Bad news. Threw a rod and blew up my RS2ed 3B engine

[AudiCoupeParts]

Does anyone have any ideas what would have caused my rod to snap and blow not ONE but TWO holes in my 3B block????

To give you some particulars of my engine.....


3B block and head with about 130K miles

Rebuilt head, all new gaskets. Block left stock and untouched except a good paint job.

RS2 parts....EM, IM, TB, TURBO, FPR, FR, IC, Mineha chips rated to 2.5bar, 2.5 vmap PT, 1.5 WGS, oil windage tray. Everything new or in super used condition.

Spec 3plus clutch that bites very well.

Was power shifting from 2nd to 3rd and the rod blew at about 5300 RPMS climbing out at WOT and the boost gauge pegged at beyond 25PSI (off the scale).

Big fist size hole in block created behind the starter motor, and golf ball sized hole on the left side of the block at the top bolt for the motor bracket mounting point.


Anyone have an idea? I never had the car on a rolling road test yet, so I don't know what kind of HP she was getting but she could stuff you into the back of your seat.

I know Mineaha spiced up the chips beyond stock RS2 HP levels from what he told me.

Maybe 350HP range maybe a tad higher.

What could have happened???? Looking for all to jump in and give their 2 pence worth or 2 cents worth of knowledge!!!

TIA

Joe
www.audicoupequattro.com

[Jamo]

Looking at your spec and it becaomes clear, unfortunately you ran an RS2 turbo on stock rods.

The RS2 turbo has proven time and again that it can destroy stock rods in a jiffy as it produces torque beyond the rod safety limit and will bend them quite easily if driven aggressively.

[220bhp]

Oil pump is it new or old, and was it the rod nearest the fly wheel.

[Jamo]

Question is that 2.5 bar absolute or relative?

[terrybullwon]

I have some nicee looking 3B block here that a RS2 turbo chucked a rod at

Should be a rule of thumb to up grade the rods with this turbo.

[a4kquattro]

Looking at your spec and it becaomes clear, unfortunately you ran an RS2 turbo on stock rods.

The RS2 turbo has proven time and again that it can destroy stock rods in a jiffy as it produces torque beyond the rod safety limit and will bend them quite easily if driven aggressively.

disagree. nothing different between AAN rods and 3B rods, yet the AAN doesn't have this problem? The answer: pre-ignition.

[EspenW]

The rod most likely bent due to spark-hop, which caused pre-ignition.
Electrical resistance in the combustion chamber was so high that the current that was supposed to go to the spark plug went to the next cylinder instead.
Resistance increases exponentially with boost.
Likely incorrect width rotor in the distributor (Audi lists wrong part) might have contributed.
A/F mixture ignites at the wrong time (way too early), and the piston/rod is greeted with the full force of the combustion while on its way to TDC.
This happens on 3B due to the single coil setup. ABY/AAN/ADU with individual coils do not suffer from this. They are not immune to pre ignition, but they do not suffer from spark-hop, so the rate of bent rods on these is much, much lower.
Mulitiple ADU's out there running 440+ pounds of torque w/o problems.
Solution for 3B is uprated single coil ignition or conversion to individual coils.

[AudiCoupeParts]

Oil pump is it new or old, and was it the rod nearest the fly wheel.

It was actually two rods that went. #5 nearest the Flywheel and #3, about center but I have not yest confirmed the second one exactly. But #5 is for sure.

Oil pump is original but always has shown 5bar under load and I run Mobil1 full syn oil which I checked daily.

Joe

[S2central.net]

'electrical resistance in the combustion chamber' ?????????????

I'd agree with a spark-hop theory here, caused by a dissy / rotor arm problem but nothing to do with combustion chamber resistance - I just can't visualise that at all.

Paul

[AudiCoupeParts]

Question is that 2.5 bar absolute or relative?

Not sure. I would imagine relative pressure since the highest petrol octane we have over here is 93 octane. I don't think I could get absolute boost levels like that without race petrol.

[AudiCoupeParts]

disagree. nothing different between AAN rods and 3B rods, yet the AAN doesn't have this problem? The answer: pre-ignition.

I have found on etka that all the 3B,7A, ABY, AAn. share the SAME rod part numbers so agree that the rod is not the culprit.

[EspenW]

It's simple, Paul
Increasing charge density increases the resistance for the spark to jump from the spark plug tip to ground. This increases exponentially and not linearly with boost.
This is the reason why upgraded ignitions are often required on cars running (much) more power than stock. The resistance can become so high that the current finds an easier path to ground inside the distributor cap, firing a cylinder that has less charge density (thus less resistance) in the combustion chamber. Use of the wrong, wide rotor makes this much more likely to happen.

[AudiCoupeParts]

'electrical resistance in the combustion chamber' ?????????????

I'd agree with a spark-hop theory here, caused by a dissy / rotor arm problem but nothing to do with combustion chamber resistance - I just can't visualise that at all.

Paul

I agree with Paul. I don't see that 'electrical resistance in the combustion chamber', but I also cannot imagine spark jump at around 5300 RPMS either since I have driven the car for months now and shifted at higher revs without issue. Also, this was only the second time I was power shifting with my newly broken-in SPec clutch. Before the new spec was installed I would spin the stock clutch disk and never get to full torque when I accelerated.

[AudiCoupeParts]

Yes, I do have the "wider" rotor. Oh no.....

[EspenW]

I have found on etka that all the 3B,7A, ABY, AAn. share the SAME rod part numbers so agree that the rod is not the culprit.

Indeed, they do. Mihnea mapped RS'2 with stock turbos and rods are running 620nm of torque w/o throwing rods. Chck the width of the rotor tip. Would not be surprised if it is the 17mm version that Audi (and Bosch) lists for the 3B. Scarily, this is the wrong one, the correct one is a much narrower 11mm. The wide one makes it more likely for the spark to hop to the wrong cylinder when boost (and resistance) goes up.