B56

92.8mm stroke.

What should my rod length be?

Do I have to customize the piston design other than ordering pistons for an 82.5mm bore?

TIA.

Mandingo®

have you calculated mean piston speed @ specific rpm yet?

B56

oh boy, I have more homework to do. No I have not. Can you explain the what, and how?

FixedWing

Normally, you would use stock length rods and have custom pistons made. You probably don't want to shorten the rods any more than stock given that you are using a larger throw crank.

Stephen

B56

Just to make sure I understand this correctly, with a 92.8mm stroke and stock rod lenghts of 154 and using stock pistons, The piston would pop out the top of the cylinder bore, correct?

If I have pistons made with the pin boss pushed up more towards the face of the piston, the piston wont pop out of the bore because the rod is pinned higher up in the piston?

Its hard to convey this without a photo. If you understand what I'm saying, am I understanding this correctly?

FixedWing

<center><img src="http://gallery.rennlist.com/albums/album624/DSC05474b.jpg"></center><p>
You also need to determine what compression ratio that you want to run. that will affect the piston height also. Generally, a car with big turbos will want a slightly lower compression ratio. This is more efficient.

Stephen

silva

Piston Speed (millimeters/ second)= StrokeX2XRPM/60<ul><li><a href="http://www.csgnetwork.com/pistonspeedcalc.html">Piston Speed</a></li></ul>

Roque

Lower compression just lowers the charge temperature and therefore detonation is less likely. And turbocharged cars already have knock tendencies due to high charge temps.

A higher compression ratio has a higher thermal efficiency. Audi's current turbo charged engines are direct injection which allow for a higher compression ratio since the fuel can be precisely injected at various times to prevent knock. Pretty nice.

FixedWing

and between the two, it was more efficient to compress with the turbocharger than mechanically with the engine.

Stephen

Roque

efficient. The best it can be is around 78%, but it depends on where you are on the map. It is much lower in other areas. This adds heat into the cycle which is not good.

Mechanically compressing the fluid also has inefficiencies, but you are just adding to it with turbocharger. That's why Audi increased the compression ratio on its new TFSI 2.0L engines and it wasn't easy to do.

Don't get me wrong, I still prefer turbos for many reasons...