Rb25 W/ Wiseco 86.5 Froged Pistons P2W Question *** For The Builders

[drpheel]

After having the infamous ring land failure on the stock bottom end I have decided to go with new pistons and rods for this season , The car will be running Wiseco 86.5 pistons and I would like to know what kind of P2W (piston to wall) clearance you guys are using. I know the 0.0025 Wiseco recommends is way to tight for a high boost application with pump gas. I have already talked to Wiseco and have a ball park Idea on what i want to run but I would like to have information from the builders as to what you guys are running.

Wiseco 86.5 : K578M865AP

Brian Crower rods

running 2 bars on 94 Octane

supporting mods

Thanks for reading and please inform me if you want any other info on the build

Edited June 12, 2014 by drpheel

[XKLABA]

I have those exact pistons in my 2630 and we tightened them up to 2 thou, car has seen 28psi on E85 but at 30psi it miss fired due to backpressure from the turbos

Motor has been running since Feb last year, cold dry comp tested two weeks ago and all 6 were within 5 psi of each other

[djr81]

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Edited June 12, 2014 by djr81

[drpheel]

I have those exact pistons in my 2630 and we tightened them up to 2 thou, car has seen 28psi on E85 but at 30psi it miss fired due to backpressure from the turbos

Motor has been running since Feb last year, cold dry comp tested two weeks ago and all 6 were within 5 psi of each other

Wow! running them 0.0020 instead of the recomended 0.0025? i know Wiseco says the coating will wear down about 0.0005 but maybe the fact that you are using E85 and not seeing the same combustion temperature as a pump gas engine at the same power level

Thanks for your input, I will take note of this information

[djr81]

Not sure what alloy Wiseco use but most pistons are about 4 thou.

[drpheel]

Not sure what alloy Wiseco use but most pistons are about 4 thou.

Wiseco uses 2618

2618 alloy , low silicone. This makes the piston more malleable and causes them to deform rather than shatter under extreme pressures. therefore the piston will expand more under heat = more p2w clearance they will have about 15% greater tensile strength and about 10% greater fatigue endurance then 4032. High HP application usual put the p2w clearance loose to prevent the piston from sticking to the cyl wall if any unwanted expansion occurred and sacrifice a little blow-by on idle until they warm up and eventual wear of the cyl wall over time.

4032 alloy, high silicone will have less expansion, low p2w clearance but when they go out .... they BLOW out. they will more likely shows less sing of wear in the cyl over the long run then 2618 because they will be very little difference in size at operating temperature letting the builder use a tighter P2w clearance. so less slap in the cyl when getting up to operating temp and less wear on the cyl walls.

Funny quote from the Honda guys forum ; Build it loose, only you will know OR build it tight and EVERYONE will know

[djr81]

Wiseco uses 2618

Funny quote from the Honda guys forum ; Build it loose, only you will know OR build it tight and EVERYONE will know

Well 4 thou is pretty normal for 2618.

Actually you build it loose and everyone will know - because it will rattle like a b!tch on start up. Dont have any noise out of mine with 4 thou but it might get a bit colder where you live.

Just for interests sake:

http://www.jepistons.com/PDFs/TechCorner/SCPDrawings/piston_instrc2618.pdf

Compared to

http://www.jepistons.com/PDFs/TechCorner/SCPDrawings/piston_instrc4032.pdf

And for other, old school stuff - the clearance is 5 thou.

http://www.aclperformance.com.au/NissanRB26DETTForgedPistons.htm

Anyway if you check the JE docs carefully it recommends more clearance for turbo motors for obvious reasons.

[drpheel]

Well 4 thou is pretty normal for 2618.

Actually you build it loose and everyone will know - because it will rattle like a b!tch on start up. Dont have any noise out of mine with 4 thou but it might get a bit colder where you live.

Just for interests sake:

http://www.jepistons.com/PDFs/TechCorner/SCPDrawings/piston_instrc2618.pdf

Compared to

http://www.jepistons.com/PDFs/TechCorner/SCPDrawings/piston_instrc4032.pdf

And for other, old school stuff - the clearance is 5 thou.

http://www.aclperformance.com.au/NissanRB26DETTForgedPistons.htm

Anyway if you check the JE docs carefully it recommends more clearance for turbo motors for obvious reasons.

Great info ! thanks again I will have to call wiseco back because i know the coating they have on the pistion skirts goes down about 0.0005 when it wears out so il have to take that in consideration to. altho this is what Wiseco says about the coating on the webpage :

Some of our forged pistons offer our new ArmorGlide™ skirt coating, which is the result of testing, development, and benchmarking through Wiseco’s rigorous in-house dyno program. The outcome is the ultimate in skirt coating toughness, lubrication, and bond technology working together to minimize friction, maximize horsepower, and provide improved wear resistance. Not only is ArmorGlide™ a high-tech lubricant that reduces friction, but it also allows the piston to be fitted tighter within the bore allowing a better ring seal and reduced noise from piston rock.

Not sure if that is done for the initial seal /break in for the rings and eventually wears out to give a little more clearance when pushing it harder. Il get on the phone with Wiseco ( if i get the line ) and report back my findings !

Thanks again for your input #@djr81