took motor apart...look what i found..pics

[180sx]

but i did see hydralock do that too.... depending on turbo size and ur engines compression rate at 20 psi u may have had enough of final compression to lifted the head for that split second

[WDRacing]

I've never seen detonation bend a rod...the piston will crack to pieces first. The problem has to be manufacture related..it's ALWAYS the number 3.

[180sx]

if its e not de than it has no oil squirters boost spike and timing spike produced way too much final compression for long skinny overheated rod to handle ...

manufacturers defect thow? crank journal on #3 is wierd ? or engine was rebuild by a wierdo for that diffect?

[Craving4Boost]

20 psi on what turbo size? and is it e or de

HMM WELL KA FIRES 1342 so looks like it was boost spike/detonation related 1 was on exhaust stroke , 3 was on compression stroke ...was.... and 4 was on intake...explains why # 3 rod looks like that ... what u controll timing with? it was quiet aggresive at the time of the spike ....

i think if it was over rev piston would be hanging on the side of the block

craving 4 boost how do bearing look like ?

ka rods are long and skinny so they don't like detonation much nor do factory pistons with those skiny ringlands.

stock de can handle up to 400whp if fine tuned properly and about 200 whp without tuning or with ur crappy safc etc

i control the timing with a msd BTM. the bearings look fine to me. i did not have enough fuel obviously with my 370cc injectors

[180sx]

craving4boost s in ur case ... not enogh fuel would detonate and thats past tdc so with gas blowby , rings/pistons would of start melting/cracking . u have bent rods and almost new pistons)are ur pistons non oem?(. no i take back what i sad it had to be hydra lock only way... .
Modified by 180sx at 6:48 PM 1/7/2006

[Chezedik]

most of them are bent though, with the exception of number one. And that wouldn't be detonation, it would be explosion! That is to say it would have to be a fierce few pings to bend the rod w/o cracking the pistons. I think what we are all used to seeing is the ringlands breaking, from numberous inaudible pings, but what if just a few SERIOUSLY audible ones occured? I think the piston is scuffed that way for a very obvious reason. It was bound against the walls.

[nissanfanatic]

Considering Ivan ran 25psi+ on a GT32(IIRC..??)ALL THE TIME and the OK guys run 20psi+ on stock engines ALL THE TIME, I'd say certian enough to disqualify that being the cause of his rod......destruction.

FACE IT, headgaskets and pistons go before the rods on KAs...common sense... Pistons tend to go first if detonation is present whereas headgaskets go if preignition is present(your lean condition would fall under this category).

[Chezedik]

I would think hydraulic lock would be obvious when the head came off, though. I don't know that is weird.

[WDRacing]

In my semi pro opinion...lol...It's not detoantion at all, even if it was present at the time of the breakage. I don't know what exactly the problem is, but using a forged rod is the only way around it, ad that is a bandaid in my opinion as well. Somthing is giving way, either the cylinder wall, crank or rod.

The KA is no where near as strong as we earlier thought. Some people may make huge numbers, but they are just biding time before a rod bends or snaps.

This resent occurence in bad motors really makes one reconsider the SR vs. KA option. Being in Asia for 6 years, I never saw an SR throw a rod...EVER.

WD

[nismofly]

im going to have a billet titanium #3 rod/piston

[Chezedik]

But just the one, right?

[UK-SRi]

The reason No3 main goes is because of the firing order, it means that bearing is rocking more than the others. That sort of a bend is a severe overpressure, look on SR20 for a severe overpressure that caused hydolock to bend all four. Dont forget that the moment the exhaust valve opens all the water will boil away, so you want see much sign of it. The only way is to deduce from the damage what happened. In an NA engine rods are damaged in tension, in a turbo they are damaged in compression. If the piston had canted there would be scuff marks on the bore and piston where the force was applied.

Mike

[Chezedik]

Do go on, do you mean on an NA motor that the rod damage occurs as the piston is 'leaving' the crank it stretches and fatigues the metal, and when the metal looses the tension it flexes back in a kinked shape? So then what you are saying is that on a turbo motor the boost pressure causes a cushion and therefore a compreesion force as the piston continues moving, causing it to bend accordingly, as we see in his, perhaps. But where does hydalock fit into this? Also, I think it is interesting that you mentioned it boiling, I never thought about it, but under the compressive forces it may (and engine heat) it may get hot enough to immediately steam away when 'decompressed', for lack of a better term. Did I smell what you're steppin' in?

[180sx]

hydrolock is #1 sourse for bent rods with no piston damage . head lifted from all the pressure enough for coolant to drip into 3/4 during boosrt spike. or some other fluid somehow got into 3/4 , cuz piston would suffer the damage during detonation.

could be dramatic timing jump and it fired btdc or preignition thus pushing crank counterwise for split sec before it reached tdc . force on piston from ignition as well on the rod from crank traveling clockwise. that pretty much pressed a rod like a mechanical press would .

but sr don't throw rods cuz rods are so much shorter , destroke ka , loose the purpose and it won't throw rods neither.

[Craving4Boost]

what would we sacrafice by destroking the KA?

[nismofly]

the rod length wouldnt change the stroke, stroke is more affected by the crank, youd actually have to lengthen the stroke to make up for the travel lost by decreasing rod length

But just the one, right?

oh yeah, no way i can afford $5k just for rods and pistons

[UK-SRi]

In an NA motor it tends to be the rod caps coming off but in a turbo motor the compressive forces are higher. The triple point of water is ~350 Centigrade if the cylinder is below that temp then liquid water will stay liquid if there is enough of it. but the moment the pressure is released by any valve opening it will boil away quite quickly. As the next poster said it could have preignited and fireed on the compression stroke. But there would be visible damage to the piston and cylinder wall for any other scenario apart from those two.

Mike

[Chuckdst]

Hi I am new to the forum and not that familiar with the KA engines (they have only been around for 15 years). My question is does the KA crank suffer from oil starvation at high RPM (7,000 & up) do to centrifugal force throwing oil out of it. On the L/Z engines some people cross drill the cranks for this reason (the U20 Roadster engine is cross drilled from the factory). I don’t know what your crank and/or rod bearing looks like, but have you or any one had this type problem or has Nissan fixed this problem on the KA.
Modified by Chuckdst at 6:35 AM 1/10/2006

[Chezedik]

It's been a while, but it occurs to me that it may be drilled. I know either side of the bearings had ports for oil. But on the rods there were no mating holes, and so I would think it was just done that way just to make install easier.

[180sx]

u looked at na ant T chrysler pt/ 2.0 sx and the difference is T rods are forged and balanced on the bottom with weights while na rods are missing balancing weight and made out of cheaper non forged metal.

as well piston on T is shorter with bigger forged ringland vs na but both use ^ piston tops and T runs just over 8 compression.

and bearings have holes in them...vs na