ADU vs. 2.5L Tdi (AEL) conrod and piston

[Pisobiker]

For anybody who might be interested in, I put here some more numbers on these parts.
Take into account numbers are rounded to the closest half of mm so might not be precise enaugh for manufacturing purposes.

Here again comparison mesurements:

1) CONRODS:

1.1) center to center lenght: both 144 mm

1.2) total weight (with bearings):
- RS2 636 gr;
- AEL 692 gr;

1.3) big end weight (with bearings):
- RS2 470 gr;
- AEL 495 gr;

1.4) small end weight (with bearing):
- RS2 166 gr;
- AEL 197 gr;

(weights might have a small percentage of error due to not "professional" scale and small amounts of oil left over them)

1.5) RS2 pin hole diameter (with bearing) is 20 mm; AEL is 26 mm;

1.6) RS2 conrod has "end to end" oil hole through it. AEL has two oil holes on top of small end, feeding pin's bearing.

1.7) AEL conrod has significantly bigger center longitudinal (end to end) reinforcement;

1.8) RS2 conrod tapers from big to small end from 25mm of width to 20 mm, while AEL is 25mm all the way.

[Pisobiker]

AEL piston numbers are of course not very interesting, but just for information completeness here piston comparisons as well:

2) PISTONS weight with pin and clips:

ADU 496 gr;
AEL 844 gr.

(here again weights might have a small percentage of error due to not "professional" scale and small amounts of oil left over them)

[Pisobiker]

here is a drawing with ADU piston main dimensions (always rounded to the closest half of mm):

[Pisobiker]

I was asked (as a joke) if the Tdi piston could have been machined to suite S2 engines, .... so here is the answer:

NO !!


and AEL piston drawing:

[Billman]

Can Someone use the AEL Conrods with custom Pistons as a cheap solution to make the engine stronger??

Greetings

[Mihnea]

Stronger for what? Stock rods can hold 600 Nm with no problems, how much more than that do you want???

[Billman]

As far as i know the stock Rods bent at applications over 450 PS !

Greetings

[Mihnea]

PS is not what bends the rods, but torque is!!!!! you can have 1000 HP at 12000RPM, this will only mean 595 Nm of torque.

you have to figure that HP is only a function of torque vs. RPM, or a theoretical value, and HP will never bend rods.

[Billman]

I mentioned the PS number for easy usage!

Have you seen many 2.2 Liter 5 cylinders rev at 12000 ?

The Stock RS2 engine makes 410, with minor tuning mods you go over 500! So i am near to the limit (600 mentioned by you) if i want to go with larger turbochargers ect!

[Pisobiker]

Billman, what Mihnea was saying of course was an exaggeration of what actually is the reality. Conrods bend over too high combustion forces (therefore peak torque limits) with very little influence of rpm (not at all for practical purposes), while break for having reached fatigue limit and too high inertial loads (therefore the connection with rpm).

This means if you assume max safe torque for the conrods is lets say 550 Nm (56 Kgm) and safe redline is lets say 7500 rpm, given you can run the 550 Nm up to redline, you will get about 595 Hp without any conrod issue.

Problem is a turbocharger capable of 500 Hp on your 2.2L engine @ 7500 rpm (therefore pushing some 1.7-1.8 bar boost at that rpm), is very likely to be able to run 2.3-2.4 bar peak boost at about half that rpm, therefore exceeding by far the 550 Nm limit we previously have assumed. So you won't be able to push 100% out of that turbocharger in the midrange due to conrod issues.

In my opinion the reason for putting a "Power limit" to conrods instead of torque, is the fact on high perf. NA engines and in very high performance forced induction engines, peak torque rpm coincides with the peak Hp rpm, therfore leading to a direct link between power and conrod limit. Maybe easier to use, but still a mistake from a conceptual point of view.


going to the Tdi conrod issue, you might well use the Tdi conrods with custom pistons having a 25mm wrist pin. But a so big pin will sensibly increase weight of the piston+pin assembly, therfore increasing inertial loads and lowering max rpm limit. Don't think any application in the range of 500-600 Hp and 700-750 Nm would need a wrist pin that big.


Marco

I mentioned the PS number for easy usage!

Have you seen many 2.2 Liter 5 cylinders rev at 12000 ?

The Stock RS2 engine makes 410, with minor tuning mods you go over 500! So i am near to the limit (600 mentioned by you) if i want to go with larger turbochargers ect!

[caterpillar]

you may use a spacer in the littleend of conrods,a bushing,or so on,but i never heard it been done.then you may use 20mm xbolt in custommade pistons.remember the change of deckheigth on AEL (236mm).ADU and 3B's have only 220mm. max rev on the race 5syl was 9500 on s1 and imsa gto

[Billman]

@ Pisobiker
Thanks for the explenation, i knew that it is not appropiate to use HP for Conrod issues but it is more familiar!

you may use a spacer in the littleend of conrods,a bushing,or so on,but i never heard it been done.then you may use 20mm xbolt in custommade pistons.remember the change of deckheigth on AEL (236mm).ADU and 3B's have only 220mm. max rev on the race 5syl was 9500 on s1 and imsa gto

If a spacer can be used between the conrod and the piston wrist pin then can't we use the AEL conrods with the RS2 pistons (maybe a little space is needed for the upper Conrod part!

I ask for using the AEL conrods for a cost effective option instead of Stronger Conrods!

Any idea of how much the AEL conrods can handle?

Thanks

[Audi_CQ]

PS is not what bends the rods, but torque is!!!!!

What about "pinging" / detonation because of bad fuel / mapping etc. Probably a real "rod-killer" ?

[Mihnea]

What about "pinging" / detonation because of bad fuel / mapping etc. Probably a real "rod-killer" ?

Well, yeah, if you look at ppl saying "Carillos are ****, I've bent 3 of them" or "Eurospec rods are crap, I've broken them", I can tell you most of these people had tuning problems before anything else.

you can have the stiffest rods in the world, if the tuning is not right and the engine detonates badly, there's no chance the best rods in the world won't bend/break.

Mihnea

[Billman]

I think the only advantage on AEL rods is that they are relative cheap and a little stronger than the RS2! But still they are cast and very heavy!

Greetings