Budget 10:1 Piston Option (interesting)

[Jarrett]

I require you to make a member's ride thread in Other Automotive of that 260Z NOW!

[deevergote]

I think i'll have to "Just do what PR CB7 said.".

He quoted that SO out of context!

He's right, though. We're not tinkering with bleeder valves and SAFCs anymore. Even the most basic free tuning software offers pretty powerful control over engine management, especially in the hands of someone capable.



The 2.0L engine is the "World Engine" or "GEMA" engine (Global Engnie Manufacturing Alliance)... basically, from my understanding anyhow, the block was co-designed by Hyundai, Mitsubishi, and Daimler-Chrysler. The heads are all independently created by the respective manufacturers, and as mentioned, I'm sure the internals vary. However... if the Genesis pistons work, why not the Evo pistons? Or the Caliber pistons (non-SRT-4... they were 88mm in the 2.4L, though based on the same engine)? That would triple the options for sourcing pistons, and one may be a better design than another.



And yes... MRT for the 260 or ban!

[mtnickel]

The difference is the rod length. For whatever reason, Genesis's version of the engine decided to use longer rods, thus decreasing the compression hieght (moving the wrist pin higher on the piston). The other versions have it considerably lower resulting in a piston that would travel higher than the deck height.
The genesis even has a different engine code: G4KF (vs 4B11T)..

He quoted that SO out of context!

He's right, though. We're not tinkering with bleeder valves and SAFCs anymore. Even the most basic free tuning software offers pretty powerful control over engine management, especially in the hands of someone capable.



The 2.0L engine is the "World Engine" or "GEMA" engine (Global Engnie Manufacturing Alliance)... basically, from my understanding anyhow, the block was co-designed by Hyundai, Mitsubishi, and Daimler-Chrysler. The heads are all independently created by the respective manufacturers, and as mentioned, I'm sure the internals vary. However... if the Genesis pistons work, why not the Evo pistons? Or the Caliber pistons (non-SRT-4... they were 88mm in the 2.4L, though based on the same engine)? That would triple the options for sourcing pistons, and one may be a better design than another.



And yes... MRT for the 260 or ban!

[mtnickel]

And regarding tuning, yes I'm aware of our wonderful tuning options. I'm trying to decide whether it will be worth it to upgrade to Ectune from crome free (with freelog to datalog).
I've turboed the f22a years ago (back when i became a member) and used crome pretty successfully (once i decided to not be an idiot: boosting on stock map sensor, boosting with no tune, etc.).

I WILL get around to doing this build. WHEN is the big question.
Thanks for the comments guys!

Mark

[CB7/KA8]

You just gave me a great idea for the spare F23 block I have sitting in my basement. Unlike the F22, I wouldn't have to spend money boring the block. So, the only issue would be ring size as you mentioned. Hopefully stock F23 rings would work.

Pics of 260Z with a Skyline engine or it never happened!!

[Jarrett]

That would be a swap that should be less reliant on claying for clearance as the compression heights match.

[xkjnboix]

i know this is an old thread.... and you arent talking about a honda or acura but,

here is an h22a 3gp ( b20luda ) 11:1 compression, crower cams, obviously forged pistons and rods.

high compression + boost.

[TuneAccordingly]

I think I may just have to try this though. I was going to go with F22a speed-pro hypereutectics (which i've had decent success with before (see 2-3 year old post, haha)), but i think this has to be done. $35 to clay a piston would be worth it in my opinion. Worst case scenario: pistons don't fit, out $35. Pistons do fit, complete build, too much pinging under boost...lower boost and live with a more snappy high compression F-series turbo (5-8 lbs predicted).

Anyways, I'm rambling now, but wanted to keep this alive and spur more discussion!

Regards
Mark

How well did the speed pro hypereutectics do? I'm really thinking about going this route

[Jarrett]

The K20A2 pistons have a 30mm compression height and are common upgrades to the F23A. Since all of the cheap aftermarket rods on eBay for the H23A/F22A/B are 142mm then that makes up for the .5mm in compression height lost going to a shorter piston. A longer rod is always a good thing. With a factory K20A2 piston you'd need a 1mm overbore but you'd be at 11.25:1 static compression. Without the rod you'd be at 10.73:1.

[mtnickel]

Now even a forged option available out of China? I know authenticBoosting supplies kinugawa turbos which are actually quality pieces, so these may be good as well...

http://www.ebay.com/itm/Forged-Pisto...a61d81&vxp=mtr

86mm bore
30mm Compression height (1.181”)

Dish volume unknown but probably ok. At a level deck on the genesis they make 9.3:1. I doubt it has a large head volume.

Mark

[mtnickel]

A quick search on the genesis forum netted me some stock pistons for $50+shipping. Rings are a little pricey at $65, but should be intersting to see.


I will likely pick up a junkyard motor, see how long it lasts at around 250-270whp. If it lasts, I may be happy. On the side I'll pick up another block to build with these 86mm pistons. Probably add a few fun power adders since it will have roughly 10:1 compression. Cams, IM, 550+ injectors, etc.

Will keep you guys posted.

[Jarrett]

$65 is per ring pack or for the set of four? I just bought one K20Z3 ring pack from Majestic and it was $27 for one cylinder. I thought that was steep.

[mtnickel]

Luckily the same rings were available on 2007 GEMA and theta engines (2.0L compass, cobalt, many others). Those engines as well have a lot higher compression, but would be another alternative to a good High compression NA build. More difficult finding what stock Compression height is on all of them however.

As an update, The pistons have arrived.

Will be doing some measurements later on.

What I do know is that the piston small ends will likely need to be machined narrower. I may just do with with my calipers and a belt sander. Take .5-1mm off each side. Also use my .1G china scale to balance them after to make them even. Since there's no floating bronze bearing to muck up, should be ok.

My other dilemma is the piston pin offset. There is a lot of chatter on the K20 being able to be used just flipped around. If you figure out the engine rotation and where the intake/exhaust valves are, you'd realize this isn't ideal. You can either get the wrist pin offset correct, or you can get the valve reliefs in the right spot...not both.

This piston as well is the same, so I need to determine if maybe there will be enough P2V clearance even with the ports reversed. Will also measure stock pin offset and this set. I know there is some by my crude circumference measurement (difficult to explain, but I marked where the pin center was with a piece of paper wrapped all the way around the piston, if it was centered, the distances for the marks would be the same, but it wasn't).

Lots to think about and fiddle with.

[Speedz]

any updates?