Choda

iTrader: (1)

I was hoping for that 100+ w the cam. Springs. And 2-3 more psi. I think with those changes 600 might be possible

Dream crusher strikes again!!! You are killing me man.


Well here's the deal guys. I'll dyno it and 1/4 mile it at 12 psi to show what the cam, springs and motor rebuild did for power.

Then I'll go up a couple psi. As long as I stay consistent w what I have already done. Which is about 23hp per psi. Well see

Atomic

iTrader: (42)

Theres diminishing returns with turning up the boost, at some point you get no extra power with more boost. Youll need to run that turbo as hard as it will go to make 600. Dont fear the boost!

lxcoupe

iTrader: (9)

Rich, how does spinning a turbo to its max affect IATs (all other components remaining equal)? I realize for every given motor using any given turbo, there is a linear relationship of some sort between boost and IATs, but does a threshold of some sort exist where if you pass it, you can't make any power without meth even though the turbo will physically make more boost?

Atomic

iTrader: (42)

If you look at a compressor map the lines are efficiency islands, or areas of constants efficiency. In the middle is the best (the "sweet spot") and as you move away from that the compressor gets less and less efficient, meaning more of the "work" that the compressor is doing is going towards making heat vs compressing the air.

What compressor maps dont tell you directly is power required by the turbine to spin the compressor. Once the compressor is near the right edge (the choke line), it takes exponentially more power to spin in harder. Going up the choke line (more boost) does not make any more power since you are not moving any more air, and the amount of power it takes to compress it further is greater than or equal to the amount of power the additional boost will make in terms of better VE of the engine. Not to mention the overall density of the charge will probably decrease because the compressor is so inefficient at that point.

So the answer to your question is the choke line is the limit of the compressor. Meth will help you a little bit by gaining back some density in the form of lower temperature and more knock resistance, but at that point is a band-aid for needing a larger turbo.

Choda

iTrader: (1)

So you're telling me there's a chance

Atomic

iTrader: (42)

Small but its there!

lxcoupe

iTrader: (9)

Choda sorry for asking these questions in your thread. Rich thanks for the fantastic explanation. I didn't realize that a turbo could "run of steam" yet still make more boost and that you could actually make more boost and not make more power. Talk about turbo 101...

Choda

iTrader: (1)

^^ yep. I think of it like fuel. There's psi and flow.

Which is why when I replace this 70 with a 76 and leave the wastegate Spring at 12psi the 76 is going to me moving a lot more air.

mdwatts11

iTrader: (4)

Looking good Jacks. Can't wait to see some videos!

slvrram

Just finished reading through this. Excellent thread. Hoping you see your coveted 600hp. I'm in the middle of a similarish build, but with a LM7/4l80 and heavily worked 706's.