evoniners

So exactly how do forged pistons and rods make so much more hp from the same 93 octane fuel as say a stock block. Aren't you limited to timing advancement due to knock just like with oem pistons and rods? Are tuners allowing more knock to take place because they know the forged pistons and rods can put up with the abuse?

LetsGetThisDone

iTrader: (1)

On pump gas, it depends on turbo size. On the stock turbo, you prob won't make more power with a built block unless its an increase from a stroker crank. But you can run a larger turbo harder. Setup's with bigger t3 framed turbos like a Xona 78-64 can make upwards of 600whp on pump gas.

CeliOnce

iTrader: (3)

Assuming you're going with stock crank/piston/rod geometry, the engine build itself won't make extra power. It just allows you to make a lot of power without things breaking in the engine.

"Allowing for more knock" isn't a thing because when you tune you tune for no knock or as low knock as possible as detonation robs power as well.

evoniners

So lets say you have two 4g63 longblocks both are 2.0 L and they both have the same shortblock, one has the oem internals the other has forged internals. When you go to tune both blocks from what I have read in these forums is that you advance the timing and try and get the a/f ratio to where it's making maximum torque and horsepower without running into so many counts of knock. So my question is what's to say they both don't run into knock at the same maximum hp & tq value. Is there something with forged internals that gives it a higher knock threshold?

ronaldo9

iTrader: (2)

The simple answer to your question is no. The posts above are spot on. Hope I don't sound like an *** or being pretentious but think about the definition of knock.
"Engine knock, or pinging, occurs when a separate pocket of air-fuel mixture ignites after the spark has ignited the air-fuel mixture within the combustion chamber. Engine knock can be prevented using higher octane fuels, retarding ignition timing, or by using a lower compression ratio, among other solutions."
To answer your first question say you are on 93... you can only run so much timing before you induce knock so you are spot on. With the built motor you can however increase the boost to higher levels without damaging the internals compared to a stock motor. Also bare in mind if the components of the forged internals are lighter than the stock motor that will free up hp as well.

LetsGetThisDone

iTrader: (1)

If you find the MBT of the fuel on a stock motor with whatever turbo you're running, you aren't going to make more power by putting rods/pistons in it. You won't be able to turn the boost up because more boost will bring knock at the same timing if you're already optimized.

Teal2nnr

iTrader: (7)

With forged internals you can run higher cylinder pressures without worrying as much about bending a rod..etc. The more cylinder pressure you have, the more force is exerted on the piston top, which in turn forces the rod down and rotates the crank. This torque over time is HP.


Knock has nothing to do with a built motor being able to make more power then a stock motor. If you're running high knock counts your engine isn't being very efficient and wouldn't be making more power anyway.


If you're looking for a good book to read on the subject, I would start with

It will answer a TON of questions you're probably thinking about.