Thoughts on Rods and Pistons

[popdemonic]

Datasheet said 9.3:1 for stock AAN.
I believe in Australia there's a well known company manufactured the rods for AAN there.
you might be better get them off there.

[igor136]

No.

Stock wrist pins just break at 750-800hp. With uprated wrist pins you can push a little more, how much i dont know. Usually at this power range it is easier to upgrade pistons and use 22mm wrist pins.

The question is why the pins break. Pin turns in the connecting rod bearings.
But there is a solution when the piston pin stands fixed in the piston rod. He turns only in the piston. This solution exists for over 50 years. Why our engines that do not have? I do not know. Perhaps the reason: more oil - less heat. But when you have a piston pin that turns into rod bush (bearing), but do not have enough oil, then the piston pin is broken. Maybe it's a good solution for the SR402, but the highway when you drive 300 km at 200 km / h ???
Another thing.
Replacement pistons, how good they are? Measure the top of the replacement piston, then measure the OEM Mahle. The difference may be 0.5 mm for the same declaration. Why, piston spreads. Less quality, more spread .
It is very nice if you have a detonation in the cylinder when the engine is cold. Then piston play football in cylinder. It's very good for oil consumption also. You always must to have a bottle of oil in the car.
This is my thinking. Yours advice, experience??
Apologies to the bad grammar, I'm trying. This is an interesting topic.

[Thuppu]

It's not by oil starvation the pinns break. Thay start to bend and then snap. They just have a limit they can hold. Some brake sooner than another, can be because of how aggressive mapping, knock, material fatigue etc.

Also how much the pistons expand doesn't tell anything of the quality. They are just different alloys, materials. You choose a alloy for the purpose you need. For example 4032 alloy is used by many custom piston manufacures. It's a good alloy for universal forged piston use. Can tolerate a lot of beating and expands less than 2618 alloy. Then again 2618 alloy is used when you need even more. This alloy expands a lot, so you need really big piston to wall clearance. That can lead to cold piston slap and high oil consumption.

Stock pistons are some other alloy than 4032, they can take really tight piston to wall clearance(0.03mm), so they expand very little. If rings and cylinders are in good condition oils consumption is zero.

[igor136]

I agree with you about the pins.
What is for you the better choice: when pin turns in the connecting rod bearings or when stand fixed?
I think it's better when it turns.

[GazzaG60]

the costs mount when you work the block. andy has change from 1k for the bits but with block work, assembly and parts to assemble, new pumps etc not much change from another grand if any at all. then its gotta be run in right and machinds right. a fair few variables. if you dont work the block then its a lot cheaper. i feel a lot can be gauged from how it ran and sounded before, visible bore wear etc.

i dont the the OP will break pins on a 35r to be honest. gotta be looking at 600hp ish really there. mapping is always the thing that holds it together. i do agree its good to know the limit. id hope a set of good aftermarket pistons would have pins that hold up.

the way i see this one is either get 3-4k ready for a good block build and refresh or just fit the rods and maybe skim a bit off.

[Thuppu]

In fact Audi stock piston pinns are quite strong. For example Wiseco and JE basic pinns are much weaker. You need to go "HD" pinns.

[Thuppu]

I agree with you about the pins.
What is for you the better choice: when pin turns in the connecting rod bearings or when stand fixed?
I think it's better when it turns.

In these Audi I5 engines the pinn should turn in the rod bearing, and it should be quite tight to the piston. There usually are lubricating holes on the rod. Some other engines can have it the other way alround.

[SteveH]

I've sure someone made new pins with a deeper wall thickness.

[rst]

I've sure someone made new pins with a deeper wall thickness.

Wiseco for example offers only wrist pins too.
Here are 4mm wall thickness:

http://www.summitracing.com/int/parts/wis-s623/overview/

If this is not enough then these with 5mm wall thickness:

http://www.summitracing.com/int/parts/wis-s708

I would suggest to use forged pistons over 700hp with 22mm pins and rods with oil hole.

[Thuppu]

Wiseco is well know of their poor pins. Propably the stock pin will hold more than the Wiseco HD. If I remember right, the wall thickness on the stock pin is thicker than 5mm.

[rst]

This car has Wiseco pistons with HD wrist pins. If i remember correctly they are 20mm.

https://www.youtube.com/watch?v=aUzE5XPAmv4

Estimated power 1100-1200hp 1.8T.

[rxl]

is there any right side to fit the aftermarket rods?

[igor136]

Always, like oem

[rxl]

Ant that would be?

[Kieron20V]

Big end at the bottom, small end at the top. Teehee.