MR RIZK

iTrader: (7)

Have a standad set of Wiseco 8.8 pistions for my build. The spec sheet that comes with it recommends a piston to bore of 0.0025 with a finished bore size 3.7795

I have read that some builders like to add an additional 0.001 of clearance like when using Arias pistions and high boost to allow for expansion.

Does anyone have any recomendations if I need to deviate from the supplied Wiseco spec?

Cheers,
Michael

Sharif@Forged

iTrader: (92)

Always follow the spec sheet's finished bore size and piston to wall clearance. These figures vary depending on the type of material used in the piston, it's expansion rate, intended usage and many other factors. Although I feel that 2.5 thou is a little tight, it's probably because that Wiseco shelf piston uses a higher silicon content that what you make find in other pistons. The Arias shelf piston suggests 3 thou, and the Arias Extreme Duty 5 thou.

End of the day, follow the spec sheet when comes to fitting pistons.

ttg35fort

iTrader: (2)

The specified piston to cylinder wall clearance for Wiseco's is 0.003" (3 thousandths) for N/A motors, and 0.0035" (3.5 thousandths) for FI motors.

MR RIZK

iTrader: (7)

Thanks guys..

ttg35fort the spec sheet that came with it clearly says "Suggested Clearance: 0.0025". I know if you coat the pistons you can run them a bit tighter as the the wiseco are pre coated on the skirt.

ttg35fort please can you let me know why you believe a clearence of 0.0035. I also thought 0.0025 was a bit tight but I have nothing else to go on.

One thing I also noticed was that this pistons have some oxidisation on them. Will this cause an issue, see attached? If the pistons are susceptible to moisture then they should be shipped oiled or at least with the silica sachets in the box.

Michael

ttg35fort

iTrader: (2)

I spoke directly with an engineer at Wiseco. You should probably give Wiseco a call, tell them about your build, and get their recommendation for your particular motor. I'm not sure why the spec sheet you have says 0.0025", while I was told 0.0030" for NA and 0.0035" for FI. I'll leave that one for the Wiseco engineers.

Also, I am assuming that your pistons are 2618 aluminum. When I spoke to Wiseco some 9 months ago, it was indicated to me that all of their VQ pistons are 2618. If they have started using 4032 for VQ pistons, that might explain the tighter tolerances. 4032 expands less than 2618.

MR RIZK

iTrader: (7)

I give them a buzz and post back answer.

Sharif@Forged

iTrader: (92)

This would be my guess. Arias shelf pistons are made from 4032 but all of the extreme duty stuff is made from 2618. Wiseco probably doesnt something similar with their clearance reco's.

MR RIZK

iTrader: (7)

I got an email back from Wiseco. They mentioned for higher boost it is recommended to increase the clearance. .0035".

High boost is subjective. To me 18psi on a Z is high where 18psi on a EVO is normal. I have asked them to clarify "high" boost and about the oxidisation but have not got a response.

What would you consider to be high boost?

I'm running 7psi on my stock block with a HKS GT3037 and 1.12 AR. I'm guessing that I would be around the 15 psi mark after the build

ttg35fort

iTrader: (2)

I would consider 15 psi to be high boost on a VQ.

Sharif@Forged

iTrader: (92)

Based on that, I would run .0035 and play it safe.

accordfreak

iTrader: (15)

let us know what you eventually go with. i have the same pistons.

NNOCENT

iTrader: (7)

good info, please post back a concrete answer as soon as you can.

MR RIZK

iTrader: (7)

Got through to Wiseco support. According the tech they indicate high boost is like 20psi and above. With 15psi the recomendation was to stick to 0.0025".

Honestly I have no idea. I we will probably end up with 0.0030" and use a extended run in period.

phunk

iTrader: (21)

well, consider that the purpose behind the piston to wall clearance is to leave room for piston expansion. that is obviously a function of heat, rather then actual boost pressure.

i wouldnt compare boost pressure to a 4 cylinder car... while it will be hard to relate exactly how much heat expansion you will experience compared to an EVO... i would think it lands you a little closer to use a comparison of how much power per cylinder you are expecting rather then boost pressure. if you expect to have as much heat energy in each cylinder as an EVO running "high boost", i would go with the larger wall clearance! but of course, now youre left with the question, how much boost in an EVO is "high boost" LOL... cause some guys run 30, some guys run 40+.

lol, i would just go the "high boost" route.

streetzlegend

iTrader: (2)

Correct me if I am wrong, but how does the "boost level" determine what clearance to go with. Shouldnt it be based on horsepower if anything, considering you can make 400whp at 7psi, and also make the same 400whp at 15psi with a crappy turbo. (just an example).

This is the one mistake I made when boring my block, I did not specify exactly how much clearance I wanted, the builder just asked me for my estimated power goals, and he went based off that using the Wiseco supplied document in the box. Hopefully they are not too right, I do however get alot of slapping around till its at operating temp, so maybe they are on the loose side.

Nathan

If you can hear them, there loose

streetzlegend

iTrader: (2)

Yeah, everyday. I dont drive till its gone. which normally at around 160degrees it starts going away.

Guru

iTrader: (9)

I always go 0.0035 on boosted Wiseco's. Always worked perfectly. Some guys run them at 0.0040 for extremely high HP levels (over 1000 HP).

ttg35fort

iTrader: (2)

That sounds correct. My new motor has custom 97mm Wisecos made for GTM. The spec sheet on those states 0.004". I just received the spec sheet last week (after my above posts) and was a little surprised by this since Wiseco specifies 0.0035" for off-the-shelf pistons when used for high boost. Perhaps it has something to do with the custom design and/or anticipated use, I'm not sure. Both are 2618 alloy.

MR RIZK

iTrader: (7)

maybe they just got sick of owners ringing up wiseco to confirm the clearences