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Old 06-19-2010, 10:38 AM   #1 (permalink)
Master EcoModder
Join Date: Jun 2010
Location: Australia
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Delivery 'Boy - '86 Suzuki Mighty Boy
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Real world results from exhaust and boost change

Once upon a time I had a Legacy GT. Not the best car for economy, but it had enough grunt to tighten my seatbelt on a hard launch. And that's why this post is in the off topic section.

Up a certain hill near a certain town in NZ it goes from a 50km/h speed zone to 100km/h, up a steep hill and merging onto a highway (three lanes wide at the merge point). The average car can get to 100km/h by the top of the hill. My legacy could top 135 out of the box when I changed up at 6000rpm (for other reasons, but the redline was at 7000).

I then got a boost controller, and O2 sensor reading kit, and boost guage. So naturally I turned the boost up.

Going from 8psi to 14 resulted in a speed increase to 145km/h with no other changes. So I gained 10km/h.

Then I came across a cheap exhaust system. $100 for a 2.5" turbo back exhaust with a single resonator and no cat (not required under NZ law at the time). So I bought it and installed it. And my top speed rose another 10km/h to 155...

It's worth noting that the boost increase was really felt, wheras the exhaust had comparitively little (noise was another story, but I'm talking about power). I'm putting this down to the fact that boost affected peak torque soon afer I put my foot down, and it was unlikely that the exhaust was restrictive at 3000rpm. However once you got near 5000, the story would have been different.

Just thought I should share my story.

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