Stroker conrods

[Henka]

So, I've got my hands on a AAT bottom end. I haven't picked it apart, haven't even picked it up yet. Anyways, I've looked through "all" the threads on stroker-this and stroker-that, I still have som questions:

- How long rods do I need to be able to run stock ABY compression height?
- How much hp can the stock ABY pistons take?
- Go for rods or go for pistons?

[AnLe]

Don't understand your question, conrod lenght is dependent of piston and other parts.

If you mean how long rod is needed if used ORginal pistons, then answer is easy, block is 16mm taller than shortblock, do your math

[Henka]

Ummm? Don't understand the question? What part of "stock ABY compression height" didn't you understand?

Now, the block is 16mm taller, the crank is 95.5-86.4=9.1mm longer. So this means I need 144+(16-9.1)=150.9mm rods. Now, then... I've done the math, happy? So now do I know what rods to buy? Nope. Wonder why? Let's try it your way then. I would have 144+16=160mm rods. I have not heard of anyone using 160mm rods, but, I've done the math. Now, please tell me, 150.9mm rods or 160mm rods? Aha - maybe none of them? Maybe something in between?

Oh and, what do you mean by shortblock? Both blocks (AAT and ABY) are just as long, they do have a difference in deck height

[AnLe]

well if you use 30mm tall pistons from eurospeck = hondas je pistons, you need 159mm long rods, if you use 32,8mm tall orginal pistons 155,5mm long rods is close.


Your math is wrong: 95,5 stoke is up and down, so its blockheight-piston compression height - (95,5/2)


236-32,8=203,2
95,5/2=47,75
203,2-47,75=155,45

and then add to lenght that you want to be deckheigt clearance, 0,7mm is my opinion. Orginal does not come so much over deck, newer measured it.

but if you use different pistons all this is wasted.

[Henka]

Yep, you got me there. You are absolutly right.

So if I understand you correctly, a 155mm rod would give me a 0.45mm squish (deckheight clearence)? Isn't that too little?

[AnLe]

we may have language prob here, technical terms are allways hard.

155,45 long rods would be EVEN to deck and my opinion is that 0,7mm over deck is good, that would make rod 155,45+0,7mm BUT that would make compratio higher than orginal, becouse it does orginally go just 0,1-0,3 over deck, this is just memory, not an actual measurement.

But alllllllways measure everything your self, do not drust anybody, it is your engine, and believe it or not the truth is NOT in the internet.

I have so many times got "race" or quality parts with so many wrongs that I dont trust any measurement that i have not made my self. Its cheaper that way.

Same goes for the calculations,

[Henka]

Geeeeeezzzz...... Note to self: think before you post. I have just got back from a vacation and, by looking back on this post, it seems I left my brains somewhere else. It's not sitting between my ears and behind my eyes, rather stuffed up you-know-where. Ah... Uh... Geeez.

We are not having lang. probs. here, I'm the prob! Let's just forget this post, huh? No, I'm going to pick up the AAT and start there. Thanks AnLe for giving me a kick in the ****, I'll get on with doing it the right way now. Over and out. Good night. C' y'all 'n da' mornin'....

[caterpillar]

henka,that was bad,hehehe,jonus use 155 mm conrods,but spm have the 158 also...the xbolt are different.

[Billman]

Don't forget this Thread!!!

What are the theoretical + or - by using longer or shorter rods?

[Henka]

Caterpillar seems to have some thoughts going about this. This is a quote from another thread:

"henka@ i think you conrods are too short....the rod and strokeratio are NOT good,with144 mm rods...similar chevrolet 5,7" and 6" .....rodlength/ stroke=at least 1,6.the higher fig,the better.with lack of torgue ,if you reduse stroke....f.x.2,5 tdiblock,and the old 1,9 or 2,1 liter crank,77,4mm,and 165(!)mm conrods
jonus have the stroker to 7500rpm with soft cut,and 7800 max.he use 155mm conrods.you may have more rpm if you have dry sump oilsystem. nearly 1000 rpm at race."

Doesn't explain why but it's food for thought.

The longer the rod, the smaller the angle between the rod and the bore centerline when the rod is at it's greatest angle. Less angle, smaller force composant ( let's call it X) in the opposite direction of the centerline of the bore. The smaller X is, the bigger the force composant in the opposite direction (let's call that Y). With a bigger Y we get a better force flow in the bore, piston, rod and crank.

On the downside of a long rod (he he), an engine with long rods take more place than an engine with short rods!

[AnLe]

there are also other things to consider the rodlengt / stroke ratio.

When you have short rod the time that piston remains in tdc is smaller, so the combustion event is different to longer rod that remains more time at the dtc.

Then there is piston speed, there is limit what oil film can protect, and passing that point is not good for the engine.

144/86,4 = is 1,67 Perfect
155/95,5 = 1,62 not signifcant difference.

BUT

to use small/short block and diesel crank, needs somethin like 140 rod
140/95,5 = 1,47 that is bad.

There was good article about dialynx 2.5 litre engine, with very good dyno results.

[Henka]

AnLe: About the Honda pistons you mentioned. What size piston pin (?) do they have? Parner has a set of 159mm rods but they are for a bigger size pin I think.

[AnLe]

dont remember actual model, but if you put hondas piston size's to calculator and use 159 long rod as eurospec uses, you get wery good comratios.

I do not have proof of it, eurospec may have made them selfes a custom piston.

I think hondas pin was 19 or 21. At least 22mm pin is needed if some serious power is wanted.

[caterpillar]

the ABT 1,8 4syl 20v have 159 mm conrod and 19 xpin.the 158mm audiconrods from stenparner are 23mm pin,for the heavy power. 158/95,5=1,65 factor.its ok...or for my engine its like this 158/94,5=167 factor... and 2555ccm,with tdi block i have a custom OETTINGERcranck,other crancks are avaible for audi 77,4-86,4,and 92,8.....i think it was like this....http://www.eurospecsport.com/crankshafts.html

[Henka]

So to use the Parner 159mm rods you really need custom pistons then?