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6.0 Turbo Build (pics)


slow6.0.

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I am not sure I agree with Kevin (Krambo) I thought the LQ4 & LQ9 were identical except for pistons?

 

I believe that the rods on the LQ4's were different (compared to the LQ9) up until 2005 where they both went to the LS2 "Style". Seeing that he has an 03, I assume he has the different rods. Other than that, he has the dished pistons which makes the compression lower than the LQ9.

 

Since you are going to do a cam swap, there may be better choices for power. If you are looking for a very streetable cam though, you found it.

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So at 550 the failure begins? Should I keep it below that or is 550 "safe" . Rule of thumb for the 302 was around 500. I blew a ringland on that engine but it wasbecause it took alot more boost to make the power. I plan on pushing around 10psi. I dont really care how much power it makes as long as its safe. Some people are saying I'm going to make alot more hp then I think. Im hoping it doesnt go to high.

OK some deeper theory here - the following thought assumes zero detonation and perfect combustion (yeah right!):

 

What you are wondering about is the absolute failure point of the top ringland, and that is dictated by the pressure generated in the cylinder as the piston compresses the charge. Trapped cylinder pressure rises with VE, in fact this is what the torque curve is, the measurement of pressure in the chamber being delivered to the crank. So, the torque peak of an engine IS ALSO the point at where maximum cylinder pressure is developed.

 

Putting this factiod to use:

 

After you rev boyond the point of Max VE (aka peak torque, or about 4100-rpm in stock LQ9) the pressure in the cylinder is FALLING because the amount of air/fuel in the cylinder is falling, which is why measured torque falls as a consequence. So after peak torque, the load on the pistons/rods is less (!) and the only worry you have after that point is the inertial loading as RPM increases. SO, you can add more boost safely as long as it's above peak torque. With a turbo and electronically controlled wastegate system you can really use this to your advantage, you can keep boost pretty low on launch to control wheelspin, then after peak torque as the motor is getting weaker you can bring in more boost, maybe even as much as 12-lbs? (that's a guess) and as long as there is no detonation the load on the pistons from the cylinder pressure is no higher than that normally seen at peak torque...

 

Hope you're following, not one of my best explainations. But this is a big reason the cetrifugal blowers and especially turbos whip the positive displacement ones, you can tailor the boost to exactly where the engine can actually use it best.

 

Mr. P. :)

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  • 7 months later...

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