Following are various graphs from dynamometer (dyno) runs I have made since I bought the IROC and started modifying it.

This graph compares 3 of the dyno runs I made in March 2001 when I still had the stock 305 under the hood with just headers, a cat-back exhaust, and a 2200 stall converter.  I had started modifying and burning my own computer chips a few months earlier.  The chips I used that day leaned out the Power Enrichment 2% in run 4 and another 2% in run 5 since it was running quite rich.

This graph compares my first run made in October 97 (GREG.001) when the car was factory stock (except for K&N air filters and a Hypertech chip) against my best run (run 5) from above.  The headers, cat-back, and custom chips helped raise the torque and horsepower curves.

I made several runs in October 2001 with the new 355 engine, but still had the stock throttle body and the stock intake runners on top of the Edelbrock manifold.  This graph compares the best run from that day with my best run from the 305 engine.

After installing ported SLP runners and a 58mm throttle body, I went back to the dyno in April 2002.  The double humps in the horsepower curve were replaced with a larger single hump. :)  I couldn't run more than 27-28 degrees of spark advance due to the 11.3 compression and mild LT4 HOT cam.

After having the cylinder head combustion chambers opened up (see http://www.erols.com/gcwestph/Heads.html), porting out the runners and manifold, and getting the tranny rebuilt, I went to a Dyno Day with several other guys from the Mid-Atlantic F-Body list.  The first graph below shows all 3 runs I made.  Run 15 is with my street chip with conservative PE (22-25%) and timing (28-30 degrees).  I made run 16 with another chip that leaned out the PE by 2% and bumped up the timing to 30-32 degrees.  Run 17 was made with another chip with the same PE but adding 2 degrees more timing from 4000 rpm and up.  At this point, the TPI intake design is the limiting factor to making more power besides other mods such as changing the cam, porting the heads, or installing long-tube headers.

This graph compares my best run with the stock runners and TB (run 8) to my best run with the lower compression (and more timing), ported runners and manifold, and a 58mm TB, along with all of the other mods performed to date.

This graph compares runs before (run 13) and after (run 17) having the heads worked on to drop the compression and porting out the SLP runners (http://www.erols.com/gcwestph/runner1-sm.jpg) and Edelbrock manifold (http://www.erols.com/gcwestph/Intake.html).  While the peak horsepower only rose by less than 12 hp, the area under the curve is much greater, particularly in the 4000+ rpm range the engine would stay in during a dragstrip run.  I gained about 9-11 hp between 4300 and 5200 rpm, 28 hp at 6000 rpm, 33 hp at 6100 rpm, 41 hp at 6200 rpm, and 46 hp at 6300 rpm.

 Last update: February 4, 2005