Hey,

If you've been tuned for an 11.1 CR but then you rebuild your engine and you bump up your CR to 12.5 and your tuning remains the same for the time being, will you run richer/leaner? An explanation would be great.

Thanks,

George

 

a/f should stay the same. the only time a/f changes is if you change the fuel curve or the way air enters the motor

 

when adding an exhaust (from a 2.25 to 2.5+ hiflow cat) to a setup tuned to run on that current ECU, does that make it run richer or leaner?

 

12.5:1 WOW!

11:1 to 12.5:1 is a big jump. what exactly are you changing? i can't even see camshafts happy in an 11:1 engine being happy in a 12.5:1 engine.

i'd get it tuned again, but i see the $ of tuning cheap insurance to protect expensive parts.

 

at that high compression cam/ignition timing is more important than fuel...

You could detonate a perfect mix if the ignition isn't firing it off fast enough.

 

What type of ignition upgrade would you recommend?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by dantastic &raquo;</TD></TR><TR><TD CLASS="quote">a/f should stay the same. the only time a/f changes is if you change the fuel curve or the way air enters the motor</TD></TR></TABLE>
So air exiting the motor wouldn't affect the a/f ratio if it was changed to, let's say:
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by jr_istheman &raquo;</TD></TR><TR><TD CLASS="quote">when adding an exhaust (from a 2.25 to 2.5+ hiflow cat) to a setup tuned to run on that current ECU, does that make it run richer or leaner?</TD></TR></TABLE>

 

get the MSD 6A

 

it should lean it out a bit. same with boost, raise the psi, raise the fuel psi

 

12.5........on what?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by tthomass &raquo;</TD></TR><TR><TD CLASS="quote">12.5........on what?</TD></TR></TABLE>
JR's car.

 

on b20/vtec TODA cams

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by jr_istheman &raquo;</TD></TR><TR><TD CLASS="quote">on b20/vtec TODA cams</TD></TR></TABLE>
O snap!

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by litterbox &raquo;</TD></TR><TR><TD CLASS="quote">
So air exiting the motor wouldn't affect the a/f ratio if it was changed to, let's say:
</TD></TR></TABLE>

The o2 sensor should adjust for any lean conditions...

IE if it does lean out the o2 should compensate by fueling more creating a stoich mix.

I'd also recomend the msd 6a

 

Not at WOT it won't be. I'd never rely on a stock O2 sensor anyways.