boost

B

Buster

New member
17-18 psi, some gains to be had with high boost, but very little. I've seen a stock turbo truck run 12.0's w/17 psi & 11.8's w/ 26 psi, same track - same day, so the're gains to be had above 17-18, but not a whole lot.
 
InvisiBill

InvisiBill

Active member
What they said. The turbo itself can be set for a fairly high psi, like Mark said 26psi. However, ~18psi seems to be about where it gets out of its efficiency range. When you run it higher than that, the extra heat pretty much cancels out any gains from the higher psi.

And like Sigo said, the stock computer can only see (and therefore provide fuel accurately for) 14.7psi. If you want to run more than 14.7psi, you should get a 3-bar MAP and chip so that the ECM can actually see the correct boost level and provide the proper amount of fuel. If you want to run more than 18 or 19psi, you'll probably want a different turbo that's more efficient at those higher pressures.

Also, psi is just one of many parts that contribute to your truck's overall output. You can get a lot more out of a truck with careful tuning than by just cranking up the boost...
 
B

Buster

New member
InvisiBill said:
What they said. The turbo itself can be set for a fairly high psi, like Mark said 26psi. However, ~18psi seems to be about where it gets out of its efficiency range. When you run it higher than that, the extra heat pretty much cancels out any gains from the higher psi.
Click to expand...

Actually I think it's back pressure that cancels out any gains, the stock turbine has to spin awfully fast to create high boost. If it was mostly due to heat we could just upgrade intercoolers and run high boost, but that's not the case.
 
InvisiBill

InvisiBill

Active member
You could be right, though I thought someone said it was due to heat... I'm not sure on the specifics of it, just the fact that cranking the stock turbo way up generally gives little or no improvement over <20psi.
 
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