Shorter pistons for long rod setup - disadvantages?

[evopwr]

Correct size (shorter) pistons must be ordered when going long rod setup (156mm rods) on the 4g63.

The good news is higher rod/stroke ratio = good.

However I want to know what are the adverse effects of running shorter pistons? From my understanding in general going shorter piston means thinner rings but looking at the CP catalogue the rings remain unchanged from standard/long rod pistons.

In general all I see is benefits from going long rod. Cost is very much the same as pistons/rods for LR setup are readily available..

Any thoughts on this?



-Alex

 

[4piknup]

I would have got raised pin pistons for my build, but they are not off the shelf for g64.
I also think you can get extra raised pins, they have buttons in the gudgeon holes that have the oil ring grooves in them.

 

[DOUGMO]

long rod 2.0 is pretty good, less thrust load.

 

[4piknup]

Idk, but maybe the higher pin means shorter skirts and less piston stability meaning noisier and more skirt wear.
Maybe.

 

[DOUGMO]

you will get higher skirt wear, but no more than a 2.3

 

[bazeng]

I'm running a long rod short piston setup in a 2.4 block.

Nothing off the shelf so I had them made.

I did increase the length and thickness of the piston skirt on the thrust sides. This was to counter the added side wall stress with the 100mm crank.

My wisecos were cracked on all skirts with the previous build hence my decision to go custom bigger stronger piston.

 

[evopwr]

thanks guys. Didn't think about pistons 'wearing out quicker' due to shorter skirt length.

I think in such situation skirt coating would be recommended.

 

[4piknup]

Factory skirts last forever, shorter ones should last nearly 1/2 as long...I dont think it counts for much.

 

[bazeng]

You'll find the coating wears out. Bold spot is common on the thrust area.

Good read here:
http://www.dsmtuners.com/threads/damaged-wiseco-pistons-not-pretty.427099/page-2

 

[bazeng]

With a shorter skirt you will get less stability in the bore at the bottom of the block.
Somewhat rocking of the piston.

With the decreased rod / stroke ratio (rod length (mm) divided by crank stroke(mm)). You will increase wear and tear overall on pistons, block, rings.

Pistons are usually tapered when manufactured due to the rocking effect.

I gave my piston manufacturer.
1. 4g64 piston
2. Stroker piston

I told him to make me a stoker piston (high pin) with the skirt design similar to the 4g64 piston.

I've revved my 2.4L to 8500rpm so far.

Keep in mind, if you are running oil squirters, you will have to look at clearances.

Also keep in mind, i had to grind my block down internally at the bore to clear the long rod length.
I am running Manley I beams 156mm rods (turbo tuff series).

 

[blackvr]

Hey Jack.. I think you are overthinking the short skirt/lower compression height piston setup .

Yes, you can buy off the shelf long rod/lower compression height piston for the G4CS Hyundai block . I'm doing one of these strokers for my own VR4 road car... and I bought 156 mm rods and the accompanying pistons off the shelf later last year. No problems ! And the skirt is about the same length as a standard 150mm rod / stroker piston .

So , like I said, I think your worrying over nothing !

 

[4piknup]

1/2 of forever is still a long time is my point, blackvr, Id say get them, no question. Noone here is building a motor and expecting 200k km+ out of it.
I went to 22mm pin as well, so I would have needed 7 bolt raised pin g64 +20thou and frankenstien 156mm rods. (6bolt b/e and 22mm gudgeon) not impossible, but the bits are bought now.

 

[blackvr]

Jack, Manley offer that very combination conrod ( Turbo Tuff I beam, extra HD) ... 156mm, 1G wide big end bearing and 22mm gudgeon pin... straight off the shelf ! Wish they did that a couple of years ago !

 

[4piknup]

I got manley rods too. I may have seen those rods.
I got wiseco 7 bolt pistons. Maybe I couldnt get raised pin pistons in 22mm pin, g64 +20 with the correct valve pockets.

There was something, maybe it was just the price. I dawdled over the choices for ages

 

[evopwr]

1G rod big end width is best anyway (on a 7 bolt crank) as you can machine the width to suit tolerances...