looks great let us know how the buildup goes.

 

That's not quite the way it works... if nothing else changed (installed piston deck height) and the piston was dished like mine, the displacement of the engine would remain the same, but the compression ratio would drop. However, these pistons will be almost even with the deck at TDC, whereas the stockers are quite a ways down in the bore, something like .300" The new pistons actually increase the compression ratio from stock (8.0~8.1) to 8.8:1.

I actually built a displacement and compression ratio calculator, if you have MS Excel:

http://www.azchatfield.net/engineperformance.xls

Also, the cams are the Crane 14's. Longer duration and higher lift than stock.

 

Chadsikle misquoted me btw. I didn't mention or think about higher displacement with my concavity comment. I was wrong in another direction, though, I thought the compresson ratio would be lower(that was the source of my no Bangy bangy comment). I didn't realize the stockers ran so low. Obviously the concavity is there to keep the compression acceptable, since the piston is going to .3 inches higher. With those pistons and the crane 14's you ought to have a real nice setup. I would bet the flow characteristics in the cylinder will be improved by that smooth curved surface, as well.

 

Yup, that's the idea. The "Ski-Jump" on the stock pistons was designed to improve low rpm, out of boost driveability.

With the higher compression, bigger cams and ported head, I'm expecting the GT3076R turbo to spool up considerably quicker... hopefully providing a big improvement in torque numbers around the 3500 rpm area. The peak numbers probably won't be alot higher than what they were before the build, but the area "under the curve" ought to be greatly improved.

 

Nice! Are u installing them yourself? Tell us how u like the products.

 

I have a question, why did you go with a piston that gives up all the advantages of the peformance dome? I understand the power drop will not be a lot, but I just hate to give up anything.

 

They are and without that he is giving up performance. The stock piston design was adapted from a design Porche developed from their racing program specifically for turbo cars. The offset dome give 3 destinct performance advantages over the old flat top design.

1) The offset dome moves the hot spot out of the center of the combustion chamber. This allows the engine to run more timing, thus more power than a flat top piston.

2) The offset dome blocks signal during valve overlap. This reduces reversion which is always been a problem on turbo engines because of the back pressure. This keeps the charge in the chamber cleaner making more power than a flat top.

3) Also the dome offset to the exhaust spools the turbo faster, and improves off boost performance.

On the SRT-4 we won the Car and Driver superfour challenge with we took all the advantages of the stock dome piston design and turned them into forged version to handle higher boost levels. The piston design is one of the thing that I credit with helping us win the event.

 

My understanding of the ski-ramp shaped piston was that it was designed to improve out of boost performance. ???

Never heard your description of the design reasons behind it or I would have done some research. Kind of late now, besides with everything else going into this engine, I'm sure the GT30 turbo will spool up really quick

 

We good luck with the engine. If I can help with anything please give us a call.

Are you using Total Seal rings?

 

Also on those pistons, take the sharp edges off the valve reliefs that will create hot spots in increase the possibility of detonation. I don't even understand why they have valve reliefs the are far enough below the deck they don't need them.