Fw: [Diy_efi] compression ratio

[Jorgen Karlsson]

Eric Wrote:

>...but I'm curious as to whether anyone has good ideas
> as to when water should start (assuming that I have a full SD mapping
> for water).  (My first application will be an I5 turbo running about
21psig
> Next up is a NA 4 banger econo motor, with high CR to get
> good thermal efficiency.)

For the I5 I think that you want to start adding water when you need to go
richer then Lambda=.82 to avoid detonation and/or excessive exhaust
temperatures.

Since you want to tune the na 4 banger for economy I guess that you will use
lots of EGR and a mixture in the lambda=1.05 to 1.12 range. I don't have any
experience with an application like that but I think that you will have to
control detonation and exhaust temperature with water alone until you feel
that a mixture richer then lambda=0.92 is called for. If I am not
misinformed about knock and exhaust temperature vs. lambda you will find
that a mixture around lambda=1 will have higher exhaust temperature and
detonate worse then one around lambda=1.1.

Jorgen



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