Ok just got my car dyno'd 85 tpi, I'm down about 10-15 hp from stock, even though the conditions 91 F didn't help and it could use a slight tuneup. What I need to know is what could be causing that erratic graph? any ideas?



[This message has been edited by Jono (edited July 09, 2001).]

The '85 LB9 was advertised as having 215 hp@ 4200 and 275 lbs/ft @ 3200. Assuming drivetrain losses at 20%(optimistic for all but the tightest automatics) this would equate to 172 hp and 220 lbs/ft at the rear wheels. So your dyno runs are very close to the advertised spec's. Assuming(again) a 3% gain for every 10° drop in temperature, you would probably pick up 10 hp at 70°F. The hot conditions would restrict airflow more as rpms increase and volumetric efficiency decreases.

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"The reasonable man adapts himself to the world.
The unreasonable one persists in trying to adapts the world to himself.
Therefore all progress depends on the unreasonable man"
--George Bernard Shaw.

check for thigns that block the air. Look in your catalyst, look at your intake. Look at anything related to air

BTW, dyno graphs are always jagged. This especially true of chassis dyno's, where it it is nearly impossible to advance throttle at alinear rate over time.

When you see a smooth curve graph, it is because the measurements are taken at set rpm points(vs continuous measurement) and the points are joined by lines or a curve(kind of like connect-the-dots).

Thanks for the informative comments, I'm glad to hear I'm not too far from stock performance (considering its 16 years old).