Just got back from the machine shop, the stock piston weighs 393 grams. The stock rods weigh 54? I think and the big end of the rod stock is the same weight as the big end on the Pauter rod.

 

I might hit you up on that, I will let you know soon. Thanks.

 

I second that...I can see myself in those...

 

he should now the direction by the size of the valve reliefs.

 

I think Wiseco started using the dimple because some people were installing the pistons backwards. I agree that no "machinist" should have any trouble determining which way they should be installed.

 

I called PolyDyn today and they said the thermal barrier coating on the crown will come off under detonation. Is this normal with other brands of coatings? Their shop is like 5 miles from my work place and I plan to pay them a visit soon. Do you guys have any request or question you would like answered? Id take a camera with me if you guys want and if they allow.

 

So then whats the point of coating them.

 

I payed a visit to their shop today and they showed me some pistons off an alcohol car and some other drag cars. The surface of the piston looked like it retained the thermal coatings even under detonation. This person i spoke with said it does take alot of detonation to take the coatings off. At the same time, it buys the pistons 9 lives if you will.

 

looks great Lorca

sounds like you're definatly going to give Matthew a run for the money.....

 

So the coating is like extra protection for pistons.. if you don't coat them, then they have a higher chance of breaking under heavy detonation... thanks for the info!

 

alcohol car is got to be making ta least 1500+ hp so I am sure you will be alright.

 

Is someone going FI here too?

 

Just got back from SEMA this morning. Absolutely amazing show.
Talked extensively with APS (David will be visiting us next wednsday), GReddy, Garrett, Carrillo, CP, JE, Arias, Wiseco, HKS, Turbonetics, PE, Mackin (Rays), A'Pexi, Hotchkis, etc etc etc.

Now, since this thread is about pistons, here's some info from CP, JE, Arias and Wiseco that I found interesting. Only Wiseco really does anything to keep piston slap to a minimal. The general attitude is "if you are building a high horsepower motor with forged internals you should not be worrying about a little noise from piston slap".

Most OEM pistons have pin offset to keep the piston quiet. Only Wiseco does this with forged pistons.

Pistons with high silicone content have lower expansion properties so the tolerances can be tighter therefore they are somewhat quieter. All the companies frown on hi sil content for high horsepower / high boost cars because detonation can cause the piston to shatter and destroy the entire motor, wheras the low sil piston will melt or deform from extreme detonation but is much less likely to grenade the motor.

All seemed to agree that molly side coats are worth the extra cost. Beeri at Arias had an interesting comment about coating the top of the piston. Beeri feels that coating the piston top is only a good idea if you do the entire combustion chamber, i.e., the head and valve faces as well. The theory being that if only the piston top is coated it will deflect heat back at the head and valves which are more fragile than the pistons. If the entire combustion chamber is coated then the heat will be more likely to exit the exhaust ports and not be absorbed y the head.

We spoke to Carrillo and Eagle about rods. Based on the intended use of the rods the smaller and lighter A beam appears to be the best choice for FI on the VQ. The I/H beam rods are recomended for high reving (8000k+) endurance racing applications. The rod is most stressed when it is at full extension and high RPM's exagerate this stress. Forced induction applications actually cushion the rod on the down stroke because there is so much more pressure (air) in the combustion chamber and the rod is strongest on the downstroke.

Lots more info but I would be typing all night.

 

I'm going to spank his TD05-18G ***!

 

Lorca, I also spoke to Barry over the phone when doing the GB....he seemed to frown upon the low or zero silicon pistons for street usage...they are too noisy and cause faster cylinder wall/ring wear. Arias makes zero, low, and high silicon pistons, and only recommends the low and zero variety for race applications. If most of your driving is done on the street...he said high silicon is best.

I guess to each his own, as there are a zillion different theories on engine buliding, and the materials that make a good built motor.

Interesting note about coating the tops...guess I wont be doing that.

 

It sounds like the discrepancy has to do with how hi a boost application we're talking about. A >20psi app may benefit from low Si and a <20psi may benefit from low Si . Most of the GB guys are targeting HP street/strip and not expecting >>20psi.

Z1 is this contrary to your discussions with the piston guys?

 

I guess it depends on the definition of "street driving". I drive my Z32 on the street all the time but I also run over 20lbs of boost all the time. Coincidentally. I have Wiseco low sil pistons and they don't make a sound.

Beeri at Arias and all the other piston companies I spoke with were pretty much unanimous that the low silicone pistons were they way to go if you are going for big power and that anyone intersted in playing with big power needs to get over it if there is a little psiton slap.

The real problem as I see it is that most people who are building up a motor are going to push the limits sometimes just because they can. Sure you *could* set it for 15-16 lbs of boost and never touch it. But what happens if you decide you want to see what it can really do and you have the turbos to push over 20psi? Curiousity just might kill that high sil cat ;-)

 

G3po,

The consenus was that the potential for some noise from piston slap did not outweigh the benefits of low Si, i.e. not prone to shattering in the event of detonation and the ability to turn the boost up to the full potential of the turbos.

Beleive me, I wish it was the other way around because the high Si pistons are slightly lighter and I can get our stuff made in either hi or low Si at the same price so the weight savings would be nice, but it just doesnt make sense to me to put a piston in there that may not be able to hold up to the peak power that the turbos / SC is cabable of making.

Also, as I said, Wiseco does make the pin offset to counteract the potential for piston slap in the liw Si pistons and in my personal experience it works.

 

Arias uses a 12% silcon content for their high silicon pistons... Low Silcon is roughly 8%, and zero silcon is 0%.

Just an FYI.


With zero silcon pistons, its not uncommong to rebuild a motor after 30K miles due to excessive ring and cylinder wall wear. You need to run clearances that are rougly twice the amount of high silicon pistons. And as everyone knows, the most damage is done duing cold start, when those pistons are loose and banging around in the cylinder.

Most of the piston companies can make a piston with any material you want....so not trying to push people to one material or the other. Just keep in mind..there are always tradeoffs....no matter what you choose.

and of course...I am biased becuase I bought the high silicon pistons....so take what I say with a grain of salt!

 

As I said above, "[b]eleive me, I wish it was the other way around because the high Si pistons are slightly lighter and I can get our stuff made in either hi or low Si at the same price so the weight savings would be nice, but it just doesnt make sense to me to put a piston in there that may not be able to hold up to the peak power that the turbos / SC is cabable of making."

I have no bias on this subject, just stating my opinion based on 4 hours of talking with these companies. I am interested in finding out if the low Si pistons with pin offset are any noisier than the hi Si pistons with no pin offset.