Here we go again...questions, comments, concerns? - Subaru WRX Forum
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post #1 of 30 Old 10-27-2009, 02:45 PM Thread Starter
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Here we go again...questions, comments, concerns?

After some lengthly conversations with my tuner. I might be interested in doing a engine build. I'm just writing this up. So, that I know where to find all my info and if other experienced members wish to comment and help.

So, here goes. After lenghty talks and possible upgrade routes discussed. I think i'm going to get my tuner to build me a engine. What I've found out so far is that they use Ron formally of axis power to do their engines. Which is nice to know. They also recommended Mahle pistons if I wanted a quieter engine. Mahle pistons are in a majority of german engines and are in porsche engines. So, this seems like a no brainer right? Wrong...their lead tech said with a warning. Don't get the weak mahle pistons. Which I had to research to find out wtf he was talking about.

Ok, so theirs two different kinds of forged piston alloys. 4032 alloy and 2618 alloy. The Mahle pistons that are known to break are of 4032 alloy. Why? Well after reading unabombers piston faq. ( Piston FAQ: Read if you are thinking about buying them! - NASIOC )
Its because 4032 alloy is made for use in N/A engines. 2618 alloy is made for blown, marine, and nitrous applications. Do they make a mahle 2618 alloy piston? Yes...they do.

The reason my tuner recommends Mahles over CPs is because they don't have the piston slap, oil burning, and blow by on cold starts. That and the over all noisey aspect that CPs tend to have. They run smooth and quiet...near stock noise levels. Now, normally why CPs are agreed to be better. Is because CPs are from what I understand only made as 2618 alloy. But, the CPs wrist pins aren't at the stock location like the Mahles. Which is where the piston slap comes from. That and the piston has to warm up and expand into the cylinder.

EJ_Rex: I was really considering the hypereutic silcia alloy pistons until I read this in unabombers piston faq.

Quote (A. Graham Bell, in his book "Forced Induction Performance Tuning" (published in 2002 by Haynes), says hypereutectic pistons are a poor choice for turbocharged engines. Hypereutectic cast pistons have twice as much silicon in the aluminum alloy as regular cast pistons (15-20% instead of only 7-8%). According to Bell, the added silicon leaves them "quite brittle and, as such, prone to breaking when subjected to detonation.")

Oh, my tuner also said eagle rods were crap. I have to talk some more on what rods to get. If I get them upgraded as well. I don't know. I want around 350 whp and piece of mind. After reading this: Public Service Announcement. "I want 400whp!" Are you sure? - NASIOC . That midniteblack posted a while back really makes me want to do a engine build before I go turbo upgrade. I don't want a piston to shit the bed while driving it hard every once in a great while.

Like the thread topic....feel free to comment. I'm just mulling over my options. Oh and I'm going to live by the K.I.S.S. (Keep it simple stupid) motto on my build. Like I said before at most: pistons, rods, and apr studs. I'm not chasing shoaf numbers, lol

EDIT: Thanks to Josh.

Compression ratios:
WRX 8.4:1
STI 8.2:1
Mahle 2618 pistons are rated 8.5:1 (which, I'm thinking will have to be accounted for in the build)
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post #2 of 30 Old 10-27-2009, 03:32 PM
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Kirt, thanks for throwing this up. I will also be referring back to this when my time comes for my engine to get built. And of course be picking your brain as you come up with more info since you have a shop to talk to and I dont anymore

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post #3 of 30 Old 10-27-2009, 04:02 PM
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I completly would say I agree with the last reply. According to that link about 400whp builds, It said something like replacing the crank and rods wasnt neccesary if you replace the pistons (which I am going to in a month or two). After that and some other pre-tuning mods before upgrading turbo kits, I want to be safe and know my engine will handle the high output. Would it be safe and give me plenty of use and span of building before i would have to worry about the crank and rods? BTW, Im installing these in my stock engine, The article kind of seemed to me that it was saying to buy a new shortblock. This is all ok right?
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post #4 of 30 Old 10-27-2009, 04:36 PM
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I have CPs in my build and they do have a little bit of slap on startup, but within a few minutes (once they heat up) they are silent. You could get the CPs swaintech coated and then you should not have the slap at all. Personally, from what I have read and what my engine builder/tuner told me he prefers the CPs b/c they are VERY stout.

I would also consider some aftermarket cams. Depending on your choosen turbo (i.e. 18G, 20G) I would go with a smaller grind such as Kelford 264/264s or Tomei 252s. I am running the Kelford 264s w/my 18G 8cm hybrid build and the powerband is awesome with PLENTY up top.

Additionally, I have STi/OEM Rods. But, I do have upgraded springs/retainers (due to the Kelford Cams) and my builder also used ARP head studs. Also, make sure you get your heads cleaned up a bit (PnP/coat wouldn't hurt) and gasket matched to whatever headgasket you are going to use.
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post #5 of 30 Old 10-27-2009, 06:07 PM Thread Starter
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OBEE: I can't comment on absolutes. But my tuner said that RON prefers new shortblocks, but lower mileage blocks can be used. Ron just has to shim it or something. Not quite sure...I'm going to get it done by a professional. Since I don't have the tools or knowledge base to properly install forged pistons in a shortblock.

c2bcoolwrx: Thanks for the comments. I'm definatly in between CPs or Mahles. I think. I know that Crawford performance uses JEs. But, I know that Ron will install CPs or Mahles. Not sure about the others. Its kinda up to what Ron will do for me realistically.
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post #6 of 30 Old 10-27-2009, 07:02 PM
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I will be honest. Ron has done a "few" engines for me now. None of which failed becuase of anything he did.. He is a great guy and will NOT try to talk you into a more expensive part to make some cash. He has always talked me out of spending cash that I don't need to. He even wanted to talk me out of spending the cash on sleeves, but also agreed that they would not be a bad idea. LOL. I trust his opinion and will also add that I am cunning coated CP short skirt pistons which also cuts down on the slap.. Give Ron a call and talk to him about things, he is more then willing to talk to you about it. I had to be his biggest nightmare when I was doing my builds, I was always blowing up his phone..

Edit: Also wanted to thank you for the props. LOL. Always nice to be mentioned..

02 WRX.. "It's fun when it runs.. Problem is that it hardly ever does..."
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post #7 of 30 Old 10-27-2009, 07:05 PM
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Your very knowledgable Turmic, thanks for your advice
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post #8 of 30 Old 10-27-2009, 07:23 PM Thread Starter
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Quote:
Originally Posted by LiL Shoaf View Post
I will be honest. Ron has done a "few" engines for me now. None of which failed becuase of anything he did.. He is a great guy and will NOT try to talk you into a more expensive part to make some cash. He has always talked me out of spending cash that I don't need to. He even wanted to talk me out of spending the cash on sleeves, but also agreed that they would not be a bad idea. LOL. I trust his opinion and will also add that I am cunning coated CP short skirt pistons which also cuts down on the slap.. Give Ron a call and talk to him about things, he is more then willing to talk to you about it. I had to be his biggest nightmare when I was doing my builds, I was always blowing up his phone..

Edit: Also wanted to thank you for the props. LOL. Always nice to be mentioned..
Anytime shoaf. I'm going to talk to my tuner some more...than probably start calling Ron once I'm ready for the build. That way I can sorta get a idea of what my tuner wants and what Ron thinks I should get. It seems like I might just need pistons and apr studs. Now, its the great debate if I want CPs that have moly added to the skirts or just get the Mahle pistons that come with Grafal on the skirts. I'm going to go back tomorrow when they're (CBRD, my tuner) testing out a custom spec'd turbo, that is going to be built by blouch, on a 04-05 sti that has CP pistons already in it. I'm going to listen to that engine run and listen to Mark's car that has the Mahle pistons in it. Just to hear what runs smoother. But, it'll give me a idea of what I want and possibly what my turbo is going to be as well. The custom spec'd turbo is a ball barring turbo that is suppost to be a great compliment to 2.5 liters like the 2.5r polka pickle is. But, deliver slightly more tq and hp. Its great the car their testing it on...is upgrading from the polka pickle to this turbo. Because the guy wants more tq. The driver is a 85 yr old man named henry. Truely a awesome senior citizen.

Edit: My tuner's first STI project car pretty much ended up with your results Shoaf. GT-35r and about 415whp. Your past that now though.

2nd Edit: From what Mark said. The Mahle 2618 alloy pistons, the better grade piston, are $50 cheaper per piston than CPs. His old 06 had the CPs in them and he went with the Mahles in his 08 STI.

Last edited by turmic; 10-28-2009 at 09:34 PM.
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post #9 of 30 Old 10-27-2009, 10:58 PM
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I am sure that either way you will be happy as far as pistons.. Depending on what you do with your valve train that is where your noise will come from.. My valves slam closed so hard it's crazy.. But I have dual springs...

I can't wait till I can afford a full tune by phil to pull all the power out of my project.

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post #10 of 30 Old 10-28-2009, 09:32 PM Thread Starter
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Ha, thats scary that there's still power left in the reserve shoaf. Unfortunately your tq doesn't go up a whole lot at that level. But, its already pretty darn high though.

On a side note, I road in a customer's car today with my tuner. Just for giggles. It was a evo 8 or 9 MR, I think. 440 whp on pump with a ewg. Damn quick, but the ewg spoils all the fun. For one, it's way to loud and secondly you hear the ewg way before you feel the power kick in. It ruins the surprise of the surge of power. Because you know its coming...

Eh, Idk. The 04-05 sti that was being worked on with CPs in it. It wasn't really that loud. But, you can can definatly hear the CPs rattling a.k.a. the piston slap. Now, this car didn't have the moly on the skirts. But, my tuner said its going to have slap regardless because the CPs wrist pins are off set. The moly will wear off and the slap will get worse as time goes on. And yes, ron built that engine too. Idk, I think i'm going Mahles. It'll keep the engine a little bit quieter and if the 2618 alloy is used. It should be just as durable as CPs.
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post #11 of 30 Old 10-29-2009, 11:31 PM Thread Starter
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Hmm...well, mark got carrillo rods and cosworth bearings in his engine build. I'm wondering what ron really thinks is all necessary. I need to get my other parts on and tuned. That way I can get serious on this project for the up and coming turbo upgrade.
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post #12 of 30 Old 10-31-2009, 11:01 AM
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Bearings are a must in my opinion, I have seen WAY too many failures.. It's not much in the way of added durrability but it is something to upgrade them.. As for rods, it's up to you, I would get them if you can afford them, this way your done with the bottom end.. You know. It's fully built..

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post #13 of 30 Old 10-31-2009, 11:48 AM
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Kirt sorry to thread jack a bit, but Ken, you are saying at a minimum get rods, bearings, pistons, and studs for a decent build? Im still trying to get all this down for after the tranny build Im still planning on/for.

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Cobbtuning.com"
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post #14 of 30 Old 10-31-2009, 01:41 PM
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yeah...it makes absolutely no sense to tear apart the bottom end and not replace everything...I made that mistake with my first 207SB build...I upgraded the studs, block bolts, rod bolts, rods, and pistons. Low and behold the only thing that I didn't upgrade was what led to my major failiure...the rod bearings...so in my opinion yes to have a decent build you for sure need to do Rods, Pistons, Bearings, Head Studs, ARP Block Bolts, and most importantly do not forget to get the full subaru gasket kit

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post #15 of 30 Old 10-31-2009, 02:16 PM
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Basco thanks for mentioning the gasket set, I kind of had that in mind, but some others might not remember the small things sometimes. Good looking out.

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Last edited by newtothegame; 10-31-2009 at 08:28 PM.
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