E30M3,

I agree with you that this is not a GB only issue, after all this is a "System" of components (engine,SC,etc). However, it is apparent that use of the GB has an adverse affect on the system. I personally doubt that it is the root cause of the failures, but I do believe it serves to amplify something that is inherent in the SC/Engine system.

The alternator bracket is not the only bracket that has exhibited a failure. The VTEC bracket has failed on both my car and SilverSurfer's car. However, the VTEC bracket failure has never been observed on its own, its always been accompanied by an alternator bracket failure or a mounting plate failure.

I'm not familiar with "Endurance Limit" or that Aluminum's is zero. But if so then that would suggest that as more miles are put onto CV brackets without cracking that the GB setup is seeing loads that don't exist in the CV setup.

I am pretty sure none of the bracket failures have been accompanied by loose/insufficiently tight bolts. Indeed the bracket I switched out yesterday had bolts that were very snug. Installed By Shad originally.

Since I am currently unemployed I don't commute in my car, not that I would use it for that purpose on a regular basis. All of the 24K miles have been for pleasure and yes some track time. I'm probably in the 70 to 80th percentile in regards to the "Level" of usage of the car... I don't drag it for instance.

If my "Endurance Limit" speculation holds out then it would seem to me that making the brackets stronger would simply serve to move the loads elsewhere, thus identifying the next weak link. If so then it seems to me that damping would be a preferred solution.

David Kennedy

 

OK
disclaimer - i don't have an SC'ed car to look at and have only the photos and descriptions to go on but i agree that this seems like metal fatigue. given the location of the bracket (vis a vis rotation) and the descriptions of the various harmonic resonance issues (and discussion of the lack of balancing that has occurred [as contrasted with a factory designed SC a la the Jag XKR or the like]) i feel that it is VERY likely that this is stress induced fatigue cracking and is caused by the lack of balancing that is also almost certainly causing the resonance.
the relationship of the GhostBooster to this is a bit more murky in my mind - but i think it is VERY likely that we will see these same results in other SC'ed cars (without the GhostBooster) over time. i think that for some reason the time to fatigue is shortened with the GhostBooster. my guess (and it is a wild ass guess I admit) is that the GhostBooster has a direct effect on the harmonic that accelerates the fatiguing process.

I think it's time to have someone look at balancing...

 

I thought that looked familiar.

Still no cracks (unless of course, you count the headlights). I knew it! The supercharger caused the headlights to crack!

Supercharged since December 7, 2000 and 7000+ supercharged miles (over 14K total). It is my daily driver and my occasional track car.

 

Jim, the early stages of the crack maybe very hard to spot unless you know exactly where to look.
From the pics (thanks David) the crack starts from the under side of the bracket (hard to see but possible) and, I'd suspect in the beginning, only to be the length of the counter bore (~1/4"). Needless to say, it would be very hard to spot in the early stages. I don't know how fast the thing would progress from there. It could be a matter of months, weeks, days or hours to go from the web of the counter-bore through the entire x-section.

All I'm trying to say here is, check it very carefully at the root of the bracket at about the 5 o'clock position (web of the counter-bore).
If it's not broken, then keep your fingers crossed (I've got mine crossed for myself so I can't help you there )

Good Luck!

 

RT, I firmly believe that you and those who support your assertions are correct.

1. Aluminum does not take to bending loads very well, especially repeated ones. It's stiff, but doesn't have much "spring" to it.

2. The way the brackets are set up appears to be a cantilevered approach off the block. The crack is appearing exactly where you'd expect it to given the stresses involved. However, due to space constraints, it may be difficult to add reinforcement and you still may have enough stress to induce a fatigue issue over time.

3. Non GB cars will see this sooner or later. So be thankful the GB guys have discovered the issue now.

Easy solution, use steel or iron. There are some other materials, but that's the simplest way. For those that have some free time on their hands, go look in your garage at your other cars. Note the composition of the accessory brackets for the A/C compressor, power steering pump and alternator (assuming you have any brackets, many cars direct mount to the block these days). If any of you can find aluminum, I'd be quite surprised. I know all mine are either the same cast material as the suspension arms (steel, grey iron?), or steel plate bracketry. And they tend to be beefy. It'll be a little heavier, and a little more costly, but you can laser cut and mill steel to the same shape as Al.

UL

 

[QUOTE]Originally posted by RT
[B]Jim, the early stages of the crack maybe very hard to spot unless you know exactly where to look.
From the pics (thanks David) the crack starts from the under side of the bracket (hard to see but possible) and, I'd suspect in the beginning, only to be the length of the counter bore (~1/4").

 

I took another look and can't find any cracks. I got out my shop light, ran my fingers over the brackets and can't find any cracks. It's a little hot right now so I'll check again when it gets cooler. Definitely no rattles though.

 

Little late to the discussion, didn't check the forum last night 'cause I was playing with my new AV Receiver and HDTV

I also talked with Shad (or Mike - I forget) a little while ago and was told the electronic fix they were working on was a voltage clamp type circuit.

For the record, I have approx. 5500 mi. total, about 4000 mi with the SC and no cracks so far.

 

[QUOTE]Originally posted by ultimate lurker
[B]Easy solution, use steel or iron.

 

Here is something of interest to you all, I just got off the phone with Modacar, they have received an email from someone in Texas that has broken brackets. Not sure who it is or if they are using a Ghostbooster set up. He is checking his email to see if he still has the original message. If I get additional information I will post it. This particular SC was purchased before the first Group Buy so it has been in the field for about 4 or 5 months.