why did the big end go?
Discussion
It's a 1986 Audi quattro turbo that has had quite a lot of work done to her to run 386up. I know it's not that much for a Quattro, but tried to keep it driveable on the track. Boost comes in at 3 1/2 grand etc.
Anyway after a track day last week end No3 big end 5h1t itself big time. I wasn't driving it at the time so not too sure what happened.
Now i'm kinda wondering what would cause it to go? Is it lack of oil, oil too hot or over reving? I can't tell about lack of oil as the strainer is full of big end so there are signs of lack of oil every where. (the guy kept driving inspite of the death rattle)
Yes, she has a rev limiter, but it dosent work when you're change down.
thanks for any thoughts
Anyway after a track day last week end No3 big end 5h1t itself big time. I wasn't driving it at the time so not too sure what happened.
Now i'm kinda wondering what would cause it to go? Is it lack of oil, oil too hot or over reving? I can't tell about lack of oil as the strainer is full of big end so there are signs of lack of oil every where. (the guy kept driving inspite of the death rattle)
Yes, she has a rev limiter, but it dosent work when you're change down.
thanks for any thoughts
aussiebruce said:
It's a 1986 Audi quattro turbo that has had quite a lot of work done to her to run 386up. I know it's not that much for a Quattro, but tried to keep it driveable on the track. Boost comes in at 3 1/2 grand etc.
Anyway after a track day last week end No3 big end 5h1t itself big time. I wasn't driving it at the time so not too sure what happened.
Now i'm kinda wondering what would cause it to go? Is it lack of oil, oil too hot or over reving? I can't tell about lack of oil as the strainer is full of big end so there are signs of lack of oil every where. (the guy kept driving inspite of the death rattle)
Yes, she has a rev limiter, but it dosent work when you're change down.
thanks for any thoughts
You might have had the bearing on the way out for quite some time. I have had similar experience - I attributed mine primarily to oil breakdown. I would generally recommend oil changes every 5000 miles for a car that gets a hard life.Anyway after a track day last week end No3 big end 5h1t itself big time. I wasn't driving it at the time so not too sure what happened.
Now i'm kinda wondering what would cause it to go? Is it lack of oil, oil too hot or over reving? I can't tell about lack of oil as the strainer is full of big end so there are signs of lack of oil every where. (the guy kept driving inspite of the death rattle)
Yes, she has a rev limiter, but it dosent work when you're change down.
thanks for any thoughts
You might also want to think about the oil level that was used on the track day. Too low and you risk starvation, too high and you risk frothing, which can result in similar issues.
Big-ends fail when:
There's a lack of oil film so the bearing picks up.
The surface speed over the bearing is so high (ie high revs) it causes cavitation which rips out bearing material.
Combustion loads are so high the rod is hammered through the oil film and crunches the shells against the crank pin
Matt
There's a lack of oil film so the bearing picks up.
The surface speed over the bearing is so high (ie high revs) it causes cavitation which rips out bearing material.
Combustion loads are so high the rod is hammered through the oil film and crunches the shells against the crank pin
Matt
Probably oil surge...high cornering forces/braking can force the oil away from the pick up pipe and temporarily starve the engine of oil. It doesnt take much!!
I did the bottom end of a Alfa 75 V6 last year on a track day, the oil light breifly flicked on -maybe 2 or 3 seconds but that was enough. Brought it in and it just didnt sound right, let it cool down before heading for home and watched in horror as the oil pressure fell slowly down to nothing in the next 10 miles before the death rattle set in!!
I did the bottom end of a Alfa 75 V6 last year on a track day, the oil light breifly flicked on -maybe 2 or 3 seconds but that was enough. Brought it in and it just didnt sound right, let it cool down before heading for home and watched in horror as the oil pressure fell slowly down to nothing in the next 10 miles before the death rattle set in!!
Gassing Station | Engines & Drivetrain | Top of Page | What's New | My Stuff