would changing the final drive affect smog results because the engine is reving higher to go the same speed when the car is on the rollers.

 

anybody?

 

no...the motor will just rev faster

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by drumking15 &raquo;</TD></TR><TR><TD CLASS="quote">no...the motor will just rev faster </TD></TR></TABLE>

 

everyone agree?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by drumking15 &raquo;</TD></TR><TR><TD CLASS="quote">no...the motor will just rev faster </TD></TR></TABLE>
I third this notion.

 

you should have no worries!

 

It will potentially affect the emissions because the fuel and spark will be running in different load and rpm cells on their respective maps (probably just RPM in this case).

For example, if you had a map where load is across (x-axis) and rpm is up (y-axis) and you geared it higher the cell that the computer fetches how much fuel to spray would move up one. That value for the fuel is ultimately stored in memory as a number so lets say that 1 is leaner and 10 is richer. If, with the first transmission you passed smog fine the value stored for fuel was 3. Since everything passed we assume the fuel mixture is correct. Now after you put the higher geared transmission in it the computer is fetching the value one cell higher on the map because rpm went up. If the value in the cell is high, say 9, it could be way too rich and would cause excessive emissions. This would only happen if the car was tuned incorrectly for your setup.

If the value did go up at all it would go to something like 4, usually the numbers are blended pretty smoothly.

 

good info

 

Thank you.

 

Absolutely... Great post!

Our CRX si have to be run in 2nd @ 15mph and third @ 25 because of the rpm limit. So the final drive ratio and or tire size does matter.