Trying to make a choice on pistons... forging material question.

[Bubba]

Building my KA-t.
I'm looking for your opinions and advise. Any and all comments will be greatly appreciated.

Ok, so I'm at the point where I'm ready to make a choice on pistons. My only issue is out of my 3 picks, Wiseco-Arias-Supertech , there are 2 different types of aluminum used.

Supertech uses the 4032, which has less thermal expansion and allows for tighter clearances.

Wiseco and Arias use the 2618 which expands a bit more but has seemed to be the top choice for a strong bottom end build for quite some time.

I also noticed between the Wiseco and Arias pistons, the Wiseco come standard with a friction coating on the skirt and are a little bit lighter.

I plan on maxing the build out at about 450hp, mainly concerned with maintaining an add-load of torque. Maybe 550 if I get a raise and a DD to allow for playing and breaking stuff, lol.

What do you think? Anyone using these brands?

[e1_griego]

I used Arias in my ka-t, but only because I found them for $200 shipped brand new lol.

[Colorado S14]

I have Arias and have no complaints, but were I to do it again I may go Wiseco due to that skirt coating.

[Bubba]

I was leaning towards Wiseco also as far as the 2618 material went but some people act like the Arias are better, or maybe it's just because they saw them on the AMS site and not the Wiseco's. LoL

[gawdzilla]

i've had good luck with wiseco's product and customer service in my RB. they did come with the coated skirts which was a plus. another factor was just availability in the US at the time i built my motor. they balanced out very well at the machine shop with my oem rods. i also called wiseco tech support to get some info on proper ring gap and they were helpful (not to mention correct). i think i also dropped one on the ground during assembly (doh) and it was still usable.

i've read that wisecos do expand more and you need to run them looser, but my motor has no piston slap whatsoever when it's cold.

i have no info on arias, but i wouldn't hesitate to buy another set of wisecos for a different application

[Tower240sx]

as long as the offset piston pin is maintained the forging that is strongest should be chosen piston slap is mainly a domestic non-offset pin issue.

Piston skirt coatings are a definite plus in any build less heat less wear less $hit in your Oil.

Wiseco sounds like the choice to me, all companies mentioned are reputable and have been around for years for a reason, if they were selling snake oil they'd have been weeded out years ago.

I also feel at the 450hp level any forged piston is gonna be happy as a pig in $hit as long as you keep detonation at bay.

[Bubba]

I guess I'm back on the Wiseco wagon. My only other concern, Wiseco's aren't offered in less than 9:1 CR.

Wiseco's were my original choice but there's more chance of me screwing something up with a higher CR. I'm used to the 8:1 and 8.5:1 motors my buddies were running, which I almost always ended up elbow deep in before long. I think I'm the only mechanically inclined person I know really.
I've played with boosted cars over the years, but this will be the first time I build my own. Was hoping for a lower CR to work around. Nothin to it but to do it I guess.

Thanks again to those that responded.

[veilside180sx]

There is nothing wrong with the 9:1 Wiseco's for making power. The difference is very small with that .5 point of compression.

We made 633 whp on Rick's with those off the shelf pistons.

[Bubba]

Sounds good. I can live with more power out of boost and a slightly quicker spool time.

Thanks guys.

[Def]

Semi-related question, how do SR/KAs fo om track with boost and a 9.0:1 CR? Any real difference as far as sensitivity to detonation?

[Bubba]

I was always taught (old skool v8 guy) that a higher CR led to the motor being more sensitive to detonation.

I was hoping someone would have mentioned it in one of the responses.

[Tower240sx]

Bubba,

It does don't let anyone fool ya,

HOWEVER...our combustion chambers and the amount of timing control in the modern engine management just means that it's much less of an issue,

lots of guys run as high as 9.5 or 10:1 on turbo applications now, it lets you get away with a little more cam duration and still be able to drive around off boost,

I assume if you're building a motor complete you will be having the car tuned on a chassis dyno so the timing and fuel will be sorted anyway.

if this was dyno queen queers dot com i'd recommend 7.2:1 and 57psi of boost for that super pimp flat as a wall torque curve that you can't get out of the parking lot with.....but a little better curve is always welcome here and you won't miss the 5 HP up top from having a degree or two less total timing under boost,

if you want a lower CR with those pistons you can order a custom HG from cometic in any thickness you like....I did this to bring my SOHC pistons in a DOHC motor back down to 10.7:1, but you lose some squish in doing so...everything is a tradeoff

Mike

[LigouriRd]

Semi-related question, how do SR/KAs fo om track with boost and a 9.0:1 CR? Any real difference as far as sensitivity to detonation?

I have been running a ka with CP 9:1 pistons since '04 and have never had any issue with detonation. Granted I have only been tracking my car two or three times a year. Starting out I only had an rpm based timing retard (Apexi ITC). I now have a tunable rom (Calum) with ¾° retard/lb of boost in those regions of the map. My knocklite is properly calibrated and has never gone off. I do run a little rich though, sometimes dipping down to 10 afr though.

For my next build I am using 9:1 Wiseco's purely because of the coating. The CP's do scuff a bit when the engine is cold.

[Def]

I was always taught (old skool v8 guy) that a higher CR led to the motor being more sensitive to detonation.

I was hoping someone would have mentioned it in one of the responses.

Oh but I did. I can see 9.0:1 working on track... I just wonder if it significantly lowers the boost threshold. Then again, I think us Nissan guys don't really push the boost near as much as Mistu guys with "similar" motors. Some kid at the track with an EVO 8/9 was running 33 PSI with the stock turbo. It was retarded, and sounded like a gargling manatee on crack going down the front straight. It never blew up all weekend FWIW...

I currently run ~13-14 psi on track. I'm betting it could do a bit more on 93 in the cooler months(stock CR, 8.5:1, stock HG), but on the hotter months I'm betting that's not too far off the limit(on a turbo that flows that much). I think 18+ PSI is just too much on track from the amount of power/heat that's created.

[Bubba]

Most of my drive time will be on the interstate and most of my mods outside of suspension will be aimed towards cooling the vital parts. I race what I drive, regardless of who thinks what. Part of my race you brought outlook.

If it will take the boost, I'll gladly feed it.

[WorkInProgressK]

Oh but I did. I can see 9.0:1 working on track... I just wonder if it significantly lowers the boost threshold. Then again, I think us Nissan guys don't really push the boost near as much as Mistu guys with "similar" motors. Some kid at the track with an EVO 8/9 was running 33 PSI with the stock turbo. It was retarded, and sounded like a gargling manatee on crack going down the front straight. It never blew up all weekend FWIW...

I currently run ~13-14 psi on track. I'm betting it could do a bit more on 93 in the cooler months(stock CR, 8.5:1, stock HG), but on the hotter months I'm betting that's not too far off the limit(on a turbo that flows that much). I think 18+ PSI is just too much on track from the amount of power/heat that's created.

Don't they have direct injection? Or the stock computer is able to retard the **** out of the ignition on signs of detonation?

In the end we are still lucky. If you have a EBC, you can pretty much have a push to pass. A+6psi for a short period never hurt anyone :) Well maybe the ego of the person your passing :D.

[Matt93SE]

sounded like a gargling manatee on crack going down the front straight.
so is that good or bad? :D

[Bubba]

Good for an Evo. I assume the gargling was inspiring? LoL

[tonto]

I think 18+ PSI is just too much on track from the amount of power/heat that's created.

how much control do you have from piston cooling (oil squirters)? i think some piston designs lend themselves better to oil cooling than others.

[Def]

how much control do you have from piston cooling (oil squirters)? i think some piston designs lend themselves better to oil cooling than others.

I think EVERYTHING just starts getting very hot at that much power. Combustion chamber, pistons, water temp, oil temp - I think it'd all be tough to keep it all happy when you're pushing the limits of pump gas.

Not saying it can't be done, but a little splash of race gas probably makes things much safer.

I've considered meth injection, but it just seems like one more PITA thing to remember at the track. Plus I'd be a bit worried something would happen to the pump and you wouldn't know until your motor was in Ikea-Hard-To-Assemble pieces all over the track.

[Bubba]

Damn ikea...

I still haven't checked to make sure Wiseco's have the offset wrist pins. Work has me strapped here lately, anyone able to confirm this? I'll save the getting bitches out at work issue for a more pressing issue if so. LoL