Icp pressure significantly lower w tune

[Deathrod]

I recently put the stock tune back on the truck and noticed a large difference in icp psi. About half throttle take off stock is about 2500 psi...with xtreme street its about 1600. I have constant pressure at a given engine speed so i know the system holds pressure. Why the hugh drop???....the drop is across the rpm range and even idle.

My only guess is it has something to do with injector timing. Is this normal and can anyone explain?

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[Tuscany]

That's normal. The tune writer has to fool the ECM to make it think it's only getting say 1500 psi as compared to 2500 psi so that the ECM will not defuel.

[Lilpooh]

Yep, what Bryan said. In order to get the correct ICP% when running a custom tune, you will need to watch/datalog your ICPv then convert volts to psi.


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[Deathrod]

Thanks for the quick replies, I was having a hard time wrapping my head around how a tune would drop it so much.