Feeler: CP Pistons, Medium Comp, 10:1

G37sHKS

Im sorry but that's not a noob question

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phunk

These pistons would cost you a little power in a NA car.

The factory compression ratio is 11:1. These pistons are 10:1. Reducing the engines natural compression ratio will reduce overall power output at any given airflow.

When people decide to upgrade their internals for more horsepower with a boosted engine, if that engine was considered a "high compression" engine in its original form, then it is common to slightly lower the compression ratio. So this is a typical procedure when doing an engine build for a NA car converted to FI.

High compression ratios are ideal for overall power and efficiency. However, once you force more air in with boost, the high compression ratio really starts to compound the pre-ignition cylinder pressures. Too much heat and pressure can cause the air-fuel mixture to self ignite early, before the spark plug sets it off. This is very bad for the engine.

So it is a balancing act. Like every choice we have to make in a performance car, there are compromises. For the sake of maximized efficiency, you want the compression ratio as high as possible. Luckily, the VQ37VHR makes lots of power with very little boost pressure. Most people will never even attempt to run as much boost as, for example, a *stock* Evo X runs. Those who go so far, would have one of the most powerful VQ's around. So, generally we do not have to lower our compression ratio nearly as much as other guys. This is great because it lets our engine be more powerful and responsive without using the boost as a crutch. Cars like EVOs and STIs drive rather poorly in comparison due to having extremely low natural power output.

Sorry if I went overboard and touched on things you already know. Just covering all bases!

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phunk

Prices quoted will be for a full set of 6, including wrist pins and piston rings.

Shop charges to install the pistons is a difficult conversation to have quickly. It is rather uncommon to install just a set of pistons. Changing pistons requires going as deep as you can into the engine, and removing literally every last component. Once this far, it is typical to do a full build-up on the engine, and upgrade every other known weak-link.

An engine build for a VQ probably costs consumers anywhere from $4,000 - $8,000 by the time it is all done. Possibly even more in many cases. Or a lot more if a turbo system and accessories are on the same invoice.

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Unique_Z

Thank you for your clarification and additional informations Phunk a little overboard wouldn't hurt

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My Z Build
UniqueZ

elperuano

Can I still get in on this?

phunk

Yup for sure... The group buy has not even started yet because people were not ready to go.

If we can ever get people together that are ready to go, this can move forward. I am set and ready to order whenever everyone else is.

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phunk

^^^ Let it be known that he is not a member of this group buy, he ordered them on his own, not from me. So I have nothing to do with his missing ETA.

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phunk

OK.

I think its time to try this again, because I am seriously ready to order my pistons. It will take until March for them to arrive, so if I want my engine ready for summer I need to get a move on!

So I have to do this now. Anyone who is IN, speak up by Monday. Then I will call and see if we have enough for any discount or not. It will take 7 sets to guarantee a discount... any less than that and I believe it is unlikely I can get the price down.

1: phunk
2: ???
3: ???
4: ???
5: ???
6: ???
7: ???

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OldBoy

I'm in. Did you ever get news for the piston/rod combo?

phunk

I failed to follow through on that. I have been reluctant to call them again because I dont want to be the annoying guy that always calls to ask difficult questions but never purchases anything, lol. I definitely will be asking that on next contact, as I need rods myself.

It might just be you and me!

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G37sHKS

Guys please jump on this!!

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Ron

Charles are these 4032 or 2618? I was planning on using Arias pistons but the ones I've seen are 2618 0% silicon content, they are stronger but they will expand more than high silicon content pistons. This means piston/wall clearance will have to be increased to compensate and I am not sure I want any piston slap on cold starts. Thoughts? Do you think 4032 forgings will support 700rwhp? What are these CP pistons rated at?

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2011 Twin Turbo PW nismo #113 - My Journal - My TT Build Thread
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phunk

I would assume they were planning on 2618 when I spoke to them, since I said power goals were 800 to infinity. I will personally run either, it makes no difference to me.. so if you guys have a preference, that is the direction we can go.

I am sure a 4032 will have no problems with the power any of us are going to make. I mean... the factory pistons have shown to be pretty much A-OK at 575-600rwhp.

I dont know if they will quote a solid HP number for a pistons since that is a dangerous game, but I can at least inquire about their recommendation for this power range.

I will go out on a limb and make the assumption that they would allow me to mix and match in the order. I believe they start from a mostly universal forging and machine them down, so it probably makes little difference to them which they machine.. pricing may be different though.

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COSMO

Mine only took 6 weeks to get...

Attached Images

10.1 CP Pistons.jpg (398.8 KB, 17 views)

phunk

This group buy is officially closed!

It takes 7 sets to get anywhere with a discount, and I have been unable to get more than 1 or 2 solid commitments at any given time.

If anyone wishes to order a set of the pistons, feel free to PM me and I can order them with standard pricing.

Mods please close the thread.

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