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The BBR Mini replaces the Drive Belt Idler with a custom Cosworth Drive Belt Idler. They claim that the OEM one is not reliable. Since BBR has the highest output tuning package on the market, they must have done some research.
Has anyone else seen this as a problem? Is BBR just being over cautious or should this be upgraded with a smaller pulley.
Randy saw his first failure this last saturday during a pulley install. He told us on sunday that this is the first one he has seen fail (the damper failed), but he maybe has just been fortunate. After seeing my tensioner out of the car I would really like to see the cosworth, seems there would be room for improvement in smaller pulley applications where the unit would have to take up more slack!?
To tell you the truth I don't know what I am talking about, since I haven't seen it apart. I just know that BBR is pretty adamant about replacing it, and with the mention of some form of an idler failing at the last pulley party I decided to bring up the question.
BBR said the engine block is quite good on the Mini and they have thrashed the engine at well over 300hp with no problems. The only weakness they saw as they started to try and break the engine was the exhaust ports being to small at 23mm. They said these were quite small for a normal engine and wholly inadequate for a forced induction engine. They also said the Drive Belt idler would fail as they tore up the engine. So they developed a Cosworth idler to fit it.
Since they have tried to tear up the engine and have really examine it while they run it hard I thought there advice might be good. They also have alot of experience on smaller forced induction engines so there might be something to this.
Back to topic I wonder if you can source these cosworth units by themselves without purchasing BBR's kit. I think this years future 240-250h.p. cars may need it.
I personally see the potential of of the ported intake, head work, cam, tb, pilo's supercharger upgrade and an intercooler upgrade along with the 19% pulley is going to be the rich man's hot set up 250 plus h.p. with all the other usual mod's I'd bet.....now were talking FAST
I believe that BBR replaces the OEM idler with a more robust units manufactured by Cosworth Technologies. I would be interesting to find out if BBR sell this idler on the open market or if any of our NAM vendor friends can speak with Cosworth as see if they can import the pieces and distribute in the US.
The second option, is that this Cosworth idler is OEM part from Aston Martin or Ford (Focus SVT).
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2004 MCS Indi Blue /W Sport, Lapis blue interior - Stock for now, but not for long.
I will try to contact BBR in the morning to see if they sell this separately. I am going to Europe in the next two weeks, so if I can get one from them I can get them to ship it to where I am at.
Yeah if you look at the BBR 275, which produces 250ft/lbs of torque, they have to replace a lot including supercharger (probably like one that M7 was showing) intercooler, head, cam, tb, gear ratios, LSD,... and it ends up be $14,000 extra British pounds. Not chump change. There other kits are well priced, which makes it sound that this is what is needed to get the power up there.
Technically EVERY pulley in that drawing is an 'idler'. The one on #1 is the tensioner, the #3 piece is a 'true' idler (used to wrap the belt around the alternator and a/c pulleys) and the #4 item is a piece used to 'delete' the a/c compressor on cars without a/c (not a US 'option'). #4 would be a good piece to locate for an all-race or minimalist MINI, it would reduce the weight up front by at least 10 pounds, couple that with the removal of the condensor, piping and hoses hanging almost entirely ahead of the front wheels would make a noticeable change in the upper end handling.
#1 and #3 are very commonplace stamped steel idler pulleys used in countless applications on the 'backside' (not ribbed) of serpentine belts. #4 is a plastic 'dummy' pully the same diameter and position of the a/c compressor. It's rather slow RPM at high engine speeds (compared to the small diameter idlers) mean that this part wont be stressed too much even in high revving, high HP applications. The problem with the small ones is that extended high speed operation tends to sling out the sealed-in grease in the ball bearings within. THe pulleys themselves are not serviceable or able to be taken apart to fit different bearings into. This is where the Cosworth-type idlers come into play. They are designed to be run at insane speeds for long periods of time.
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There's only one thing in that pic that looks like an idler, and it looks like it replaces #3 (or maybe the pulley wheel that is part of #1).
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"Well, sure, the Frinkiac-7 looks impressive, don't touch it, but I predict that within 100 years, computers will be twice as powerful, 10,000 times larger, and so expensive that only the five richest kings of Europe will own them."
It would make some sense to increase the size of the #1 or #3 pulley when there is a reduced pulley fitted to the 'charger not only to make up for the extra slack that would be there with the stock-length belt in place, but to also move the belt closer to the 'charger pulley and giving it a bit more 'wrap'. This would have an extra benefit of compressing the tensioner spring a bit more and tightening the belt as a whole. I dont know if this is done or not.
The #3 pulley would have additional strain placed upon it in a high boost situation, where the tensioner idler doesnt see anything different, because it's on the 'slack' end of the belt. The tensioner in the MINI unlike so many other cars has a steel wheel instead of the far more common plastic one. It's a tough little mill.
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MMC #28|Motoring ID RAGE666
I contacted BBR about the idler pulley. They can sell the part individually as well as any of there other parts. They manufacturer this part themselves and it is based off a Cosworth pulley. They indicated that it was the one closest to the road. Not sure which one that is, maybe Andy or Greatbear can help. They stated the price is $125 pounds, and they can ship anywhere.
What do you guys think of this? Will it add reliability to the upgrades or is it a precautious measure when attacking much higher horsepower?
When the idler freezes up usually the belt gets so hot due to friction that it melts apart. Considering that replacing a belt on a transverse engine is not exactly the 5 minute job that a normal belt replacement is, I'd say replace it. I had one freeze on my Jeep that took out the entire accessory bracketry because the idler froze and then worked out the bolt out enough for it to start wobbling which destroyed the mounting hole.
#3 mounts to the block and is on the tension side of the belt (fixed postion, closer to the front of the engine) and #1 travels with the spring tensioned follower on the slack side ( at the rear of the engine). Since both are te same diameter and therefore rotate at the same speed, one would think both have the same failure potential with respect to lube slinging. #3 might possibly be loaded more.
the AC and alternator pulleys are larger and would rotate slower.
>>#3 mounts to the block and is on the tension side of the belt (fixed postion, closer to the front of the engine) and #1 travels with the spring tensioned follower on the slack side ( at the rear of the engine). Since both are te same diameter and therefore rotate at the same speed, one would think both have the same failure potential with respect to lube slinging. #3 might possibly be loaded more.
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>>the AC and alternator pulleys are larger and would rotate slower.
John, GreatBear had a great Idea there about larger tensioner pulleys with better bearings. I know you must be a busy guy but do you think your secret workshop may be interested in developing something to correct this failure potential.
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Has anyone documented a case of failure of one of those idlers? It sounds like the known tensioner failures are documented here, and they don't have anything to do with the fixed idlers:
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"Well, sure, the Frinkiac-7 looks impressive, don't touch it, but I predict that within 100 years, computers will be twice as powerful, 10,000 times larger, and so expensive that only the five richest kings of Europe will own them."
I haven't heard of any failures except for BBR stating that they saw failures when they pushed the engine. At this point there seems that theoretically there could be failures based off of what jlm and greatbear have stated. I guess this is why I posed the question.
My ultimate concern is that I would like to maintain the longevity of my Mini while doing some mild modifications. If when changing the pulley there may be some other design elements to consider to compensate for it, I would like to examine it. I know that short term the 15% pulley is not a problem. But a lot of people haven't logged 100,000 miles on one yet either. I am guessing that since the JCW doesn't replace it, that most likely it may be okay and this may just be a concern that BBR has where they saw them failing when the engine was pushed to 400hp. Not sure.
here is some data, taken directly from my spare engine parts:
tensioner roller: 1" face, 2.55" dia, attached to a small centering boss on the bracket and held there with a bolt and depressed-center steel washer.
fixed idler: 1" face, 2.75" dia, the only locating boss is the depressed center on the stamped steel washer. There is spacer that holds the bearing away from the block.
The wheel construction is stamped steel; two halves are sandwiched around the bearing and riveted together.
the bearings are high quality with Viton seals; I would say the weak part of the design is the method of centering and holding the hub of the bearing to the block.
Harmonic balancer pulley is 5.4" dia.
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My experience in other vehicles has been the tensioner failing. I would try to beef-up this assembly. I would also try to address the idler’s mounting.
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