My experience to add fuel to the fire... - Saab Performance Bulletin Board - Saabnet.com
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My experience to add fuel to the fire...
Posted by BillJ [Email] (more from BillJ) on Fri, 8 Nov 2002 17:25:04
In Reply to: Dr Boost: another esoteric question..., Eric Law, Fri, 8 Nov 2002 15:46:57
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Some time ago, when my 9000 Aero was largely standard (just a 3" exhaust, turbo-back), I took Dr. Boost's advice and regapped my plugs from around 0.9mm to 1.1mm. The car definitely pulled better from low RPM. This was subjective, but it was a very strong impression.
After fitting "manipulated" software (as Dr. Boost would call it) from Maptun (and with a modified airbox), I took it to a dyno. It runs 1.5-1.6 bar boost. I don't want to get into arguing over the absolute figure (confirmed to within a couple of bhp on another dyno), but with brand new plugs (about 1/2 hour old) gapped to 1.1mm, they measured 290bhp and 310lbft (calculated at the flywheel). When we switched to another set of brand new plugs set to 0.9mm and let the car idle for a few minutes to warm them up, another run showed a significant increase in torque over almost the entire speed range, with peaks of 305hp and 330lbft torque.
Anyway, the power and torque increase, however you want to correct for transmission losses, was around 5%, simply by reducing the plug gap.
I can't explain this result, as it doesn't make sense and it surprised the dyno operator that the plug gap made any measureable difference.
It's possible that my DI cassette (now a couple of years old) is showing signs of age and cannot fire a large gap under high boost. I would be pretty certain that the increased torque indicates increased boost.
I don't have any signs of misfiring, though.
Interesting, though.
posted by 62.253....
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