serp belt delete = only 2.5 hp on dyno

[mans]

1998 saturn sc2

weighs 2400 lbs 1.9L engine

please see my thread. I considered deleting my alternator and power steering pump and putting in a pair of 100ah deep cycle batteries and a manual rack.

but the saturn guys responded that with the entire serp belt removed the dyno registered only 2.5hp increase.

if there is only a 2.5 hp increase how much could this save on fuel economy?

here we say that alt delete is 10% gain alone, and the ps pump should add to that. but how can that be possible if the saturn guys say its only 2.5 hp on the dyno and that means no alt, ps pump , water pump at all???

see my thread swap to manual steering rack - SaturnFans Forums

[jakobnev]

Well if you were, say, using 15hp on the highway 2.5hp would be 17% of that. After some efficiency loss due to decreased load you'd be expecting to save about 11% fuel.

But the power saved might be less that 2.5hp at lower revs.

[redpoint5]

Exactly what Jakob said. You aren't running your Saturn at 100% power all the time. If you were, you might get only a 2% increase in MPG. Typical highway cruising speeds in a typical car require 15-20hp, in which case 2.5hp becomes a much more significant portion of the total power production.

[Ladogaboy]

BUT, that 2.5 hp would be stolen all of the time. I would say that idling would be just as impacted as highway mileage. I don't know the exact hp figures, but when my car is idling, the engine load is 10-17% compared to 50-70% at highway cruise.

Then again, I think a lot of people here shut off their engines rather than idle, so that might not have as great of an impact.