push it till it leaks then back it off 2lbs of boost

 

I know every body wants to know that magic number to push. I was just hoping that some one has already been there so I can learn from their mistake instead of my own. I can tell you for certain that 10lbs is the ragged edge for cast pistons. I blew the ring lands apart on 6 pistons with only 15600 miles on my truck. Now I am up to 17800 and maybe its time for another motor lol.

 

it isnt in relation to pistons. its the tune!!!! a poor tune can destroy forged pistons. a good tune can make hyper pistons last forever

 

This is correct! I have ran up to 17PSI on my stock LQ4 pistons, and they survived. I started to lift the heads with the stock TTY bolt's but the pistons held. I race my truck weekly, with 10 sec power, 10~14PSI on the factory pistons, and rods. 14PSI is all my T76 can produce up hear at 6000' or I would be running more. The tune is VERY important in the survival of any piston, just cast are alot more fragil. Having the correct piston to wall clearance, and ring gap also plays a HUGE roll. You will most likly lift the heads with those stock bolts before you kill your pistons if your **** is right.

 

That what I was hoping. So stock bolts will start to strectch at 16-17psi. Does any one have a part number for an arp kit? Going over to the Dyno at edge products here in a couple of hours, we will see how she holds up. The only problem I have is these little injectors.

 

Bingo. I ran my LQ9 (10.1:1) to 12 psi with no damage -- oh -- no intercooler but I did have meth.

 

I guess BMEP does not apply to our engines.

There is a limit to the pressure that the pistons can take, and there is a happy medium between boost and timing. Pumping more boost in a engine does not always make the best / more HP. I am sorry guys, this is not dark art. FYI adding boost and taking out timing only raises the cylinder temperature.

 

It's simple guys.

At any given static CR, you have X amount of "luck points" the cylinder can take prior to detonation. What contributes to calculating X? Boost pressure, timing, octane, and IAT.

Want more boost without changing the CR? Reduce your timing, up your octane, cool off the charge -- or any combination of the three.


Want a lotta mo boost? CHANGE YOUR CR and balance again (with a more efficient compressor hehe).

 

Get a good tune, injectors that will support, 10-12 lbs all day.. Also hope the rest holds up(driveline)

John

 

You mean this BMEP:

"Note that BMEP is purely theoretical and has nothing to do with actual cylinder pressures. It is simply an effective comparison tool."



But I agree on the cylinder pressure thing at least. I used to have a chart of the cylinder pressures with stock components, but have since lost it.