Just wondering if gear ratios has anything to do with smog. Trying to ref my b17 swap, but I have an ls tranny. Last time I went to the ref, he didn't say anything about it, but could it have an affect on how emission operates. Ls = longer gear ratio. GSR = shorter gear ratio

 

On the dyno it does make a difference in the load. On a regular HP dyno, you can get different readings depending on which which gear the operator goes upto. Some dyno upto 3rd gear and some go to 4th (usually 1:1). Tall LS gearing will put more load on the motor for a given gear at given speed. I think overall, the difference in emissions though is small unless it causes detonation.

 

Thanks for the response. Cleared up my question.

 

I REF'd my B17 with a LS tranny...no problems.

 

My feeling is that it DOES make a difference! However I can't verify anything with solid facts.

Here is my thinking;

When they do the smog check, they put the car on rollers and take readings at 15 mph and also 25 mph. A GSR transmission would result in higher engine RPM's then what an LS transmission would.

It could lead to a difference.

If it does really matter, then the thing to do would be to borrow as tall a tire combination as possible for the test and that would alter the over-all gearing to lower engine RPM at the given MPH speed.

As with fourthgenhatchB17, I passed the referee process with an "LS transmission" under my engine.

Wes V