNC machine does not guarantee its perfection (both the u/d pulleys and l/w flywheels are manufactured by this hitech method). As a precaution, ERT has had all its unsold u/d pulleys rechecked for balance and balanced should they need it. We recommend that the u/d pulley and l/w flywheel not be installed on the same motor.
I think it appropriate here to say that ERT has never acknowledged a design problem, per se; the pulley works for the purpose designed, i.e., it provides 10 to 15 Hp more for the 3-series BMW automobiles. The problems occurring upon installation of the u/d pulley have resulted from a combination of circumstances, none of which have had to do with poor design. I hope we have provided the solutions to overcome those circumstances. We sincerely regret the problems the 10% of you, our customers, have had. Please let us know if we can help.
: I purchased the ERT pulley from Bekkers and installed in April this year. It worked fine until July. I lived in central California, where is gets hot starting in July.
: The AC belt came off twice in two weeks. The belt was messed up the first time and had to be replaced. The second time, the belt was again messed up plus messing up the fan blades, which needed to be replaced. Even the dealer mechanic noticed the misalignment of the pulleys.
: I had the pulley taken off and put back the stock pulley.
: Bekkers informed me that ERT fix to have the customer shimmed the pulley for alignment. And ERT would not admit the design flaw, nor would they agree on any refund. If most M3 owners, like me, take their cars to driving schools or spirited driving, I do not want to worry about a fan belt coming loose.
: I remember several other M3 owners had posted similar problem with the pulleys. I think we should get together and talk to ERT on the matter.
: Right now, Bekkers indicated that they have a lot of ERT pulleys on their shelf that no body wants and ERT would not even allow them to return the pulleys either.
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