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Discussion Starter #1
I was under the impression that forged pistons helped when detonating.

Could someone guide me in how forged pistons help.
 

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Forged pistons are stronger. However, detonation is still plenty strong enough to blast through even the strongest forged piston. So if you have detonation in your tune, forged pistons are not a good bandaid.
 

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Discussion Starter #3
I realize that they're stronger but I was wondering if they disperse heat more efficently.
 

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Because this motor ran for 40k miles, while being eaten alive by detonation, but still made 400 bhp:



I will never run another cast piston again after seeing what these pistons survived ;)
 

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AnthonyA182 said:
If you don't have detonation, you won't have to worry about that ;)
Since the bone stock 160 whp MR2 has detonation (knock sensor loop is built into the factory programming) you'd be hard pressed to find an MR2 motor that doesn't have any detonation ;)
 

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hahaha true, but we're talking about extremes. You don't need forged pistons as a bandaid for too much detonation. A relatively stock MR2 with a good tune is fine with cast pistons.
 

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landin said:
I was under the impression that forged pistons helped when detonating.

Could someone guide me in how forged pistons help.

Forged pistons are stronger, so it will take a lot more detonation to break them. (Quite frequently, the head gasket becomes the new "fuse" in your setup)

You can get lower static compression ratio forged pistons, like 8.5:1, or even 8.3:1. (stock is 8.8:1)

The lower CR makes detonation more unlikely when using the stock ECU. When tuning with a standalone EMS, the CR doesn't matter as much, (unless it's extremely high) since the tuner can compensate for slightly higher compression by putting in less timing advance.

HTH,

Ken
 

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KBlake said:
Forged pistons are stronger, so it will take a lot more detonation to break them.
Not true. Forging produce a better microstructure in the material. The alloy material and the process used will have a bigger impact on strength than simply the fact that its "forged".

Some cast pistons are stronger than their forged counterparts. We're working on a forged piston for a 650bhp OE application. We've found that isn't any better than some of our casting alloys.

Detonation can destroy any piston. Stress risers like valve pockets, machined features on the crown, land thicknesses, skirt forms etc will play a bigger role in impacting longevity than you think.

Lets sum it up this way, a poorly designed forged piston is still a poorly designed piston.
 

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gbouras said:
Not true. Forging produce a better microstructure in the material. The alloy material and the process used will have a bigger impact on strength than simply the fact that its "forged".

Some cast pistons are stronger than their forged counterparts.
Within the scope of the discussion, I was correct. The only cast pistons available for 3SGTE's are the OEM pistons, which are hypereutectic. This makes them great at dissapating heat, but the downside is, they are brittle, and are not very detonation resistant at all. The forged pistons I am familar with for the 3SGTE include JE, Wiseco, CP, Arias, Ross, and Jun. all of these forged pistons are more detonation resistant than the OEM pistons.

If you want to argue generalities, I believe you when you say that there are cast pistons out there that are stronger than their forged counterparts.

Ken
 

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quick question on forged pistons (because i have yet to buy mine): do they usually come polished from their respective manufacturers?
 

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diabolical1 said:
quick question on forged pistons (because i have yet to buy mine): do they usually come polished from their respective manufacturers?

they dont come polished .. they come clean out of the machine.
they only look polished... ;)

at least this goes up for Wiseco , JE and CP ... not sure on arias , ross and mahle.

here's a pic to compare ...

this is what they look on ebay :


this is what they look like in real



hard to see cause the shine so much ... but its not polished at all !
 

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thanks Turbo PePe

i asked because i started to think polishing should further help keep detonation at bay and i was curious to see if the aftermarket included it with their ware. i guess i'll have to get it done after buying the pistons.
 

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for as far as i know polishing them is a bad thing ( i supose where talking about the top of the piston ... would be the same like polishing the combustion chambers.
you'll start to get gasoline drups on the polished pieces ... in stead of spray.


this is what i read in some automotive tuner books a while a go. thats also why tuners dont polish intake ports , and dont polish valves. ....even ferrea valves come with some sanded surface on the back of the valve.
 

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Not to mention the polished surface would nearly immediately be covered in carbon. If you want to improve your pistons have them coated...there are a number of companies that do this.

If you're going to that length you better have more than a slightly built motor, however ;)
 

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93smgturbo said:
They have mad b*tch slap, I mean piston slap when cold.
And, by definition, you have to take the longblock apart to install them which means additional expense. If the person doing that work doesn't do a good job, reliability can suffer. It probably isn't worth doing for sub-300hp plans.
 
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