I've been using an AutoTap to do OBDII datalogging. I have several of the following logs containing RPM and MAF. 1 and 2 were done on the same day. 3 was done at a later date(yesterday to be exact).

1. Stock
2. Buschur cat-back /w Magnaflow
3. Buschur cat-back /w Magnaflow, Downpipe and high flow cat

I put the logs into excel and graphed them on top of one another. I made the following graphs.

RPM vs MAF
RPM vs MAF/RPM(air flow per engine revolution... sorta like boost)

The exhaust upgrades seem to greatly improve spool-up, but didn't seem to increase air flow in the upper RPM range. I can definatly feel the faster spool-up and the car seem generally faster... I was just expecting to see more air flowing.

I'll post the graphs when I get home tonight.

Thoughts?????

 

only mods to the intake side should net you MAF changes

 

So where do the gains from an exhaust upgrade come from if it's not more flow into the engine?

Guess: Less force needed to push the exhaust out of the cylinder?

 

New freeflowing exhaust unrestricts the flow of spent gases so that the gases get out the tailpipe easier/faster thus reducing backpressure in the exhuast system..

Easier exit /better flow = more efficent/powerful engine..

 

Here are the graphs. I can't believe that no one seems to be interested in this.

 

I can appreciate the effort but I only understand speed & power, can't comprehend what makes it!!! Just buy things and install them

 

I appreciate the effort as well .... thanks for putting up the find .... I've always wanted to know what kind of effect just bolt-ons would do with out messing with the ECU. Did you notice any difference in spool time with just a catback?